Metal complexes in fossil fuels: geochemistry, characterization, and processing (ACS Symposium series 344)

Publication Date: July 6, 1987 | doi: 10.1021/bk-1987-0344.fw001 Metal Complexes in Fossil Fuels Publication Date: Ju...

Author: Royston H. Filby | Jan F. Branthaver | American Chemical Society. Division of Petroleum Chemistry | American Chemical Society. Meeting

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Publication Date: July 6, 1987 | doi: 10.1021/bk-1987-0344.fw001

Metal Complexes in Fossil Fuels


ACS SYMPOSIUM SERIES

344

Metal Complexes in Fossil Fuels


Geochemistry, Characterization, and Processing Royston H. Filby,

EDITOR Washington State University

Jan F. Branthaver, EDITOR Western Research Institute

Developed from a symposium sponsored by the Divisions of Geochemistry and Petroleum Chemistry, Inc. at the 191st Meeting of the American Chemical Society, New York, New York, April 13-18, 1986

American Chemical Society, Washington, DC 1987

Library of Congress Cataloging-in-Publication Data Metal complexes in fossil fuels. (ACS symposium series, ISSN 0097-6156; 344) "Developed from a symposium sponsored by the Divisions of Geochemistry and Petroleum Chemistry at the 191st Meeting of the American Chemical Society, New York, New York, A p r i l 13-18, 1986."


Includes bibliographies and indexes. 1. Petroleum—Analysis—Congresses. 2. Complex compounds—Congresses. I. Filby, Royston H . II. Branthaver, Jan F., 1936. III. American Chemical Society. Division of Geochemistry. IV. American Chemical Society. Division of Petroleum Chemistry. V. American Chemical Society. Meeting (191st: 1986: New York, N.Y.) VI. Series. TP691.M436 1987 ISBN 0-8412-1404-2

553.2

87-14418

Copyright © 1987 American Chemical Society A l l Rights Reserved. The appearance of the code at the bottom of the first page of each chapter in this volume indicates the copyright owners consent that reprographic copies of the chapter may be made for personal or internal use or for the personal or internal use of specific clients. This consent is given on the condition, however, that the copier pay the stated per copy fee through the Copyright Clearance Center, Inc., 27 Congress Street, Salem, M A 01970, for copying beyond that permitted by Sections 107 or 108 of the U S . Copyright L a w . This consent does not extend to copying or transmission by any means—graphic or electronic—for any other purpose, such as for general distribution, for advertising or promotional purposes, for creating a new collective work, for resale, or for information storage and retrieval systems. The copying fee for each chapter is indicated in the code at the bottom of the first page of the chapter. The citation of trade names and/or names of manufacturers in this publication is not to be construed as an endorsement or as approval by A C S of the commercial products or services referenced herein; nor should the mere reference herein to any drawing, specification, chemical process, or other data be regarded as a license or as a conveyance of any right or permission, to the holder, reader, or any other person or corporation, to manufacture, reproduce, use, or sell any patented invention or copyrighted work that may in any way be related thereto. Registered names, trademarks, etc., used in this publication, even without specific indication thereof, are not to be considered unprotected by law. PRINTED IN THE UNITED STATES OF AMERICA

ACS Symposium Series M. Joan Comstock, Series Editor


1987 Advisory Board Harvey W. Blanch University of California—Berkeley

Vincent D. McGinniss Battelle Columbus Laboratories

Alan Elzerman Clemson University

W. H . Norton J. T. Baker Chemical Company

John W. Finley Nabisco Brands, Inc.

James C . Randall Exxon Chemical Company

Marye Anne Fox The University of Texas—Austin

E . Reichmanis AT&T Bell Laboratories

Martin L . Gorbaty Exxon Research and Engineering Co.

C . M . Roland U.S. Naval Research Laboratory

Roland F. Hirsch U.S. Department of Energy

W. D. Shults Oak Ridge National Laboratory

G . Wayne Ivie USDA, Agricultural Research Service

Geoffrey K . Smith Rohm & Haas Co.

Rudolph J. Marcus Consultant, Computers & Chemistry Research

Douglas B. Walters National Institute of Environmental Health


Foreword The A C S S Y M P O S I U M S E R I E S was founded in 1974 to provide a

medium for publishing symposia quickly in book form. The format of the Series parallels that of the continuing A D V A N C E S IN C H E M I S T R Y S E R I E S except that, in order to save time, the papers are not typeset but are reproduced as they are submitted by the authors in camera-ready form. Papers are reviewed under the supervision of the Editors with the assistance of the Series Advisory Board and are selected to maintain the integrity of the symposia; however, verbatim reproductions of previously published papers are not accepted. Both reviews and reports of research are acceptable, because symposia may embrace both types of presentation.

Publication Date: July 6, 1987 | doi: 10.1021/bk-1987-0344.pr001

Preface THE E X I S T E N C E O F M E T A L C O M P L E X E S I N F O S S I L F U E L S was established by Alfred Treibs in the 1930s. It is claimed by some that this work laid the foundation for the modern science of organic geochemistry. Out of it was derived the concept of the biomarker as well as definitive evidence that organic matter in fossil fuels is largely of biological origin. Since the 1930s, much work has been published on the geochemistry of porphyrins and other metal complexes in geological materials. The emphasis of most of this work is on metalloporphyrins and chlorins because these compounds possess spectral characteristics that permit detection in small concentrations and chemical properties that sometimes allow substantial purification from background materials. Investigations of geoporphyrins have featured structure determinations, the results of which have shown that a great variety and number of compounds are derived apparently from a few biological precursors as a consequence of geochemical processes. The nature of these geochemical processes has been inferred from the observed transformations. These processes are of particular interest to those who search for fossil fuels, particularly petroleum. While the geochemistry of metal complexes was being studied, it was found that metal complexes in fossil fuels cause serious problems in processing. Thus, while geochemists attempted to discover how metal complexes occur in fossil fuels, chemical engineers were trying to find ways to get them out or otherwise deal with their deleterious effects. Interaction between the two groups of researchers has been somewhat limited. This volume covers to some degree topics in the geochemistry, analytical chemistry, and processing chemistry of metal complexes in fossil fuels, principally petroleum. To the best of our knowledge, this is one of the first attempts to cover this wide array of subjects in one volume. As a result, we hope that a clearer picture of the role of these interesting compounds in the generation and use of fossil fuels emerges. We may thus learn about processing considerations through our study of geochemistry. As nonpetroleum resources are used to obtain products now derived from crude oil, metal complexes in those resources doubtless will behave chemically much as they do in petroleum. In addition, more metal complexes may be generated by reactions of organic material with intimately associated mineral matter during processing. Most of the chapters in this book come from the symposium on which this book is based. To complete the coverage of this topic, however, some IX

chapters were updated from an earlier symposium on hydrodemetallization catalysts organized by A. W. Aldag and J. Smith. A few chapters were written expressly for the book also. The wide variety of topics reflects the diversity of research in the field. We thank many people for their parts in making this book possible. We especially thank the many secretaries who typed the manuscripts and the reviewers who provided helpful and conscientious reviews. We thank the staff of the ACS Books Department, who performed the mechanics of putting the volume together. We also thank our employers, Washington State University and Western Research Institute, for the help and services we received when we prepared this volume. Jan F. Branthaver thanks the U.S. Department of Energy, Bartlesville Project Office, for its support of this project under contract number DE-FC21-83FE-60177.

Publication Date: July 6, 1987 | doi: 10.1021/bk-1987-0344.pr001

R O Y S T O N H. F I L B Y

Washington State University Department of Chemistry Pullman, WA 9 9 1 6 4 J A N F. B R A N T H A V E R

Western Research Institute University Station Laramie, WY 82070 March 2, 1987

x

Chapter 1 Geochemistry of Source

Metal

Rocks,

and

C o m p l e x e s in P e t r o l e u m , Coals:

An

Overview

Royston H. Filby and Gary J. Van Berkel

Publication Date: July 6, 1987 | doi: 10.1021/bk-1987-0344.ch001

Department of Chemistry and Nuclear Radiation Center, Washington State University, Pullman, WA 99164-1300

The geochemistry of metal complexes in fossil fuels and their precursors is almost entirely that of the metalloporphyrins. The evolution of the metalloporphyrins during early-late stage diagenesis and catagenesis of sediments involves primarily the progressive defunctionalization and reduction of chlorophylls -a, -b, -c- , -c and bacteriochlorophylls-a, -b, -d followed by metallation of the free-base porphyrins in maturing sediments. The role of the mineral matrix and sedimentary kerogens in porphyrin evolution is discussed. The geochemical processes involved in petroleum generation (migration, maturation, alteration), their effects on Ni(II) and VO(II) porphyrin evolution and implications for exploration are also discussed. The geochemistry of the Fe(III), Ga(III), and Mn(III) porphyrins in coals reflects the different, more oxic, depositional conditions of coal formation compared to those of petroleum source beds. 1

2

The p u r p o s e o f t h i s o v e r v i e w i s t o s u r v e y t h e g e o c h e m i s t r y o f t h e m e t a l l o p o r p h y r i n s and o t h e r metal complexes i n f o s s i l f u e l s . Emphas i s i s given t o the metalloporphyrins i npetroleum and source rocks because t h e s e have been t h e major f o c u s o f r e c e n t r e s e a r c h . This r e v i e w c o v e r s t h e o r i g i n and e v o l u t i o n o f t h e g e o p o r p h y r i n s from t h e b i o l o g i c a l source m a t e r i a l t o t h e i r i n c o r p o r a t i o n into crude o i l s and c o a l s . I t i s n o t i n t e n d e d t o be an e x h a u s t i v e r e v i e w o f t h e l i t e r a t u r e a n d p r e v i o u s r e v i e w s o f p o r p h y r i n g e o c h e m i s t r y (_l-9), p a r t i c u l a r l y t h e e x c e l l e n t r e v i e w s b y B a k e r a n d c o - w o r k e r s (-4, 5^, 7 ) , s h o u l d be c o n s u l t e d . The g e o c h e m i s t r y o f m e t a l c o m p l e x e s i n p e t r o l e u m a n d s e d i m e n t s that are p o t e n t i a l petroleum source rocks i s p r i m a r i l y that o f t h e N i ( I I ) a n d V O ( I I ) p o r p h y r i n s , a l t h o u g h C u ( I I ) p o r p h y r i n s may b e f o u n d i n t h e e a r l y stages o f sediment d i a g e n e s i s . A l t h o u g h t h e r e i s e v i dence f o r t h e e x i s t e n c e o f n o n - p o r p h y r i n complexes o f n i c k e l and v a n a d i u m i n c r u d e o i l s , o i l - s a n d b i t u m e n s a n d a s p h a l t s , no d i s c r e t e c o m p l e x e s h a v e b e e n u n e q u i v o c a l l y i d e n t i f i e d a n d t h e r e i s some e v i dence t h a t n o n - p o r p h y r i n s p e c i e s a r e , i n f a c t , p o r p h y r i n i c . In t h e case o f c o a l s , t h e s p e c i f i c m e t a l complexes t h a t have been i d e n t i f i e d a r e t h e G a ( I I I ) , F e ( I I I ) a n d M n ( I I I ) p o r p h y r i n s ( 9 ) .

0097-6156/87/0344-0002$ 10.50/0 © 1987 American Chemical Society

1.

FILBY A N D V A N B E R K E L

3

Overview

However, t h e g e o c h e m i s t r y o f m e t a l - o r g a n i c s p e c i e s i n l o w r a n k c o a l s , a t l e a s t , may i n v o l v e h u m a t e c o m p l e x e s o f many m e t a l s .


I.

The G e o p o r p h y r i n s The m e t a l l o p o r p h y r i n s w e r e t h e f i r s t c o m p o u n d s o f c o n c l u s i v e b i o l o g i c a l o r i g i n (10-12) i d e n t i f i e d i n petroleum, b u t t h e i r geochemical evolution i s s t i l l incompletely understood. I n p a r t , t h i s i s due t o the a n a l y t i c a l d i f f i c u l t y encountered i n t h e i s o l a t i o n and s e p a r a t i o n of s m a l l amounts o f complex m i x t u r e s o f N i ( I I ) o r V O ( I I ) homologues o f e a c h p o r p h y r i n t y p e ( d e s o x y p h y l l o e r y t h r o e t i o p o r p h y r i n , DPEP; e t i o p o r p h y r i n , e t i o ; e t c . ) and t h e i d e n t i f i c a t i o n o f i n d i v i d u a l molecular species. However, advances i n t h e i d e n t i f i c a t i o n and q u a n t i t a t i o n o f p o r p h y r i n s and t h e i r p r e c u r s o r s by mass s p e c t r o m e t r y (MS) a n d H P L C h a v e s t i m u l a t e d r e c e n t d e v e l o p m e n t s i n p o r p h y r i n g e o chemistry. N u c l e a r O v e r h a u s e r e f f e c t ( n O e ) NMR, X - r a y d i f f r a c t i o n , a n d MS/MS h a v e b e e n u s e d w i t h g r e a t s u c c e s s t o d e t e r m i n e t h e a c t u a l s t r u c t u r e s o f many i n d i v i d u a l , g e o c h e m i c a l l y s i g n i f i c a n t , m e t a l l o porphyrins. These a n a l y t i c a l advances a r e d i s c u s s e d by Q u i r k e i n t h i s volume ( 1 3 ) . T r e i b s (14) proposed a sequence o f r e a c t i o n s t o account f o r t h e transformation of plant c h l o r o p h y l l s into the geoporphyrins. The T r e i b s scheme was b a s e d on i n c o m p l e t e k n o w l e d g e o f p o r p h y r i n s t r u c t u r e s and has s i n c e undergone s i g n i f i c a n t m o d i f i c a t i o n . Despite t h e s e m o d i f i c a t i o n s , t h e c o n v e r s i o n o f c h l o r o p h y l l - a t o C32DPEPm e t a l l o p o r p h y r i n s has e s s e n t i a l l y been confirmed by t h e d e t e r m i n a t i o n of t h e s t r u c t u r e o f t h e V O ( I I ) and N i ( I I ) C D P E P complexes (15-17) a n d b y t h e t y p i n g o f i n t e r m e d i a t e s (5_, 7) . T h e s c h e m e p r o p o s e d b y T r e i b s (14) i s o u t l i n e d i n F i g u r e 1 w i t h t h e thermal s c i s s i o n o f t h e i s o c y c l i c r i n g o f t h e D P E P - p o r p h y r i n p r o p o s e d b y C o r w i n ( 1 ) shown t o a c c o u n t f o r t h e e t i o - p o r p h y r i n s w i t h o u t r e q u i r i n g a s e p a r a t e hemec o n t a i n i n g source (e.g., cytochrome c ) . Figure 2 o u t l i n e s schematic a l l y t h e b r o a d e v o l u t i o n a r y scheme o f t h e g e o p o r p h y r i n s f r o m s o u r c e m a t e r i a l t o petroleum. I n a d d i t i o n t o t h e T r e i b s scheme, t h e most i m p o r t a n t a l t e r n a t e pathways and mechanisms t h a t have been p r o p o s e d , a n d w h i c h a r e d i s c u s s e d i n t h i s r e v i e w , a r e shown i n F i g u r e 2. D e s p i t e t h e p r o g r e s s made i n r e c e n t y e a r s , t h e r e a r e many aspects of the geochemical e v o l u t i o n of the metalloporphyrins which are s t i l l not w e l l understood, f o r example: i ) The o r i g i n o f m e t a l l o p o r p h y r i n s f o r w h i c h no b i o l o g i c a l p r e c u r s o r i s known. i i ) The i n f l u e n c e o f t h e s e d i m e n t a r y e n v i r o n m e n t ( e . j * . , pH, E h , e t c . ) on m e t a l l a t i o n o f t h e f r e e - b a s e p o r p h y r i n s o r p r e c u r s o r s . i i i ) The r o l e o f t h e m i n e r a l m a t r i x i n t h e d i a g e n e t i c a n d c a t a g e n e t i c r e a c t i o n s o f p o r p h y r i n s and t h e i r p r e c u r s o r s . iv) The r o l e o f k e r o g e n a n d t h e e f f e c t s o f k e r o g e n c a t a g e n e s i s on t h e e v o l u t i o n o f t h e m e t a l l o p o r p h y r i n s i n s o u r c e r o c k s . v) The D P E P - e t i o p o r p h y r i n r e l a t i o n s h i p and t h e mechanism o f e t i o - p o r p h y r i n formation i n petroleum source rocks and c o a l s . vi) The mechanism o f f o r m a t i o n o f h i g h c a r b o n number ( ^ 3 3 ) porphyrins. vii) The e f f e c t s o f m i g r a t i o n a n d p e t r o l e u m a l t e r a t i o n processes ( m a t u r a t i o n , b i o d e g r a d a t i o n , d e a s p h a l t i n g , w a t e r w a s h i n g , e t c . ) on m e t a l l o p o r p h y r i n d i s t r i b u t i o n s i n crude o i l s . 3 2


M E T A L C O M P L E X E S IN FOSSIL FUELS

F i g u r e 1. T r e i b s - C o r w i n Scheme f o r g e o c h e m i c a l c o n v e r s i o n o f c h l o r o p h y l l - a _ t o C32 m e t a l l o p o r p h y r i n s ( f r o m 1_, 1 4 , c f , 4_, .5, 7 ) . R = p h y t y l (C20H39).

1.

FILBY A N D VAN B E R K E L

5

Overview

LEGEND


( i ) decarboxylation i ) aromatization ( i i i ) oxidative i s o c y c l i c r i n g opening ( i v ) formation of minor species via unknown nrecursors \(v) m e t a l l a t i o n reaction s ( v i ) DPEP -* e t i o conversion x ( v i i ) hydrogenation - dehydrogenation \ step

DIAGENESIS

benzoDPEP

tetrahydrobenzoDPEP Extended carbon number Porphyrins (kerogen-mineral interactions)

VOetio

Nietio

VODPEP

Ni DPEP

CATAGENESIS r e l a t i v e thermal or degradation s t a b i l i t i e s

F i g u r e 2. D i a g e n e t i c p a t h w a y s p r o p o s e d f o r e v o l u t i o n o f t h e geoporphyrins. M a j o r p a t h w a y s a r e shown w i t h s o l i d a r r o w s a n d p r o p o s e d , b u t u n c o n f i r m e d , p a t h w a y s shown w i t h b r o k e n a r r o w s . T r e i b s Scheme s t e p s l a b e l e d ( T ) . N o t shown a r e e x o c y c l i c s p e c i e s . P = porphyrin precursors (unidentified: includes reduction of v i n y l group i nmajor c h l o r o p h y l l s ) .

6



v i i i ) The m e c h a n i s m o f a s s o c i a t i o n o f p o r p h y r i n s w i t h p e t r o l e u m components (e.g., a s p h a l t e n e s , r e s i n s ) . In t h i s d i s c u s s i o n , the geochemistry of the p o r p h y r i n s i s t r e a t e d i n the f o l l o w i n g sequence: i ) Source m a t e r i a l and b i o l o g i c a l p r e c u r s o r s . i i ) D e p o s i t i o n a l environment. i i i ) Early diagenesis. i v ) L a t e d i a g e n e s i s and c a t a g e n e s i s . v) P o r p h y r i n s i n petroleum m i g r a t i o n . v i ) Petroleum a l t e r a t i o n processes. S o u r c e M a t e r i a l s and B i o l o g i c a l P r e c u r s o r s . F o s s i l f u e l s r e p r e s e n t a " l e a k " i n the g l o b a l carbon c y c l e . Although the i n o r g a n i c o r i g i n of p e t r o l e u m s t i l l has p r o p o n e n t s ( 1 8 ) , i t i s w i d e l y h e l d by g e o c h e m i s t s t h a t most p e t r o l e u m d e p o s i t s have o r i g i n a t e d from o r g a n i c m a t e r i a l preserved i n sediments deposited i n p r i m a r i l y l a c u s t r i n e or marine c o a s t a l environments (19,20). This source m a t e r i a l i s derived mostly from p h y t o p l a n k t o n i n the o x i c s u r f a c e w a t e r s w i t h c o n t r i b u t i o n s from photosynthetic b a c t e r i a (autochthonous m a t e r i a l ) , t e r r e s t r i a l l y derived organic d e b r i s transported into the sedimentary basin ( a l l o c h t h o n o u s m a t e r i a l ) , and m i c r o o r g a n i s m s a c t i n g on s u r f i c i a l l y - d e r i v e d organic remains w i t h i n the sediment. The d e p o s i t e d o r g a n i c m a t t e r undergoes a complex s e r i e s of r e a c t i o n s ( e a r l y to m i d d i a g e n e s i s ) i n v o l v i n g m i c r o b i a l and c h e m i c a l d e g r a d a t i o n o f b i o p o l y m e r i c s o u r c e m a t e r i a l , r e d o x r e a c t i o n s , and r e p o l y m e r i z a t i o n o f p r o d u c t s t o l e s s ordered "geopolymers" which under i n c r e a s i n g thermal s t r e s s form s e d i m e n t a r y k e r o g e n s ( p r e d o m i n a n t l y t y p e I and I I k e r o g e n s u n d e r marine-lacustrine conditions, 19). E s s e n t i a l to the p r e s e r v a t i o n of the o r g a n i c m a t e r i a l i n the sediment a r e a n o x i c d e p o s i t i o n a l c o n d i t i o n s that prevent a e r o b i c m i c r o b i a l r e s p i r a t i o n of the o r g a n i c matter to carbon d i o x i d e . Late diagenesis, or catagenesis, includes the breakdown o f the kerogen under i n c r e a s i n g t h e r m a l s t r e s s to g i v e , i n p a r t , the hydrocarbons of source rock bitumens which, under s u i t a b l e g e o l o g i c c o n d i t i o n s , may m i g r a t e f r o m t h e s o u r c e r o c k t o f o r m petroleum deposits i n a trap or r e s e r v o i r . U n l i k e p e t r o l e u m , c o a l s have formed p r i m a r i l y from p l a n t d e b r i s i n t e r r e s t r i a l environments under c o n d i t i o n s of h i g h o r g a n i c product i v i t y and u n d e r l e s s r e d u c i n g , o r more o x i c , c o n d i t i o n s t h a n t h o s e found i n petroleum p r o d u c i n g environments. Under these c o n d i t i o n s , t y p e - I l l kerogens are dominant (19,21). G e o p o r p h y r i n s a r e f o u n d i n h i g h a b u n d a n c e s ( i . e _ . , >10 y g / g ) o n l y i n p e t r o l e u m , a s p h a l t s , o i l s h a l e s , and a s s o c i a t e d s o u r c e r o c k s i n w h i c h t h e y o c c u r a s t h e N i ( I I ) and V O ( I I ) m e t a l c o m p l e x e s . Freeb a s e p o r p h y r i n s and m i n o r amounts o f a l l o c h t h o n o u s C u ( I I ) e t i o p o r p h y r i n s are found i n sediments i n the e a r l y stages of d i a g e n e s i s (7,22). M i n o r amounts o f g e o p o r p h y r i n s a r e found i n c o a l s (9,12, 23-26), but p r i m a r i l y as F e ( I I I ) , G a ( I I I ) o r M n ( I I I ) complexes. The p r e s e n c e o f t r i v a l e n t i r o n a n d m a n g a n e s e p o r p h y r i n s r e f l e c t s t h e l e s s r e d u c i n g d e p o s i t i o n a l environment o f c o a l s compared to p e t r o l e u m and t h e d i f f e r e n t s o u r c e m a t e r i a l s o f p e t r o l e u m and c o a l s . The s t r u c t u r a l c h a r a c t e r i z a t i o n o f t h e g e o p o r p h y r i n s h a s b e e n m o t i v a t e d , i n p a r t , by t h e n e e d t o i d e n t i f y t h e i r b i o l o g i c a l p r e c u r s o r s so t h a t t h e y c a n be u s e d a s b i o m a r k e r s . The T r e i b s s c h e m e ( 1 4 ) , as o r i g i n a l l y p o s t u l a t e d , assumes t h a t the p r e c u r s o r t o V O ( I I )

1.


7

Overview

C32DPEP i s c h l o r o p h y l l - a _ , t h e m o s t a b u n d a n t o f t h e p l a n t p i g m e n t s . A s s e v e r a l a u t h o r s h a v e p o i n t e d o u t (5_,J_,8) , c h l o r o p h y l l - ^ i s n o t t h e o n l y p r e c u r s o r t o C32DPEP a n d d i a g e n e t i c p a t h w a y s s i m i l a r t o t h a t o f T r e i b s ( 1 4 ) c a n be p r o p o s e d s t a r t i n g f r o m c h l o r o p h y l l s - b , -c_, b a c t e r i o c h l o r o p h y l l - a , and o t h e r c h l o r o p h y l l s , e x c e p t f o r t h e Chlorobium c h l o r o p h y l l s (e.g., b a c t e r i o c h l o r o p h y l l s - d ) . T h e r e i s now s t r o n g e v i d e n c e from the d e t e r m i n a t i o n o f s t r u c t u r e s o f s p e c i f i c g e o p o r p h y r i n s t h a t c h l o r o p h y l l s-b, - c j , -c_ (8,27-29) and b a c t e r i o c h l o r o p h y l l s - d ( 2 7 - 2 9 ) a l s o may be p r e c u r s o r s i n c e r t a i n d e p o s i t i o n a l environments. Examples o f c o n f i r m e d p o r p h y r i n s t r u c t u r e s and most l i k e l y p o r p h y r i n - p r e c u r s o r p a i r s a r e d i s c u s s e d i n t h i s v o l u m e by C h i c a r e l l i et_ a l . ( 8 ) . C h l o r o p h y l l s t r u c t u r e s a r e shown i n F i g u r e 3 and p o r p h y r i n s t r u c t u r e s a r e shown i n d e t a i l i n C h i c a r e l l i e t a l . ( 8 ) . The o b s e r v a t i o n t h a t t h e p e t r o l e u m p o r p h y r i n s ( b o t h DPEP a n d e t i o ) o c c u r as complex homologous s e r i e s w i t h c a r b o n numbers e x t e n d i n g c o n s i d e r a b l y b e y o n d C33 ( 3 0 - 3 2 ) was i n i t i a l l y r e g a r d e d a s e v i d e n c e f o r Chlorobium-type c h l o r o p h y l l p r e c u r s o r s as t h e s e a r e the o n l y n a t u r a l b a c t e r i o c h l o r o p h y l l s t h a t occur as homologous s e r i e s ( 3 3 ) . However, i t has been e s t a b l i s h e d t h a t the a l k y l a t i o n p a t t e r n s e x p e c t e d from b a c t e r i o c h l o r o p h y l l s - d a r e not c o n s i s t e n t w i t h those observed f o r t h e h i g h m o l e c u l a r w e i g h t D P E P - p o r p h y r i n s i n c r u d e o i l s and c a r b o n n u m b e r s w o u l d e x t e n d o n l y t o C37 ( s e e F i g u r e 3 ) . A n a l y s e s o f m a l e i m i d e s f r o m h i g h m o l e c u l a r w e i g h t g e o p o r p h y r i n s h a s shown t h a t t h e i s o b u t y l s u b s t i t u e n t o n t h e p y r r o l e r i n g a t C-8 e x p e c t e d f o r b a c t e r i o c h l o r o p h y l l - d products i s not found (4,34,35). Thus, Q u i r k e e t a l . (34) f o u n d a l k y l s u b s t i t u e n t s on m a l e i m i d e s o f up t o e l e v e n c a r b o n s w h i c h c o u l d n o t have a r i s e n from a b a c t e r i o c h l o r o p h y l l - d p r e c u r s o r . S e v e r a l mechanisms have been p r o p o s e d t o a c c o u n t f o r h i g h c a r b o n n u m b e r (>C33) p o r p h y r i n s f r o m c h l o r o p h y l l - a ( a n d o t h e r a b u n d a n t c h l o r o p h y l l s ) , v i a t r a n s a l k y l a t i o n (30,36), a l k y l a t i o n - d e a l k y l a t i o n ( 5 , 7 , 3 7 ) , and k e r o g e n b i n d i n g ( 7 , 3 8 - 4 0 ) , and i t i s i n d e e d u n n e c e s s a r y to propose a Chlorobium c h l o r o p h y l l o r i g i n . Although i t appears that Chlorobium c h l o r o p h y l l s are not major c o n t r i b u t o r s to the p o r p h y r i n s f o u n d i n p e t r o l e u m , Ocampo et_ a l . ( 2 7 - 2 9 ) h a v e s h o w n t h a t b a c t e r i o c h l o r o p h y l l s - d a r e s p e c i f i c p r e c u r s o r s t o t h r e e N i ( I I ) DPEP c a r b o x y l i c a c i d s i s o l a t e d from the Messel o i l shale. Thus, i t appears that b a c t e r i o c h l o r o p h y l l s - d c o n t r i b u t e to the source m a t e r i a l i n c e r t a i n d e p o s i t i o n a l environments but t h a t they a r e not the p r e c u r s o r s t o the m a j o r i t y of h i g h carbon-number g e o p o r p h y r i n s found i n mature sediments or petroleum. A l t h o u g h most o f the t h i r t y - f i v e p o r p h y r i n s f o r w h i c h s t r u c t u r e s h a v e b e e n c o n f i r m e d c a n be r e l a t e d t o s p e c i f i c o r s e l e c t e d c h l o r o p h y l l p r e c u r s o r s , s e v e r a l p o r p h y r i n s have been i d e n t i f i e d i n s e d i m e n t s and c r u d e o i l s f o r w h i c h no o b v i o u s p r e c u r s o r s a r e k n o w n ( 8 ) . Principal among t h i s c l a s s a r e t h o s e p o r p h y r i n s w i t h 6, 7, a n d n o n - D P E P - t y p e 5 membered c y c l o a l k a n o r i n g s ( 1 5 , 1 7 c y c l o a l k a n o , 4 1 - 4 4 ) , t h e b e n z o - D P E P and b e n z o - e t i o - p o r p h y r i n s , p r e v i o u s l y r e f e r r e d t o a s r h o d o - p o r p h y r i n s t e t r a h y d r o b e n z o - D P E P p o r p h y r i n s (THBD, p r e v i o u s l y r e f e r r e d t o as diDPEP) ( 4 7 ) . D i a g e n e t i c r e a c t i o n s i n v o l v i n g a c i d - c a t a l y z e d rearrangements or condensations of c h l o r o p h y l l d e r i v a t i v e s h a v e b e e n s u g g e s t e d f o r t h e e x o c y c l i c r i n g D P E P - 6 a n d DPEP-7 p o r p h y r i n s f o u n d i n t h e M e s s e l (29,43) and S e r p i a n o (8,41,42) s h a l e s . A b a c t e r i a l o r i g i n has been s u g g e s t e d f o r the p r e c u r s o r t o t h e V O ( I I ) benzo-DPEP-porphyrins f r o m t h e B o s c a n o i l ( 4 5 ) . The s t r u c t u r e o f t h e


2

a

n

d

t

h

e


M E T A L C O M P L E X E S IN FOSSIL F U E L S

Bacteriochlorophyll-a

Bacteriochlorophyll-b

Bacteriochlorophylls-d Far = farnesyl R, = ethyl , n-prop , i_-but R = methyl , ethyl 9

Mesoheme from hemeprotein Figure

3.

Structures

bacteriochlorophylls

of and

geoporphyrin mesoteme

from

precursors (chlorophylls, cytochromes).


1.

FILBY A N D VAN

BERKEL

Overview

9

b e n z o - D P E P - p o r p h y r i n s h a s b e e n c o n f i r m e d b y K a u r et_ a l . ( 4 5 ) t o c o n t a i n t h e a r o m a t i c r i n g a t t h e C-7 a n d C-8 p o s i t i o n s ( B - r i n g ) o n t h e m a c r o c y c l e r a t h e r t h a n t h e C-17 a n d C-18 p o s i t i o n s ( o n t h e D - r i n g ) w h i c h had been p r o p o s e d p r e v i o u s l y by B a r w i s e and R o b e r t s (47). I t would appear l o g i c a l t h a t t h e b e n z o - p o r p h y r i n s a r e dehydrog e n a t i o n p r o d u c t s o f t h e THBD s p e c i e s ; h o w e v e r , t h i s w o u l d r e q u i r e re-examination o f t h e s t r u c t u r e o f t h e C33THBD s p e c i e s p r o p o s e d b y Barwise and Roberts (47) i n which t h e e x o c y c l i c r i n g i s a t t a c h e d t o t h e C-17 a n d C-18 p o s i t i o n s , o r c o n s i d e r a t i o n t h a t t h e THBD i s o l a t e d from t h e E l L a j u n s h a l e (47) i s t h e p r e c u r s o r t o a d i f f e r e n t benzoDPEP s t r u c t u r e t h a n t h e o n e r e p o r t e d f r o m t h e B o s c a n o i l ( 4 5 ) . The THBD- a n d b e n z o - p o r p h y r i n s p e c i e s a n d t h e i r p o s s i b l e i n t e r - r e l a t i o n s h i p s a r e shown i n F i g u r e 2 w i t h o u t i d e n t i f i c a t i o n o f p r e c u r s o r s . I n F i g u r e 2, t h e 6-membered r i n g i s s h o w n a t t h e C-7 a n d C-8 p o s i tions. U n t i l r e c e n t l y t h e benzo- and THBD-porphyrins had been i d e n t i f i e d o n l y a s t h e m e t a l c o m p l e x e s (31,^5,4^,4_7) , b u t B a k e r a n d L o u d a ( 4 6 ) a n d Q u i r k e e_t a _ l . ( 4 8 ) h a v e s h o w n t h a t t h e f r e e - b a s e forms are present i n immature b l a c k Cretaceous and J u r a s s i c s h a l e s and i n an immature T u n i s i a n s h a l e , r e s p e c t i v e l y , i n d i c a t i n g t h a t t h e benzo a n d THBD s p e c i e s may b e f o r m e d e a r l y i n t h e d i a g e n e t i c s e q u e n c e a n d have, a s y e t , u n i d e n t i f i e d p r e c u r s o r s , as suggested by Kaur e t a l . (45). T h e s e p o r p h y r i n s t h u s r e p r e s e n t a n i n t e r e s t i n g c l a s s t h a t may have c o n s i d e r a b l e u t i l i t y i n c o r r e l a t i o n o r depositional-environment reconstruction studies (49). The e t i o - p o r p h y r i n s i n p e t r o l e u m a n d s e d i m e n t a r y s y s t e m s w e r e o r i g i n a l l y i n t e r p r e t e d by T r e i b s t o be F e ( I I I ) complexes (10-12) d e r i v e d f r o m heme p r o t e i n s . Glebovskaya and V o l k e n s t e i n (50) l a t e r s u g g e s t e d t h e s e t o be N i ( I I ) e t i o - c o m p l e x e s . Although there i s s t i l l u n c e r t a i n t y about t h e mechanisms o f f o r m a t i o n o f e t i o - p o r p h y r i n s ( 1 , 5 , 7 , 4 7 , 5 0 - 5 2 ) i t i s now w e l l e s t a b l i s h e d t h a t t h e v a s t m a j o r i t y o f e t i o - p o r p h y r i n s i n l a c u s t r i n e / m a r i n e sedimentary sequences and i n p e t r o l e u m have been d e r i v e d from c h l o r o p h y l l s o r b a c t e r i o c h l o r o p h y l l s v i a o x i d a t i v e opening o f t h e i s o c y c l i c r i n g on t h e D P E P - p o r p h y r i n p r e c u r s o r s (47,52) r a t h e r than t h e r m a l s c i s s i o n o f t h e r i n g and c o n v e r s i o n o f DPEP-to e t i o - p o r p h y r i n s a s o r i g i n a l l y p r o p o s e d by C o r w i n (jL) a n d l a t e r b y D i d y k et_ a l . ( 5 1 ) . T h u s a d i a g e n e t i c s c h e m e for the etio-porphyrins with a chlorin precursor p a r a l l e l to that f o r t h e D P E P - p o r p h y r i n s Oi.je. , T r e i b s scheme) i s shown d i a g r a m a t i c a l l y i n F i g u r e 2. C h i c a r e l l i jet a l . ( 8 ) h a v e p o i n t e d o u t , h o w e v e r , t h a t etioporphyrin-III complexes i n s e d i m e n t s c o u l d have been d e r i v e d from d e c a r b o x y l a t i o n o f mesoporphyrin-IX, a d i c a r b o x y l i c a c i d , which has been i s o l a t e d a s t h e F e ( I I I ) c o m p l e x i n c o a l s ( 5 3 ) , a n d w h i c h p r o b a b l y o r i g i n a t e d f r o m t h e heme o f c y t o c h r o m e s p r e s e n t i n t h e coal-forming environment. Fookes (54), however, c o n c l u d e d t h a t t h e Ni(II) etio-porphyrins (including Ni(II) etioporphyrin-III) i n Julia Creek o i l s h a l e were d e r i v e d from c h l o r o p h y l l s and n o t from c y t o c h r o m e d e g r a d a t i o n p r o d u c t s , a s may b e t h e c a s e f o r c o a l s ( 5 3 ) f o r m e d i n a more o x i c e n v i r o n m e n t t h a n t h a t o f t h e J u l i a C r e e k s e d i m e n t s . L e s s i s known a b o u t t h e p r e c u r s o r s t o t h e G a ( I I I ) , M n ( I I I ) a n d F e ( I I I ) porphyrins (predominantly e t i o - t y p e ) found i n c o a l s , because of the d i f f i c u l t y o f o b t a i n i n g absolute s t r u c t u r e s . T h i s i s due l a r g e l y t o t h e a n a l y t i c a l d i f f i c u l t i e s a s s o c i a t e d w i t h t h e much lower p o r p h y r i n c o n t e n t s o f c o a l s and l i g n i t e s compared t o p e t r o l e u m a n d a s s o c i a t e d s e d i m e n t s ( g e n e r a l l y 100 U g / g f o r p e t r o leum). B o n n e t t e t a l . (9) have r e v i e w e d t h e g e o c h e m i s t r y o f p o r p h y -


10


r i n s i n c o a l s and c o n c l u d e d t h a t , d e s p i t e t h e much more o x i c n a t u r e of the t e r r e s t r i a l c o a l d e p o s i t i o n a l environment compared to a n o x i c m a r i n e s e d i m e n t s , and t h e s u b s e q u e n t d e g r a d a t i o n o f much o f t h e a u t o c h t h o n o u s p l a n t and b a c t e r i a l c h l o r o p h y l l s , t h e e t i o - p o r p h y r i n s are predominantly c h l o r o p h y l l degradation products. However, t h e y p o i n t o u t t h a t h e m e - b a s e d c y t o c h r o m e p i g m e n t s a l s o may be important contributors. P a l m e r ejt a l . ( 2 5 ) a l s o c o n c l u d e d t h a t t h e e t i o p o r p h y r i n s f o u n d i n c o a l s (and t h e i r p r e c u r s o r s i n p e a t s ) a r e d e r i v e d f r o m c h l o r o p h y l l s and t h a t o p e n i n g o f t h e i s o c y c l i c r i n g o c c u r r e d e a r l y i n the d i a g e n e t i c sequence u n d e r t h e more o x i c c o n d i t i o n s of the d e p o s i t i o n a l environment. I n summary, t h e m a j o r c h l o r o p h y l l s (-a, - b , - c ) a n d b a c t e r i o c h l o r o p h y l l s (-a, -b) a p p e a r t o be t h e p r i m a r y s o u r c e m a t e r i a l s o f the g e o p o r p h y r i n s found i n sedimentary systems. However, c o n t r i b u t i o n s o f b a c t e r i o c h l o r o p h y l l s - d may h a v e b e e n i m p o r t a n t i n s p e c i f i c d e p o s i t i o n a l e n v i r o n m e n t s (e.j*. , t h e M e s s e l s h a l e ) and t h e c y t o c h r o m e s may be m i n o r p r e c u r s o r s t o t h e M ( I I I ) e t i o - p o r p h y r i n s f o u n d in coals. I n F i g u r e 2, s p e c i f i c p r e c u r s o r s o f t h e p e t r o l e u m p o r p h y r i n s are thus not i d e n t i f i e d . E a r l y D i a g e n e s i s o f C h l o r o p h y l l s and P r o d u c t s . In the o r i g i n a l T r e i b s scheme, t h e d i a g e n e t i c c o n v e r s i o n o f c h l o r o p h y l l - a . t o V O ( I I ) C 3 2 D P E P i n v o l v e d d e m e t a l l a t i o n , h y d r o l y s i s o f t h e p h y t y l and c a r b o m e t h y o x y g r o u p s , r e d u c t i o n , a r o m a t i z a t i o n and decarboxylation t o g i v e C 3 2 D P E P w h i c h i s m e t a l l a t e d by V 0 (Figure 1). These r e a c t i o n s were c o n s i d e r e d to o c c u r under i n c r e a s i n g thermal s t r e s s as a r e s u l t o f s e d i m e n t c o m p a c t i o n and b u r i a l . I t i s now evident t h a t t h e s e d i a g e n e t i c s t a g e s o v e r l a p a n d t h a t t h e s e q u e n c e i s comp l i c a t e d b y c o m p e t i n g r e a c t i o n s o r a l t e r n a t e p a t h w a y s (e._g. , e a r l y s c i s s i o n of the i s o c y c l i c r i n g (29,47), etc.) that are not part of t h e o r i g i n a l T r e i b s scheme ( s e e F i g u r e 2 ) . Much o f the a v a i l a b l e i n f o r m a t i o n on c h l o r o p h y l l d i a g e n e s i s has b e e n o b t a i n e d by B a k e r and h i s g r o u p f r o m t h e s t u d y o f Deep Sea D r i l l i n g P r o j e c t (DSDP) m a r i n e sediments. These s t u d i e s have been c o m p r e h e n s i v e l y r e v i e w e d by B a k e r a n d L o u d a (_5,7) who c o n s i d e r t h e g e o c h e m i c a l e v o l u t i o n o f t h e p o r p h y r i n s to begin w i t h the phorbides. Thus, the i n i t i a l stages of chlorophyll-a_ decomposition to pheophorbide-a (precursor to pyropheop h o r b i d e - a _ ; F i g u r e 1) a r e c h e m i c a l l y o r b i o l o g i c a l l y m e d i a t e d i n t h e water column o r i n the upper s e d i m e n t a r y l a y e r . The i n i t i a l stages of pheophorbide-a d i a g e n e s i s i n the newly formed sediment i n v o l v e d e f u n c t i o n a l i z a t i o n , w h i c h may be c h e m i c a l l y o r m i c r o b i a l l y m e d i a t e d , to give dihydroporphyrins. B a k e r a n d L o u d a (_5,7) r e g a r d t h e p r e s e r v a t i o n o f m i n o r amounts o f c h l o r i n s (and hence e t i o - p o r p h y r i n s ) t o o c c u r o n l y u n d e r o x i c c o n d i t i o n s a n d h i g h c h l o r o p h y l l i n p u t , e_.j*. , b o t t o m w a t e r s and s u r f a c e s e d i m e n t s o x y g e n a t e d by c u r r e n t s . The r e l a t i v e l y abundant N i ( I I ) e t i o - p o r p h y r i n s and e t i o - p o r p h y r i n c a r b o x y l i c a c i d s found i n the t h e r m a l l y immature M e s s e l o i l s h a l e (27,28) and i n J a p a n e s e P l i o c e n e m u d s t o n e s (55) and t h e free-base e t i o - p o r p h y r i n s i n t h e G a f s a B a s i n c h e r t (48) s u p p o r t s t h e i d e a o f i s o c y c l i c r i n g opening during e a r l y diagenetic stages (5,7,47). T h i s c o n c l u s i o n i s s u p p o r t e d by t h e p r e s e n c e , i n t h e M e s s e l o i l s h a l e , o f N i ( I I ) e t i o - p o r p h y r i n c a r b o x y l i c a c i d s ( p r o p i o n i c g r o u p on C-17) w h i c h i m p l i e s t h a t r i n g s c i s s i o n has o c c u r r e d b e f o r e decarboxylation of the pheophorbide s p e c i e s (29). B a k e r a n d L o u d a (5_,_7) a l s o h a v e shown t h a t i n most s e d i m e n t s , t h e p h o r b i d e and p o r p h y r i n s p e c i e s i n 2 +


1.


Overview

11

the bitumen a r e d e c a r b o x y l a t e d and have proposed t h a t d e c a r b o x y l a t i o n o c c u r s i n two m o d e s . In the m a j o r i t y of cases, low temperature (8-20°C) m i c r o b i a l d e c a r b o x y l a t i o n may p r e d o m i n a t e . Strictly thermal decarboxylation of metalloporphyrin carboxylic acids i s probably c o m p l e t e a t 50 -60 C u n d e r g e o l o g i c a l c o n d i t i o n s . Thus, i n F i g u r e 2 t h e m a j o r p a t h w a y i s shown a s d e c a r b o x y l a t i o n o f p h o r b i d e species w i t h t h e T r e i b s pathway as a minor one. B a k e r a n d L o u d a (_5,7) h a v e d e m o n s t r a t e d c o m p l e t e dehydroporphyrin t o p o r p h y r i n t r a n s i t i o n s i n two s e d i m e n t a r y s e q u e n c e s ( B l a c k Sea a n d Guayamas B a s i n , G u l f o f C a l i f o r n i a ) . I n both sequences the p r o f i l e s a r e s i m i l a r and t h e a r o m a t i z a t i o n step t o g i v e t h e free-base p o r p h y r i n s begins a t depths corresponding t o sediment temperatures b e t w e e n 2 0 a n d 3 0 C a n d i s e s s e n t i a l l y c o m p l e t e b e t w e e n 50 a n d 60 C. Mass s p e c t r o m e t r i c e x a m i n a t i o n o f t h e f r e e - b a s e p o r p h y r i n s found i n s e d i m e n t c o r e s f r o m many r e g i o n s (.5,7) i n d i c a t e s t h a t e x t r a c t a b l e f r e e - b a s e p o r p h y r i n s a r e a l i m i t e d n u m b e r o f h o m o l o g u e s ( C 2 8 ~ C 3 2 ) °f DPEP. T h u s , a t t h i s d i a g e n e t i c s t a g e ( 5 0 - 6 0 C) n e i t h e r t h e e x t e n d e d c a r b o n n u m b e r r a n g e a n d h i g h MW ( ^ 3 3 ) DPEP p o r p h y r i n s , n o r t h e e t i o porphyrins t y p i c a l o f petroleum m e t a l l o p o r p h y r i n s ( o r o f mature source rocks) a r e observed. B a k e r a n d L o u d a (.5,7) o b s e r v e d m i n o r amounts o f f r e e - b a s e e t i o s p e c i e s , h o w e v e r , i n two s p e c i f i c l o c a t i o n s (San M i g u e l Gap, C a l i f o r n i a b o r d e r l a n d s a n d t h e Guayamas B a s i n , Southern r i f t ) . These e t i o - p o r p h y r i n s were c h a r a c t e r i z e d by b e i n g h i g h l y d e a l k y l a t e d (C23-C30) and t o have p r o b a b l y a r i s e n from a l l o c h thonous t e r r e s t r i a l input o f d e a l k y l a t e d Cu(II) e t i o - p o r p h y r i n s from coal weathering (7) f o l l o w e d by i n - s i t u d e m e t a l l a t i o n , p o s s i b l y on clay surfaces. A s i m i l a r o r i g i n has been proposed (22) f o r t h e h i g h l y d e a l k y l a t e d C u ( I I ) and N i ( I I ) e t i o - p o r p h y r i n s o b s e r v e d i n immature sediments (i.e_., d e m e t a l l a t i o n o f C u ( I I ) e t i o - p o r p h y r i n f o l l o w e d by N i ( I I ) c h e l a t i o n ) . T h i s c o n t r a s t s w i t h t h e f i n d i n g s o f Q u i r k e et_ a^L. ( 4 8 ) , who h a v e s h o w n a b u n d a n t h i g h molecular-weight free-base (C29-C32)etio-porphyrins i n the Gafsa Basin chert, which appear t o have a r i s e n by e a r l y d i a g e n e t i c i s o c y c l i c - r i n g o p e n i n g . R e c e n t l y Q u i r k e e_t a d . ( 4 8 ) h a v e s h o w n t h a t t h e p r e d o m i n a n t l y f r e e - b a s e p o r p h y r i n s o f t h e G a f s a B a s i n i m m a t u r e c h e r t c o n t a i n C32 a n d C33 b e n z o - D P E P - p o r p h y r i n s . S i m i l a r o b s e r v a t i o n s h a v e b e e n made b y B a k e r a n d L o u d a ( 4 6 ) , who i d e n t i f i e d t h e s e f r e e - b a s e p o r p h y r i n s i n Jurassic-Cretaceous black shales of the Falkland Plateau. These p o r p h y r i n s , w h i c h have been p r e v i o u s l y d e t e c t e d i n o i l s h a l e s and petroleum as N i ( I I ) o r VO(II) complexes, have not been p r e v i o u s l y reported as free-base species. A l t h o u g h t h e s e s p e c i e s may b e d e r i v e d from b a c t e r i o c h l o r o p h y l l s - d by r e a c t i o n s y e t u n i d e n t i f i e d (45,48), e a r l y d i a g e n e t i c f o r m a t i o n from c h l o r o p h y l l - b by an e x t e r n a l c y c l i z a t i o n r e a c t i o n may be p o s s i b l e ( 4 8 ) . H o w e v e r , n e i t h e r t h e i r p r e c u r s o r c h l o r o p h y l l s n o r t h e i r d i a g e n e t i c pathways c a n be e s t a b l i s h e d a t t h i s time. A l t h o u g h i t may be c o n c l u d e d t h a t , i n g e n e r a l , m e t a l c h e l a t i o n o c c u r s d u r i n g l a t e d i a g e n e s i s , p r e d o m i n a n t l y by t h e f u l l y aromatized p o r p h y r i n s p e c i e s ( l a r g e l y w i t h DPEP, b u t a l s o w i t h e t i o s p e c i e s ) , t h e r e i s e v i d e n c e t h a t c h e l a t i o n o f p h o r b i d e s may o c c u r u n d e r c e r t a i n c o n d i t i o n s , and t h a t sediment mineralogy i s probably a d e t e r m i n i n g factor. S h i o b a r a a n d T a g u c h i ( 5 5 ) h a v e shown t h e p r e s e n c e o f m e t a l l a t e d phorbides i n immature Japanese sediments. The a b u n d a n c e s of the carboxylated metal species decreased r a p i d l y w i t h i n c r e a s i n g

12



sediment depth. Z e l l m e r a n d Man ( 5 6 , 5 7 ) h a v e shown t h a t t h e r a t e s o f C u ( I I ) c h e l a t i o n o f t h e m o d e l compounds d e o x o m e s o p y r o p h e o p h o r b i d e - a m e t h y l e s t e r (DOMPP) a n d t h e p o r p h y r i n d e o x o p h y l l o e r y t h r i n m e t h y l e s t e r (DPE) d e p e n d o n s o l v e n t c o n d i t i o n s . Under p o l a r p r o t i c s o l v e n t c o n d i t i o n s , Cu(DOMPP) a r o m a t i z e s t o C u ( D P E ) f a s t e r t h a n Cu(DOMPP) forms. T h u s , a l t h o u g h no C u ( I I ) p h o r b i d e s o r p o r p h y r i n s , o t h e r t h a n the h i g h l y d e a l k y l a t e d " a l l o c h t h o n o u s " e t i o - p o r p h y r i n s ( 2 2 ) , have b e e n shown t o o c c u r i n s e d i m e n t s , i t i s p o s s i b l e t h a t C u ( I I ) t e t r a p y r r o l e s e n t e r the d i a g e n e t i c p r o c e s s as c l a y - m i n e r a l a s s o c i a t e d s p e c i e s and w h i c h a r e n o t i s o l a t e d a s s u c h . L a t e D i a g e n e s i s and C a t a g e n e s i s . L a t e d i a g e n e s i s i s t h e s t a g e i n t h e e v o l u t i o n of the geoporphyrins during which metal c h e l a t i o n , p r i m a r i l y by t h e f u l l y a r o m a t i z e d p o r p h y r i n s p e c i e s , t a k e s p l a c e . During c a t a g e n e s i s , which i s the p r i n c i p a l stage of o i l g e n e r a t i o n from k e r o g e n , t h e d i s t r i b u t i o n and t y p e s o f m e t a l l o p o r p h y r i n s i n t h e s o u r c e r o c k u n d e r g o c h a n g e s due p r i m a r i l y , b u t n o t s o l e l y , t o t h e r m a l e f f e c t s (5,7,38). I n t h e s e s t a g e s o f p o r p h y r i n d i a g e n e s i s and t h e r m a l m a t u r a t i o n , t h e r o l e s o f t h e m i n e r a l m a t r i x a n d t h e k e r o g e n may be i m p o r t a n t , but are not w e l l understood. The S e d i m e n t a r y E n v i r o n m e n t a n d M e t a l l o p o r p h y r i n F o r m a t i o n . Metallat i o n r e s u l t s i n g r e a t e r s t a b i l i t y o f t h e p o r p h y r i n m a c r o c y c l e and r e s u l t s i n i t s p r e s e r v a t i o n throughout the g e o l o g i c a l r e c o r d . ^ A l t h o u g h o t h e r m e t a l l o p o r p h y r i n s s u c h a s C u ( I I ) , G a ( I I I ) ( a s GaOH ), M n ( I I I ) , and F e ( I I I ) a r e found i n s e d i m e n t s (22,58) and c o a l s (1,23-26), N i ( I I ) and V ( I V ) ( a s V 0 + ) a r e t h e p r e d o m i n a n t p o r p h y r i n s f o u n d i n s e d i m e n t s , s h a l e s , and c r u d e o i l s ( 2 - 5 ) • B a k e r a n d L o u d a 05,7_) h a v e r e v i e w e d t h e e v i d e n c e f o r m e t a l l a t i o n of f r e e - b a s e p o r p h y r i n s d u r i n g l a t e d i a g e n e s i s . These a u t h o r s conc l u d e d t h a t m e t a l l a t i o n i s p r e d o m i n a n t l y by N i i n the maturing sediment. Thus, d a t a f o r a sediment p r o f i l e from the T a r f a y a B a s i n show a smooth t r a n s i t i o n f r o m 8 5 % f r e e - b a s e p o r p h y r i n t o 100% N i ( I I ) porphyrins w i t h i n c r e a s i n g depth. From t h e s e d a t a and f r o m a c o r r e s p o n d i n g p r o f i l e (100% f r e e - b a s e t o 100% m e t a l l o p o r p h y r i n ) from t h e San M i g u e l Gap, i t was c o n c l u d e d t h a t N i c h e l a t i o n was e s s e n t i a l l y complete at depths corresponding to a temperature of a p p r o x i m a t e l y 60°C. A l t h o u g h C u ( I I ) a n d N i ( I I ) e t i o - p o r p h y r i n s w e r e p r e s e n t i n t h e S a n M i g u e l Gap s e d i m e n t s , many o f t h e s e w e r e a t t r i b u t e d t o a l l o c h t h o n o u s i n p u t o f h i g h l y d e a l k y l a t e d C u ( I I ) and N i ( I I ) p o r p h y r i n s f r o m t e r r e s t r i a l s o u r c e s ( 2 2 ) . The v i r t u a l a b s e n c e o f V O ( I I ) p o r p h y r i n s f r o m s e d i m e n t s a t t h i s d i a g e n e t i c s t a g e was a t t r i b u t e d b y B a k e r and Louda (5,7) t o a d i f f e r e n t c h e l a t i o n pathway f o r V O ( I I ) p o r p h y r i n s i n s e d i m e n t s (i.<e., " b o u n d " t o k e r o g e n ) . However, Baker and L o u d a (46) h a v e r e c e n t l y d e s c r i b e d V O ( I I ) D P E P - p o r p h y r i n s , p r e d o m i n a n t l y C ^ and C32, from F a l k l a n d P l a t e a u J u r a s s i c - C r e t a c e o u s s h a l e s t h a t c o n t a i n N i ( I I ) DPEP o f s i m i l a r c a r b o n n u m b e r s a n d w h i c h a l s o c o n t a i n f r e e - b a s e p o r p h y r i n s . These sediments a l s o c o n t a i n f r e e - b a s e , N i ( I I ) , a n d V O ( I I ) THBD a n d b e n z o - D P E P p o r p h y r i n s . Baker a n d L o u d a ( 4 6 ) c o n c l u d e d t h a t t h e p r e s e n c e o f V O ( I I ) DPEP p o r p h y r i n s i n t h i s s u i t e o f s e d i m e n t s w h i c h show i n c o m p l e t e t e t r a p y r r o l e m e t a l l a t i o n , i n d i c a t e s e a r l y r e l e a s e from t h e i r "bound" s t a t e i n the kerogen. H o w e v e r , a s t h e y s t a t e , t h e p r e s e n c e o f V O ( I I ) DPEP p o r p h y r i n s i n t h e s e s h a l e s , c o - e x i s t e n t w i t h N i ( I I ) and f r e e - b a s e species, i n d i c a t e s that m e t a l l a t i o n of the " f r e e " porphyrin species 2

2

2

+

1.

FILBY AND

b y VO may o c c u r i n c e r t a i n d e p o s i t i o n a l e n v i r o n m e n t s . Thus, the d o m i n a n c e o f one m e t a l i o n ( N i or V0 +) i n p o r p h y r i n s of p r e c a t a g e n e t i c s e d i m e n t s may be r e l a t e d m o r e t o t h e d e p o s i t i o n a l e n v i r o n ment t h a n t o s e l e c t i v e b i n d i n g o f V O ( I I ) p o r p h y r i n s t o e v o l v i n g k e r o g e n s , o r o t h e r d i f f e r e n t p a t h w a y s f o r t h e two m e t a l s p e c i e s . The p r e d o m i n a n c e o f N i ( I I ) a n d V O ( I I ) s p e c i e s among t h e g e o p o r p h y r i n s has been i n t e r p r e t e d as e v i d e n c e f o r a b i o l o g i c a l o r i g i n o f t h e n i c k e l and v a n a d i u m i n t h e c o m p l e x e s ( 5 9 ) . Lewan and M a y n a r d (60) , however, have c o n c l u d e d t h a t t h e e n r i c h m e n t o f n i c k e l and vanadium i n sedimentary bitumens r e l a t i v e to t y p i c a l m a r i n e - b i o t a s o u r c e s show t h a t , e x c e p t f o r r a r e e x c e p t i o n s , t h e s o u r c e o f n i c k e l a n d v a n a d i u m c a n n o t be e n d e m i c a n d t h a t t h e w a t e r c o l u m n o v e r l a y i n g t h e s e d i m e n t was t h e l i k e l y s o u r c e o f t h e m e t a l s f o r c h e l a t i o n . Thus, e f f e c t i v e m e t a l l a t i o n would r e q u i r e an "open" s e d i m e n t , _i.e_., d i f f u s i o n of metal i o n s from the o v e r l y i n g water column. T h i s "open" s y s t e m p r o p o s e d b y L e w a n a n d M a y n a r d ( 6 0 ) may n o t b e a n e c e s s a r y c o n s t r a i n t b e c a u s e c l a y - m i n e r a l s u r f a c e s i n more compacted, deeper s e d i m e n t s may be t h e m e t a l - i o n s o u r c e f o r m e t a l l a t i o n , a p r o c e s s w h i c h most l i k e l y i n v o l v e s a m i n e r a l s u r f a c e g i v e n t h e i n s o l u b i l i t y of t h e f r e e - b a s e and t h e m e t a l l o p o r p h y r i n s i n w a t e r . The f o r m a t i o n o f N i ( I I ) a n d V O ( I I ) p o r p h y r i n s i n t h e m a t u r i n g sediment thus r e s u l t s from a combination of f a c t o r s , i n c l u d i n g the abundance and s p e c i a t i o n o f t h e m e t a l s i n t h e s e d i m e n t a r y environment and t h e thermodynamic and k i n e t i c s t a b i l i t y o f t h e m e t a l l o p o r p h y r i n s over g e o l o g i c a l time (60,61). A few e l e m e n t s , b e c a u s e o f t h e i r l o w a b u n d a n c e s i n s e d i m e n t s , may n o t f o r m s i g n i f i c a n t a m o u n t s o f m e t a l l o p o r p h y r i n s , even though these m e t a l l o p o r p h y r i n s a r e r e l a t i v e l y s t a b l e (61) . Chemical s p e c i a t i o n of the element i s e x t r e m e l y i m p o r t a n t s i n c e an e f f i c i e n t m e t a l - i o n c a r r i e r (60-62) i s n e c e s s a r y f o r porphyrin metallation. I f the a p p r o p r i a t e o x i d a t i o n s t a t e of the m e t a l i s n o t p r e s e n t a t a s u i t a b l e c o n c e n t r a t i o n , m e t a l l a t i o n may n o t o c c u r r e l a t i v e t o o t h e r c o m p e t i n g d i a g e n e t i c r e a c t i o n s (e_.j*., d e g r a d a t i o n o f t h e p o r p h y r i n s ) . Lewan and Maynard (60) c a l c u l a t e d t h e Eh-pH s t a b i l i t y f i e l d s o f t h e f i r s t t r a n s i t i o n s e r i e s d i v a l e n t c a t i o n s and f o u n d t h a t u n d e r t h e r e d u c i n g c o n d i t i o n s o f p e t r o l e u m f o r m a t i o n C u , C r , and T i w o u l d n o t be a v a i l a b l e f o r m e t a l l a t i o n , but t h e o t h e r c a t i o n s would be. They c o n c l u d e d t h a t the abundance o f N i ( I I ) and V O ( I I ) p o r p h y r i n s r e l a t i v e t o o t h e r m e t a l l o p o r p h y r i n s o f t h e f i r s t t r a n s i t i o n s e r i e s m u s t be due t o t h e h i g h t h e r m o d y n a m i c and k i n e t i c s t a b i l i t y o f t h e N i and V 0 porphyrin macrocycle i n the sedimentary environment. B a k e r a n d L o u d a 05,7) h a v e n o t e d t h a t t h e r e i s a w e a k c o r r e l a t i o n between h i g h - s u l p h u r h i g h - a s p h a l t e n e c r u d e o i l s and t h e i r s o u r c e r o c k e x t r a c t s , and h i g h e r V O ( I I ) r e l a t i v e t o N i ( I I ) p o r p h y r i n c o n t e n t compared t o samples w i t h l o w e r s u l f u r and a s p h a l t e n e c o n t e n t s . They suggested that a s u l f u r s p e c i e s ( n o t s p e c i f i e d ) may a c t a s a c a t a l y s t f o r f o r m a t i o n o f the V O ( I I ) p o r p h y r i n s . However, i t i s more l i k e l y t h a t t h e s e d i m e n t a r y e n v i r o n m e n t w h i c h r e s u l t e d i n t h e high s u l f u r contents of the organic matter (anoxic, production of b i o g e n i c H S) l i m i t e d t h e f o r m a t i o n o f N i ( I I ) p o r p h y r i n s by l o w e r i n g the c o n c e n t r a t i o n of N i by p r e c i p i t a t i o n o f N i S . Under t h e s e c o n d i t i o n s a t pH-

MP = metalloporphyrin H2P = f r e e - b a s e porphyrin H^p2+ = porphyrin d i c a t i o n

LEGEND

2+ [M -20H-(H 0) _ -H P^-clay]

deprotonation

CO

Li_

mineral-porphyrin reactions

desorption

[M -(K 0) -clay]

adsorption

2

HP

SOLUTION |



1.


Overview

17

t i o n o f t h i s a s s o c i a t i o n by g e n e r a t i n g m e t a l l o p o r p h y r i n s by p y r o l y s i s of kerogens from M i s s i s s i p p i a n - D e v o n i a n o i l s h a l e s . L a b o r a t o r y e x p e r i m e n t s h a v e a l s o s h o w n t h a t m i n e r a l s may p l a y a r o l e i n s t r u c t u r a l a l t e r a t i o n o f porphyrins and p o r p h y r i n precursors d u r i n g c a t a g e n e s i s (36,51,76-78). The m o s t s i g n i f i c a n t c h a n g e s i n t h e c o n t e n t , t y p e s a n d d i s t r i b u t i o n o f p o r p h y r i n s i n a sediment that occur as c a t a g e n e s i s proceeds include: i ) a decrease i n t h e DPEP/etio r a t i o (5,7,38,47,51); ( i i ) a decrease i n the N i ( I I ) porphyrin t o VO(II) porphyrin r a t i o 0 5 , ^ , 3 8 ) ; ( i i i ) a l k y l a t i o n (31) and d e a l k y l a t i o n (51) o f t h e p o r p h y r i n s ; and ( i v ) t h e appearance o f a l t e r n a t e p o r p h y r i n s e r i e s (e.£. , b e n z o a n d THBD) a n d v e r y h i g h m o l e c u l a r w e i g h t p o r p h y r i n s (7,8,22,38). (i) DPEP/etio Ratio. The D P E P / e t i o r a t i o h a s b e e n u s e d a s a s e n s i t i v e i n d i c a t o r o f t h e thermal m a t u r i t y o f a sediment (79). With i n c r e a s i n g thermal s t r e s s the r a t i o decreases as the e t i o - t y p e p o r p h y r i n s become r e l a t i v e l y more a b u n d a n t t h a n t h e D P E P - t y p e (7,38,47,51). I t w a s o r i g i n a l l y p r o p o s e d b y C o r w i n (1) a n d l a t e r b y D i d y k e_t a l . ( 5 1 ) t h a t c l e a v a g e o f t h e DPEP i s o c y c l i c r i n g a s a r e s u l t o f thermal s t r e s s accounted f o r t h i s change, but i n l a b o r a t o r y h e a t i n g e x p e r i m e n t s B u r k o v a et^ a l . ( 5 2 ) f o u n d t h a t t h e r m a l c o n v e r s i o n o f V O ( I I ) DPEP- t o e t i o - t y p e p o r p h y r i n s o c c u r r e d o n l y t o a l i m i t e d e x t e n t ( c a . , 5 % ) . Barwise (80) proposed t h r e e a d d i t i o n a l mechanisms t h a t w o u l d l o w e r t h e D P E P / e t i o r a t i o , a l l o f w h i c h may c o n t r i b u t e i n v a r y i n g degrees t o t h e o v e r a l l change. These mechanisms a r e : 1) o x i d a t i v e c l e a v a g e o f t h e DPEP i s o c y c l i c r i n g d u r i n g e a r l y d i a g e n e s i s f o r m i n g e t i o - p o r p h y r i n s ; 2) p r e f e r e n t i a l t h e r m a l d e s t r u c t i o n o f DPEP-type p o r p h y r i n s ; and 3) p r e f e r e n t i a l g e n e r a t i o n o f e t i o p o r p h y r i n s from kerogen d u r i n g c a t a g e n e s i s , which w i l l d i l u t e t h e DPEP-rich bitumen present i n t h e sediment p r i o r t o kerogen catagenesis. Of t h e mechanisms p r o p o s e d by B a r w i s e , o n l y t h e s e c o n d w o u l d cause changes i n t h e DPEP/etio r a t i o o f p o r p h y r i n s i n maturing oils. Oxidative cleavage o f the i s o c y c l i c r i n g during e a r l y diagenesis has been s u g g e s t e d f o r t h e predominance o f t h e e t i o - p o r p h y r i n s i n c o a l (7,9,25). Early-stage cleavage o f the i s o c y c l i c r i n g i n a r e d u c i n g environment i s a l s o i m p l i e d by t h e presence o f N i ( I I ) e t i o p o r p h y r i n c a r b o x y l i c a c i d s i n t h e M e s s e l o i l s h a l e ( 2 7 - 2 9 ; _i«_e. , cleavage has occurred p r i o r t o decarboxylation). I f i t i s assumed t h a t no t h e r m a l DPEP-to e t i o - p o r p h y r i n c o n v e r s i o n o c c u r s , t h e n a r a p i d change i n D P E P / e t i o r a t i o c o u l d be a c c o u n t e d f o r by o n l y s m a l l d i f f e r e n c e s i n t h e t h e r m a l s t a b i l i t y o f t h e s e two p o r p h y r i n t y p e s as suggested by Barwise (80). The o b s e r v a t i o n s o f M a c k e n z i e e t a l . ( 3 8 ) and o t h e r s (7,52^ i n d i c a t e t h a t t h e DPEPp o r p h y r i n s o f both N i ( I I ) and V O ( I I ) a r e t h e r m a l l y l e s s s t a b l e than t h e e t i o - s p e c i e s w i t h N i ( I I ) DPEP b e i n g t h e l e a s t s t a b l e o f a l l . I n t e r e s t i n g l y , R o s s c u p a n d Bowman ( 8 1 ) s h o w e d i n a l a b o r a t o r y s t u d y t h a t N i ( I I ) a l k y l - p o r p h y r i n s a r e t h e r m a l l y more s t a b l e t h a n t h e i r VO(II) counterparts. U n f o r t u n a t e l y , no i n f o r m a t i o n o n t h e D P E P / e t i o r a t i o o f e i t h e r m e t a l s p e c i e s was g i v e n i n t h i s s t u d y . B a k e r et_ a l . (82) f o u n d t h a t o n l y N i ( I I ) e t i o - p o r p h y r i n s s u r v i v e d i n s e d i m e n t s under t h e thermal s t r e s s imposed by c l o s e p r o x i m i t y t o a diabase s i l l , i n d i c a t i n g a higher thermal s t a b i l i t y of N i ( I I ) etio-porphyrins than a l l the other porphyrin types. H o w e v e r , M a c k e n z i e et_ a l . ( 3 8 ) found t h a t t h e N i ( I I ) D P E P / e t i o r a t i o d e c r e a s e d more r a p i d l y w i t h

18


depth i n maturing sediments than d i d the V O ( I I ) p o r p h y r i n s . They a l s o f o u n d w i t h Ol.e_., d e p t h ) t h a t t h e N i ( I I ) p o r p h y r i n s VO(II) s p e c i e s . Therefore, the r e l a t i v e g e o p o r p h y r i n s a p p e a r s t o be:


corresponding r a t i o for increasing thermal stress disappeared f a s t e r than the thermal s t a b i l i t i e s of the

V O ( I I ) e t i o > N i ( I I ) e t i o >_ V O ( I I ) D P E P > N i ( I I ) D P E P B a r w i s e (80) examined a s u i t e o f s a m p l e s from a G u l f o f Suez f o r m a t i o n and f o u n d t h a t t h e c o n c e n t r a t i o n o f V O ( I I ) DPEP-porphyrins d e c r e a s e d and e t i o - p o r p h y r i n s i n c r e a s e d c o i n c i d e n t w i t h t h e o n s e t o f p e t r o l e u m g e n e r a t i o n , a n d t h e maximum c o n c e n t r a t i o n o f e t i o p o r p h y r i n s r e a c h e d a l e v e l g r e a t e r t h a n t h e i n i t i a l DPEP c o n c e n t r a tion. T h e r e f o r e , e v e n i f t o t a l c o n v e r s i o n o f DPEP- t o e t i o porphyrins occurred, another source of porphyrins i n these sediments w o u l d be n e e d e d t o e x p l a i n t h e s e o b s e r v a t i o n s . B a r w i s e (80) i n t e r p r e t e d t h i s t o be d u e t o p r e f e r e n t i a l g e n e r a t i o n o f s u b s t a n t i a l q u a n t i t i e s of e t i o - t y p e p o r p h y r i n s from kerogen. Van B e r k e l and F i l b y (40) showed t h a t b o t h V O ( I I ) and N i ( I I ) DPEP- and e t i o p o r p h y r i n s c o u l d be g e n e r a t e d f r o m k e r o g e n b y p y r o l y s i s , a l t h o u g h t h e D P E P / e t i o r a t i o o f t h e V O ( I I ) p o r p h y r i n s m e a s u r e d b y HPLC d e c r e a s e d as p y r o l y s i s t e m p e r a t u r e i n c r e a s e d . Mass s p e c t r o m e t r i c a n a l y s i s ( 8 3 ) i n d i c a t e d t h e same t r e n d f o r N i ( I I ) a s f o r V O ( I I ) p o r p h y r i n s , but t h e D P E P / e t i o r a t i o d e c r e a s e d more r a p i d l y w i t h temperature f o r the N i ( l l ) p o r p h y r i n s . Thus, the r e l a t i v e abundances o f N i ( I I ) and V O ( I I ) p o r p h y r i n s g e n e r a t e d f r o m t h e k e r o g e n w i l l i n f l u e n c e the f i n a l DPEP/etio r a t i o of the bitumen. In f a c t , Van B e r k e l and F i l b y (40) showed t h a t t h e N i / V r a t i o , N i ( I I ) p o r p h y r i n / V O ( I I ) p o r p h y r i n r a t i o , and the D P E P / e t i o r a t i o o f t h e b i t u m e n a c c u m u l a t i n g i n a s o u r c e r o c k may i n c r e a s e , d e c r e a s e , o r r e m a i n c o n s t a n t d e p e n d i n g on t h e k e r o g e n c o m p o s i t i o n and temperature regime. T h e s e c h a n g e s i n a n a c c u m u l a t i n g b i t u m e n may be s u b s t a n t i a l because the kerogens i n t h i s s t u d y were found to l i b e r a t e a f a r g r e a t e r amount o f n i c k e l and v a n a d i u m c o m p l e x e s d u r i n g p y r o l y s i s t h a n t h e c o r r e s p o n d i n g amount o f t h e m e t a l c o m p l e x e s i n t h e b i t u m e n i s o l a t e d from the shale. K e r o g e n t h u s c a n g e n e r a t e DPEP- and e t i o - p o r p h y r i n s o f b o t h N i ( I I ) a n d V O ( I I ) . What h a s n o t b e e n c o n s i d e r e d i s t h e c o m b i n e d e f f e c t o f t h e g e n e r a t i o n o f p o r p h y r i n s f r o m t h e k e r o g e n and t h e r m a l m a t u r a t i o n o f t h e p o r p h y r i n s i n b o t h t h e i n h e r i t e d and t h e c a t a g e n e t i c bitumen. The a p p a r e n t g e n e r a t i o n o f l a r g e a m o u n t s o f e t i o p o r p h y r i n s d u r i n g c a t a g e n e s i s o b s e r v e d b y B a r w i s e ( 8 0 ) may b e d u e to the r e l a t i v e thermal s t a b i l i t i e s of the p o r p h y r i n s . I f the r a t e o f DPEP d e s t r u c t i o n i s g r e a t e r , a n d e t i o d e s t r u c t i o n s m a l l e r , than the r a t e of p o r p h y r i n g e n e r a t i o n from the kerogen, the net e f f e c t w o u l d be t h e g e n e r a t i o n o f p r e d o m i n a n t l y e t i o - p o r p h y r i n s . ( i i ) N i c k e l to Vanadyl P o r p h y r i n R a t i o . Baker e t a l . (5,7,82, 84) a n d M a c k e n z i e e_t a l . ( 3 8 ) h a v e n o t e d a d e c r e a s e i n t h e N i ( I I ) porphyrin to VO(II) p o r p h y r i n r a t i o w i t h i n c r e a s i n g maturation i n s u i t e s of sediments which have undergone i n c r e a s i n g l e v e l s of t h e r m a l stress. As d i s c u s s e d i n t h e p r e v i o u s s e c t i o n , b a s e d on t h e r m a l s t a b i l i t i e s a l o n e , one w o u l d p r e d i c t an i n c r e a s e i n t h e V O ( I I ) t o N i ( I I ) porphyrin r a t i o w i t h increasing thermal stress. However, other f a c t o r s are probably i n v o l v e d i n determining the N i ( I I ) to VO(II) porphyrin r a t i o .

1.


19

R e d u c t i o n i n t h e N i ( I I ) / V O ( I I ) p o r p h y r i n r a t i o may be d u e t o clay-mineral catalyzed demetallation r e s u l t i n g i n the k i n e t i c a l l y controlled accumulation of VO(II) porphyrins r e l a t i v e to N i ( I I ) porphyrins. B e r g a y a a n d V a n Damme ( 7 0 ) f o u n d n o m e a s u r a b l e d i f f e r e n c e i n the d e m e t a l l a t i o n r a t e s o f N i ( I I ) and V O ( I I ) t e t r a p h e n y l p o r p h y r i n (TPP) on c l a y m i n e r a l s . However, i f d e m e t a l l a t i o n o f t h e N i ( I I ) p o r p h y r i n s i s f a v o r e d , even s l i g h t l y , i n the s e d i m e n t a r y environment over g e o l o g i c time, a decrease i n the N i ( I I ) to VO(II) p o r p h y r i n r a t i o w i t h i n c r e a s i n g m a t u r a t i o n ( t e m p e r a t u r e - t i m e ) w o u l d be n o t e d . F u r t h e r m o r e , i t has been demonstrated i n l a b o r a t o r y e x p e r i m e n t s t h a t V O ( I I ) p o r p h y r i n s a r e more s t a b l e t o d e m e t a l l a t i o n i n an a c i d e n v i r o n ment ( 8 5 ) a n d N i ( I I ) o c t e t h y l p o r p h y r i n (OEP) c a n be c o n v e r t e d t o V O ( I I ) OEP, w h e r e a s V O ( I I ) OEP c a n n o t be c o n v e r t e d t o N i ( I I ) OEP (38), thus i n d i c a t i n g d e m e t a l l a t i o n / r e m e t a l l a t i o n as a p o s s i b l e mechanism f o r t h i s o b s e r v e d change. However, n a t u r a l sequences o f m e t a l l o - ( N i + v s V 0 + ) p o r p h y r i n h o m o l o g i e s do n o t s u p p o r t t h i s (5,7,38). Generation of VO(II) p o r p h y r i n s from the kerogen d u r i n g c a t a g e n e s i s h a s a l s o b e e n p r o p o s e d b y B a k e r a n d L o u d a 05,7) t o a c c o u n t for these observations. N i c k e l p o r p h y r i n s a r e c o n s i d e r e d t o form as " f r e e " or solvent e x t r a c t a b l e species from free-base p o r p h y r i n s of l i m i t e d homology, whereas the V O ( I I ) p o r p h y r i n s form i n a "bound" o r nonextractable state l i n k e d to kerogen. When t h e r m a l s t r e s s b r e a k s the kerogen-porphyrin l i n k a g e , the VO(II) p o r p h y r i n s are released t o t h e b i t u m e n w i t h e x t e n d e d c a r b o n number r a n g e s . This proposal i s b a s e d on e v i d e n c e t h a t N i ( I I ) D P E P - p o r p h y r i n s o f l i m i t e d homology a r e found i n a l l but the most immature s e d i m e n t s , whereas V O ( I I ) p o r p h y r i n s a r e more commonly i s o l a t e d f r o m s e d i m e n t s w h i c h have undergone a moderate degree of t h e r m a l s t r e s s . T h i s concept i s s u p p o r t e d by i n d i r e c t e v i d e n c e f r o m a number o f s t u d i e s ( 3 8 , 4 7 , 8 0 , 8 4 ) . A t t h e p r e s e n t t i m e , t h e r e i s no s a t i s f a c t o r y e x p l a n a t i o n f o r the apparent kerogen-enhanced bonding of p r i m a r i l y VO(II) p o r p h y r i n s , and e v i d e n c e p r e s e n t e d by Van B e r k e l and F i l b y (40) i n d i c a t e s t h i s c o n c e p t n e e d s t o be r e v i s e d . T h e r e i s a l s o no f i r m e v i d e n c e t h a t c h e m i c a l b o n d i n g v i a C-C b o n d s o c c u r s . R e c e n t a n a l y s e s h a v e shown some k e r o g e n s t o c o n t a i n s i g n i f i c a n t q u a n t i t i e s o f b o t h o r g a n i c a l l y bound n i c k e l and vanadium (39,40,86,87). S p i r o e_t a l . ( 8 7 ) f o u n d t h a t t h e N i / V r a t i o o f t h e k e r o g e n i n some I s r a e l i o i l s h a l e s a n d the N i ( I I ) t o V O ( I I ) p o r p h y r i n r a t i o o f the a s s o c i a t e d bitumen were s i m i l a r , i n d i c a t i n g t h a t t h e r e may b e a c o r r e l a t i o n b e t w e e n t h e p o r p h y r i n c o n t e n t s o f t h e bitumen and t h e n i c k e l and vanadium contents of the kerogen. Van B e r k e l and F i l b y (40) m e a s u r e d m i n e r a l - f r e e c o n c e n t r a t i o n s o f n i c k e l a n d v a n a d i u m o f 2 1 3 0 a n d 700 y g / g , r e s p e c t i v e l y , i n New A l b a n y o i l - s h a l e k e r o g e n a n d 350 a n d 3260 y g / g , r e s p e c t i v e l y , i n t h e Woodford o i l s h a l e . A l s o , Van B e r k e l (83) d e m o n s t r a t e d t h a t t h e r e i s a c o r r e l a t i o n between t h e N i / V r a t i o s o f t h e k e r o g e n , b i t u m e n , and a s p h a l t e n e s o f c e r t a i n o i l shales. F o r m a t i o n o f a p o r p h y r i n - k e r o g e n a s s o c i a t i o n (e.j*. , chemis o r p t i o n ) v i a i n t e r a c t i o n of m e t a l l o p o r p h y r i n s i n the sediment w i t h the kerogen i s h i g h l y probable g i v e n the p o l a r n a t u r e of the p o r p h y r i n s , and i s s u p p o r t e d by t h e work o f Nguyen and F i l b y ( 8 8 ) . They d e m o n s t r a t e d t h a t a s p h a l t e n e s and b o t h N i ( I I ) o c t a e t h y l p o r p h y r i n (OEP) a n d N i ( I I ) m e s o p o r p h y r i n I X d i m e t h y l e s t e r (DME) f o r m e d s t r o n g a s s o c i a t i o n s (ir-ir b o n d i n g o r f u n c t i o n a l g r o u p a s s o c i a t i o n ) , w i t h 2


Overview

2

20

M E T A L C O M P L E X E S IN F O S S I L F U E L S


N i ( I I ) DME h a v i n g g r e a t e r a f f i n i t y f o r t h e a s p h a l t e n e s t h a n N i ( I I ) OEP. The f a c t t h a t k e r o g e n a n d a s p h a l t e n e s a r e p r o b a b l y structurally r e l a t e d ( 8 9 , 9 0 ) s u g g e s t s t h a t p o r p h y r i n s may a s s o c i a t e w i t h k e r o g e n i n a s i m i l a r manner. T h u s , N i ( I I ) a n d V O ( I I ) p o r p h y r i n s may p h y s i s o r b a n d / o r c h e m i s o r b s t r o n g l y t o t h e k e r o g e n w i t h t h e V O ( I I ) more s t r o n g l y a s s o c i a t e d t h a n t h e N i ( I I ) s p e c i e s b a s e d on t h e g r e a t e r p o l a r i t y of the former. P h i l p a n d G i l b e r t ( 9 0 ) h a v e a l s o demons t r a t e d t h a t o t h e r b i o m a r k e r s (e_.£., g a m m a c e r a n e ) a r e p r e s e n t i n k e r o g e n s and a r e n o t bonded t o t h e k e r o g e n but p r o b a b l y " a s s o c i a t e . " This process might e x p l a i n the d i f f e r e n c e s i n apparent kerogen a f f i n i t y o f t h e N i ( I I ) and V O ( I I ) p o r p h y r i n s p e c i e s i n s e d i m e n t s . I n t h e s t u d y b y V a n B e r k e l a n d F i l b y ( 4 0 ) , i t was s h o w n t h a t a decrease i n the N i ( I I ) p o r p h y r i n to VO(II) p o r p h y r i n r a t i o i n the bitumen can o c c u r as a r e s u l t o f the g e n e r a t i o n o f m e t a l l o p o r p h y r i n s from kerogen d u r i n g p y r o l y s i s , but the change i n t h i s r a t i o depends on t h e c o m p o s i t i o n 0i.e_., n i c k e l and v a n a d i u m c o n t e n t s ) o f t h e kerogen. (iii) Alkylation/Dealkylation. D u r i n g l a t e d i a g e n e s i s and c a t a g e n e s i s the s e d i m e n t a r y p o r p h y r i n s a r e found t o e x i s t as homologous s e r i e s (4,31,34) w i t h c a r b o n numbers w e l l b e l o w and above t h e e x p e c t e d C32 p r e d i c t e d b y t h e T r e i b s s c h e m e ( F i g u r e 1 ) . Among t h e f i r s t e x p l a n a t i o n s f o r the e x t e n d e d carbon numbers were t r a n s a l k y l a t i o n (31) and e v o l u t i o n o f p o r p h y r i n s f r o m b a c t e r i o c h l o r o p h y l l s (e.jg. , C h l o r o b i u m ) t h a t e x i s t a s h o m o l o g o u s s e r i e s ( 3 1 , 3 3 ) . I t has b e e n shown i n l a b o r a t o r y e x p e r i m e n t s ( 3 7 , 5 1 , 7 6 , 7 7 ) t h a t t h e m o l e c u l a r w e i g h t s of the g e o p o r p h y r i n s d e c r e a s e as t h e r m a l s t r e s s i s i n c r e a s e d as a r e s u l t o f a l k y l c l e a v a g e from the p o r p h y r i n m a c r o c y c l e and, c o n c u r r e n t l y , h i g h e r c a r b o n number p o r p h y r i n s a r e p r o d u c e d i n t h e sample v i a a t r a n s a l k y l a t i o n p r o c e s s . Q u i r k e et_ a l . ( 3 4 ) s h o w e d t h a t t h e s u b s t i t u t i o n p a t t e r n on t h e m a l e i m i d e s f r o m B o s c a n o i l showed a p r e d o m i n a n t m e t h y l , 1 1 - a l k y l p a t t e r n i n d i c a t i n g a s p e c i f i c p r o c e s s was i n v o l v e d i n e x t e n d i n g a l k y l a t i o n . Transalkylation w o u l d be e x p e c t e d t o p r o d u c e a r a n d o m a l k y l a t i o n p a t t e r n on t h e porphyrins. A s m e n t i o n e d e a r l i e r , t h e C h l o r o b i u m c h l o r o p h y l l s do n o t h a v e an a l k y l a t i o n p a t t e r n c o n s i s t e n t w i t h t h e e x t e n d e d p o r p h y r i n homologues f o r w h i c h s t r u c t u r e s have been d e t e r m i n e d . Thermal c r a c k i n g o f p o r p h y r i n s c h e m i c a l l y bound t o t h e k e r o g e n m a t r i x has been s u g g e s t e d (7,34) t o a c c o u n t f o r the h i g h e r homologues. O e h l e r e_t a^L. ( 9 1 ) h a v e s h o w n t h a t t e t r a p y r r o l e c o m p l e x e s c a n b e c o m e " g r a f t e d " onto c e l l u l a r macromolecules. T h e s e c o m p l e x e s may t h e n be incorporated i n t o the proto-kerogen matrix during kerogen formation. A s s i m i l a t i o n of p o r p h y r i n p r e c u r s o r s or immature m e t a l l o p o r p h y r i n s i n t o kerogen d u r i n g d i a g e n e s i s c o u l d take p l a c e through a l k y l (e. j * . , a n t i - M a r k o v n i k o v a d d i t i o n t o t h e k e r o g e n t o t h e v i n y l group on t h e p o r p h y r i n p r e c u r s o r , 34) o r c a r b o n y l s u b s t i t u e n t s (i.e_.» e s t e r a n d ether l i n k a g e s , 5,7,61), f o r example. Breakdown o f kerogen d u r i n g c a t a g e n e s i s m i g h t r e l e a s e t h e s e complexes i n d i s c r e t e form o r bound t o f r a g m e n t s o f k e r o g e n (i_.e_., a s p h a l t e n e s ) . However, p r e l i m i n a r y d a t a f r o m t h e p y r o l y s i s o f k e r o g e n ( 4 0 ) s h o w s no i n d i c a t i o n t h a t t h e p o r p h y r i n s g e n e r a t e d d u r i n g k e r o g e n c a t a g e n e s i s a r e c h e m i c a l l y bound t o t h e m a t r i x v i a C-C b o n d s . T h i s i s b a s e d on t h e o b s e r v a t i o n t h a t p o r p h y r i n homologs generated from the kerogen extend t o carbon n u m b e r s no h i g h e r t h a n t h o s e p o r p h y r i n s p r e s e n t i n t h e b i t u m e n ( 8 3 ) . C o m p a r i s o n o f t h e a l k y l s u b s t i t u t i o n p a t t e r n s o n t h e two s e t s o f


1.


Overview

21

p o r p h y r i n s w o u l d be a b e t t e r i n d i c a t i o n o f a b o n d i n g mechanism s i n c e these s h o u l d d i f f e r f o r t h e p o r p h y r i n s w h i c h were bound t o t h e kerogen compared t o those p r e s e n t i n a f r e e s t a t e i n t h e bitumen o r a s s o c i a t e d w i t h t h e kerogen by a mechanism o t h e r than d i r e c t c h e m i c a l bonding. I n summary, t h e mode o f a s s o c i a t i o n o f t h e p o r p h y r i n s w i t h t h e k e r o g e n h a s n o t b e e n d e t e r m i n e d ; some p o s s i b l e m e c h a n i s m s a r e : (a) P h y s i s o r p t i o n / c h e m i s o r p t i o n o f d i s c r e t e p o r p h y r i n s . (b) C h e m i c a l b o n d i n g o f p o r p h y r i n s o r t h e i r p r e c u r s o r s t o t h e kerogen matrix through a l k y l , e s t e r l i n k a g e s , e t c . , o r through a x i a l bonding to the metal i o n . (c) M o l e c u l a r s i e v e t r a p p i n g o f d i s c r e t e p o r p h y r i n s o r t h e i r p r e c u r s o r s i n t h e r e l a t i v e l y open k e r o g e n p o l y m e r i c s t r u c t u r e . ( i v ) Very High M o l e c u l a r Weight P o r p h y r i n s and A l t e r n a t e Porphyrin Series. S e v e r a l w o r k e r s have r e p o r t e d h i g h m o l e c u l a r weight N i ( I I ) and VO(II) porphyrin-type complexes i n s i z e e x c l u s i o n c h r o m a t o g r a p h i c (SEC) f r a c t i o n s o f a s p h a l t i c m a t e r i a l (92,93). B l u m e r a n d Rudrum ( 9 3 ) i s o l a t e d t e t r a p y r r o l e c o m p l e x e s o f h i g h m o l e c u l a r w e i g h t (>1000 d a l t o n s ) a s d i m e r s , a n d a h o m o l o g o u s s e r i e s o f c o m p l e x e s w i t h MW>20,000 w a s i s o l a t e d f r o m a T r i a s s i c o i l s h a l e (92). However, i t i s d e b a t a b l e whether these l a t t e r s p e c i e s a r e discrete high molecular-weight porphyrins. Nguyen and F i l b y ( 8 8 ) h a v e s h o w n t h a t N i ( I I ) DME a d s o r b e d ( o r c h e m i s o r b e d ) o n t o a s p h a l t e n e s from a c h l o r o f o r m s o l u t i o n i s d i s t r i b u t e d throughout t h e asphaltene molecular-weight r a n g e s ( f r o m >8000 t o < 1 0 0 0 ) d u r i n g SEC s e p a r a t i o n . H e n c e , SEC s e p a r a t i o n s do n o t s e p a r a t e p o r p h y r i n s p e c i e s f r o m h i g h m o l e c u l a r - w e i g h t bitumen components w i t h w h i c h they a r e c h e m i c a l l y associated. The THBD a n d b e n z o - p o r p h y r i n s ( u s u a l l y minor components) have been i d e n t i f i e d i n s e v e r a l s t u d i e s a s t h e N i ( I I ) o r V O ( I I ) complexes. Baker and Louda (7) proposed i n i t i a l l y t h a t these complex p o r p h y r i n s were o r i g i n a l l y bound t o t h e k e r o g e n m a t r i x . F o r example, t h e benzo-porphyrins c o u l d a r i s e from a D i e l s - A l d e r type a d d i t i o n w i t h a quinone type s t r u c t u r e i n t h e bitumen o r kerogen ( 4 ) , o r by condens a t i o n o f s i d e c h a i n s on t h e p o r p h y r i n p r e c u r s o r d u r i n g d i a g e n e s i s (7_,47). The f o r m a t i o n o f b o t h t h e THBD a n d b e n z o - D P E P s p e c i e s c a n b e r a t i o n a l i z e d b y a d i a g e n e t i c scheme i n w h i c h t h e t e t r a h y d r o b e n z o p o r p h y r i n i s formed from a f u n c t i o n a l i z e d c h l o r o p h y l l p r e c u r s o r v i a external cyclization. Subsequent a r o m a t i z a t i o n o f t h e newly-formed six-membered r i n g w i t h i n c r e a s e d thermal m a t u r a t i o n produces t h e benzo-porphyrin. However, i t i s n o t c l e a r w h i c h s p e c i e s o r i g i n a t e s f i r s t , and i f , i n f a c t , i n t e r c o n v e r s i o n v i a hydrogenation/dehydrogenation a c t u a l l y takes place. The p l a c e m e n t o f t h e e x o c y c l i c r i n g o f t h e THBD ( 4 7 ) a n d b e n z o - D P E P ( 4 5 ) s p e c i e s o n d i f f e r e n t p o s i t i o n s of the porphyrin macrocycle argues a g a i n s t t h i s hypothesis (46,48). The p r e s e n c e o f t h e s e p o r p h y r i n s i n i m m a t u r e s e d i m e n t s a s f r e e - b a s e forms i n d i c a t e s t h a t t h e e x o c y c l i c r i n g f o r m a t i o n mechanism does n o t n e c e s s a r i l y i n v o l v e kerogen b i n d i n g b u t does p o i n t t o t h e importance of m i n e r a l surfaces i n promoting such r e a c t i o n s . C a t a l y t i c a d d i t i o n and r e a r r a n g e m e n t o f p o r p h y r i n p r e c u r s o r s and p o r p h y r i n s on m i n e r a l s u r f a c e s as a source f o r these a l t e r n a t e s e r i e s i s an area o f porphyr i n g e o c h e m i s t r y w h i c h s h o u l d be g i v e n more a t t e n t i o n . A s c h e m a t i c d i a g r a m o f t h e p o s s i b l e p o r p h y r i n p a t h w a y s i n k e r o g e n i s shown i n F i g u r e 5. N o t i n c l u d e d i n t h i s d i a g r a m a r e p o s s i b l e r e a c t i o n s o f metalloporphyrins involving the kerogen-mineral interface.

2

PP HP MP K

K

K

release

K-MP-K

1

K-PP-Kl i K

Figure

5.

Resorption

Suggested

2

H P-K

2

H P-K

2

HP

release

PP MP

1 BITUMEN |

MATRIX

KEROGEN

1 BITUMEN

kerogen-porphyrin association

mechanisms.

a s s o c i a t i o n = physisorb/chemisorb; chemical bonding ( a l k y l , e s t e r , l i n k a g e s , e t c . ) ; trapping ( e . £ . , molecular s i e v e ) , desorption = d i s a s s o c i a t i o n without breaking chemical bond, catagenetic release = d i s a s s o c i a t i o n r e q u i r i n g the breakinq o f chemical bonds, e i t h e r keroqen-porphyrin linkages o r i n kerogen matrix (e.g_. , release o f trapped s p e c i e s ) .

catagenetic release MP-K

catagenetic

PP-K catagenetic A release

LEGEND

associate

into matrix

polymerization

into matrix

polymerization

porphyrin precursor free-base porphyrin metalloporphyrin ( N i ( I I ) or VO(11)) kerogen; K' = kerogen fragment

"non-porphyrin" or high MW porphyrin

catagenetic

I

4

2

K-H P-K

K

associate

or


r

C

00 00

o

00

m

x

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to to

1.

FILBY AND

VAN B E R K E L

Overview

23


The E f f e c t o f P e t r o l e u m M i g r a t i o n o n M e t a l l o p o r p h y r i n D i s t r i b u t i o n s . The m e c h a n i s m o f m o b i l i z a t i o n o f b i t u m e n i n a s o u r c e - r o c k a n d m i g r a t i o n o f a crude o i l to a t r a p o r r e s e r v o i r has not been a d e q u a t e l y e x p l a i n e d and i s s t i l l c o n t r o v e r s i a l ( 1 9 , 9 4 , 9 5 ) . Two m a j o r s t a g e s a r e i n v o l v e d ; t h e s e may be d e f i n e d a s : ( i ) primary migration i n which d i s p e r s e d bitumen m i g r a t e s w i t h i n the source rock to form d i s c r e t e o i l g l o b u l e s , u l t i m a t e l y l e a d i n g to e x p u l s i o n of o i l from t h e s o u r c e r o c k i n t o more p o r o u s p a t h w a y s ; and ( i i ) s e c o n d a r y m i g r a t i o n of t h i s o i l i n t o t r a p s or r e s e r v o i r s (94). Neither process i s w e l l u n d e r s t o o d and the b e h a v i o r o f m e t a l l o p o r p h y r i n s i n the s o u r c e r o c k b i t u m e n d u r i n g m i g r a t i o n i s e s s e n t i a l l y unknown. Durand (94) a n d L e y t h a u e s e r et_ a l . ( 9 5 ) have concluded t h a t the p r i m a r y m i g r a t i o n s t a g e i n v o l v e s a number o f c h r o m a t o g r a p h i c e f f e c t s t h a t a c t on b i t u m e n c o m p o n e n t s . L e y t h a u e s e r et_ a l . ( 9 5 ) h a v e s h o w n t h a t t h e main s t a g e o f p r i m a r y m i g r a t i o n i s p r o b a b l y p r e c e d e d by an e a r l y stage of o i l e x p u l s i o n i n which strong chromatographic e f f e c t s r e s u l t from a complex h y d r o c a r b o n - w a t e r - m i n e r a l phase i n t e r a c t i o n . Thus, the e a r l y m i g r a t i n g f l u i d f r o n t i s e n r i c h e d i n l i g h t , l e s s p o l a r , h y d r o c a r b o n s and t h e r e s i d u e r e m a i n i n g i n t h e s o u r c e r o c k i s composed o f more p o l a r h i g h e r m o l e c u l a r - w e i g h t s p e c i e s . Although the metalloporphyrins were not s t u d i e d i n t h i s i n v e s t i g a t i o n , f r a c t i o n a t i o n w o u l d be e x p e c t e d t o o c c u r b a s e d on p o r p h y r i n p o l a r i t y and relative a f f i n i t y for mineral surfaces. The o v e r a l l e f f e c t on a s h o r t t i m e s c a l e (i_.e_., e q u i v a l e n t t o t h a t o b s e r v e d i n a c h r o m a t o g r a p h i c column) i s t o produce an o i l w h i c h c o n t a i n s lower p r o p o r t i o n s o f p o l a r c o m p o u n d s (e_.£., a s p h a l t e n e s a n d m o r e p o l a r p o r p h y r i n s ) than does the a s s o c i a t e d s o u r c e - r o c k bitumen. However, m i g r a t i o n on a g e o l o g i c a l time s c a l e , or over l a r g e d i s t a n c e s , i n which a b a r r i e r may be e v e n t u a l l y r e a c h e d , w i l l e l i m i n a t e s u c h c h r o m a t o g r a p h i c e f f e c t s Oi.e_., e q u i v a l e n t t o c o m p l e t e e l u t i o n f r o m a c o l u m n i n t o a reservoir). C h a k h m a c h k e v et_ a l . ( 9 6 ) have attempted to s i m u l a t e g e o l o g i c m i g r a t i o n o f p o r p h y r i n s i n t h e l a b o r a t o r y by p a s s i n g an o i l w i t h a h i g h VO(II) p o r p h y r i n content through c l a y - s a n d columns. These a u t h o r s f o u n d t h a t p o l a r V O ( I I ) p o r p h y r i n s were r e t a i n e d on t h e column r e l a t i v e t o n o n - p o l a r V O ( I I ) p o r p h y r i n s ( n o t d e f i n e d ) and t h a t the DPEP/etio r a t i o i n the i n i t i a l e f f l u e n t s were lower than the crude o i l r a t i o , as expected from p o l a r i t y c o n s i d e r a t i o n s . However, no s y s t e m a t i c v a r i a t i o n was n o t e d i n l a t e r e f f l u e n t s . A l t h o u g h no e x p l a n a t i o n was g i v e n , t h e v a r i a t i o n i n t h e D P E P / e t i o may h a v e r e s u l t e d f r o m a c o m b i n a t i o n o f i n c r e a s e d p o l a r i t y o f DPEP v e r s u s e t i o f o r a g i v e n c a r b o n number and t h e i n c r e a s e i n p o l a r i t y f o r a given series with decreasing a l k y l substitution. The a u t h o r s a t t r i buted the changes i n the DPEP/etio r a t i o of the VO(II) p o r p h y r i n s i n t h e W. S u r g u t o i l s s t u d i e d b y B u r k o v a et_ a l . ( 9 7 ) to l a t e r a l m i g r a t i o n e f f e c t s w i t h i n t h e W. S u r g u t dome. B u r k o v a ejt a l . ( 9 7 ) also concluded that chromatographic e f f e c t s during m i g r a t i o n r e s u l t e d i n t h e l e a s t m i g r a t e d P r a v d a o i l c o n t a i n i n g v i r t u a l l y no n o n - p o l a r V O ( I I ) p o r p h y r i n s w h i l e t h e g e n e t i c a l l y r e l a t e d m o s t m i g r a t e d W. S u r g u t o i l s a r e d e p l e t e d i n p o l a r V O ( I I ) p o r p h y r i n s . F u r t h e r w o r k on the mechanism o f p o r p h y r i n - s u b s t r a t e i n t e r a c t i o n s d u r i n g o i l m i g r a t i o n i s o b v i o u s l y needed. A l t h o u g h chromatographic e f f e c t s change the o r i g i n a l m e t a l l o p o r p h y r i n d i s t r i b u t i o n o f a b i t u m e n d u r i n g m i g r a t i o n , i t may be p o s s i b l e to " r e c o n s t r u c t " the porphyrin d i s t r i b u t i o n s of the sourcer o c k b i t u m e n by e x a m i n a t i o n o f t h e p o r p h y r i n c o n t e n t s o f t h e s o u r c e -

24



r o c k b i t u m e n and c r u d e o i l a s p h a l t e n e s . S e v e r a l a u t h o r s h a v e shown t h a t b i o m a r k e r s c a n be t r a n s p o r t e d b y a s p h a l t e n e s i n a c r u d e o i l a n d p r o t e c t e d f r o m b i o d e g r a d a t i o n a f t e r emplacement i n a r e s e r v o i r and t h a t t h e s e b i o m a r k e r s c a n be l i b e r a t e d b y p y r o l y s i s ( 9 8 , 9 9 ) . Porp h y r i n s r e t a i n e d w i t h i n the asphaltene m i c e l l e s of m i g r a t i n g o i l s may be s i m i l a r l y p r o t e c t e d f r o m c h r o m a t o g r a p h i c e f f e c t s a n d may not h a v e b e e n s u b j e c t e d t o f r a c t i o n a t i o n a s may h a v e t h e " f r e e " p o r p h y r i n s present i n the hydrocarbon (maltenes) f r a c t i o n . The a p p l i c a t i o n o f m e t a l l o p o r p h y r i n d i s t r i b u t i o n s to m i g r a t i o n problems i s d i s c u s s e d f u r t h e r by B r a n t h a v e r and F i l b y (100) i n t h i s v o l u m e . M e t a l l o p o r p h y r i n s i n Crude O i l s . As p r o d u c t s o f k e r o g e n m a t u r a t i o n w i t h i n the " o i l window," c r u d e o i l s c o n t a i n m e t a l l o p o r p h y r i n s t h a t r e f l e c t the c a t a g e n e t i c stage of p o r p h y r i n e v o l u t i o n . Although t h e r e i s a r e c e n t r e p o r t o f a F e ( I I ) DPEP p o r p h y r i n i n a F e - r i c h Venezuelan o i l (101), the porphyrins i n crude o i l s are almost e n t i r e l y t h e d e f u n c t i o n a l i z e d N i ( I I ) a n d V O ( I I ) e t i o - , DPEP-, a n d m i n o r - s e r i e s (THBD, b e n z o - e t i o , b e n z o - D P E P ) . The F e ( I I ) p o r p h y r i n r e p o r t e d b y F r a n c e s k i n e_t a l . ( 1 0 1 ) was s e p a r a t e d f r o m J o b o ( V e n e z u e l a ) c r u d e o i l a n d was c h a r a c t e r i z e d b y M o s s b a u e r , UV, and mass s p e c t r o m e t r y . The d a t a p r e s e n t e d , h o w e v e r , c a n n o t be i n t e r p r e t e d as c o n c l u s i v e i d e n t i f i c a t i o n because the Mossbauer c h e m i c a l s h i f t and q u a d r o p o l e - s p l i t t i n g parameters are c o n s i s t e n t w i t h F e ( I I I ) inorganic s a l t s a n d t h e UV d a t a a r e s i m i l a r t o t h o s e f o r N i ( I I ) p o r p h y r i n s . A l s o , t h e MS d a t a a r e c o n s i s t e n t w i t h N i ( I I ) THBD. M a s s s p e c t r a a r e n o t s h o w n , h e n c e i s o t o p i c c l u s t e r s w h i c h a r e d i f f e r e n t f o r N i o r Fe p o r p h y r i n s c a n n o t be c o m p a r e d . Thus, the o n l y p o r p h y r i n s t h a t have been i d e n t i f i e d i n crude o i l s a r e those t h a t have been i d e n t i f i e d i n sedimentary sequences. Free-base porphyrins are g e n e r a l l y of very l o w a b u n d a n c e 05,7.) a n d a l t h o u g h m e t a l l o p o r p h y r i n c a r b o x y l i c a c i d s have been r e p o r t e d i n younger ( P l i o c e n e , M i o c e n e , C r e t a c e o u s ) c r u d e o i l s (102,103), i t i s not c l e a r whether they are of primary o r i g i n . B a k e r a n d L o u d a (5_,7) h a v e s h o w n t h a t t h e r m a l d e c a r b o x y l a t i o n o f p o r p h y r i n s p e c i e s i n s e d i m e n t s s h o u l d o c c u r b e l o w 60°C, i..e_., b e l o w t h e " o i l w i n d o w " (50-150°C a p p r o x i m a t i o n ) w h e r e c a t a g e n e s i s takes place. The p r e s e n c e o f c a r b o x y l a t e d m e t a l l o p o r p h y r i n s may t h u s be s e c o n d a r y and r e s u l t f r o m i n c o r p o r a t i o n i n t o t h e m i g r a t i n g petroleum from l e s s mature sedimentary sequences i n the m i g r a t i o n pathway. The p r e s e n c e o f v e r y h i g h m o l e c u l a r - w e i g h t porphyrins (i.e., >1000 d a l t o n s ) i n c r u d e o i l s a n d o i l s h a l e s h a s b e e n r e p o r t e d b y s e v e r a l authors (92,93,104,105). Blumer and Snyder (92) r e p o r t e d p o r p h y r i n - t y p e UV s p e c t r a i n c o m p o n e n t s o f a T r i a s s i c o i l s h a l e w i t h MW up t o 2 0 , 0 0 0 d a l t o n s a n d d i m e r i c s p e c i e s o f m e t a l l o p o r p h y r i n s h a v e been i d e n t i f i e d ( 9 3 ) . There i s a l s o evidence that v e r y h i g h molecular-weight porphyrins i n crude o i l s are a l k y l porphyrins, s i m i l a r to t h o s e s p e c i e s f o u n d i n c r u d e o i l s , and t h a t t h e s e a s s o c i a t e with high molecular-weight p o l a r s p e c i e s (i_.e_., a s p h a l t e n e s ) i n c r u d e o i l s , as d i s c u s s e d p r e v i o u s l y . A l t h o u g h T r e i b s (11,12,14.) r e p o r t e d t h e p r e s e n c e o f V O ( I I ) p o r p h y r i n s i n 66 c r u d e o i l s , t h e r e h a v e b e e n no s y s t e m a t i c s t u d i e s r e p o r t e d o f the abundances o f m e t a l l o p o r p h y r i n s i n c r u d e o i l s as a f u n c t i o n of the d e p o s i t i o n a l environment of the source m a t e r i a l , age o f s o u r c e r o c k s , l o c a l i t y , o r c r u d e o i l c o m p o s i t i o n . Table I s u m m a r i z e s some r e p r e s e n t a t i v e N i ( I I ) a n d V O ( I I ) p o r p h y r i n c o n t e n t s

trace 2 2.5 e t i o > THBD > b e n z o - e t i o ~ b e n z o - D P E P T h i s o i l c o n t a i n s b o t h DPEP a n d e t i o - p o r p h y r i n s w h i c h a r e p r e s e n t i n w i d e c a r b o n number r a n g e s ( 2 5 t o g r e a t e r t h a n 4 0 c a r b o n s ) t y p i c a l o f p o r p h y r i n s e x t r a c t e d from mature sediments. Q u i r k e et_ c l L . ( 1 1 5 ) h a v e r e c e n t l y s h o w n ( b y MS/MS) t h a t B o s c a n o i l c o n t a i n s c o m p l e x n o n - p o l a r p o r p h y r i n s w i t h up t o 48 c a r b o n s and t h a t t h e s e u n u s u a l p o r p h y r i n s a r e b e n z o - p o r p h y r i n s w i t h no p y r r o l e - r i n g a l k y l s u b s t i t u e n t g r e a t e r t h a n C]_. W h e t h e r t h e s e c o n t a i n m o r e t h a n o n e b e n z o r i n g o r a r e s u b s t i t u t e d on t h e monobenzo-ring i s n o t c l e a r , b u t they r e p r e s e n t a m i n o r s p e c i e s i n B o s c a n t h a t c a n n o t be d i r e c t l y r e l a t e d to s p e c i f i c c h l o r o p h y l l p r e c u r s o r s a n d , t o d a t e , have n o t been i d e n t i f i e d i n sedimentary sequences. The a b u n d a n c e s o f t h e m i n o r p o r p h y r i n s e r i e s i n crude o i l s have been determined o n l y i n o i l s w i t h r e l a t i v e l y h i g h p o r p h y r i n c o n t e n t s , e_.j*., B o s c a n a n d A t h a b a s c a o i l s a n d ( 3 1 , 4 9 ) , b u t t h e y p r o b a b l y o c c u r i n many c r u d e s . The g e n e t i c r e l a t i o n s h i p s among t h e DPEP a n d e t i o - p o r p h y r i n s and t h e r e l a t i o n s h i p between t h e N i ( I I ) a n d V O ( I I ) s p e c i e s d i s c u s s e d i n t h e s e c t i o n on t h e e v o l u t i o n o f p o r p h y r i n s i n m a t u r i n g sediments i s r e f l e c t e d i n the nature o f the porphyrins i n crude o i l s , although no s y s t e m a t i c s t u d i e s o f t h e i n t e r r e l a t i o n s h i p s among t h e p o r p h y r i n types i n crude o i l s o r comparisons w i t h sedimentary p o r p h y r i n s have been r e p o r t e d . I t i s a p p a r e n t f r o m t h e c r u d e o i l d a t a shown i n


1.


Overview

27

T a b l e I t h a t a g e n e r a l i z a t i o n c a n n o t be made a s t o t h e N i ( I I ) t o V O ( I I ) p o r p h y r i n r a t i o as a f u n c t i o n o f s o u r c e - r o c k o r r e s e r v o i r age, a s h a s b e e n made b y M a c k e n z i e et_ a l . ( 3 8 ) f o r s e d i m e n t a r y s e q u e n c e s . S e v e r a l a u t h o r s (116-118) have a t t e m p t e d t o c o r r e l a t e Ni/V r a t i o s i n o i l s w i t h age, but the r e s u l t s a r e c o n f l i c t i n g (104,119). The decrease i n the N i ( I I ) to VO(II) p o r p h y r i n r a t i o w i t h i n c r e a s i n g m a t u r a t i o n i n sediments (22) has n o t been c o n f i r m e d f o r c r u d e o i l s ; Hodgson (116) c o n c l u d e d t h e o p p o s i t e f r o m s t u d i e s o f o i l s f r o m t h e W. C a n a d a B a s i n . A s M a c k e n z i e e_t aJL. ( 3 8 ) h a v e p o i n t e d o u t f o r sedimentary sequences, the N i ( I I ) to VO(II) p o r p h y r i n v a r i a t i o n w i t h age d e p e n d s on a) t h e r e l a t i v e t h e r m a l s t a b i l i t i e s o f N i ( I I ) and V O ( I I ) p o r p h y r i n s , and b) t h e a c i d - c a t a l y z e d d e m e t a l l a t i o n stabilities o f t h e p o r p h y r i n s . F o r c r u d e o i l s , t h e s e r e l a t i v e e f f e c t s w i l l be d i f f e r e n t compared t o the s e d i m e n t a r y environment because m i n e r a l c a t a l y z e d r e a c t i o n s may be l e s s s i g n i f i c a n t . In a d d i t i o n , another i m p o r t a n t f a c t o r may be d e m e t a l l a t i o n c a u s e d b y H2S r e l e a s e d d u r i n g o i l m a t u r a t i o n i n the r e s e r v o i r . T h e r e i s a l s o no o b v i o u s c o r r e l a t i o n o f t h e D P E P / e t i o r a t i o o f c r u d e o i l p o r p h y r i n s w i t h r e s e r v o i r a g e , a s shown i n T a b l e I I . However, Yen and S i l v e r m a n (120) have c o n c l u d e d t h a t t h e D P E P / e t i o r a t i o f o r a number o f u n r e l a t e d c r u d e o i l s d o e s show a d e c r e a s e w i t h depth. B a r w i s e and P a r k ( 7 9 ) , on t h e o t h e r h a n d , h a v e p r e s e n t e d q u a l i t a t i v e d a t a o n f o u r o i l s g e n e r a t e d f r o m t h e same s o u r c e r o c k b u t r e s e r v o i r e d a t d i f f e r e n t d e p t h s (no l o c a t i o n s o r a g e c i t e d ) . The H P L C c h r o m a t o g r a m s o f t h e d e m e t a l l a t e d p o r p h y r i n s show a d e c r e a s e i n the DPEP/etio r a t i o w i t h depth, but the a u t h o r s p o i n t out t h a t the s h a l l o w e r o i l s have been e x t r e m e l y b i o d e g r a d e d . I f thermal conversion of DPEP- t o e t i o - p o r p h y r i n s d o e s n o t o c c u r , t h e c h a n g e i n t h e DPEP/e t i o r a t i o o f o i l s m a t u r i n g i n r e s e r v o i r s m u s t be t h e r e s u l t o f p r e f e r e n t i a l degradation of DPEP-porphyrins (thermal decomposition, d e m e t a l l a t i o n , etc.) r e l a t i v e to the e t i o species. I t i s clear that f u r t h e r w o r k n e e d s t o be d o n e o n t h e e f f e c t o f m a t u r a t i o n o f c r u d e o i l s on t h e m e t a l l o p o r p h y r i n d i s t r i b u t i o n s i n o r d e r t h a t c o m p a r i s o n s c a n be made w i t h t h e d i a g e n e t i c - c a t a g e n e t i c p a t h w a y s t h a t a r e b e t t e r documented i n s e d i m e n t s . M e t a l l o p o r p h y r i n s i n Crude O i l Components. The d i s t r i b u t i o n o f N i ( I I ) a n d V O ( I I ) p o r p h y r i n s among t h e c o m p o n e n t s o f a c r u d e o i l o r b i t u m e n i s o f d i r e c t s i g n i f i c a n c e t o o i l - o i l and o i l - s o u r c e c o r r e l a t i o n s and, i n p a r t i c u l a r , t o m e t a l l o p o r p h y r i n b e h a v i o r d u r i n g m i g r a t i o n and p e t r o l e u m a l t e r a t i o n p r o c e s s e s . M e t a l l o p o r p h y r i n s d i s t r i b u t e among p e t r o l e u m components d u r i n g such f r a c t i o n a t i o n p r o c e s s e s as a s p h a l tene p r e c i p i t a t i o n (31,111), d i s t i l l a t i o n ( 1 0 3 ) , and c h r o m a t o g r a p h i c s e p a r a t i o n (13) b a s e d e i t h e r on f u n c t i o n a l i t y o r m o l e c u l a r w e i g h t . A major problem i n the q u a n t i t a t i v e d e t e r m i n a t i o n or i s o l a t i o n of porphyrins i n crude o i l s i s the d i f f i c u l t y of separating the p o r p h y r i n s from o t h e r p e t r o l e u m components, p a r t i c u l a r l y from the a s p h a l t e n e s w i t h w h i c h s t r o n g c h e m i c a l a s s o c i a t i o n s a r e formed (121-123). B a k e r and P a l m e r (4) h a v e shown t h a t t h e D P E P / e t i o r a t i o of Boscan p o r p h y r i n s i s d i f f e r e n t f o r the p o r p h y r i n s i n t h e m a l t e n e s a n d f o r t h e p o r p h y r i n s when d e m e t a l l a t e d a n d e x t r a c t e d f r o m t h e t o t a l c r u d e o i l . A l t h o u g h t h i s c o m p a r i s o n i s between V O ( I I ) p o r p h y r i n s and t o t a l p o r p h y r i n s , the comparison i s v a l i d because the VO(II) porphyr i n s a r e o f much g r e a t e r a b u n d a n c e t h a n t h e N i ( I I ) p o r p h y r i n s i n

DPEP/etio

Pravda

(49)

0.22

(5) (97)

2.4 0.2

3.1

(A)

Oil 3

W.

La

3

3

total

a

a

Cretaceous

Cretaceous

Cretaceous

Cretaceous

Cretaceous

Cretaceous

Cretaceous

Geologic

Age

Ages

0.49

0.56

1.6

1.4

1.8

0.7

1.2

DPEP/etio

of D i f f e r e n t

demetallated porphyrins.

Surgut

a

River

Lake

Paz

Peace

Cold

Athabasca

Burgan

Boscan

measured f o r V 0 ( I I ) p o r p h y r i n s ; o t h e r s from

Jurassic

Jurassic

Gela

a

Triassic

Regusa

Triassic

Boundary

Lake

Pennsylvanian

Tensleep

(137)

(5)

Reference

R a t i o s o f Some C r u d e O i l s

1.3

2.9

Devonian

Grosmont

2.0

Devonian

3

DPEP/etio

Alberta

Age

DPEP t o E t i o

Geologic

II.

Oil

Table


(97)

(107)

(49)

(49)

(49)

(D

Reference

JH m x m oo 2

2

00


1.


29

Overview

B o s c a n o i l ( T a b l e I ) . D i d y k et_ a l . ( 1 0 7 ) a l s o r e p o r t e d t h a t t h e DPEP/etio r a t i o of demetallated porphyrins (predominantly VO(II)) from the a s p h a l t e n e s of the La Paz Cretaceous o i l (Table I I ) i s a p p r o x i m a t e l y t w i c e t h a t o f t h e c r u d e o i l ( 0 . 9 6 v s 0.56) a n d t h a t t h e c a r b o n n u m b e r r a n g e was s m a l l e r . D i d y k et_ a l . ( 1 0 7 ) i n t e r p r e t e d t h e s e r e s u l t s t o i n d i c a t e a d i s t r i b u t i o n b a s e d on p o r p h y r i n p o l a r i t y . S t r o n g and F i l b y (49) have i n v e s t i g a t e d t h e d i s t r i b u t i o n o f V O ( I I ) p o r p h y r i n s ( D P E P , e t i o , THBD, b e n z o ) i n A t h a b a s c a o i l s a n d b i t u m e n and components. They o b s e r v e d t h a t the d i s t r i b u t i o n s o f the p o r p h y r i n types i n the porphyrin aggregate ( e x t r a c t i o n of o i l w i t h toluenem e t h a n o l ) , the m a l t e n e s , an n-pentane e x t r a c t o f the a s p h a l t e n e s ( r e s i n s ) , and a m e t h a n o l - a c e t o n e e x t r a c t o f t h e a s p h a l t e n e s were d i f f e r e n t a n d c o u l d be e x p l a i n e d o n t h e b a s i s o f V O ( I I ) p o r p h y r i n a f f i n i t y f o r the asphaltenes, equating approximately to p o r p h y r i n p o l a r i t y , w h i c h i s dependent upon a) p r e s e n c e o r a b s e n c e o f an i s o c y c l i c r i n g , b) c a r b o n number ( v i z . d e g r e e o f a l k y l a t i o n ) , and c ) t h e n u m b e r o f u n s u b s t i t u t e d (3 p o s i t i o n s ( 3 4 , 6 1 ) . The a p p r o x i m a t e o r d e r o f a f f i n i t y f o r t h e a s p h a l t e n e s was o b s e r v e d t o b e : e t i o < DPEP < THB < b e n z o - e t i o ~ b e n z o - D P E P The m e t a l l o p o r p h y r i n s d i s t r i b u t e i n a c r u d e o i l o r b i t u m e n b e t w e e n the l o w p o l a r i t y , l o w m o l e c u l a r w e i g h t h y d r o c a r b o n b u l k phase and the a s p h a l t e n e m i c e l l e s i n the o i l which c o n t a i n both h i g h m o l e c u l a r w e i g h t n o n - p o l a r and low m o l e c u l a r - w e i g h t p o l a r s p e c i e s . The D P E P / e t i o r a t i o changes i n the t r a n s i t i o n from a v e r y p o l a r asphaltene core (highest DPEP/etio) through the i n t e r m e d i a t e p o l a r i t y outer r e g i o n of the m i c e l l e to the b u l k low p o l a r i t y hydrocarbon phase (lowest DPEP/etio r a t i o ) . The a s s o c i a t i o n o f t h e p o r p h y r i n s w i t h t h e a s p h a l t e n e s a p p e a r s t o be b a s e d o n p o l a r i t y , a n d p r o b a b l y i s a n e x p r e s s i o n o f TT-TT i n t e r a c t i o n s a n d / o r f u n c t i o n a l g r o u p b o n d i n g t o t h e m e t a l i o n a s s u g g e s t e d by Yen (104) and by Nguyen and F i l b y ( 8 8 ) . The l a t t e r a u t h o r s s h o w e d t h a t N i ( I I ) m e s o p o r p h y r i n I X d i m e t h y l e s t e r ( l a b e l e d w i t h 6 % i ) and N i ( I I ) 0 E P added to a t o l u e n e s o l u t i o n of A t h a b a s c a o i l sand bitumen d i s t r i b u t e d between the a s p h a l t e n e s and the maltenes w i t h the Ni(II)DME a d s o r p t i o n g r e a t e r than t h a t of Ni(II)0EP. Separation of the asphaltenes i n t o molecular weight f r a c t i o n s b y GPC s h o w e d t h a t N i ( I I ) D M E was d i s t r i b u t e d among a l l molecular weight f r a c t i o n s i n a s i m i l a r p a t t e r n to that observed f o r the i n h e r e n t N i c o n t e n t ( p o r p h y r i n and n o n - p o r p h y r i n ) o f t h e a s p h a l tenes. T h u s , t h e o b s e r v a t i o n o f p o r p h y r i n UV s p e c t r a i n h i g h m o l e c u l a r weight a s p h a l t e n e f r a c t i o n s (92,93,106) does not n e c e s s a r i l y imply m e t a l l o p o r p h y r i n s of unusual s t r u c t u r e (104). E f f e c t s o f B i o d e g r a d a t i o n on P o r p h y r i n s i n O i l s . The e f f e c t s o f b i o d e g r a d a t i o n and a s s o c i a t e d w a t e r w a s h i n g on p o r p h y r i n d i s t r i b u t i o n s have a l s o n o t been f u l l y i n v e s t i g a t e d . B a r w i s e and P a r k (79) c o n c l u d e d t h a t b i o d e g r a d e d o i l s f r o m a m a t u r a t i o n sequence had t o t a l d e m e t a l l a t e d p o r p h y r i n d i s t r i b u t i o n s (e_.j>., D P E P / e t i o r a t i o s ) s i m i l a r to those of r e l a t e d non-degraded o i l s of s i m i l a r m a t u r i t y , although no q u a n t i t a t i v e d a t a w e r e p r e s e n t e d . P a l m e r (124) s t u d i e d t h e VO(II) p o r p h y r i n s from a s e r i e s of g e n e t i c a l l y r e l a t e d h i g h l y degraded seep o i l s , r e s e r v o i r b i o d e g r a d e d , and n o n - d e g r a d e d o i l s f r o m C o l o m b i a . She f o u n d t h a t t h e D P E P / e t i o r a t i o s , t h e s e r i e s m a x i m a ( C f o r DPEP, C29 f o r e t i o ) a n d t h e c a r b o n n u m b e r r a n g e s w e r e v e r y s i m i l a r f o r t h e three related o i l s . She d i d n o t i c e , h o w e v e r , t h a t i n t h e m o s t degraded seep o i l the V O ( I I ) p o r p h y r i n s were e n r i c h e d r e l a t i v e to 3 1

30

M E T A L C O M P L E X E S I N FOSSIL F U E L S


M i ( I I ) p o r p h y r i n s compared w i t h non-degraded o i l s . I t i s not c l e a r , however, whether t h i s enrichment i s a r e s u l t of s e l e c t i v e b i o l o g i c a l processes ( s e l e c t i v e degradation of N i ( I I ) porphyrins), of s e l e c t i v e d i s s o l u t i o n by a s s o c i a t e d w a t e r w a s h i n g , o r o f s e l e c t i v e o x i d a t i o n of N i ( I I ) p o r p h y r i n s r e l a t i v e t o the V O ( I I ) s p e c i e s . S t r o n g and F i l b y (49) have a l s o c o n c l u d e d t h a t b i o d e g r a d a t i o n had l i t t l e e f f e c t on V O ( I I ) p o r p h y r i n d i s t r i b u t i o n s i n t h e h i g h l y d e g r a d e d A l b e r t a o i l sands. M e t a l l o p o r p h y r i n s i n C o a l s . T h r e e m a j o r d i f f e r e n c e s a r e e x h i b i t e d by the p o r p h y r i n s i n c o a l s compared t o t h o s e f o u n d i n p e t r o l e u m and petroleum source rocks: i ) The c o a l m e t a l l o p o r p h y r i n s a p p e a r t o be c h e l a t e s o n l y o f t r i v a l e n t F e ( I I I ) , G a ( I I I ) , and M n ( I I I ) , compared t o t h e d i v a l e n t i o n s N i ( I I ) and V O ( I I ) o f p e t r o l e u m m e t a l l o p o r p h y r i n s ( 9 , 2 3 , 2 4 , 2 6 ) . i i ) The a b u n d a n c e s o f t h e m e t a l l o p o r p h y r i n s i n c o a l s a r e v e r y much l o w e r t h a n f o r m o s t c r u d e o i l s — t y p i c a l l y l e s s t h a n 10 y g m e t a l l o p o r p h y r i n / g - c o a l (9,23-26). i i i ) The c o a l p o r p h y r i n s a r e a l m o s t e n t i r e l y e t i o - s p e c i e s , w i t h t h e e x c e p t i o n o f t r a c e s o f DPEP i n some l o w - r a n k b i t u m i n o u s c o a l s (9,25) and l i g n i t e s (125,126). Because o f t h e i r low abundances, the c o a l p o r p h y r i n s have r e c e i v e d much l e s s a t t e n t i o n t h a n h a v e t h e i r p e t r o l e u m c o u n t e r p a r t s . The presence of t r i v a l e n t metal ions i n the c o a l p o r p h y r i n s i s evidence of m e t a l l a t i o n c o n d i t i o n s c o n s i d e r a b l y more o x i c t h a n f o u n d i n m a r i n e s e d i m e n t a r y e n v i r o n m e n t s i n w h i c h t h e d i v a l e n t N i ( I I ) and V O ( I I ) porphyrins predominate. T h i s o b s e r v a t i o n , p l u s the v e r y low m e t a l l o p o r p h y r i n abundances i n c o a l s , i s evidence t h a t i n the t e r r e s t r i a l e n v i r o n m e n t i n w h i c h c o a l s f o r m , most o f t h e c h l o r o p h y l l s a r e degraded. A l t h o u g h P a l m e r e_t a l . ( 2 5 ) h a v e c o n c l u d e d t h a t t h e e t i o p o r p h y r i n s found i n c o a l s have been d e r i v e d from c h l o r o p h y l l s v i a e a r l y o x i d a t i v e c l e a v a g e o f t h e i s o c y c l i c r i n g , B o n n e t t et_ a l . ( 1 2 6 ) h a v e p r e s e n t e d c o n v i n c i n g e v i d e n c e t h a t c y t o c h r o m e s may b e i m p o r t a n t precursors to the F e ( I I I ) porphyrins i n coals. They i d e n t i f i e d G a ( I I I ) , M n ( I I I ) , a n d F e ( I I I ) p o r p h y r i n s i n a T u r k i s h l i g n i t e (e_.£., 30 y g t o t a l p o r p h y r i n s / g - c o a l ) , w i t h t h e F e ( I I I ) s p e c i e s a c c o u n t i n g f o r 95% o f the p o r p h y r i n s . S m a l l amounts o f f r e e - b a s e p o r p h y r i n s and c h l o r i n s were i d e n t i f i e d . The F e ( I I I ) s p e c i e s w e r e s h o w n t o c o n t a i n a mono- a n d a d i - c a r b o x y l i c a c i d a n d t h e l a t t e r was s u g g e s t e d t o b e the F e ( I I I ) complex o f m e s o p o r p h y r i n - I X ( b a s e d on c o m p a r i s o n o f t h e methyl ester with synthetic Fe(III) mesoporphyrin-IX dimethyl e s t e r ) . The p r o b a b l e d i a g e n e t i c p a t h w a y s f o r t h e c o a l p o r p h y r i n s a r e s h o w n i n F i g u r e 6, b a s e d l a r g e l y o n t h e w o r k o f B o n n e t t e t a l . ( 1 2 6 ) . B o n n e t t e_t a l . ( 9 ) a n d P a l m e r e t a l . ( 2 5 ) h a v e s h o w n t h a t , i n g e n e r a l , the abundances of p o r p h y r i n s i n c o a l s decrease w i t h c o a l r a n k and a r e v i r t u a l l y a b s e n t f r o m a n t h r a c i t e s . Thus, as c o a l i f i c a t i o n proceeds from peats through sub-bituminous c o a l s , to b i t u m i nous c o a l s , the abundance o f the c a r b o x y l a t e d p o r p h y r i n s d e c r e a s e r a p i d l y , t h e F e ( I I I ) / G a ( I I I ) p o r p h y r i n r a t i o d e c r e a s e s , and t h e w e i g h t e d mean o f t h e m o l e c u l a r m a s s e s d e c r e a s e s . The o r i g i n o f t h e metal ion i n coal porphyrins i s , at present, obscure. Bonnett et a l . (9) have s u g g e s t e d t h a t , because G a ( I I I ) p o r p h y r i n s a r e f o u n d i n c o a l s and n o t i n b i o l o g i c a l s y s t e m s , t h e G a + i o n ( a s G a O H ) i s s e c o n d a r y a n d t h u s t h e Fe^+ i o n f o u n d i n t h e F e ( I I I ) e t i o - p o r p h y r i n s i n c o a l may n o t be t h e b i o l o g i c a l ¥e^ i o n p r e s e n t i n t h e heme p r e c u r s o r . 3

+

2 +


1.


Overview

chlorophyll

C

3 0

,C

2 8

(e.£.

FeP

F i g u r e 6. P o s s i b l e d i a g e n e t i c pathways of geoporphyrins i n c o a l s ( m o d i f i e d f r o m 1 2 6 , 2 5 ) . P a t h w a y A: biochemical F e ^ retained. P a t h w a y B: precursor demetallation; F e ^ inserted geochemically. +

+

32


I n F i g u r e 6, t h e t w o p a t h w a y s a r e s h o w n a s A ( b i o c h e m i c a l F e ^ + r e t a i n e d ) and B ( d e m e t a l l a t i o n f o l l o w e d by r e - i n s e r t i o n o f F e ^ ) . Fowever, t h e f a c t t h a t t h e F e ( I I I ) / G a ( I I I ) p o r p h y r i n r a t i o decreases w i t h c o a l i f i c a t i o n may a l s o i n d i c a t e a t r a n s m e t a l l a t i o n p r o c e s s , o r the g r e a t e r s t a b i l i t y o f G a ( I I I ) p o r p h y r i n s . G a l l i u m i s thought t o occur i n c o a l s a s s o c i a t e d i n t h e c l a y m i n e r a l f r a c t i o n (127) and t h e m i n e r a l s u r f a c e may a c t a s t h e s o u r c e o f G a ( I I I ) f o r t h e m e t a l l a t i o n or t r a n s m e t a l l a t i o n o f a p r e c u r s o r t o form t h e G a ( I I I ) p o r p h y r i n . B o n n e t t e_t a^L. ( 1 2 6 ) h a v e p r o p o s e d t h a t a " P o r p h y r i n I n d e x o f C o a l i f i c a t i o n " be u s e d a s a measure o f c o a l rank. This index i s c a l c u l a t e d f r o m t h e w e i g h t e d mean o f t h e p o r p h y r i n m o l e c u l a r m a s s e s d e t e r m i n e d by mass s p e c t r o m e t r y ( c f . ,25). +


Non-Porphyrin Metal

Complexes:

Geochemical S i g n i f i c a n c e

The p r e v i o u s d i s c u s s i o n h a s f o c u s e d o n N i ( I I ) , V O ( I I ) , F e ( I I I ) , G a ( I I I ) and Mn(III) p o r p h y r i n s i n crude o i l s , c o a l s , and i n sediment a r y sequences c o n t a i n i n g maturing o r g a n i c matter. H o w e v e r , many o t h e r t r a c e elements a r e p r e s e n t i n crude o i l s (104,105) and a l t h o u g h t r a c e element d i s t r i b u t i o n s have been used f o r g e o c h e m i c a l c o r r e l a t i o n s , as d i s c u s s e d elsewhere i n t h i s volume (100), t h e c h e m i c a l n a t u r e o f t h e m e t a l s p e c i e s i s n o t known. Some o f t h e t r a c e e l e m e n t c o n t e n t o f m o s t c r u d e s may b e p r e s e n t i n a s s o c i a t e d m i n e r a l m a t t e r , entrained formation waters o r present as s a l t s of organic acids. Most o f t h e t r a c e element c o n t e n t o f c r u d e o i l s i s a p p a r e n t l y a s s o c i a t e d w i t h t h e a s p h a l t i c component (105) and t h e p o s s i b i l i t y o f complexation o f metal i o n s i n t o t h e a s p h a l t e n e s s t r u c t u r e has been proposed (104-106). During the i n i t i a l stages o f sedimentation, organic substances undoubtedly p l a y an important r o l e i n metal i o n t r a n s p o r t and spec i a t i o n (128,129) a n d a l a r g e number o f s i m p l e o r g a n i c compounds ( e . g . , a m i n o a c i d s , q u i n o n e s , e t c . ) h a v e b e e n shown t o f o r m m e t a l complexes i n sediments (130). However, p r o b a b l y more i m p o r t a n t i n metal s p e c i a t i o n a r e t h e humic substances t h a t have l a r g e c a p a c i t i e s for metal complexation ( 1 3 1 ) a n d w h i c h may b e p r e c u r s o r s t o k e r o g e n . This aspect of metal-organic geochemistry i s beyond t h e scope o f t h i s a r t i c l e a n d h a s been r e v i e w e d by Saxby (130) . Of c o n s i d e r a b l e g e o c h e m i c a l i n t e r e s t a r e t h e m e t h y l - a n d p h e n y l a r s o n i c a c i d s i d e n t i f i e d by F i s h and Brinckman (132) i n methanol e x t r a c t s o f Green R i v e r o i l s h a l e . These compounds a r e t h e o n l y e x a m p l e s o f t r u e o r g a n o m e t a l l i c compounds ( i . e _ . , c o n t a i n i n g c a r b o n metal bonds) i d e n t i f i e d i n f o s s i l f u e l s . T h e s e c o m p o u n d s may n o t , however, be o f p r i m a r y o r i g i n ( i . e . , formed i n t h e e a r l y d i a g e n e s i s s t a g e ) a n d may h a v e f o r m e d b y k e r o g e n c a t a g e n e s i s p r o d u c t s r e a c t i n g w i t h the mineral s k u t t e r u d i t e (Co,Fe,Ni)As4 present i n the shale (133). J a g a n a t h a n e_t a l . ( 1 3 3 ) s u g g e s t e d a n o r g a n i c - m a t t e r s k u t t e r u d i t e r e a c t i o n to account f o r the formation o f organoarsenicals during oil-shale retorting. The r e c o g n i t i o n t h a t m o s t c r u d e o i l s c o n t a i n n i c k e l a n d v a n a d i u m i n p o r p h y r i n and non-porphyrin forms ( a s s o c i a t e d predominantly with the asphaltenes) has l e d t o e f f o r t s t o i d e n t i f y t h e non-porphyrin species. As s t a t e d p r e v i o u s l y , t h e e x t r a c t a b l e m e t a l l o p o r p h y r i n s n o r m a l l y account f o ra s m a l l f r a c t i o n o f t h e t o t a l n i c k e l and vanadium contents o f crude o i l s . Branthaver (119) i n t h i s volume has reviewed much o f t h e e v i d e n c e f o r t r u e n o n - p o r p h y r i n n i c k e l a n d v a n a d i u m


1.

FILBY AND

VAN B E R K E L

Overview

33

s p e c i e s , as opposed to the concept of the n o n - p o r p h y r i n s p e c i e s b e i n g p o r p h y r i n s s t r o n g l y a s s o c i a t e d w i t h a s p h a l t e n e s a n d w h i c h do not e x h i b i t t y p i c a l s p e c t r o s c o p i c p r o p e r t i e s or y i e l d free-base porphyrins with t y p i c a l demetallation procedures. The e x i s t e n c e o f n o n - p o r p h y r i n s p e c i e s has not been c o n c l u s i v e l y e s t a b l i s h e d because no n o n - p o r p h y r i n n i c k e l o r v a n a d i u m c o m p l e x e s h a v e b e e n u n e q u i v o c a l l y i d e n t i f i e d i n petroleum constituents. Erdman and H a r j u (134) and N g u y e n a n d F i l b y ( 8 8 ) h a v e shown t h a t p e t r o l e u m a s p h a l t e n e s a r e c a p a b l e o f c o m p l e x i n g l a r g e amounts o f V O ( I I ) , C u ( I I ) and N i ( I I ) , but the n a t u r e of the complexing l i g a n d s i n the a s p h a l t e n e s has not been determined. I t seems u n l i k e l y , h o w e v e r , t h a t t h e s e l i g a n d s a r e f r e e - b a s e p o r p h y r i n s . A s p h a l t e n e s c o n t a i n a number o f h e t e r o a t o m f u n c t i o n a l i t i e s ( e . j * . , p h e n o l i c - O H , r i n g - N , e t c . ) t h a t a r e good l i g a n d s f o r the f o r m a t i o n of complexes of t r a n s i t i o n metal i o n s . B e c a u s e no n o n - p o r p h y r i n c o m p l e x e s o f n i c k e l a n d v a n a d i u m h a v e been i d e n t i f i e d i n crude o i l s or s o u r c e - r o c k bitumens, the o r i g i n and g e o c h e m i c a l s i g n i f i c a n c e o f t h e n o n - p o r p h y r i n n i c k e l and v a n a d i u m i n c r u d e o i l s c a n n o t be a s s e s s e d . The f a c t t h a t t h e m o s t a b u n d a n t o r g a n i c a l l y c o m b i n e d nrporphyrin metals i n crude o i l asphaltenes a r e n o r m a l l y n i c k e l and vanadium s u g g e s t s a g e n e t i c r e l a t i o n s h i p between t h e p o r p h y r i n and n o n - p o r p h y r i n s p e c i e s . Yen (104) has s u g g e s t e d t h a t t h e n o n - p o r p h y r i n c o m p l e x e s may i n f a c t be m e t a l l o porphyrin degradation products that remain a s s o c i a t e d w i t h the asphaltene structure. A l t h o u g h n o n - p o r p h y r i n n i c k e l and v a n a d i u m s p e c i e s may o c c u r i n c r u d e o i l s , a s p h a l t s , e t c . , t h e i r p r e s e n c e i n the bitumens o f m a t u r i n g sediments has not been e s t a b l i s h e d . There may, i n f a c t , be a g e n e t i c r e l a t i o n s h i p b e t w e e n n o n - p o r p h y r i n n i c k e l and v a n a d i u m s p e c i e s i n k e r o g e n s f r o m m a t u r i n g s e d i m e n t s and t h o s e p r e s e n t i n s o u r c e r o c k b i t u m e n s and c r u d e o i l s a s h a s b e e n demons t r a t e d f o r the m e t a l l o p o r p h y r i n s (40). Conclusions The g e o c h e m i c a l e v o l u t i o n o f t h e D P E P - p o r p h y r i n s i s c o n s i s t e n t w i t h t h e scheme p r o p o s e d by T r e i b s i n 1936. Subsequent m o d i f i c a t i o n s t o t h e scheme i n c l u d e t h e i d e n t i f i c a t i o n o f o t h e r c h l o r o p h y l l (-b, -c_) a n d b a c t e r i o c h l o r o p h y l l (-a, - b , -d) p r e c u r s o r s a n d t h e r e c o g n i t i o n of s i m i l a r pathways f o r e t i o - p o r p h y r i n s i n which i s o c y c l i c r i n g o p e n i n g o f a DPEP p r e c u r s o r o c c u r s e a r l y i n d i a g e n e s i s . The l a t t e r c o n c e p t i s more s t r o n g l y s u p p o r t e d by t h e a v a i l a b l e e v i d e n c e t h a n t h e DPEP t o e t i o - p o r p h y r i n c o n v e r s i o n o r i g i n a l l y p r o p o s e d b y C o r w i n . C h l o r o p h y l l s a p p e a r t o be t h e m a j o r p r e c u r s o r s f o r t h e M ( I I I ) m e t a l l o p o r p h y r i n s i n c o a l s , a l t h o u g h c y t o c h r o m e s may c o n t r i b u t e t o t h e precursors to Fe(III) porphyrins. D e s p i t e much r e c e n t p r o g r e s s i n p o r p h y r i n g e o c h e m i s t r y , t h e r e are several aspects that require further i n v e s t i g a t i o n . i ) The o r i g i n o f t h e e t i o - p o r p h y r i n s h a s n o t b e e n c o n c l u s i v e l y determined. The m a j o r p a t h w a y o f e t i o - p o r p h y r i n e v o l u t i o n i n s e d i m e n t s a p p e a r s t o be o x i d a t i v e i s o c y c l i c - r i n g o p e n i n g o n DPEP precursors during e a r l y d i a g e n e s i s r a t h e r than thermal conversion of DPEP t o e t i o - p o r p h y r i n s . The d e c r e a s e i n t h e D P E P / e t i o r a t i o w i t h i n c r e a s i n g thermal s t r e s s i n sediments or crude o i l s appears to r e s u l t f r o m t h e p r e f e r e n t i a l d e g r a d a t i o n o f DPEP r e l a t i v e t o e t i o porphyrins. This e f f e c t i s g r e a t e r f o r N i ( I I ) porphyrins than f o r V O ( I I ) p o r p h y r i n s . F u r t h e r r e s e a r c h on t h e D P E P - e t i o - p o r p h y r i n


34


r e l a t i o n s h i p i s warranted by the use o f DPEP/etio r a t i o s i n c o r r e l a t i o n , m a t u r i t y , and sedimentary environment r e c o n s t r u c t i o n s t u d i e s . i i ) The r e l a t i o n s h i p between t h e c h e m i s t r y o f t h e d e p o s i t i o n a l environment a n d m e t a l s p e c i a t i o n o f t h eg e o p o r p h y r i n s needs t o be better substantiated. Evidence i n d i c a t e s that h i g h l y reducing, H2Sr i c h , environments favor theformation o f VO(II) porphyrins by i n h i b i t i n g N i ( I I ) porphyrin formation through p r e c i p i t a t i o n o f NiS. The m a j o r f a c t o r s t h a t c o n t r o l m e t a l s p e c i a t i o n , h o w e v e r , h a v e n o t been determined. I n p a r t i c u l a r , r e s e a r c h on t h ee f f e c t s o f m i n e r a l components and o r g a n i c m a t t e r on p o r p h y r i n m e t a l l a t i o n i s needed. i i i ) The f a c t o r s t h a t d e t e r m i n e p o r p h y r i n s t a b i l i t y i n t h e g e o l o g i c a l r e c o r d a r e n o t w e l l known. The mechanisms o f t h e r m a l d e g r a d a t i o n , d e m e t a l l a t i o n ( e i t h e r a c i d c a t a l y z e d o r H2S i n d u c e d ) , t r a n s m e t a l l a t i o n , a n d d e a l k y l a t i o n need t o be determined b o t h f o r porphyrins i n sediments as w e l l a s i n o i l s . Thermodynamic d a t a on i n d i v i d u a l porphyrins are l a r g e l y lacking. iv) Kerogen appears t o p l a y an important r o l e i nthe sequestering o f m e t a l l o - o r free-base porphyrins (or precursors) and i n t h e subsequent r e l e a s e o f m e t a l l o p o r p h y r i n s i n c a t a g e n e s i s . Both N i ( I I ) a n d V O ( I I ) p o r p h y r i n s a r e r e l e a s e d f r o m k e r o g e n s , a s a r e DPEP a n d etio species. The s t a g e o f k e r o g e n e v o l u t i o n a t w h i c h p o r p h y r i n s o r t h e i r p r e c u r s o r s become i n c o r p o r a t e d n e e d s t o b e d e t e r m i n e d . The r e l a t i v e a f f i n i t i e s o f d i f f e r e n t kerogen types f o r the m e t a l l o p o r p h y r i n c l a s s e s a l s o need t o be measured. v) M i n e r a l - p o r p h y r i n i n t e r a c t i o n s have r e c e i v e d l i t t l e a t t e n tion. Evidence e x i s t s t h a t the h i g h l y a c i d i c nature o f s w e l l i n g c l a y surfaces plays a s i g n i f i c a n t r o l e i nporphyrin m e t a l l a t i o n d e m e t a l l a t i o n r e a c t i o n s a n d t h a t s u c h r e a c t i o n s may d e t e r m i n e t h e r e l a t i v e s u r v i v a l s o f d i f f e r e n t metal complexes. Recent work o n t h e mechanisms o f m i n e r a l - o r g a n i c m a t t e r r e a c t i o n s i npetroleum f o r m a t i o n s h o u l d be extended t o p o r p h y r i n - m i n e r a l assemblages. v i ) T h e o r i g i n a n d t h e g e o c h e m i c a l p a t h w a y s o f t h e THBD a n d benzo-porphyrins i n sedimentary sequences a r e , a s y e t , undetermined. I d e n t i f i c a t i o n o f t h e i r precursors and determination o f t h e i r pathways i s o f v a l u e b e c a u s e o f t h e i r p o t e n t i a l f o r u s e i n c o r r e l a t i o n studies. v i i ) D e s p i t e many p u b l i s h e d s t u d i e s , t h e n a t u r e o f " n o n p o r p h y r i n " complexes o f N i ( I I ) and VO(II) i n crude o i l s i s v i r t u a l l y unknown. I d e n t i f i c a t i o n o f these species i nboth o i l s and sourcerock bitumens should p r o v i d e i n f o r m a t i o n on t h egeochemical pathways of non-porphyrin complexes, i f they e x i s t . v i i i ) The v e r y l o w c o n c e n t r a t i o n s o f M ( I I I ) m e t a l l o p o r p h y r i n s i n c o a l s i n d i c a t e s a d e p o s i t i o n a l e n v i r o n m e n t i n w h i c h most o f t h e c h l o r o p h y l l i n p u t h a s been degraded. However, t h e s t r o n g a s s o c i a t i o n of N i ( I I ) and VO(II) porphyrins w i t h o i l shale kerogens i m p l i e s that m e t a l l o p o r p h y r i n s may b e p r e s e n t i n c o a l s i n a b u n d a n c e s m u c h h i g h e r than r e p o r t e d but, because o f t h e i r a s s o c i a t i o n w i t h c o a l macerals, c a n n o t be e x t r a c t e d w i t h c o n v e n t i o n a l s o l v e n t s .

Literature Cited 1. 2.

Corwin, A.H. Proc. 5th World Petroleum Congress 1960, paper V-10, Section V, 119-29, New York. Dunning, H.N. Intern. Series of Monographs on Earth Sciences 1963, 16 (I.A. Breger, cf), 367-430.

1. FILBY AND VAN BERKEL 3. 4. 5. 6.


7. 8. 9. 10. 11. 12. 13. 14. 15. 16. 17. 18. 19. 20. 21. 22. 23. 24. 25. 26. 27. 28. 29. 30. 31. 32. 33. 34.

Overview

35

Hodgson, G.W.; Baker, B . L . ; Peake, E. In "Fundamental Aspects of Petroleum Geochemistry"; Nagy, B. and Colombo, U . , Eds.; Elsevier: Amsterdam, 1967; pp. 197-260. Baker, E.W.; Palmer, S.E. In "The Porphyrins"; Dolphin, D., Ed.; Vol. IA; Academic Press: New York, 1978; pp. 486-552. Baker, E.W.; Louda, J.W. In "Advances in Organic Geochemistry, 1981"; Bjorøy, M., Ed.; John Wiley: London, 1983; pp. 401-21. Maxwell, J . R . ; Quirke, J.M.E.; Eglinton, G. In "Internationales Alfred Treibs Symposium, 1979"; Prashnowsky, A . A . , Ed.; Universitat Wurzburg: Munich, 1980; pp. 37-55. Baker, E.W.; Louda, J.W. In "Biological Markers in the Sedimentary Record"; John, R.B., Ed.; Elsevier: Amsterdam, 1986; pp. 125-225. Chicarelli, I.M.; Kaur, S.; Maxwell, J.R. (this volume). Bonnet, R.; Burke, P . J . ; Czechowski, F. (this volume). Treibs, A. Ann. Chem. 1934, 509, 103-14. Treibs, A. Ann. Chem. 1934, 510, 42-62. Treibs, A. Ann. Chem. 1935, 517, 172-96. Quirke, J.M.E. (this volume). Treibs, A. Angew. Chemie 1936, 49, 682-86. Quirke, J.M.E.; Maxwell, J . R . ; Eglinton, G.; Sanders, J.K.M. Tetrahedron Lett. 1980, 21, 2987-90. Fookes, C.J.R. J . Chem. Soc., Chem. Commun. 1983, 1472-73. Ekstrom, A . ; Fookes, C.J.R.; Hambley, T . ; Loeh, H . J . ; Miller, S.A.; Taylor, J . C . Nature 1983, 206, 173-74. Gold, T . ; Gordon, B . E . ; Streett, W.; Bilson, E . ; Patnaile, P. Geochim. Cosmochim. Acta 1986, 50, 2411-18. Tissot, B.P.; Welte, D.H. "Petroleum Formation and Occurrence," 2nd Ed.; Springer Verlag: Berlin, 1984. Tissot, B.P. Bull. Am. Ass. Petrol. Geol. 1984, 68, 545-63. Durand, B. In "Kerogen"; Durand, B . , Ed.; Editions Technip.: Paris, 1980; pp. 13-34. Baker, E.W.; Louda, J.W. Org. Geochem. 1984, 6, 183-92. Bonnett, R.; Czechowski, F. Nature 1980, 283, 465-67. Bonnett, R.; Czechowski, F. Phil. Trans. Roy. Soc. London Ser. A. 1981, 300, 51-63. Palmer, S.E.; Baker, E.W.; Charney, L . S . ; Louda, J.W. Geochim. Cosmochim. Acta 1982, 46, 1233-41. Bonnett, R.; Burke, P . J . Geochim. Cosmochim. Acta 1985, 49, 1487-89. Ocampo, R.; Callot, H . J . ; Albrecht, P. J . Chem. Soc., Chem. Commun. 1985, 198-200. Ocampo, R.; Callot, H . J . ; Albrecht, P. J . Chem. Soc., Chem. Commun. 1985, 200-201. Ocampo, R.; Callot, H . J . ; Albrecht, P. (this volume). Baker, E.W. J . Am. Chem. Soc. 1966, 88, 2311-15. Baker, E.W.; Yen, T . F . ; Dickie, J . P . ; Rhodes, R . E . ; Clark, L . F . J . Am. Chem. Soc. 1967, 89, 3631-39. Thomas, D.W.; Blumer, M. Geochim. Cosmochim. Acta 1964, 28, 1147-54. Holt, A.S.; Purdie, J.W.; Wasley, J.W.F. Can. J. Chem. 1966, 44, 88-93. Quirke, J.M.E.; Shaw, G . J . ; Soper, P.D.; Maxwell, J.R. Tetrahedron 1980, 35, 3261-67.


36

METAL COMPLEXES IN FOSSIL FUELS

35. Barwise, A . J . G . ; Whitehead, E.V. In "Advances in Organic Geochemistry, 1979"; Maxwell, J . R . ; Douglas, A . G . , Eds.; Pergamon Press: Oxford, 1980; pp. 181-92. 36. Bonnett, R.; Brewer, P.; Noro, K.; Noro, T. J . Chem. Soc., Chem. Commun. 1972, 562-63. 37. Bonnett, R.; Brewer, P.; Noro, K.; Noro, T. Tetrahedron 1978, 34, 379-85. 38. Mackenzie, A.S.; Quirke, J.M.E.; Maxwell, J.R. In "Advances in Organic Geochemistry, 1979"; Maxwell, J . R . ; Douglas, A . G . , Eds.; Pergamon Press: Oxford, 1980; pp. 239-48. 39. Van Berkel, G . J . ; Filby, R.H. In "Geochemical Biomarkers"; Yen, T . F . ; Moldowan, J . M . , Eds.; Gordon and Breach Publishers: London (in press). 40. Van Berkel, G . J . ; Filby, R.H. (this volume). 41. Wolff, G.A.; Murray, M.; Maxwell, J . R . ; Hunter, B.K.; Sanders, J.K.M. J . Chem. Soc., Chem. Commun. 1983, 922-24. 42. Chicarelli, M.I.; Wolff, G.A.; Murray, M.; Maxwell, J.R. Tetrahedron 1984, 40, 4033-39. 43. Ocampo, R.; Callot, H . J . ; Albrecht, P.; Kintzinger, J.P. Tetrahedron Lett. 1984, 25, 2589-92. 44. Fookes, C.J.R. J . Chem. Soc., Chem. Commun. 1983, 474-76. 45. Kaur, S.; Chicarelli, M.I.; Maxwell, J.R. J . Am. Chem. Soc. 1986, 108, 1347-48. 46. Baker, E.W.; Louda, J.W. Org. Geochem. 1986, 10, 904-14. 47. Barwise, A . J . G . ; Roberts, I. Org. Geochem. 1984, 6, 167-76. 48. Quirke, J.M.E.; Yost, R.A.; Britton, E.D.; Trichet, J . In "Geochemical Biomarkers"; Yen, T . F . ; Moldowan, J . M . , Eds.; Gordon and Breach Publishers: London (in press). 49. Strong, D.; Filby, R.H. (this volume). 50. Glebovskaya, E.A.; Volkenstein, M.V. J . Gen. Chem. (USSR) 1948, 18, 1440-51. 51. Didyk, B.M.; Alturki, Y.I.A.; Pillinger, C.T.; Eglinton, G. Nature 1975, 256, 563-65. 52. Burkova, U.N.; Ryadova, O.V.; Serebrennikova, O.V.; Titov, V . I . Geokimiya 1980, 9, 1417-21. 53. Bonnett, R.; Burke, P . J . ; Rezka, A. J . Chem. Soc., Chem. Commun. 1983, 1085-87. 54. Fookes, C.J.R. J . Chem. Soc., Chem. Commun. 1985, 706-8. 55. Shiobara, M.; Taguchi, K. In "Advances in Organic Geochemistry, 1975"; Campos, R.; Coni, J., Eds.; ENADISMA: Madrid, 1977; pp. 237-51. 56. Zellmer, P.P.; Man, E.H. Org. Geochem. 1983, 5, 43-49. 57. Zellmer, P.P.; Man, E.H. Org. Geochem. 1984, 7, 223-29. 58. Palmer, S.E.; Baker, E.W. Science 1978, 201, 49-51. 59. Manskaya, S.M.; Drozdova, T.V. "Geochemistry of Organic Substances"; Pergamon Press: Oxford, 1968. 60. Lewan, M.D.; Maynard, J.B. Geochim. Cosmochim. Acta 1982, 46, 2547-60. 61. Quirke, J.M.E. (this volume). 62. Lewan, M.D. Geochim. Cosmochim. Acta 1984, 48, 2231-38. 63. Moldowan, J . M . ; Sundararaman, P.; Schoell, M. Org. Geochem. 1986, 10, 915-26. 64. Robertson, J.M. J . Chem. Soc. 1936, 1195-1209. 65. Buchler, J.W. In "Porphyrins and Metalloporphyrins"; Smith, K.M., Ed.; Elsevier: Amsterdam, 1975; pp. 157-237.


1. FILBY AND VAN BERKEL Overview

37

66. Johns, W.D. Ann. Rev. Earth Planet Sci. 1979, 7, 183-98. 67. Whitacher, A . H . ; Dyson, P. Oil and Gas J. 1980, 156-66. 68. Tannenbaum, E . ; Kaplan, I.R. Geochim. Cosmochim. Acta 1985, 49, 2589-2604. 69. Tannenbaum, E . ; Kaplan, I.R. Bull. Am. Ass. Petrol. Geol. 1986, 70, 1156-65. 70. Bergaya, F . ; Van Damme, H. Geochim. Cosmochim. Acta 1982, 46, 349-60. 71. Horsefield, B.; Douglas, A.G. Geochim. Cosmochim. Acta 1980, 44, 1119-31. 72. Espitalie, J.; Madec, M.; Tissot, B. Bull. Amer. Ass. Petrol. Geol. 1980, 64, 59-66. 73. Espitalie, J.; Senga Makadi, K.; Trichet, J . In "Advances in Organic Geochemistry, 1983"; Schenk, P.A.; De Loeuw, J.W.; Lijmbach, G.W.M., Eds.; Pergamon Press: Oxford, 1984; pp. 365-82. 74. Spiro, B. Org. Geochem. 1984, 6, 543-59. 75. Jeong, K.M.; Koblynoki, T.P. Prepr. Div. Petrol. Chem. ACS 1983, 28, 209-19. 76. Casagrande, D . J . ; Hodgson, G.W. Nature 1971, 233, 123-24. 77. Casagrande, D . J . ; Hodgson, G.W. Geochim. Cosmochim. Acta 1974, 38, 1745-58. 78. Ikan, R.; Aizenshtat, Z . ; Baedecker, M . J . ; Kaplan, I.R. Geochim. Cosmochim. Acta 1975, 39, 173-85. 79. Barwise, A . J . G . ; Park, P.J.P. In "Advances in Organic Geochemistry, 1981"; Bjorøy, M., Ed.; John Wiley: London, 1983; pp. 668-74. 80. Barwise, A.J.G. (this volume). 81. Rosscup, R . J . ; Bowman, D.N. Prepr. Div. Petrol. Chem. ACS 1967, 12, 77-81. 82. Baker, E.W.; Palmer, S.E.; Huang, W.Y. In "Initial Reports of the Deep Sea Drilling Project-XLI"; Vol. 41; Lancelot, Y . ; Siebold, W., Eds.; U.S. Govt. Printing Office: Washington, 1977; pp. 825-37. 83. Van Berkel, G.J. Ph.D. Dissertation; Department of Chemistry; Washington State University, 1987. 84. Baker, E.W.; Palmer, S.E.; Huang, W.Y.; Rankin, J.G. In "Analytical Chemistry of Liquid Fuel Sources"; Uden, P.C.; Siggia, S.S.; Jensen, H.B. Advances in Chemistry Series No. 170; American Chemical Society: Washington, 1978; pp. 159-80. 85. Erdman, J . G . ; Walter, J . N . ; Wanson, W.E. Div. Petrol. Chem. ACS 1957, 2, 259-67. 86. Riley, K.W.; Saxby, J.D. Chem. Geol. 1982, 37, 265-75. 87. Spiro, B.; Dinur, D.; Aizenshtat, Z. Chem. Geol. 1983, 39, 184-214. 88. Nguyen, S.N.; Filby, R.H. (this volume). 89. Bandurski, E. Energy Sources 1982, 6, 47-66. 90. Philp, R.P.; Gilbert, T.D. Geochim. Cosmochim. Acta 1985, 49, 1421-32. 91. Oehler, J . H . ; Aizenshtat, Z . ; Schopp, W.J. Bull. Amer. Ass. Petrol. Geol. 1974, 58, 124-32. 92. Blumer, M.; Snyder, W.D. Chem. Geol. 1967, 2, 35-45. 93. Blumer, M.; Rudrum, M. J . Inst. Petrol. 1970, 56, 99-106. 94. Durand, B. In "Advances in Organic Geochemistry, 1981"; Bjorøy, M., Ed.; John Wiley: London, 1983; pp. 117-128.


38


95. Leythaeuser, D.; Mackenzie, A . ; Schaefer, R.G.; Bjorøy, M. Bull. Amer. Ass. Petrol. Geol. 1984, 68, 196-219. 96. Chakhmachkev, V.A.; Burkova, V.N.; Zharkov, N . I . ; Punanova, S.A.; Serebrennikova, O.V.; Titov, V . I . Geokhimiya 1985, 381-86. 97. Burkova, V.N.; Serebrennikova, O.V.; Titov, V . I . Geokhimiya 1978, 945-50. 98. Rubinstein, I.; Spyckerelle, C . ; Strausz, O.P. Geochim. Cosmochim. Acta 1979, 43, 1-6. 99. Rubinstein, I.; Strausz, O.P. Geochim. Cosmochim. Acta 1979, 43, 1887-94. 100. Branthaver, J . F . ; Filby, R.H. (this volume). 101. Franceskin, P . J . ; Gonzalez-Jimenez, F . ; La Rosa, M.G.; Abrams, O.; Katan, L. Hyperfine Interact. 1986, 28, 825-8. 102. Hodgson, G.W.; Peake, E . ; Baker, B.L. In "Athabasca Oil Sands: K.A. Clark Volume"; Carrigy, M.A., Ed.; Information Series 45; Research Council of Alberta: Edmonton, 1963; pp. 75-100. 103. Dunning, H.N.; Moore, J.W.; Bieber, N.; Williams, R.B. J . Chem. Eng. Data 1960, 5, 546-9. 104. Yen, T.F. In "Role of Trace Metals in Petroleum"; Yen, T . F . , Ed.; Ann Arbor Science: Ann Arbor, 1975; pp. 1-30. 105. Filby, R.H. In "Role of Trace Metals in Petroleum"; Yen, T . F . , Ed.; Ann Arbor Science: Ann Arbor, 1975; pp. 31-58. 106. Jacobs, F.S. Ph.D. Dissertation; Department of Chemistry; Washington State University, 1982. 107. Didyk, B.; Alturki, Y . I . A . ; Pillinger, C.T.; Eglinton, G. Chem. Geol. 1975, 15, 193-208. 108. Goulon, J.; Retournard, A . ; Frient, P.; Goulon-Ginet, C . ; Berthe, C . ; Muller, J.F.; Poncet, J.L.; Guilard, R.; Escalier, J . C . ; Neff, B. J . Chem. Soc. Dalton Trans. 1984, 1095-1103. 109. Rosscup, R . J . ; Pohlmann, H.P. Preprints Div. Petrol Chem. ACS 1967, 12, A103-109. 110. Branthaver, J . F . ; Wu, G.Y.; Sugihara, J.M. Preprints Div. Petrol. Chem. ACS 1967, 12, A73-75. 111. Sugihara, J . M . ; Branthaver, J . F . ; Wu, G.Y.; Weatherbee, C. Preprints Div. Petrol. Chem. ACS 1970, 15, C5-12. 112. Gransch, J . A . ; Eisma, E. In "Advances in Organic Geochemistry, 1966"; Hobson, G.D.; Speers, G.C., Eds.; Pergamon: Oxford, 1970; pp. 69-86. 113. Hajibrahim, S.K.; Quirke, J.M.E.; Eglinton, G. Chem. Geol. 1981, 32, 173-88. 114. Johnson, J . V . ; Britton, E.D.; Yost, R.A.; Quirke, J.M.E.; Cuesta, L . L . Anal. Chem. 1986, 58, 1325-29. 115. Quirke, J.M.E.; Perez, M.; Britton, E.D.; Yost, R.A. In "Geochemical Biomarkers"; Yen, T . F . ; Moldowan, J . M . , Eds.; Gordon and Breach: London (in press). 116. Hodgson, G.W. Bull. Amer. Ass. Petrol. Geol. 1954, 38, 2537-54. 117. Al-Shahristani, H . ; Al-Atiya, M.J. Geochim. Cosmochim. Acta 1972, 36, 929-37. 118. Saban, M.; Vitorovic, O.; Vitorovic, D. In "Symposium on Characterization of Heavy Crude Oils and Petroleum Residues"; Editions Technip.: Paris, 1984; pp. 122-27. 119. Branthaver, J . F . (this volume). 120. Yen, T . F . ; Silverman, S.R. Preprints Div. Petrol. Chem. ACS 1969, 14, E32-39. 121. Tynan, E . C . ; Yen, T.F. Fuel 1969, 43, 191-208.


1.

FILBY AND VAN BERKEL

Overview

39

122. Yen, T . F . ; Boucher, L.J.; Dickie, J . P . ; Tynan, E . C . ; Vaughan, G.B. J . Inst. Petrol. Geol. 1969, 55, 87-99. 123. Vaughan, G.B.; Tynan, E . C . ; Yen, T.F. Chem. Geol. 1970, 6, 203-19. 124. Palmer, S.E. Abstract, 186th Amer. Chem. Soc. Meeting; Washington, DC, 1983. 125. Bonnett, R.; Czechowski, F. Phil. Trans. Roy. Soc. Lond. A 1981, 300, 51-63. 126. Bonnett, R.; Burke, P . J . ; Czechowski, F . ; Rezka, A. Org. Geochem. 1984, 6, 177-82. 127. Dalton, I.M.; Pringle, W.J.E. Fuel 1962, 42, 41-48. 128. Krauskopf, K.B. Geochim. Cosmochim. Acta 1956, 9, 1-32. 129. Hallbero, R.O.; Bubela, B.; Ferguson, J . Geomicrobiol. J . 1980, 2, 99-113. 130. Saxby, J.D. Rev. Pure. Appl. Chem. 1969, 19, 131-50. 131. Choudhry, G.G. Toxicol. Envir. Chem. 1983, 6, 127-71. 132. Fish, R.H.; Brinckman, F.E. Preprints Div. Petrol. Chem. ACS 1983, 28, 177-80. 133. Jaganathan, J.; Mohan, M.S.; Zingaro, R.A. Fuel 1986, 65, 266-69. 134. Erdman, J . G . ; Harju, P.H. Preprints Div. Petrol. Chem. ACS 1962, 7, 43-56. 135. Tissot, B.P. Bull. Amer. Ass. Petrol. Geol. 1984, 68, 545-63. 136. Yang, Z . ; Li, Y . ; Cheng, Z . ; Zhang, D. In "Geochemical Biomarkers"; Yen, T . F . ; Moldowan, J . M . , Eds.; Gordon and Breach: London (in press). 137. Hoffman, C . F . ; Strausz, O.P. Bull. Amer. Ass. Petrol. Geol. 1986, 70, 1113-28. 138. Shi, J . Y . ; Mackenzie, A.S.; Alexander, R.; Eglinton, G.; Gowar, A.P.; Wolff, G.A.; Maxwell, J.R. Chem. Geol. 1982, 35, 1-31. RECEIVED March 30, 1987

Chapter 2 Sedimentary

Porphyrins:

Unexpected

Structures,

Occurrence, and Possible Origins M. Inês Chicarelli, Surinder Kaur, and James R. Maxwell


Organic Geochemistry Unit, University of Bristol, School of Chemistry, Cantock's Close, Bristol BS8 1TS, United Kingdom

The occurrences of sedimentary porphyrins whose structures have been fully or partially established are reviewed. The compounds range from components with carbon skeletons providing clear evidence of specific precursor chlorophylls to those which are not obviously related to known biological pigments. Three examples from the latter category are reported: a C component from Serpiano o i l shale (Triassic, Monte San Giorgio, Switzerland), containing a fused ring system, and two components (C , C ) from Gilsonite bitumen (Eocene, Utah, U.S.A.), containing a methyl-substituted, five membered exocyclic alkano ring. In addition, evidence is presented that Boscan crude o i l contains extended (> C ) monobenzoporphyrins. 34

32

33

33

In m o l e c u l a r selected before

organic

members

geochemistry,

assignment

of the s t r u c t u r e s of

o f any c l a s s o f b i o l o g i c a l

markers

i s essential

t h e d i s t r i b u t i o n s o f t h e c l a s s i n q u e s t i o n can be used i n an

a p p l i e d sense. Such assignments i n v o l v e e i t h e r s y n t h e s i s o f s u s p e c t e d compounds and c o i n j e c t i o n mass s p e c t r o m e t r y ) isolation (e.g.

with

of individual

using

nuclear

crystallography). compounds then

A

(e.g. using

a sedimentary components magnetic

knowledge

provides

combined

gas chromatography-

fraction

c o n t a i n i n g them, o r

and d i r e c t

resonance

structure analysis

spectroscopy

of the d e t a i l e d

or

structures

a b a s i s f o r : ( i ) understanding

the o r i g i n s

and d i a g e n e t i c pathways i n v o l v e d i n t h e i r f o r m a t i o n , ( i i ) u s i n g

0097-6156/87/0344-0040$08.00/0 © 1987 American Chemical Society

X-ray

of the their

2.

CHICARELLI ET AL.

distributions

41

Sedimentary Porphyrins

f o r correlation

and m a t u r a t i o n

studies,

and

in

p r o v i d i n g i n f o r m a t i o n about d e p o s i t i o n a l environment. To

date,

most

o f the

developments

b i o l o g i c a l marker geochemistry

i n , and a p p l i c a t i o n s

of,

have been a s s o c i a t e d w i t h s t e r o i d s and

t r i t e r p e n o i d s ; t h i s r e s u l t s from a f a i r l y d e t a i l e d knowledge o f t h e i r o r i g i n s and

g e o l o g i c a l f a t e ( 1 ) . D e s p i t e the f a c t t h a t the

of sedimentary these

compounds

geochemical vanadyl

n o t been

very

occurrence

i n the e a r l y

extensively

used

1930's,

i n applied

s t u d i e s . They occur w i d e l y and m a i n l y as n i c k e l - I I and/or ( 2 ) , although

occurrences

example

complexes Publication Date: July 6, 1987 | doi: 10.1021/bk-1987-0344.ch002

p o r p h y r i n s was r e c o g n i s e d

have

complexes

restricted for

alkyl

o f other

manganese-II,

i n coals

generally smaller metal

iron-Ill

c h e l a t e s have (3,4)

and c o p p e r - I I

amounts and more been

reported,

and g a l l i u m - I I I

complexes

(5_>^0

i n immature

oceanic

sediments (7,£). Free base s p e c i e s have a l s o been d e t e c t e d i n o c e a n i c sediments

(9-11)

availability effectively these

and s h a l e s

of efficient

(12,13).

HPLC and ~~*H

In

recent

NMR t e c h n i q u e s

years, the

has c o n t r i b u t e d

t o the s t r u c t u r e e l u c i d a t i o n o f i n d i v i d u a l components o f

complex

mixtures.

HPLC,

used

on an a n a l y t i c a l

scale

(14),

a l l o w s the d i s t r i b u t i o n t o be o b t a i n e d e f f i c i e n t l y and r o u t i n e l y , and the i s o l a t i o n

o f mg amounts o f i n d i v i d u a l

components i n h i g h

purity

when used on a p r e p a r a t i v e s c a l e under normal (15) o r r e v e r s e d phase (16,17) c o n d i t i o n s . "^"H NMR, i n c o n j u n c t i o n w i t h s t u d i e s , has

now become the most i m p o r t a n t

n.O.e. d i f f e r e n c e

and w i d e l y used method o f

s t r u c t u r e assignment. Since

the

first

full

assignments, a

a e t i o p o r p h y r i n s , a C^y ( D partial an

determination

e x o c y c l i c alkano

from

a variety

studies

have

exocyclic

the

concerned

ring,

which

or partly In relation

pigments, these whose

after

carbon

precursors,

(b)

can

mainly

five

have

to origins

probably

an

components. Indeed, the p o r p h y r i n s have now

I , I I and r e f e r e n c e s

related

to selected

skeletons

biological

can

types

of

be r e l a t e d t o

o n l y be r e l a t e d

(d) compounds whose carbon

obviously related

having

of structural

f o u r c a t e g o r i e s : (a) compounds

s p e c i f i c p r e c u r s o r s , (c) compounds which can at p r e s e n t

variety

i n terms o f p r e c u r s o r

compounds whose carbon

s p e c i f i c p r e c u r s o r s , and

(8) w i t h

e l u c i d a t e d . These

components

a wide

(Tables

be d i v i d e d i n t o c a n be

been

with

sedimentary

established

skeletons

C-^ component

s t r u c t u r e s o f a number o f compounds

exhibit

thirty

d e m e t a l l a t i o n , o f two

(2) component (1£>1^)> and the

more r e c e n t l y w i t h f u n c t i o n a l i s e d

fully

therein).

£32

a

o f g e o l o g i c a l samples

s t r u c t u r e s o f more than been

d

(20) o f a d e m e t a l l a t e d ring,

been

alkano

t y p e s , and

n

t o non-

s k e l e t o n s are

not

t o known p r e c u r s o r s . In a d d i t i o n , i t i s

u s e f u l t o d e f i n e another

category

( e ) , c o m p r i s i n g compounds

of a type whereby the s t r u c t u r e which o c c u r s n a t u r a l l y may have been

42


Table

I.

Reported

Occurrences of Individual Alkyl Sedimentary Organic Matter

Occurrence (Structure )

a(l-4,8,9,12 ,13 )

18-21

b(5,8,9,ll,14)

22-24

c(2,8)

25

d(2,4,6,8-10)

26-28

e(7,8**,10**)

29

f(9)

30

g(2**)

4


§

Porphyrin

Reference

§

Porphyrins

Structural (Structure )

in

Type

8-14

15-17

18,19

20,21

b(25 ) §

h(22)

i(23,24)

*

Present

reported +

Occurrence:

shale: N.E.

England;

Parachute and c o a l s , El

Ni(ll)

e)

d)

Monte

Julia

Messel

Creek,

V=0 c o m p l e x e s

(unless

Creek

o i l shale:

o i l shale:

Green

shale:

Basin,

Eocene,

San G i o r g i o ,

River

Eocene,

formation,

see 4 (and r e f . t h e r e i n ) .

Lajjun

Maracaibo

stated

Uinta

Cretaceous, near Uinta

c)

otherwise);

Basin,

Jordan;

Utah, Marl

Toolebuc

Darmstadt,

In t h i s c a s e ,

Upper-Cretaceous,

Basin,

Switzerland;

presented

A s s i g n m e n t by c o m p a r i s o n w i t h

i n this

metal not

i)

b) S e r p i a n o o i l

Boscan

H NMR s p e c t r u m .

Permian

formation,

USA; g)

2 characterised

paper.

literature

USA; Slate:

W. Germany;

Utah,

Venezuela.

§ Structural studies **

and/or

a) G i l s o n i t e bitumen:

Mid-Triassic,

Australia;

h)

as

for simplicity.

crude

f)

shale,

Queensland, Abelsonite:

several

as F e ( I I I )

lignites complex;

o i l : Cretaceous,

CHICARELLI ET AL.

Table

II.

43


Reported

Occurrences of Individual Functionalised in Sedimentary Organic Matter

Occurrence*

Reference

Porphyrin


(Structure)

Structural

Porphyrins

Type

(Structure)

e(26-29,31-35) 9(30)

e(36) c(37,38)

36

*

Reported

as N i ( I I )

characterised + Occurrence:

as

complexes

Fe(III)

only,

and

c , e and g , s e e T a b l e

with

Ga(III) I

37,38

the exception complexes

(38

of

30 w h i c h

and

ref.

h a s been therein).

44


chemically

modified

purification

i n some

procedures.

way as a r e s u l t

Careful

compounds which

may be c a n d i d a t e s

order

confusion

t o avoid

naturally

components occur

for this

between

i n t h e sediment

and a

compounds w i t h i n each c a t e g o r y the

attention a

of the i s o l a t i o n or has

to

category

diagenetic

be

paid

reaction occurring

laboratory reaction.

Examples o f

a r e g i v e n as f o l l o w s . Although

as N i ( I I )

and/or

V=0 complexes

o t h e r w i s e ) , they a r e l i s t e d as t h e f r e e base f o r

to

(artefacts) i n

a l l of

(unless stated

convenience.

Compounds r e l a t e d t o s e l e c t e d p r e c u r s o r types ( T a b l e s I , I I ) This category

i n c l u d e s d e o x o p h y l l o e r y t h r o e t i o p o r p h y r i n ( 8 ) i t s e l f and


i t s C-^ c o u n t e r p a r t sedimentary

alkyl

( 9 ) , which appear t o occur almost

ubiquitously i n

p o r p h y r i n m i x t u r e s and a r e p r o b a b l y

[as the N i ( I I )

and V=0 complexes] t h e two most abundant p o r p h y r i n s i n t h e geosphere, the q u a n t i t i e s p r o b a b l y

f a r outweighing

any b i o l o g i c a l

pigment. They

have been proposed as a r i s i n g from d e f u n c t i o n a l i s a t i o n o f c h l o r o p h y l l £

on t h e b a s i s o f i t s h i g h

s h o u l d be n o t e d , be

additional

precursors

pathways. S i m i l a r (10)

relative

abundance i n t h e b i o s p h e r e . I t

however, t h a t o t h e r c h l o r o p h y l l s ( e . g . 41,42) c o u l d and c o u l d

undergo

compounds i n t h e c a t e g o r y

analogous

degradative

i n c l u d e t h e C-^g analogue

o f 8 and 9 and t h e c a r b o x y l i c a c i d s 26-29,31,32. Other

alkyl

p o r p h y r i n examples a r e r e p r e s e n t e d by a w i d e l y o c c u r r i n g C-^g mono /5H aetioporphyrin 17),

and

(18,19).

( 5 ) , t h e C^*

the In t h e case

and

C31

a

C-^

o f 15-19,

n

d ^39 15,17-butanoporphyrins

(15-

(15^-methyl)-15,17-propanoporphyrins i t has been

proposed

e x o c y c l i c a l k a n o r i n g has formed by way o f a c o n d e n s a t i o n a f u n c t i o n a l i s e d i n t e r m e d i a t e on t h e d e g r a d a t i v e pathway

that the r e a c t i o n of

(23,31-33).

Compounds r e l a t e d t o s p e c i f i c p r e c u r s o r s (Table I , I I ) The carbon s k e l e t o n o f a C-^ mono /5H-13,15-ethanoporphyrin ( 1 1 ) , p r e s e n t i n S e r p i a n o o i l s h a l e m a i n l y as t h e vanadyl complex, has been suggested (24) as a r i s i n g from d e g r a d a t i o n o f c h l o r o p h y l l ID ( 4 0 ) . The o c c u r r e n c e i n Messel s h a l e o f components w i t h a m e t h y l - s u b s t i t u t e d f i v e membered e x o c y c l i c r i n g (20,21) and r e l a t e d a c i d (36) l e d t o t h e s u g g e s t i o n (16,34) o f a d i a g e n e t i c a c i d c a t a l y s e d rearrangement o f an i n t e r m e d i a t e from c h l o r o p h y l l c ( 4 1 ) , which o c c u r s o n l y i n c e r t a i n types o f a l g a e . F u r t h e r e v i d e n c e of a m i c r o b i a l input t o t h i s immature s h a l e by way o f p h o t o s y n t h e t i c b a c t e r i a came from t h e d i s c o v e r y o f t h e h i g h e r ( C - ^ t o C ^ ) p o r p h y r i n a c i d s (33-35; 17). I n t h i s c a s e , t h e r e i s c l e a r e v i d e n c e t h a t t h e sedimentary p r o d u c t s have a r i s e n from b a c t e r i o c h l o r o p h y l l s d ( 4 3 ) .

2.

CHICARELLI ET AL.

45


Compounds r e l a t e d t o n o n - s p e c i f i c p r e c u r s o r s ( T a b l e s I , I I ) Compounds o f t h i s type a r e perhaps best r e p r e s e n t e d by c e r t a i n o f the aetioporphyrins.

Aetioporphyrin

opening

a t some stage i n t h e d e g r a d a t i v e pathway o f the f i v e membered

equally

ring

i n the precursor

apparent,

decarboxylation acid

whose

a ( 3 9 ) , or other

however,

NMR spectrum

indistinguishable

from

or a degradative

that

o f mesoporphyrin

H

chlorophylls,

i t could

product.

have

IX [ 3 0 , i r o n ( I I I ) has been

product

o f cytochromes,

many micro-organisms)

i s

from A di-

properties

isolated

were

as t h e F e ( I I I ) c o u l d be a

s i n c e most organisms

c o n t a i n cytochromes w i t h

It

arisen

complex].

and chromatographic

the l a t t e r

by way o f

complex from c o a l s , and i t was proposed t h a t t h e d i - a c i d diagenetic Publication Date: July 6, 1987 | doi: 10.1021/bk-1987-0344.ch002

(19) a s

from

exocyclic

chlorophyll

I I I (2) has been suggested

arising

(including

s u b s t i t u t e d mesohaem

p r o s t h e t i c groups ( 4 ) . Compounds not o b v i o u s l y r e l a t e d t o known p r e c u r s o r s (Table I ) Two r e c e n t examples e x e m p l i f y so-called

rhodoporphyrins

t h e problem. D e s p i t e t h e f a c t t h a t the

have

been

w i d e l y i n sediments and p e t r o l e u m s , that

t h e two major

porphyrins

(23,24).

exocyclic envisage,

ring

rhodoporphyrins These

found

however,

contain

i n a l l chlorophylls; the suggestion

t o occur

i n Boscan o i l a r e monobenzo[g]-

components

how t h e benzene

c h l o r o p h y l l , although

known f o r many y e a r s

o n l y r e c e n t l y has i t been shown

ring

the five

membered

i t i s difficult

could

arise

of a bacterial

from

origin

to

a known has been

made ( 3 6 ) . Components p o s s i b l y of a r t e f a c t o r i g i n (Table I I ) The

isolation

o f two p o r p h y r i n a l c o h o l s (37,38),

component 37 b e i n g

the h y d r o x y l a t e d c o u n t e r p a r t o f the most abundant a l k y l p o r p h y r i n i n the geosphere, r a i s e s t h e p o s s i b i l i t y the

isolation

possibility exocyclic

procedure

comes ring

from

position

used

t h a t they might be a r t e f a c t s o f

to obtain

the reported

them from

Marl

hydroxylation,

o f a synthesised

slate.

This

a t t h e same

(13^-methyl)-13,15-ethano

p o r p h y r i n when chromatographed on s i l i c a ( 4 0 ) . Present

Study

Apart from reviewing t h e occurrences p o r p h y r i n s r e p o r t e d t o o u r knowledge,

of individual we r e p o r t here

sedimentary structural

46


s t u d i e s o f t h r e e sedimentary

a l k y l p o r p h y r i n s which

appear t o b e l o n g

t o c a t e g o r y (d) as a r e s u l t of t h e i r unusual s t r u c t u r e s , although the p o s s i b i l i t y of t h e i r being artifacts i s also considered. The t h r e e 1 2 components a r e : ( i ) a C-^ (13 -methyl)-13,15-ethano-13 ,17-prop13 (15 )-enoporphyrin

from

S e r p i a n o o i l s h a l e ( c f . Table

I),(ii) a

C-^ and a C-^ (13^-methyl)-13,15-ethano-porphyrin from Gilsonite bitumen (cf_. Table I ) . In a d d i t i o n , p r e l i m i n a r y e v i d e n c e i s p r e s e n t e d that (cf.

the Boscan o i l shown r e c e n t l y t o c o n t a i n monobenzoporphyrins Table I ) c o n t a i n s h i g h e r m o l e c u l a r weight components o f t h i s

t y p e , adding

f u r t h e r c o m p l e x i t y t o u n d e r s t a n d i n g the o r i g i n o f t h e s e


o t h e r c a t e g o r y (d) compounds.

Experimental 1. Methods: Low r e s o l u t i o n mass s p e c t r a were o b t a i n e d , u s i n g the d i r e c t

insertion

probe, on a F i n n i g a n 4000 s p e c t r o m e t e r c o u p l e d t o an INC05 2300 d a t a system.

C o n d i t i o n s : e m i s s i o n c u r r e n t 350uA; i o n i s a t i o n

v o l t a g e 40eV,

s o u r c e 250°C and probe programmed from 90° t o 300°C. High s p e c t r a were r e c o r d e d on a VGMS9 s p e c t r o m e t e r system.

Conditions: ionisation

coupled

v o l t a g e 70eV, s o u r c e

resolution

t o a VG

data

200°C and probe

programmed from 50° t o 250°C; r e s o l u t i o n 10,000; p e r f l u o r o k e r o s e n e as internal reference. H NMR

s p e c t r a l d a t a f o r the i n d i v i d u a l p o r p h y r i n s , as z i n c ( I I )

c h e l a t e s , were o b t a i n e d on a JE0L

and/or

on a

Bruker WH 400 i n s t r u m e n t . Samples were examined i n (CD^)^CfJ/5%

FX200 FT

instrument

C^D^N

or C D /55o C^D^N. C o n c e n t r a t i o n s were t y p i c a l l y 6

of

decoupling

previously High system

using

and

n.O.e.

a

liquid

Spectra

150

solvents similar, programme

s t u d i e s have

chromatography

P h y s i c s SP8700

and Rheodyne 7125 i n j e c t o r . an

LDC

Analytical each

experiments

. Details

been d e s c r i b e d

(22-24). performance

performed using

2-4mg ml

6

1202

Spectromonitor

runs were performed x

4.6

mm)

connected

(HPLC)

analyses

ternary solvent

Detection

(400 nm) was

II variable

wavelength

were

delivery obtained detector.

u s i n g t h r e e columns ( S p h e r i s o r b i n series,

using

a

S3W;

combination

of

as d e s c r i b e d i n 14. The p r e p a r a t i v e - s c a l e c o n d i t i o n s were except

that

there

were

minor

( 1 5 ) , and the a n a l y s e s were

column (250 x 10 mm).

changes

performed

in on

the

solvent

Spherisorb

The components o b t a i n e d were demonstrated

>95% pure by a n a l y t i c a l

HPLC.

S5W

t o be

2.

CHICARELLI ET A L .

2.

Isolation:

The

isolation

47


o f rhodoporphyrins

described previously

from

Boscan

crude

o i l has been

( 3 6 ) . The t o t a l m e t a l l o p o r p h y r i n s were e x t r a c t e d

from S e r p i a n o o i l s h a l e and G i l s o n i t e bitumen a s d e s c r i b e d p r e v i o u s l y (22,23;18).

The i n d i v i d u a l

compounds o b t a i n e d by p r e p a r a t i v e - s c a l e

HPLC were c o n v e r t e d t o t h e i r

z i n c ( I I ) c h e l a t e s and p u r i f i e d

( S i Q ^ g e l G, 5% a c e t o n e / t o l u e n e ) . V o l a t i l e under high-vacuum

(generally

NMR a n a l y s e s . G e n e r a l

impurities

were

by TLC removed

100°C; 10 ^ T o r r ; c a . 5h) p r i o r

spectroscopic properties

to H

o f 2 5 , 12, 13

are

summarised as f o l l o w s : 1

a)

(13 -methyl)-13.15-ethano-3,8-diethyl-2,7,12,18-tetramethyl2

2

13 ,17-prop-13 (15^)-enoporphyrin Publication Date: July 6, 1987 | doi: 10.1021/bk-1987-0344.ch002

C

H

N

r e c

(25):

HRM5:

found

500.2952,

u i r e s

34 36 4 l 500.2944; EIMS(40eV) s i g n i f i c a n t i o n s : 500 ( 1 0 0 % ) , 485 ( 1 9 ) , 250 ( 2 0 ) ; u v / v i s ( C H C 1 ) : X = 512, 548, 582, 639nm; z z i max 9

9

r e l . i n t . 100:17:33:13, Soret 416nm;

H NMR, see t e x t .

1

b)

(13 -methyl)-13,15-ethano-8,17-diethyl-2,3,7,12,18-pentamethyl-

porphyrin EIM5

(12):

HRM5: found

(40eV) s i g n i f i c a n t

ions:

H

476.2946, C 2 3 3

N 6

4

requires

476.2940;

476 ( 1 0 0 % ) , 461 ( 3 5 ) , 448 ( 1 5 ) ,

238

(40) ; u v / v i s ( C H C 1 ) : A = 500, 533, 564, 618nm (IV>11>I>111), 1 z z max Soret 400nm; H NMR, s e e t e x t . c) ( 1 3 - m e t h y l ) - 1 3 , 1 5 - e t h a n o - 3 , 8 , 1 7 - t r i e t h y l - 2 , 7 , 1 2 , 1 8 - t e t r a m e t h y l 9

9

X

1

porphyrin (13):

EIMS (40eV) s i g n i f i c a n t

i o n s : 490 ( 1 0 0 % ) , 475 ( 2 5 ) ,

(40); uv/vis ( C H C 1 ) : A = 500, 532, 565, 618nm ( I V > I I > I > I I I ) , i z z max S o r e t 400nm; H NMR, s e e t e x t . Structural Studies

245

1.

9

9

1

(13 -methyl)-13,15-ethano-3,8-diethyl-2,7,12,18-tetramethyl2

2

13 ,17-prop-13^(15 )-enoporphyrin This mainly

C^H^N^

species

was i s o l a t e d ,

a s t h e V=0 complex),

performance

liquid

corresponds

formally

spectrum i s markedly

(25):

from

chromatography. to a

after

d e m e t a l l a t i o n (present

Serpiano

o i l shale

Although

the molecular

rhodo-type

component,

using

high weight

the electronic

d i f f e r e n t from t h a t expected f o r such a s p e c i e s

(41) . The H NMR spectrum o f t h e Z n ( I I ) complex ( F i g u r e 1; Table I I I ) i n d i c a t e d t h e presence o f 4 /5-methyls, 2 / J - e t h y l s , 1 CH^CH-moiety, 3 meso-H's, 1 o l e f i n i c - H and 2 more - C H 2 - s i g n a l s ( s e e 42 f o r p r e l i m i n a r y r e p o r t ) . Based on t h e r e s u l t s o f t h e s e l e c t i v e d e c o u p l i n g e x p e r i m e n t s , t h e e x o c y c l i c r i n g moiety below c o u l d be proposed:

American Chemical Society. Library

115516th St., N.W. Washington, D.C. 20036


48


10

'

9

7

'

6

'

5

4

2

3

8 (ppm)

Figure

1

1. 200 MHz H NMR

1

spectrum o f ( 1 3 - m e t h v l ) - 1 3 , 1 5 - e t h a n o 2

2

3,8-diethyl-2,7,12,18-tetramethyl-13 ,17-prop-13

(15 )-enoporphy-

rin

indicate

( 2 5 , as

enhancements observed.

zinc

complex)

observed;

i n CDCly

dotted

arrow

Arrows

indicates

weak

n.O.e. n.O.e.

2.

CHICARELLI ET AL.


Table

200

III.

MHz

49


l

H

NMR

da ta

component

for

n ..0 . e .

2 5• ( a s

*

zinc

Code

complex)

i n CDCl-j

A s s i gnment

S(ppm)

Multiplicity

9 . 46

s

n .d .

meso-Ha

H-20

9 . 43

s

n .d .

meso-Hb

H-10

9 . 31

s

3 . 39

meso-Hc

H-5

6 . 73

dd

no i n . 0.6 >.

CH-A

CH-15

4 . 93

bq

2 . 06

CH-B

, , 1 CH-13

• *

3 .9 6 3. 9 0

m

§

9

I *

m

§

h.

43,

9 ., 3 1 ,

3.43

39,

3 ., 2 7 ,

1.70,

3 . 54

d

9. 43,

3. 43

s

n .d .

3 . 3 9§

s

9. 46,

3 . 2 7§

m

n .d .

d

4. 93,

2 ., 0 6 1 ., 7 0

+

+

t

1. , 6 8

+

+

t

*

Chemical

used

in

although 2d),

observed

+

shifts

Figure

where

1

CH-jCH-B

confirmed

b = broad.

9 ,. 3 1 ,

(x2)

2

CH -18

3

3

and d

seen

§ Partially

by d e c o u p l i n g . s = singlet,

when

8

CH CH-B

Ch^CH-13

CH CH 3

2

CH CH -8

CH CH

2

CH CH -3

signal

overlapping

3

irradiated. * * Weak

irradiation

t = triplet,

q =

1

2

3

signals.

++ S i m u l t a n e o u s

d = doublet,

3

?

3

3.90, 3.39

CH -2,7 CH -15^

2

9 • 31,

2

CH -12

CH-j-c

3 .54

3

CH -b

3

ca. 3.94

4

CH CH -8,3

CH -a

CH -D

enhancements

n . d . r not determined,

m = multiplet,

3

2 ,. 0 6

3

and 2 .

2

2

CH CH

3

43,

9

(I -

CH -15

CH -C 1.68

2

1

2

+

Codes

n.O.e., (Figure quartet,


50


D The n.O.e e x p e r i m e n t s l i s t e d i n Table I I I were performed under low power i r r a d i a t i o n t o a l l o w good f r e q u e n c y s e l e c t i v i t y . Some o f them a r e d i s c u s s e d as f o l l o w s ( s e e a l s o F i g u r e 2 ) : ( i ) i r r a d i a t i o n o f CH^-a a t 3.54 ppm caused an enhancement i n meso-H^ a t 9.43 ppm and i n the CH-j d o u b l e t (2.06 ppm), t h u s p r o v i d i n g e x t r a e v i d e n c e f o r the p o s i t i o n o f CH^-a i n r e l a t i o n t o t h e e x o c y c l i c r i n g moiety ( F i g u r e 2 a ) ; ( i i ) i r r a d i a t i o n o f t h e two o v e r l a p p i n g t r i p l e t s (CH^Cr^'s) a t c a . 1.69 ppm enhanced t h e s i g n a l s o f the CH-^Cr^'s, as w e l l as o f t h e o v e r l a p p i n g CH-^-c and CH^-d ( b o t h were enhanced, as i n d i c a t e d by the i n t e n s i t y o f t h e n.O.e.) and t h e meso-H's a t 9.31 (H ) and 9.43 (H. ) —

ppm

(Figure

2d); similar

(r7,Z7,32);

(iii)

irradiation

of

C

connections

irradiation

have

been

a t c a . 3.94

the p a r t i a l l y

overlapping

ppm

D

observed

before

( i . e . simultaneous

CH^CH^

(x2) and

Ch^-C

s i g n a l s ) r e s u l t e d i n enhancements o f t h e s i g n a l s from meso p r o t o n s H and H

c

(9.31 and 9.43 ppm), CH -b (3.43 ppm), CH »s c and d (both a t

b

3

3.39 ppm), CH ~D 2

triplets

(3.27 ppm)

(CH-jCh^'s)

experiment ( i i ) ,

3

and o f t h e two p a r t i a l l y

a t c a . 1.69 ppm

(Figure

overlapping

2 c ) . B e a r i n g i n mind

t h e enhancements o f t h e two m e t h y l s (c + d ) , t h e two

meso-H's and t h e two t r i p l e t s were a t t r i b u t e d t o c o n n e c t i o n s w i t h t h e two methylenes CH^-D

were

a t 3.90 ppm, w h i l e

attributed

eliminate p o s s i b i l i t i e s the

to

These

results

o f s t r u c t u r e s w i t h two e t h y l groups

flanking

same meso-H, o r w i t h

ring;

(iv) irradiation

t h e enhancements o f t h e CH-^-b and

irradiation

two e t h y l s

o f meso-H

of

CH -C. 2

a t t a c h e d t o t h e same

pyrrole

a t 9.31 ppm c o n f i r m e d t h e s p a c i a l

c o n n e c t i o n s w i t h CH^-c ( o r d) and a CH-^CH,^ group. Thus, s t r u c t u r e examined

25 c o u l d

be a s s i g n e d . The component

was

by mass s p e c t r o m e t r y under c h e m i c a l i o n i s a t i o n , u s i n g H

reagent g a s ; the spectrum

i s compatible with

the proposed

also 2

as

structure

(23). 1

2. ( 1 3 - m e t h y l ) - 1 3 , 1 5 - e t h a n o - 8 , 1 7 - d i e t h y l - 2 , 3 , 7 , 1 2 , 1 8 - p e n t a m e t h y l p o r p h y r i n (12) and C-^ c o u n t e r p a r t ( 1 3 ) : These components, i s o l a t e d as t h e f r e e bases from G i l s o n i t e bitumen, i n which they o c c u r as the N i ( I I ) complexes, where examined by NMR

CHICARELLI ET AL.


51


2.

F i g u r e 2. Examples o f n.O.e. e x p e r i m e n t s performed on component 25 ( a s z i n c complex) i n C D C l y The i n s e r t i n (a) shows t h e expanded meso-H r e g i o n o f t h e normal spectrum; i n ( c ) they show expanded r e g i o n s o f t h e normal spectrum ( t o p ) and o f t h e n.O.e. d i f f e r e n c e spectrum ( b o t t o m ) . Arrows i n d i c a t e n.O.e. enhancements observed. A s t e r i s k i n d i c a t e s point of i r r a d i a t i o n .

52


at 200

and 400

MHz

i n two d i f f e r e n t

solvents

[(CD ) C0/5£ C ^ N 3

and

2

C^D^/5% C^D^N]. The s p e c t r a of 12 ( e . g . F i g u r e 3) showed the presence of 5 0 - m e t h y l s , 2 0 - e t h y l s and the e x o c y c l i c I V ) . The

ring

was

3 meso-H's. The

determined

by

-CH^HChy- moiety i n

decoupling experiments (Table

a p p r o p r i a t e n.O.e. s t u d i e s were performed and the r e s u l t i n g

c o n n e c t i o n s between / J - s u b s t i t u e n t s and meso-protons The very

H NMR

similar

absence

to

of

the

C-^

a t ca_.

4.12

2

and

not shown] were

c o u n t e r p a r t 12,

1.94

ppm ppm

except

f o r the

(CH^-3) which was

replaced

( C H C H ~ 3 ) . In summary, the 3

2

c o n n e c t i o n s between the 4 ^ - m e t h y l s , 3 / S - e t h y l s , 3 meso-H's and

the

-CH CHCH -

12,

2

moiety

3

establishing Publication Date: July 6, 1987 | doi: 10.1021/bk-1987-0344.ch002

those

of the resonance a t c a . 3.56

by resonances

were e s t a b l i s h e d .

s p e c t r a of 13 [as z i n c ( I I ) complex;

the

were

obtained

compound

as

in

the

same

way

as

for

(13^-methyl)-13,15-ethano-2,8,17-tri-

e t h y l - 2,7,12,18-tetramethylporphyrin. It

is

noteworthy

that

the

C^

compound

2

(12)

was

isolated

p r e v i o u s l y from G i l s o n i t e bitumen and the s t r u c t u r e g i v e n as 44 ( 4 3 ) . U n f o r t u n a t e l y , t h a t sample

was

isolated

p u r i t y and q u a n t i t y ; a l s o , the CH^ a residual

p r o t o n resonance

f o r ^"H NMR

a t C-13

[ v i z . of

1

studies

i n lower

i s masked i n (CD-^CO by

(CH-^CO i m p u r i t y ] and

l e d to

assignment of the methyl s u b s t i t u t e d , f i v e membered e x o c y c l i c r i n g a s i x membered than

one

ring.

solvent

T h i s emphasises

f o r "^H

NMR

the

importance

analyses of

f o s s i l p o r p h y r i n s which can be i s o l a t e d

the

of

small

using

quantities

oil:

A sequence

on

of p r o c e d u r e s

allowed

and

isolation

involving

HPLC u s i n g of a

flash

normal

variety

of

of

conveniently.

3. High m o l e c u l a r weight b e n z o p o r p h y r i n s from Boscan crude

demetallation

as

more

and

chromatography r e v e r s e d phase

fractions

enriched

silica,

conditions

i n porphyrins

showing rhodo-type c h a r a c t e r i s t i c s (36; see a l s o r e f e r e n c e s t h e r e i n ) . Reversed phase

HPLC then a f f o r d e d

the two

t y p e , which were a s s i g n e d i n the u s u a l way having

structures

rhodo-type

23

uv/visible

and

24

was

C^g,

m o l e c u l a r weight with

molecular

monobenzoporphyrins

benzene

ring,

(>

ions

a

fraction

(Figure t o be

4a).

corresponding

with

clear

that

suggesting i n d i r e c t l y

beyond C-^ are a l s o monobenzoporphyrins

from

the C-^ that

the

(44).

this

a

concentrated i n

C-^^), e x t e n d i n g t o

components i s o l a t e d

i t i s already

this

Electron at

least

formally

w i t h an e x o c y c l i c a l k a n o r i n g ( F i g u r e 4 b ) .

s t u d i e s of i n d i v i d u a l p r o g r e s s but

obtained

the f r a c t i o n

components

components o f

monobenzo[g]porphyrins,

( 3 6 ) . In a d d i t i o n ,

spectrum

impact mass s p e c t r o m e t r y showed higher

major as

fraction

to H

NMR

are i n

component c o n t a i n s

a

components e x t e n d i n g

1

'

1

' I '/ 102

l

/ > » • i • • ' |' • ' 5b 1

' ' 1

1

6

6

b (ppm)

' • '' |' ' ' • 50 1

' ' ' ' ' » ' ! '' 45

1

3

2

• ' '' ' ' ' • ' I 40

1

» '

1

' ''' ' ' ' 35

1

Figure 3. 400 MHz H NMR spectrum of (lS^methylJ-l 3,15-ethano-8,17-diethyl-2,3,7,l 2,18pentamethylporphyrin (12, as zinc complex) in C D /5% C D N; arrows indicate n.O.E. enhancements observed. Inserts: (a) expansion of the exocyclic ring protons; (b) alter irradiation of C H C H at 4.118 ppm to decouple the C H C H at 1.937 ppm.

1

I • • • • ' I 104 103


[/ 20

/

1

i 18

' f 16

' i


Table

IV.

400

MHz

H NMR

data

for

component

C D /5£ 6


S

(ppm)

Multiplicity

12

5

*

n.O.e.

s

1 0 ., 323

s

3. 6 8 7 ,

( 3.628 ,

1 0 ., 2 1 5

s

3 ., 5 6 4 ,

3.556

dd(o

A B

4 ,. 9 1 9

dd(3

B C

( 3 . 687 ) , §

16 . 6 , 6. 4,

3

4 . 502

BC m

4.919

zinc

complex)

+

3.628,

Assignment

meso

3.590 3.590 )

8

H-20

meso

H-10

meso

H-5

4 ., 9 1 9

CH (A)-13

2

n ., d .

CH (B)-13

2

2

4.502)

16 . 6 , 2. 2,

5.653

2

4.502) n ., d .

4 .. 1 1 8

q(7.7,

3 .. 9 8 6

q(7.7,

1 . 778)

3 ., 6 8 7

d(1.0,

4 . 502 )

1 . 937 )

CH CH(C)-13 3

1 0 .. 323 , 3 .628 , 1 0 .. 3 2 3 ,

3.564,

CH CH -8

1.937

2

3

1.778

CH CH -17

1 .963

CH -12

2

3

3

3, . 6 2 8

s

1 0 ,. 3 2 9

CH -18

3 . 590

s

1 0 ,. 3 2 9

CH -2

3 . 564

s

1 0 ,. 2 1 5

CH -7

1 0 ,. 2 1 5

CH -3

3 .556

s

**

in

5

1 0 . 329

5 ., 6 5 3

(as

C D N

6

3

3

3

3

d(7.1,

4 . 502)

n

.d.

CH^H-13

1 .937**

t(7.7,

4 . 118)

n

.d.

CH CH -8

1 .778

t(7.7,

3 . 986 )

n

.d.

CH CH -17

1 .963

*

3

when

Hz, S

partial

S coupled

signal

nuclei.

irradiated.

s a t u r a t i o n of

+

3

3

Chemical

§ Weak

shifts

enhancement

c l o s e meso-H. * *

Partially

where also

enhancements observed

overlapping

due

signals.

1

2

2

seen to

1

2.

CHICARELLI ET AL.

n


0.4


F i g u r e 4. U V / v i s i b l e (a) and EI probe mass (b) s p e c t r a l a

demetallated

chromatographic

fraction

isolated

crude o i l , and e n r i c h e d i n h i g h m o l e c u l a r weight

from

data f o r Boscan

benzoporphyrins.

56


Origin

Considerations

It i s d i f f i c u l t having

the

since

no

to r a t i o n a l i s e

unusual known

this

dietary

study

feature, of

a

origin fused

25

i t s presence (45).

in

It

such

of

precursor

although

presence

being is

Serpiano

transformation the

f o r the a

of

the

On

shale

C-13"*"

that

reflects

the

fossil

methyl

other chlorin

metabolism

therefore,

also

in

(25),

the

i n a sponge o f a

a t t r i b u t e d to

pigments

component

moiety

feature.

possible,

oil

Serpiano

exocyclic ring

showed the o c c u r r e n c e

chlorophyll

presence

an

of

c h l o r o p h y l l contains

hand, a r e c e n t with

feature

of the

metabolic

water

column,

substituent

is

a

complicating factor. Publication Date: July 6, 1987 | doi: 10.1021/bk-1987-0344.ch002

The a l s o be

possibility considered,

condensation

of

a

of

this

C-^

porphyrin

f o r i n s t a n c e , by compound

such

way

as

being

of

45,

an

an

artefact

unexpected

during

the

can

internal

treatment

with

methanesulphonic a c i d , a f t e r the F r i e d e l - C r a f t s a c e t y l a t i o n procedure employed f o r s e p a r a t i o n of components w i t h a /5H s u b s t i t u e n t from

co-

occurring

[as

the

solely

the

fully

copper(II)

alkylated species

complex] w i t h

deacetylated

counterpart

detect

compound

this

component w i t h

the

compound i s not total

porphyrins

the

after

(after

HPLC procedure s i m i l a r of

Such

sedimentary problems

a

that

vanadyl which

(23).

the

The

failure

prove t h a t

possibility

C-^

C^^

the

C-^

in

the

could

be

complex i n the

would

be

developed be

to

monoacetylated

porphyrins

might

45

unknown p o r p h y r i n

This

search

to

15

does not

by s e a r c h i n g f o r the vanadyl

metalloporphyrins.

any

of

demetallation).

of

acid afforded

base

a r t e f a c t formed from an

Serpiano

eliminate

free

treatment

u s i n g an separation

Treatment

methanesulphonic as

seven membered r i n g

an

e a s i l y excluded

(24,32).

total

facilitated

by

recently for (46),

and

associated

the

would

with

the

(12,13) s h a r e

with

demetallation procedure. The

two

demetallated

the d e m e t a l l a t e d of a methyl has

not

the

a precursor

Messel

with a

s u b s t i t u e n t at

been r e p o r t e d

c o u l d be

o i l shale

five

at C-15

Gilsonite

f u s e d r i n g Serpiano

porphyrins

component the s t r u c t u r a l

C-13*. As

i n any

i n d i c a t e d above, t h i s

biological

the

feature

t e t r a p y r r o l e pigment

f o r the sedimentary compounds. The of

feature

n i c k e l ( I I ) complex

of

a

which

discovery C-^

in

component

membered e x o c y c l i c r i n g c o n t a i n i n g a methyl s u b s t i t u e n t

l e d t o the s u g g e s t i o n

of an a c i d - c a t a l y s e d rearrangement o f

a d i a g e n e t i c product

of c h l o r o p h y l l c f o r the o r i g i n of the e x o c y c l i c

ring

this

(340 • B e a r i n g

Gilsonite

porphyrins

structures

such

represented

as f o l l o w s :

as

in

being the

mind,

one

formed

in

Gilsonite

could C^

an

perhaps

analogous compound

envisage way

which

to can

the give be

2.

C H I C A R E L L I ET A L .


Messel C-^ component The

G i l s o n i t e C-^ component

G i l s o n i t e component r e p r e s e n t e d

/J-ethyl s u b s t i t u e n t

i n any

c o n d e n s a t i o n r e a c t i o n proposed (34) i n the Messel component would not absence o f any o t h e r

component and because

i n t h i s way has,

i n a p o s i t i o n ( i . e . at C-2)

ethyl or vinyl substituent

the

57


the two

biological

however, a

not known t o have an

tetrapyrrole; also,

the

t o account f o r the e x o c y c l i c r i n g leave a C

information,

2

substituent

i t appears t h a t

a t C-13. I n the

Serpiano

G i l s o n i t e components may be r e l a t e d i n some way

o f t h e methyl

substituent

a t C-13

.

Indeed,

the

two

s t r u c t u r a l t y p e s c o u l d even have a common p r e c u r s o r : R

Precursor Tetrapyrrole

As

indicated

rearrangement

earlier,

i t i s difficult

o f a known c h l o r o p h y l l which

monobenzo[g]-porphyrins

23 and 24, a l t h o u g h

could

to give

propose rise

the p o s s i b i l i t y

to

a the

of a

58


bacterial

origin

for

their

precursor

has

been

suggested

f u r t h e r c o m p l e x i t y i s added by the p r e l i m i n a r y e v i d e n c e a

pseudo-homologous

least

C}g>

series

i . e . components

of

such

with

components

several

S t r u c t u r a l s t u d i e s of the components > C-^ additional about

the

alkylation. origin

of

This the

may

provide

extending

additional

(36).

A

that there i s up

carbon

to

at

atoms.

s h o u l d r e v e a l the s i t e s of further information

monobenzo[g]porphyrins

or

either

about

the

d e g r a d a t i v e pathways g i v i n g r i s e to them.


Wider Geochemical C o n s i d e r a t i o n s Although i t i s d i f f i c u l t a t p r e s e n t to e n v i s a g e p l a u s i b l e o r i g i n s f o r some o f the sedimentary p o r p h y r i n s t r u c t u r e s now known, a knowledge of the s t r u c t u r e s of as many of the sedimentary components as p o s s i b l e s t i l l p r o v i d e s a more r e l i a b l e f o u n d a t i o n f o r comparative s t u d i e s of the o v e r a l l d i s t r i b u t i o n s i n d i f f e r e n t samples. For example, i t i s w e l l known from the d i s t r i b u t i o n s o b t a i n e d by HPLC t h a t the abundance of components w i t h an e x o c y c l i c a l k a n o ring relative to their aetioporphyrin counterparts decreases with i n c r e a s i n g e x t e n t of m a t u r a t i o n (47-50). T h i s concept i s r e a d i l y i l l u s t r a t e d i n F i g u r e 5, which shows the HPLC d i s t r i b u t i o n s of the demetallated porphyrins reported previously for four unrelated samples (21,23,50,51). Two o f the samples have been used e x t e n s i v e l y to p r o v i d e i n d i v i d u a l sedimentary p o r p h y r i n s f o r s t r u c t u r a l s t u d i e s ( T a b l e s I , I I ) : (a) G i l s o n i t e bitumen of Eocene age from the U i n t a B a s i n (USA); the d e p o s i t i o n a l environment of the source rock of t h i s sample i s thought t o have been l a c u s t r i n e and s t r o n g l y s a l i n e ( 5 2 ) . (b) Serpiano o i l shale, Triassic, from Monte San Giorgio, S w i t z e r l a n d , w i t h an e n c l o s e d marine d e p o s i t i o n a l environment. The o t h e r two samples a r e : (c) Guang-33 o i l , an immature o i l s h a l e of Eocene age from Jiangham s a l t l a k e b a s i n ( c e n t r a l - e a s t e r n C h i n a , Hubei P r o v i n c e ; 5 3 ) . (d) An immature sample of Kimmeridge c l a y of J u r a s s i c age from mainland U.K., from a s h a l l o w marine d e p o s i t i o n a l environment ( 5 0 ) . The p o r p h y r i n d i s t r i b u t i o n i n G i l s o n i t e bitumen i s more mature than the o t h e r t h r e e samples i n h a v i n g a h i g h e r abundance of a e t i o p o r p h y r i n s , which e l u t e w i t h r e t e n t i o n times l e s s than 32 minutes. Interestingly, the second most abundant component i n Gilsonite, the C-^ component w i t h the methyl substituted five membered e x o c y c l i c r i n g (12) has been c h a r a c t e r i s e d i n Guang33 o i l by comparison o f s p e c t r a l d a t a , and co-chromatography w i t h the component i s o l a t e d from G i l s o n i t e ( 5 1 ) , a l t h o u g h the s t r u c t u r e of the component was p r e v i o u s l y g i v e n i n c o r r e c t l y as 44 ( 4 3 ) . I t i s noteworthy t h a t i t

b)

30

30

(ENCLOSED MARINE)

SERPIANO SHALE:

20

(STRONGLY SALINE LACUSTRINE)

GILSONITE B I T U M E N :

JjJ

\ 40

A

40

OIL:

30

( S T R O N G L Y SALINE LACUSTRINE)

GUANG

T i m e (min)-

20

(SHALLOW

MARINE)

(j) KIMMERIDGE CLAY:

20

C)

30

12

40

Figure 5. High-performance liquid chromatograms of the total porphyrins (after demetallation) from four unrelated geological samples.

Q)

CL

a)



1: R " 2

= CH , R

8

2: R ' ' ' 1

3

5

2

= CH ,R ' ' '

= C H ^ ,R

9

= H

= CH , R ' '

6

= CH CH

9

= H or

4

6

3

3a: R ' ' ' ' 3b: R ' ' "

= CH ,R ' '

4

2

3c:

5

4

6

R " ' 2

7

5

8

4a: R " ' "

5

3

1

= CH , R

= CH CH , R

!

3

3

,

5

C H

5

'

,

9

CH CH , R

3

5

4

7

3

7

= CH , R '

6

CH , R

2

R

C H

.,2,5,7

R R

R

4,6

]

=

CH CH 2

1.2,4,7

3

3

4

R

=

CH ,

R

!

=

CH , 3

=

2

R '

5

R

6,8

R

6,8

R

6,8

3

- CH CH , ?

6,8

3

CH CH , 2

3

R

3

= CH CH , 2

3,5

3

1.3,4,7

CH CH , 2

3

=H

3

CH CH ?

=

3'

CH , R '

=H

3

2,4,6

2,4

=H

CH^CH,, R ~- H T " 3 ' 3,8 _ CH CH , R 2

= CH , R

, 3 , 5 , 7 __

8

3

3

1

8

3

6

2 , 8

2,4,6

CH,, R

2

= CH CH , R

3

1,3,5,7,

R '

3

- CH CH , R

3

1-3,5,7,

= CH CH ,

2

R '

y

3

2

4 , 6

6

4

3

D

- CH , R '

4

6,9

7 6 9 CH CH , R ^ ' ' =H ?

2

=H

9

3

2

4,7

CH , R '

H or

9

3

2

3

8

=H

9

3

CH CH , R

2,4,7

CH , R

1,5,7

13: R

I4d:

4,7

3

10: R ' ' '

14c:

2

3

CH , R

8

1,3,5,7

1

14b:

CH CH , R 2

R

1-3,5,7 9: R

14a:

6

= H or

9

3

7

2

3

7: R '

12: R

?

= H or

9

3

= CH CH , R

4 , 8

R

3 >

= CH CH , R ?

7

3

6: R ' ' '

11: R

6

2

= CH , R ' '

1,3,5,8 1

8: R

5

3

5

4b: R 1 - 3 . 5 . 6 , 8 5: R

3

3

7

3

3

1

8

1

3

3

3d: R ' " ' 1

1

= CH , R ' '

8

=H

7

2

8

9

3

8

2


= CH CH , R

1

3

3

= H or = H or = H cr -- H


CHICARELLI ET AL. Sedimentary Porphyrins


62 M E T A L C O M P L E X E S IN FOSSIL F U E L S


CHICARELLI ET AL. Sedimentary Porphyrins

64


does not o c c u r i n e i t h e r o f the two marine samples; i t s presence i n two samples from lacustrine, strongly saline depositional environments s u g g e s t s t h a t i t might be a s s o c i a t e d w i t h such a type o f environment. F u r t h e r s t u d i e s o f the p o r p h y r i n d i s t r i b u t i o n s from a wide variety of samples a r e n e c e s s a r y t o show whether these d i s t r i b u t i o n s c a n , i n d e e d , p r o v i d e i n f o r m a t i o n about d e p o s i t i o n a l environments. Conclusions 1.

The

number


emphasises in

of

sedimentary

porphyrin structures

now

elucidated

the remarkable c o m p l e x i t y o f the m i x t u r e s which can o c c u r

sediments

and

petroleums.

This

complexity

arises

from

the

v a r i a t i o n s which can o c c u r i n the d i a g e n e t i c r e a c t i o n s which a l t e r variety

of

precursors,

s t r u c t u r e s of s e v e r a l

mainly

of the compounds cannot

r e l a t e d t o known b i o l o g i c a l 2.

The

determination

correcting has

only

chlorophylls.

addition,

a t p r e s e n t be

a

the easily

pigments.

of

three

novel

a p r e v i o u s misassignment been found

In

to date

structures

f o r one

is

described,

o f them. T h i s component

i n high r e l a t i v e

abundance

in

samples

from l a c u s t r i n e , s t r o n g l y s a l i n e , d e p o s i t i o n a l environments. 3.

Although p o s s i b l e

clear,

a

knowledge

comparison

of

the

origins of

o f many o f the compounds a r e not

their

structures

distributions

obtained

yet

provides

more

effective

by

from

different

HPLC

sediments and p e t r o l e u m s . 4. In o r d e r t o u n d e r s t a n d the o r i g i n s of the more unusual s e d i m e n t a r y components and

the d e g r a d a t i v e pathways l e a d i n g

t o them,

structural

e l u c i d a t i o n work s i m i l a r t o t h a t d e s c r i b e d and reviewed h e r e i n s h o u l d be

applied

samples

and

to

components

from

those examined

older

isolated

samples

with

from

contemporary

a milder

sedimentary

thermal h i s t o r y

than

t o date ( T a b l e I , I I ) .

Acknowledgments We a r e g r a t e f u l t o the B r i t i s h P e t r o l e u m p i c and the N a t u r a l Environment Research C o u n c i l (GR3/2951 and GR3/3758) f o r p r o v i d i n g HPLC and MS f a c i l i t i e s , r e s p e c t i v e l y . Two o f us thank the B r a z i l i a n N a t i o n a l Research C o u n c i l , CNPq (M.I.C.) and the N a t u r a l Environment Research C o u n c i l (S.K.) r e s p e c t i v e l y f o r Research S t u d e n t s h i p s . D r s . M. Murray (University of B r i s t o l ) , 0. Howarth and E. Curzon ( U n i v e r s i t y of Warwick) a r e g r a t e f u l l y acknowledged f o r r u n n i n g NMR s p e c t r a and Dr. T. Peakman f o r v a l u a b l e d i s c u s s i o n s . Dr. K.A.G.

2.

C H I C A R E L L I ET AL.


65

MacNeil ( U n i v e r s i t y o f B r i s t o l ) i s thanked f o r HRMS a n a l y s e s , and R. Pitt f o r assistance with the i s o l a t i o n o f t h e two G i l s o n i t e porphyrins.

Literature Cited


1. For example: Ourisson, G.; Albrecht, P.; Rohmer, M. Pure and Appl. Chem. 1979, 51,709-29; Mackenzie, A.S.; Brassell, S.C.; Eglinton, G.; Maxwell, J.R. Science 1982, 217, 491-504; Brassell, S.C.; Eglinton, G; Maxwell, J.R. Biochem. Soc. Trans. 1984, 57586; and references therein. 2. For example: Maxwell, J.R.; Quirke, J.M.E.; Eglinton, G. In "Internationales Alfred-Treibs-Symposium 1979"; Prashnowsky, A.A., Ed.; Universität Würzburg, Munich, 1980; pp. 37-55; and references therein. 3. Bonnett, R.; Czechowski, F. Phil. Trans. R. Soc. Lond. Ser. A, 1981, 300, 51-63 4. Bonnett, R.; Burke, P . J . ; Reszka, A. J . Chem. Soc., Chem. Commun. 1983, 1085-87 5. Bonnett, R.; Czeckowski, F. Nature 1980, 283, 465-67 6. Bonnett, R.; Czeckowski, F. J . Chem. Soc., Perkin Trans. I, 1984, 125-31 7. Palmer, S.E.; Baker, E.W. Science 1978, 201, 49-51 8. Louda, J.W; Baker, E.W. In "Initial Reports of the Deep Sea Drilling Project"; Yeats, R.S.; Haq, B.U. and the Shipboard Party, Ed.; U.S. Government Printing Office: Washington, 1981; vol. 63, pp. 785-818 9. Palmer, S.E.; Huang, W.Y.; Baker, E.W. In "Initial Reports of the Deep Sea Drilling Project-XLIIIL"; Tucholke, B . E . ; Vogt, P.R. and the Shipboard Party, Ed.; U.S. Government Printing Office: Washington, 1979; vol. 43, pp. 657-61 10. Baker, E.W.; Louda, J.W. In "Advances in Organic Geochemistry 1981"; Bjorøy, M. et a l . , Ed.; J . Wiley & Sons, Chichester 1983, pp. 401-21 11. Baker, E.W.; Louda, J.W. In "Advances in Organic Geochemistry 1985", Julich, in press 12. Treibs, A. Angew. Chem. 1936, 49, 682-86 13. Regtop, R.; Crisp, P.T.; E l l i s , J . Proc. 1st. Australian Workshop on Oil Shale 1983,73-5 14. Barwise, A.J.G.; Evershed, R.P.; Wolff, G.A.; Eglinton, G.; Maxwell, J.R. J . Chromatogr. 1986, 368, 1-9; and references therein. 15. Chicarelli, M.I.; Wolff, G.A.; Maxwell, J.R. J . Chromatogr. 1986, 368, 11-19; and references therein.

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16. Ocampo, Commun. 17. Ocampo, Commun.


R.; 1985, R.; 1985,

Callot, H.J.; Albrecht, P. J. 189-200 Callot, H.J.; Albrecht, P. J. 200-01; and references therein.

18. Quirke, J.M.E.; Eglinton, G.; Maxwell, 1979, 101, 7693-97

J.R.

Chem. Soc., Chem. Chem. Soc., Chem. J.

Am. Chem. Soc.


19. Quirke, J.M.E.; Maxwell, J.R. Tetrahedron 1980, 36, 3453-56 20. Quirke, J.M.E.; Maxwell, J.R.; Eglinton, G.; Sanders, J.K.M. Tetrahedron Lett. 1980, 21, 2987-90 21. Wolff, G.A. Ph. D. Thesis, University of Bristol, Bristol, 1983 22. Chicarelli, M.I.; Wolff, G.A.; Maxwell, J.R. J. Chem. Soc., Chem. Commun. 1985, 723-24 23. Chicarelli, M.I. Ph. D. Thesis, University of Bristol, Bristol, 1985 24. Chicarelli, M.I.; Maxwell, J.R. Tetrahedron Lett. 1984, 25, 470104 25. Krane, J.; Skjetne, T . ; Telnaes, Tetrahedron 1983, 39, 4109-19

N.; Bjorøy,

M.; S o l l i , H.

26. Fookes, C.J.R. J. Chem. Soc., Chem. Commun. 1985, 706-08 27. Fookes, C.J.R. J. Chem. Soc., Chem. Commun. 1983, 1472-73 28. Ekstrom, A.; Fookes, C.J.R.; Hambley, T . ; Loeh, H . J . ; Miller, S.A.; Taylor, J.C. Nature 1983, 206, 173-174 29. Ocampo, R. Thesis Docteur ès Sciences, U n i v e r s i t éLouis Pasteur de Strasbourg, Strasbourg, 1985 30. Storm, C.B.; Krane, J.; Skjetne, T.; Telnaes, N.; Branthaver, J . F . ; Baker, E.W. Science 1984, 233, 1075-76 31. Wolff, G.A.; Murray, M.; Maxwell, J.R.; Hunter, B.K.; Sanders, J.K.M. J. Chem. Soc., Chem. Commun. 1983, 922-24 32. Chicarelli, M.I.; Wolff, G.A.; Murray, M.; Maxwell, J.R. Tetrahedron 1984, 40, 4033-39 33. Fookes, C.J.R. J. Chem. Soc., Chem. Commun. 1983, 1474-76 34. Ocampo, R.; Callot, H.J.; Albrecht, P.; Kintzinger, J.P. Tetrahedron Lett. 1984, 25, 2589-92 35. Barwise, A.J.G.; Roberts, I. Org. Geochem. 1984, 6, 167-76 36. Kaur, S.; Chicarelli, M.I.; Maxwell, J.R. J. Am. Chem. Soc. 1986, 108, 1347-48 37. Habermehl, G.G.; Springer, G.; Frank, M.H. Naturwissenschaften 1984, 71, 261-63 38. Bonnett, R.; Burke, J.P. In this volume; and references therein 39. Krane, J.; Skjetne, T.; Telnaes, N.; Bjorøy, M.; Schou, L . ; S o l l i , H. Org. Geochem. 1984, 6, 193-201

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40. Ponomarev, G.V.; Shul'ga, A.M. Khim. Geterotsikl. Soedin. 1984, 19, 485-89; Chem. Abstr. 1984, 101, 110796a 41. Baker, E.W.; Palmer, S.E. In "The Porphyrins"; Dolphin, D., Ed.; Academic Press, New York, 1978; vol. IA, pp. 485-551 42. Chicarelli, M.I.; Maxwell, J.R. Tetrahedron Lett. 1986, 27, 465354


43. Wolff, G.A.; Chicarelli, M.I.; Shaw, G . J . ; Evershed, R.P.; Quirke, J.M.E.; Maxwell, J.R. Tetrahedron 1984, 40, 3777-86 44. Kaur, S., unpublished data 45. Karuso, P.; Bergquist, P.R.; Buckleton, J.S.; Cambie, R.C.; Clark, G.R.; Rickard, C.E.F. Tetrahedron Lett. 1986, 27, 2177-78 46. Sundararaman, P. Anal. Chem. 1985, 57, 2204-06 47. Mackenzie, A.S.; Quirke, J.M.E.; Maxwell, J.R. In "Advances in Organic Geochemistry 1979"; Douglas, A.G.; Maxwell, J . R . , Eds.; Pergamon Press, Oxford, 1980; pp. 239-48 48. Barwise, A.J.G.; Park, P.J.D. In "Advances in Organic Geochemistry 1981"; Bjorøy, M. et a l . ; J . Wiley & Sons, Chichester, 1983, pp. 668-74 49. Shi, Ji-Yang; Mackenzie, A.S.; Alexander, R.; Eglinton, G.; Gowar, A.P.; Wolff, G.A.; Maxwell, J.R. Chem. Geol. 1982, 35, 131 50. Farrimond, P.; Comet, P.; Eglinton, G.; Evershed, R.P.; Hall, M.A.; Park, D.W.; Wardroper, A.M.K. Mar. Pet. Geol. 1984, 1, 34054 51. Xu Fenfang; Sheng Guoying; Fu Jia Mo; Evershed, R.P.; Jiang Jigang Geochimica 1985, 358-62; Chem. Abstr. 1986, 104, 71337s 52. Sugihara, J.M.; McGee, L.R. J . Org. Chem. 1957, 22, 795-98 53. Fu Jia Mo; Sheng Guoying; Peng Pingan; Brassell, S.C.; Eglinton, G.; Jiang Jigang In "Advances in Organic Geochemistry 1985"; Julich, in press RECEIVED November 10, 1986

Chapter 3 Evidence for Porphyrins of Bacterial and Algal Origin in Oil Shale R. Ocampo, H. J. Callot, andP.Albrecht


Département de Chimie, UA 31, UniversitéLouis Pasteur, 1, rue Blaise Pascal, 67008 Strasbourg, France

The petroporphyrins from the immature Messel o i l shale consist almost exclusively of alkylporphyrins and monocarboxylic acids, complexed with nickel. Sixteen structures of pure isolated products (including ten carboxylic acids) were determined. Two groups of pigments could be specifically correlated with algal (chlorophylls c + c') and bacterial (bacteriochlorophylls d) precursors, while the remaining structures confirm a non specific chlorophyllic origin. The survival of a major monocarboxylic acid fraction with concomittant skeletal modifications both confirm the immaturity of the shale and underline the complexity of the diagenetic routes. The t r a n s f o r m a t i o n o f c h l o r o p h y l l i n t o petroporphyrins was f i r s t s u g g e s t e d i n 1 9 3 4 - 3 6 when T r e i b s p r o p o s e d w h a t i s now known a s " T r e i b s scheme" ( 1 ) ( F i g u r e 1 ) .

COOM« COOR Chlorophyll a R = Phytyl Figure

M-DPEP C

32

1. T h e T r e i b s ' s c h e m e l e a d s f r o m C h l o r o p h y l l t o DPEP p e t r o p o r p h y r i n s by a sequence o f geochemical t r a n s f o r m a t i o n s .


3.

O C A M P O ET AL.

Porphyrins of Bacterial and Algal Origin

69


A l t h o u g h p e t r o p o r p h y r i n s were l a t e r d e t e c t e d i n a v a r i e t y o f sediments t h e knowledge o f t h e i r p r e c i s e s t r u c t u r e " r e g r e s s e d " as mass s p e c t r o m e t r y r e v e a l e d v e r y c o m p l e x m i x t u r e s (2-5). I n recent years t h edevelopment o f very e f f i c i e n t chromatographic ( e . g . HPLC) and s p e c t r o s c o p i c t e c h n i q u e s ( F T NMR a n d NOE) h a s a l l o w e d s e v e r a l groups (6-23) t o overcome the problems o f s e p a r a t i o n and t o a s s i g n the structures o f a limited number o f petroporphyrins. Crystal s t r u c t u r e s by X-ray d i f f r a c t i o n confirmed t h e a s s i g n m e n t s f o r two products (20-21). A l l s t r u c t u r e s d e s c r i b e d from o i l shales are compatible w i t h c h l o r o p h y l l i c p r e c u r s o r s as i n d i c a t e d by t h e p r e s e n c e , i n many c o m p o u n d s , o f a n i s o c y c l i c f i v e - m e m b e r e d r i n g , b y specific modifications a t position C-3, e t c . I n one i n s t a n c e a s p e c i f i c p r e c u r s o r , c h l o r o p h y l l b , was s u g g e s t e d b y t h e l o s s o f t h e C-7 s u b s t i t u e n t ( 2 2 ) . However, s e v e r a l f u n d a m e n t a l q u e s t i o n s c o n c e r n i n g t h e o r i g i n a n d the t r a n s f o r m a t i o n s o f the p e t r o p o r p h y r i n s remained almost unanswered a. w i t h t h e e x c e p t i o n c i t e d a b o v e n o s p e c i f i c c h l o r o p h y l l p r e c u r s o r c o u l d be a t t r i b u t e d t o t h e p e t r o p o r p h y r i n s ; i n consequence the r o l e o f porphyrins as biomarkers o f sediments and petroleum r e mained l i m i t e d ; b. a l t h o u g h i n t e r m e d i a t e s i n t h e " T r e i b s * s c h e m e " , e s p e c i a l l y c a r b o x y l i c a c i d s , c o u l d be v a l u a b l e m a t u r a t i o n i n d i c a t o r s , t h e y were unknown, a g a i n w i t h o n l y one e x c e p t i o n (21) ; c. c o n f l i c t i n g h y p o t h e s e s ( 2 4 - 2 6 ) c o n c e r n i n g t h e p e t r o p o r p h y r i n s w i t h C-number h i g h e r t h a n t h a t e x p e c t e d f r o m c h l o r o p h y l l a ( > 3 2 i n t h e a l k y l s e r i e s ) c o u l d n o t be d i s c u s s e d u n t i l s u c h compounds were p u r i f i e d a n d t h e i r s t r u c t u r e s c l e a r l y a s s i g n e d : do t h e y a r i s e from b a c t e r i a l homologated "Chlorobium c h l o r o p h y l l s " ( F i g u r e 3) o r from t r a n s a l k y l a t i o n ( a l k y l a t i o n - d e a l k y l a t i o n ) o f pigments d e r i v e d from "normal" c h l o r o p h y l l s ? We c h o s e t o s t u d y t h e M e s s e l o i l s h a l e f o r s e v e r a l r e a s o n s . T h e s e d i m e n t was d e p o s i t e d a t t h e b o t t o m o f a l a k e f i l l i n g a n a r r o w r i f t w i t h i n t h e Odenwald p l a t e a u ( n e a r D a r m s t a d t , West Germany). I t i s d a t e d from Eocene (45-49 Myr ; c o n t e m p o r a r y t o t h e s i n k i n g o f t h e R h i n e v a l l e y ) a n d was n e v e r b u r i e d u n d e r more t h a n a f e w m e t e r s o f s a n d a n d g r a v e l . I t i s t h u s r a t h e r i m m a t u r e a s shown b y e a r l i e r g e o c h e m i c a l s t u d i e s w h i c h i d e n t i f i e d a l a r g e number o f l i p i d s f r o m t h e s h a l e ( 2 7 - 2 8 ) . P a l e o n t o l o g i c a l a n d g e o l o g i c a l s t u d i e s (29) i n d i c a t e d t h a t t h e l a k e w a t e r s w e r e c a l m , p a r t l y a n a e r o b i c a n d i n a warm t r o p i cal environment. A l l these data suggested that the petroporphyrins s h o u l d be w e l l p r e s e r v e d and indeed e x t r a c t i o n o f the s h a l e , f o l l o w e d by s e p a r a t i o n a n d s t r u c t u r a l d e t e r m i n a t i o n ( 3 0 - 3 3 ) l e d u s t o i d e n t i f y s i x t e e n n i c k e l c o m p l e x e s ( F i g u r e 2 ) w h i c h a c c o u n t e d f o r more t h a n 9 0 % of the e x t r a c t i b l e p e t r o p o r p h y r i n s . C a r b o x y l i c a c i d s (60-70% o f the t o t a l p o r p h y r i n f r a c t i o n , char a c t e r i z e d as t h e i r methyl e s t e r s ) outweigh t h e a l k y l p e t r o p o r p h y r i n s and t h i s c o n f i r m s t h e i m m a t u r i t y o f t h e M e s s e l o i l s h a l e . The d i s t r i b u t i o n o f the a c i d s does n o t r e f l e c t t h a t o f t h e a l k y l p e t r o p o r p h y r i n s , i n p a r t i c u l a r , compound 7 i s a m i n o r component o f t h e a c i d f r a c t i o n w h i l e i t s decarboxylated counterpart 6 dominates t h e a l k y l f r a c t i o n . T h e f a c t t h a t some o f t h e s e a c i d s (8, 9, 10 a n d 11, p h y l l o a n d p y r r o p o r p h y r i n s e r i e s ) show a d e g r a d e d i s o c y c l i c r i n g i n d i c a t e s t h a t a l i n e a r " T r e i b s * scheme" s h o u l d be r e p l a c e d b y s e v e r a l d i a g e n e t i c routes i nwhich t h ed e c a r b o x y l a t i o n o f the p r o p i o n i c s i d e - c h a i n


70


may o c c u r b e f o r e o r a f t e r m a j o r s k e l e t a l m o d i f i c a t i o n s . T h i s s u g g e s t s t h a t some c o m p o u n d s c a l l e d e t i o p o r p h y r i n s i n t h e l i t e r a t u r e o n l y o n uhe b a s i s o f t h e i r c o m p o s i t i o n a n d o f t e n c o r r e l a t e d t o t h e products o f t h e r m a l r i n g o p e n i n g o f DPEP'S may i n f a c t o r i g i n a t e i n an early d e g r a d a t i o n o f t h e 5-membered r i n g o f t h e c h l o r o p h y l l s .

COOH

COOH

F i g u r e 2. P e t r o p o r p h y r i n s i d e n t i f i e d Messel o i l shale.

COOH

COOH

after

their

isolation

from t h e

3.

O C A M P O ET AL.

71



Of more f u n d a m e n t a l i m p o r t a n c e i s t h e s t r u c t u r e o f t w o g r o u p s o f petroporphyrins v i z 14-16 a n d 5-7. T h e f i r s t g r o u p o f c o m p o u n d s p o s s e s s e s a carbon framework which i s o n l y c o m p a t i b l e w i t h b a c t e r i o c h l o r o p h y l l s d, p o s i t i o n s 8 a n d 12 b e i n g s p e c i f i c a l l y h o m o l o g a t e d (34-35) ( F i g u r e 3 ) . The s t r u c t u r e s o f t h e components o f t h e s e c o n d g r o u p o f petroporphyrins 5 - 7 are t y p i c a l o f rearrangement products o f c h l o r o p h y l l c ( o r c') (36-37) s i n c e o n l y t h e s e c h l o r o p h y l l s ( F i g u r e 3 ) , which bear an a c r y l i c instead o f a propionic s i d e - c h a i n , a r eable t o undergo such a rearrangement.

Chlorophyll

Figure

c ( o r c' )

3. S p e c i f i c p r e c u r s o r s

o f the

Bacteriochlorophylls d R = Farnesyl R'= E t , n - P r , i - B u , n e o - p e n t y l R"= Me, E t Messel o i l shale's

porphyrins.

The i d e n t i f i c a t i o n o f s p e c i f i c p r e c u r s o r s f o r s i x o f the p e t r o p o r p h y r i n s from Messel o i l shale demonstrates the b a c t e r i a l and a l g a l i n p u t i n t h e o r g a n i c m a t t e r s i n c e b a c t e r i o c h l o r o p h y l l s d are s p e c i f i c f o r Chlorobium group photosynthetic b a c t e r i a , and chlor o p h y l l s c a n d c' f o r a l g a e . The i m p o r t a n c e o f t h e a l g a l c o n t r i b u t i o n i s i l l u s t r a t e d by t h e f a c t t h a t 6 i s t h e major product o ft h e a l k y l p e t r o p o r p h y r i n f r a c t i o n . T h i s i s i n agreement w i t h the abundance i n t h e s h a l e o f s t e r o i d s a n d t e r p e n o i d s whose o r i g i n i s a t t r i b u t e d t o microalgae andb a c t e r i a (27-28). Although i t i s n o tp o s s i b l e , from simple s t r u c t u r a l c o n s i d e r a t i o n s , t o a t t r i b u t e a s p e c i f i c p r e c u r s o r f o r t h e r e m a i n i n g compounds, a l l s t r u c t u r e s may b e i n t e r p r e t e d s t a r t i n g f r o m c h l o r o p h y l l i c p r e c u r sors ( c h l o r o p h y l l s a, b, c and c' ; b a c t e r i o c h l o r o p h y l l s a and b ; l o w e s t homolog o f b a c t e r i o c h l o r o p h y l l s d ) . The a b s e n c e o f t r u e e t i o p o r p h y r i n s ( a l k y l s o n p y r r o l e s e x c l u s i v e l y ) may b e c o r r e l a t e d a g a i n w i t h the i m m a t u r i t y o f the s h a l e . Comparison o f the above r e s u l t s w i t h the problem evoked i n the i n t r o d u c t i o n s h o w s t h a t , a t l e a s t i n t h e c a s e o f t h e M e s s e l o i l s h a l e , we can f i n d s e v e r a l answers : a. s p e c i f i c p r e c u r s o r s o f petroporphyrins c a n be found and confirm t h ee x i s t i n g g e o l o g i c a l and geochemical data : under oxygenated waters containing algae, photosynthetic b a c t e r i a o f the Chlorobium group (not e x c l u s i v e ) f l o u r i s h e d i n the a n a e r o b i c l a y e r s ;

72


b. c a r b o x y l i c a c i d s , k e y - i n t e r m e d i a t e s i n t h e " T r e i b s ' s c h e m e " , can be major c o n s t i t u e n t s o f t h e p o r p h y r i n f r a c t i o n , under f a v o r a b l e c o n d i t i o n s , a n d a r e i n t e r p r e t a t i o n o f t h e d i a g e n e t i c scheme i n t e r m s of m u l t i p l e routes i snecessary ; c. a t l e a s t i n t h e c a s e o f t h e M e s s e l s h a l e , t h e o n l y "high molecular weight" e x t r a c t i b l e petroporphyrins a r e i n t e r p r e t a b l e i n t e r m s o f b a c t e r i a l i n p u t ; n o e v i d e n c e was f o u n d f o r a n y c o n t r i b u t i o n o f t r a n s a l k y l a t i o n r e a c t i o n s ( n o r was a n y f o r a D P E P ^ ^ e t i o p o r p h y r i n s transformation).


Although these r e s u l t s concern one r a t h e r p e c u l i a r environment, these n o v e l s t r u c t u r a l d a t a g i v e a new i n s i g h t i n t o t h e o r i g i n , d i a g e n e s i s and s i g n i f i c a n c e o f p e t r o p o r p h y r i n s i n s e d i m e n t s . In particular, the identification o f specific precursors f o rseveral petroporphyrins w i l l f a v o r t h e i r r a t i o n a l useas b i o l o g i c a l markers o f sediments and petroleum. A c k n o w l e d g m e n t s : We t h a n k D r . J . P . K i n t z i n g e r a n d M r s E . Krempp f o r t h e i r a s s i s t a n c e i n t h e NMR s t u d i e s , t h e C.N.R.S., U n i v e r s i t e L o u i s P a s t e u r a n d CONACYT ( M e x i c o ) f o r f i n a n c i a l s u p p o r t a n d t h e M a n a g e m e n t of t h e Messel M i n e f o r s h a l e s a m p l e s . We f u r t h e r t h a n k D r . von Koenigswald, Hessisches Landesmuseum, D a r m s t a d t , FRG, f o r h e l p f u l d i s c u s s i o n s andh e l p i n t h e sample c o l l e c t i o n .

Literature Cited 1. Treibs, A. Angew. Chem. 1936, 49, 682-6. 2. Dean, R. A.; Whitehead, E. V. 6th World Petroleum Congr., Sect. V, 1963, p. 261. 3. Thomas, D. W.; Blumer, M. Geochim. Cosmochim. Acta 1964, 28, 1147-54. 4. Baker, E. W. J . Am. Chem. Soc. 1966, 88, 2311-5. 5. Baker, E. W.; Yen, T. F.; Dickie, J . P.; Rhodes, R. E . ; Clark, L. F. J . Am. Chem. Soc. 1967, 89, 3631-9. 6. Quirke, J . M. E.; Eglinton, G.; Maxwell, J . R. J . Am. Chem. Soc. 1979, 101, 7693-7. 7. Quirke, J . M. E.; Maxwell, J . R.; Eglinton, G.; Sanders, J . K. M. Tetrahedron Lett. 1980, 21, 2987-90. 8. Quirke, J . M. E.; Maxwell, J . R. Tetrahedron 1980, 36, 3453-6. 9. Fookes, C. J . R. J . Chem. Soc., Chem. Commun. 1983, 1472-3. 10. Fookes, C. J . R. J . Chem. Soc., Chem. Commun. 1983, 1474-6. 11. Wolff, G. A.; Murray, M.; Maxwell, J . R.; Hunter, B. K.; Sanders, J . K. M. J . Chem. Soc., Chem. Commun. 1983, 922-4. 12. Wolff, G. A.; Chicarelli, M. I.; Shaw, G. J.; Evershed, R. P.; Quirke, J . M. E.; Maxwell, J . R. Tetrahedron 1984, 40, 3777-86. 13. Krane, J.; Skjetne, T.; Telnaes, N.; Bjoroy, M.; S o l l i , H. Tetrahedron 1983, 39, 4109-19. 14. Storm, C. B.; Krane, J.; Skjetne, T.; Telnaes, N.; Branthaver, J . F . ; Baker, E. W. Science 1984, 223, 1075-6. 15. Chicarelli, M. I.; Wolff, G. A.; Maxwell, J . R. J . Chem. Soc., Chem. Commun. 1985, 723-4. 16. Chicarelli, M. I.; Wolff, G. A.; Murray, M.; Maxwell, J . R. Tetrahedron 1984, 40, 4033-9. 17. Fookes, C. J. R. J . Chem. Soc., Chem. Commun. 1985, 706-8.

3. OCAMPO ET AL. 18. 19. 20. 21. 22. 23. 24.


25. 26.

27. 28. 29. 30. 31. 32. 33. 34. 35. 36. 37.


73

Chicarelli, M. I.; Maxwell, J . R. Tetrahedron Lett. 1986, 27, 4653-4. Verne-Mismer, J.; Ocampo, R.; Callot, H. J.; Albrecht, P. Tetrahedron Lett., in press. Ekstrom, A.; Fookes, C. J . R.; Hambley, T.; Loeh, H. J.; Miller, S. A.; Taylor, J . C. Nature 1983, 306, 173-4. Habermehl, G. G.; Springer, G.; Frank, M. H. Naturwissenschaften 1984, 71, 261-3. Chicarelli, M. I.; Maxwell, J . R. Tetrahedron Lett. 1984, 25, 4701-4. Kaur, S.; Chicarelli, M. I.; Maxwell, J . R. J . Am. Chem. Soc. 1986, 108, 1347-8. Mackenzie, A. S.; Quirke, J . M. E.; Maxwell, J . R. In "Advances in Organic Geochemistry 1979"; Douglas, A. C.; Maxwell, J . R.; Eds.; Pergamon Press, Oxford, 1980; pp. 239-48. Quirke, J . M. E . ; Shaw, G. J.; Soper, P. D.; Maxwell, J . R. Tetrahedron 1980, 36, 3261-7. Baker, E. W.; Louda, J . W. In "Advances in Organic Geochemistry 1981"; Bjoroy, M.; Albrecht, P.; Cornford, C.; De Groot, K.; Eglinton, G.; Galimov, E.; Leythaeuser, D.; Pelet, R.; Rullkotter, J . ; Speers, G.; Eds.; Wiley, London, 1983; pp. 401-21. Michaelis, W.; Albrecht, P. Naturwissenschaften 1979, 66, 420-1. Robinson, N. Ph.D. Thesis, University of Bristol, U.K., 1985. Von Koenigswald, W. Geol. Jb. Hessen 1980, 108, 23-38. Ocampo, R.; Callot, H. J.; Albrecht, P.; Kintzinger, J . P. Tetrahedron Lett. 1984, 25, 2589-92. Ocampo, R.; Callot, H. J.; Albrecht, P. J . Chem. Soc., Chem. Commun. 1985, 198-200. Ocampo, R.; Callot, H. J.; Albrecht, P. J . Chem. Soc., Chem. Commun. 1985, 200-1. Ocampo, R. Ph.D. Thesis, U n i v e r s i t éLouis Pasteur de Strasbourg, France, 1985. Smith, K. M.; Goff, D. A.; Fajer, J.; Barkigia, K. M. J . Am. Chem. Soc., 1982, 104, 3747-9. Smith, K. M.; Goff, D. A.; Fajer, J.; Barkigia, K. M. J . Am. Chem. Soc. 1983, 105; 1674-6. Jackson, A. H. In "Chemistry and biochemistry of plant pigments"; Goodwin, T., Ed.; 2nd ed., vol. 1; Academic Press, New York, 1976; pp. 1-63. Dougherty, R. C.; Strain, H. H.; Svec, W. W.; Uphaus, R. A.; Katz, J . J . J . Am. Chem. Soc. 1970, 92, 2826-33.

RECEIVED November 10, 1986

Chapter 4 Rationalization for the Predominance of Nickel and Vanadium Porphyrins in the Geosphere J. M. E. Quirke


Department of Chemistry, Florida International University,TamiamiTrail, Miami, FL 33199

The predominance of nickel and vanadium porphyrins, over other metalloporphyrins in the geosphere may be explained by taking into account four factors: the abundances of the metals, and their environment within the sediments and/or the water column, the stability of the nitrogen-metal bonds, and the lability of the bridge positions of the metal porphyrin complexes.

Since the o r i g i n a l isolation of porphyrins from a variety of sedimentary environments, two t y p e s o f metal complex -the n i c k e l ( I I ) and v a n a d y l (V=0)- have dominated g e o p o r p h y r i n c h e m i s t r y . (J_,2) The reason f o r the s e l e c t i o n o f these two metals i s not immediately o b v i o u s i n view o f t h e a r r a y o f p o t e n t i a l m e t a l c a n d i d a t e s , some o f which, e.g. chromium ( I I I ) , can form more s t a b l e complexes than either nickel o r vanadium. ( F i g . 1, .3,4) problem i s further c o m p l i c a t e d because the t i m i n g o f the metal insertion i n the d e g r a d a t i v e pathway from the c h l o r o p h y l l s to the geoporphyrins i s not w e l l understood. Thus i t i s u n c l e a r whether m e t a l insertion occurs i n t h e water column, o r i n t h e water column-sediment boundary, o r w i t h i n t h e sediments. One p o s s i b l e e x p l a n a t i o n i s based on t h e p r o b a b i l i t y t h a t t h e metals i n o r g a n i c r i c h sediments o c c u r as t h e i r s u l p h i d e s because such sediments have h i g h c o n c e n t r a t i o n s o f hydrogen s u l p h i d e . F o r metal s u l p h i d e s w i t h low s o l u b i l i t y products e.g. copper ( I I ) s u l p h i d e t h e metal i o n would be p r e s e n t i n v e r y low c o n c e n t r a t i o n s , and t h e r e f o r e would be l e s s l i k e l y to chelate with the porphyrins than those s u l p h i d e s w i t h h i g h e r s o l u b i l i t y p r o d u c t s . T h i s argument i s n o t n e c e s s a r i l y sound. The m e t a l i o n s i n s o l u t i o n , a l b e i t i n v e r y low c o n c e n t r a t i o n , c o u l d chelate with porphyrins and c h l o r i n s , f o r c i n g more m e t a l ion into solution u n t i l the porphyrins were T t l e


*

Mg

Ca

Sr

Ba

Na

K

Rb

Cs

Lanthanides

Be

Li

La

Fig.

*

Y

Sc

Ce

Pr

Ta

Nb

V

Nd

W

Mo

Cr

Re

Mn

Sm

Os

Ru

Fe

Eu

Ir

Rh

Co

Gd

Pt

Pd

Tb

Au

Ag

Cu

with

Ni

1 E l e m e n t s known t o Form C h e l a t e s

Hf

Zr

Ti

Ho

Tl

In

Ga

Al

B

Porphyrins.

Dy

Hg

Cd

Zn


Er

Pb

Sn

Ge

Si

Tm

Bi

Sb

As

Yb

Lu

—i

S3

o c

76



c o m p l e t e l y c h e l a t e d . In a d d i t i o n , the s o l u b i l i t y p r o d u c t argument cannot r e a d i l y account f o r the p o s s i b i l i t y that the porphyrins undergo c h e l a t i o n on t h e m i n e r a l s u r f a c e . A d i f f e r e n t approach t o r a t i o n a l i s i n g the s e l e c t i v i t y of the c h e l a t i o n o f the geoporphyrins w i l l be p r e s e n t e d . The hypothesis encompasses both the n a t u r e o f t h e metal p r i o r t o c h e l a t i o n and t h e s t a b i l i t y o f the m e t a l l o p o r p h y r i n s a f t e r c h e l a t i o n . I t i s assumed that the d i f f e r e n t s k e l e t a l types o f p o r p h y r i n (I) will behave s i m i l a r l y i n the c h e l a t i o n process, although the absolute rates of c h e l a t i o n may d i f f e r f o r each s k e l e t a l type of geoporphyrin. The f a c t o r s which i n f l u e n c e c h e l a t i o n a r e as f o l l o w s : a) The a v a i l a b i l i t y o f e f f i c i e n t metal i o n c a r r i e r s . b) The abundance o f the elements. c ) The s t a b i l i t y o f the metal-nitrogen bond i n the porphyrin complex. d) The s t a b i l i t y o f the m e t a l - n i t r o g e n bond i n p o r p h y r i n s i n t h e g e o l o g i c a l environment. e) The l a b i l i t y o f t h e p o r p h y r i n meso ( b r i d g e ) p o s i t i o n s . T h i s h y p o t h e s i s has the v i r t u e o f being sufficiently flexible so t h a t i t can be used t o examine the p o s s i b i l i t y o f m e t a l i n s e r t i o n e i t h e r a t the water column-sediment i n t e r f a c e o r deeper down i n the sediment. The h y p o t h e s i s may be f u r t h e r r e f i n e d by as more d a t a a r e o b t a i n e d on t h e n a t u r e o f t h e p o r p h y r i n s bound on m i n e r a l m a t r i c e s .

4.

QUIRKE

Predominance of Nickel and Vanadium Porphyrins

11

R e s u l t s and D i s c u s s i o n


Each o f t h e f i v e parameters i n t h e model w i l l be d i s c u s s e d i n t u r n . The p o s t - c h e l a t i o n parameters a r e i n t e r r e l a t e d , and t h e r e f o r e t h e s e f a c t o r s are discussed together. The Importance o f t h e Ion C a r r i e r . The n a t u r e o f t h e i o n c a r r i e r i n the s e d i m e n t a r y environment i s o f p r i m a r y importance i n d e t e r m i n i n g the p o s s i b i l i t y o f c h e l a t i o n because t h e f i r s t s t a g e i n t h e m e t a l i n s e r t i o n i s the deconvolution o f t h e m e t a l i o n from the i o n carrier. Very s t a b l e i o n c a r r i e r s a r e v e r y i n e f f i c i e n t r e a g e n t s f o r the m e t a l l a t i o n o f the p o r p h y r i n s . In t h e l a b o r a t o r y , h i g h l y charged m e t a l i o n s a r e more d i f f i c u l t t o i n s e r t than lower valence species because t h e n e g a t i v e l y charged anions, and/or the n e g a t i v e l y polarised ligands a r e more tightly bound t o t h e metal. T h i s i s particularly significant for the insertion of tetraand p e n t a - v a l e n t m e t a l s , many o f which form s t a b l e metalloporphyrins. The l a b o r a t o r y s y n t h e s e s o f such compounds u s u a l l y require vigorous c o n d i t i o n s , and o f t e n use water s e n s i t i v e m e t a l l a t i n g agents (e.g. T i C l ^ , S i C l ^ , A 1 C 1 , RÂIH). (3) Thus, s i l i c o n p o r p h y r i n s a r e among the most s t a b l e complexes known, b u t they a r e n o t found i n nature because t h e s i l i c o n o c c u r s i n s i l i c a t e s , which a r e too s t a b l e to p a r t a k e i n t h e m e t a l l a t i o n p r o c e d u r e . Germanium, and aluminium a r e u n l i k e l y to chelate with porphyrins i n t h e sediments because t h e ions will n o t be r e a d i l y available for complexation i n the s e d i m e n t a r y environment. S i m i l a r l y , chromium ( I I I ) porphyrins are e x c e p t i o n a l l y s t a b l e ; however, chromium ( I I I ) i o n c a r r i e r s a r e v e r y u n r e a c t i v e . ( 3 ) Gold ( I I I ) porphyrins a r e a l s o s t a b l e , but they a r e n o t p r e v a l e n t i n n a t u r e because g o l d o c c u r s p r i m a r i l y as t h e n a t i v e m e t a l , which i s q u i t e i n e r t . 3

F o r many t r a n s i t i o n e l e m e n t s , t h e n a t u r e o f t h e i o n s i n aqueous s o l u t i o n i s complex. C o n s i d e r t h e group IVB e l e m e n t s . T i t a n i u m would appear t o be a good candidate f o r c h e l a t i o n i n the g e o l o g i c a l environment. I t i s abundant, ( T a b l e I ) and forms stable porphyrin complexes. However, t h e n a t u r e o f t h e t i t a n i u m i n aqueous s o l u t i o n p r e c l u d e s c h e l a t i o n . There i s no s i m p l e s o l v a t e d T i i o n , because of Jjljie h i g h charge t o r a d i u s r a t i o , n o r i s t h e r e e v i d e n c e o f s i m p l e TiO i o n s . ( 5 ) The major m i n e r a l form o f t i t a n i u m i s t i t a n i u m o x i d e , a s t a b l e compound, which i s a poor i o n c a r r i e r . S i m i l a r problems a r ^ encountered w i t h z i r c o n i u m . There i s no i n d i c a t i o n o f Zr o r ZrO i n s o l u t i o n . Instead, polymeric forms o f ZrO seem dominant. Such species w i l l further h i n d e r the m e t a l l a t i o n p r o c e s s . Hafnium i s l i k e l y t o p r e s e n t t h e same d i f f i c u l t y i n t h e l i g h t o f the v e r y g r e a t s i m i l a r i t i e s i n the c h e m i s t r y o f t h e s e two e l e m e n t s . ( 6 ) In aqueous s o l u t i o n , molybdenum and t u n g s t e n can o c c u r ina number o f forms i n c l u d i n g t h e molybdate and t u n g s t a t e a n i o n s . Such s p e c i e ^ w i l l n o ^ l e n d t h e m s e l v e s e a s i l y t o c h e l a t i o n . ( 3 ) The c a t i o n s of Mo and Mo are bimolecular.(7) Vanadium i s the e a s i e s t o f the t e t r a v a l e n t elements t o i n s e r t i n the l a b o r a t o r y using a t e t r a v a l e n t c h e l a t i n g agent. (_3,4_) The metallation i s effected rapidly i n refluxing aqueous a c e t i c acid using vanadyl sulphate as t h e c h e l a t i n g agent. In a d d i t i o n i t i s abundant both i n the water column and i n t h e s e d i m e n t a r y rocks


78

Table

I.

Average

Abundances

of

Metalloporphyrins


Element

Al Si Ti V Cr Mn Fe Co Ni Cu Ga Ge As Y Zr Nb Mo Ru Rh Pd Ag In Sn Sb La Ce Pr Nd Sm Eu Gd Tb Dy Ho Er Tm Yb Lu Hf Ta W Re Os Ir Pt Au Tl Bi

Seawater Concentration (ppm,

<
Athabasca S i m i l a r t o t h e e t i o / D P E P v a r i a t i o n s , b u t more p r o n o u n c e d , were t h e v a r i a t i o n s i nthe r a t i o s o f e t i o t o minor p o r p h y r i n s e r i e s , such a s t e t r a h y d r o b e n z o (THBD), benzo-DPEP, a n d b e n z o - e t i o p o r p h y r i n s . This r a i s e s t h e p o s s i b i l i t y t h a t t h e m i n o r s e r i e s p o r p h y r i n s ( e . j * . , THBD, b e n z o ) may h a v e v a l u e i n c o r r e l a t i o n s t u d i e s , p a r t i c u l a r l y s i n c e these p o r p h y r i n s have r e c e n t l y been d e t e c t e d i n s e d i m e n t s a s t h e f r e e bases (27,28) w i t h a s y e t - t o - b e determined p r e c u r s o r s a n d d i a g e n e t i c pathways. The s i m i l a r p a t t e r n s o b s e r v e d f o r a l l t h e e t i o / o t h e r porphyrin r a t i o s w i t h depth argues against formation o f e t i o - p o r p h y r i n s i n t h e s e o i l s b y a d i r e c t DPEP t o e t i o c o n v e r s i o n b e c a u s e t h e r e i s n o a p p a r e n t g e n e t i c r e l a t i o n s h i p b e t w e e n DPEP a n d the minor s e r i e s p o r p h y r i n s . Non-Porphyrin

Complexes a n d Geochemical C o r r e l a t i o n s

The g e o c h e m i c a l s i g n i f i c a n c e a n d u t i l i t y o f n o n - p o r p h y r i n n i c k e l a n d vanadium complexes i n crude o i l s i s d i f f i c u l t t o a s s e s s because no d i s c r e t e complexes have been i d e n t i f i e d and t h e i r o r i g i n i s obscure. The f a c t t h a t t h e m o s t a b u n d a n t o r g a n i c a l l y c o m b i n e d n o n - p o r p h y r i n metals i n crude o i l asphaltenes a r e normally n i c k e l and vanadium suggests, however, a g e n e t i c r e l a t i o n s h i p between t h e p o r p h y r i n and non-porphyrin s p e c i e s . Yen (29) h a ssuggested t h a t t h e non-porphyrin c o m p l e x e s may i n f a c t b e m e t a l l o p o r p h y r i n d e g r a d a t i o n p r o d u c t s t h a t remain i n asphaltene s t r u c t u r e s . Branthaver (30) h a s determined that Ni/V r a t i o s a r e s i m i l a r throughout s e v e r a l g e l permeation c h r o m a t o g r a p h y (GPC) f r a c t i o n s o f B o s c a n c r u d e o i l . Porphyrin c o n t e n t s v a r y g r e a t l y among t h e s e f r a c t i o n s . I none f r a c t i o n , a l l m e t a l s a r e a c c o u n t a b l e a s p o r p h y r i n s , w h i l e i n a n o t h e r most m e t a l s are apparently non-porphyrinic. Other f r a c t i o n s a r e i n t e r m e d i a t e . T h i s would f u r t h e r support a g e n e t i c r e l a t i o n s h i p between p o r p h y r i n s and n o n - p o r p h y r i n s i f t h e s e f i n d i n g s were v e r i f i e d i n o t h e r c r u d e s . A l t h o u g h n o n - p o r p h y r i n n i c k e l a n d v a n a d i u m s p e c i e s may o c c u r i n crude o i l s , a s p h a l t s , e t c . , there i s l i t t l e i n f o r m a t i o n on t h e i r o c c u r r e n c e i nt h e bitumens o f source r o c k s w i t h w h i c h o i l s c o u l d be correlated. T h e r e may, i n f a c t , b e a c o r r e l a t i o n b e t w e e n n i c k e l a n d

Rock

Rock

Oil-Source

Oil-Source

Basin

Suite of o i l s :

Oil-Oil

no

Venezuela, Boscan Maracaibo Basin

Oil-Oil

Venezuela Lake

W.

Oil-Oil

location

oils

Maracaibo

S e n l i , and o t h e r c o n t i n e n t a l oil fields, China

Boscan o i l , Venezuela (Maracaibo Basin)

o i l , Gabon

Rock

Oil-Source

Ozouri

W. V e n e z u e l a L a k e (Lake Maracaibo)

Rock

Oil-Source

Applications of Porphyrins

Region-Occurrence

I.

Correlation

Table

and O i l - S o u r c e

show s i m i l a r i t i e s

HPLC c h r o m a t o g r a m s u s e d t o c o r r e l a t e sequence o f o i l s a t d i f f e r e n t l e v e l s of m a t u r i t y

HPLC f i n g e r p r i n t s of Boscan o i l s

Attempts c o r r e l a t i o n o f Cretaceous and T e r t i a r y o i l s with r e s e r v o i r depth b a s e d o n VOP c o n t e n t s

16

L8

26

73

A p p l i c a t i o n of DPEP/etio r a t i o s c o r r e l a t i o n w i t h source rocks

for

18

23

U s e d HPLC d e m e t a l l a t e d p o r p h y r i n c h r o m a t o g r a m s t o show c o r r e l a t i o n o f Boscan o i l s t o La Luna shale

Spectroscopic determination of NiP a n d VOP o f o i l s a n d k n o w n s o u r c e rock

26

Reference

Rock C o r r e l a t i o n s

C o r r e l a t e s Cretaceous and T e r t i a r y crudes w i t h L a Luna source r o c k on b a s i s o f VOP c o n t e n t s

Comments

in Oil-Oil


Grosmont F o r m a t i o n A l b e r t a , Canada

A l b e r t a o i l sand

Oil-Oil

deposits

bitumen,

C o r r e l a t i o n of Athabasca, Cold Lake, and Peace R i v e r o i l sands on b a s i s o f D P E P , e t i o , THBD, a n d b e n z o p o r p h y r i n abundances

D P E P / e t i o r a t i o s o f VOP u s e d t o c o r r e l a t e bitumen i n Devonian Grosmont Formation with Cretaceous Athabasca deposit

to correlate

Oil-Oil

DPEP/etio r a t i o s used degraded o i l s

Colombia

Oil-Oil

oils

HPLC c h r o m a t o g r a m s u s e d t o d e t e r m i n e m a t u r i t y sequence o f S h e n g l i o i l s (approx. DPEP/etio r a t i o s )

Shengli O i l Field,

Oil-Oil

China

U s e d VOP c o n t e n t s a n d D P E P / e t i o r a t i o s to d i s t i n g u i s h between J u r a s s i c and Cretaceous bitumoids

E a s t C a u c a s u s F o o t h i l l s , USSR (bitumoids and crude o i l s )

C o r r e l a t e s m i g r a t e d o i l s on p r o p o r t i o n s o f p o l a r / n o n - p o l a r VOP a n d D P E P / e t i o ratios

Oil-Oil

USSR

W.

Oil-Oil

Surgut O i l F i e l d ,



90


vanadium s p e c i e s i n kerogens from m a t u r i n g sediments and those p r e sent i n crude o i l a s p h a l t e n e s . R e c e n t l y , s e v e r a l a u t h o r s (31-34) demonstrated that o i l shale kerogen concentrates c o n t a i n s u b s t a n t i a l q u a n t i t i e s o f o r g a n i c a l l y combined n i c k e l and vanadium. Van B e r k e l and F i l b y (32) measured m i n e r a l - f r e e c o n c e n t r a t i o n s o f n i c k e l and v a n a d i u m o f 2 1 3 0 a n d 7 0 0 yg/g> r e s p e c t i v e l y , i n New A l b a n y o i l - s h a l e k e r o g e n a n d 3 5 0 a n d 3 2 6 0 Ug/g» r e s p e c t i v e l y , i n t h e W o o d f o r d o i l - s h a l e kerogen. A l t h o u g h t h e y showed t h a t b o t h k e r o g e n s g e n e r a t e d N i ( I I ) and V O ( I I ) p o r p h y r i n s on p y r o l y s i s , o n l y a s m a l l f r a c t i o n o f t h e t o t a l m e t a l was r e l e a s e d f r o m t h e k e r o g e n . I t was n o t p o s s i b l e t o d e t e r m i n e what f r a c t i o n o f t h e n i c k e l a n d v a n a d i u m i n t h e k e r o g e n was porphyrinic. During kerogen c a t a g e n e s i s , molecules a s s o c i a t e d w i t h petroleum a s p h a l t e n e s a r e thought t o form as i n t e r m e d i a t e s i n the c o n v e r s i o n o f k e r o g e n t o h y d r o c a r b o n s ( 3 5 ) , a s s h o w n i n F i g u r e 1. T h u s , a n a s p h a l tene m o i e t y formed from kerogen p r o b a b l y c o n t a i n s N i ( I I ) and V O ( I I ) porphyrin s u i t e s s i m i l a r to those present i n the parent kerogen, a n d may a l s o c o n t a i n t h e n o n - p o r p h y r i n c o m p l e x e s t h a t may b e p a r t o f the k e r o g e n s t r u c t u r e . Recent work (32) i n d i c a t e s t h a t t h e m e t a l l o p o r p h y r i n s p r o b a b l y a r e n o t bonded by a l i p h a t i c l i n k a g e s t o t h e k e r o g e n b u t may b e s t r o n g l y c h e m i s o r b e d , o r t r a p p e d i n t h e p o l y m e r i c structure. K e r o g e n s may t h u s r e t a i n p o l a r n i c k e l a n d v a n a d i u m n o n p o r p h y r i n s p e c i e s i n a s i m i l a r f a s h i o n a n d t h e s e may b e p a r t o f asphaltene s t r u c t u r e s a f t e r f o r m a t i o n from the maturing kerogen. Thus, t h e a s p h a l t e n e s o f s o u r c e r o c k bitumens and r e s u l t i n g crude o i l s may c o n t a i n n o n - p o r p h y r i n m e t a l c o m p l e x e s t h a t a r e c h a r a c t e r i s t i c of t h e s o u r c e - r o c k kerogens and t h e i r g e o c h e m i c a l h i s t o r y and thus o f p o t e n t i a l use i n c o r r e l a t i o n studies. An a l t e r n a t i v e o r i g i n f o r t h e n o n - p o r p h y r i n c o m p l e x e s i n a s p h a l t e n e s may b e t h a t t h e a s p h a l t e n e s e v o l v i n g from kerogen i n source r o c k s complex Ni2+, V0^+ and o t h e r i o n s from m i n e r a l s u r f a c e s . I f t h i s i s the case, the non-porphyrin m e t a l s i n c r u d e o i l a s p h a l t e n e s may s t i l l r e f l e c t t h e s o u r c e r o c k e n v i r o n m e n t ( b u t n o t n e c e s s a r i l y t h e k e r o g e n c o m p o s i t i o n ) and be o f value i n correlation studies. The g e o c h e m i c a l r e l a t i o n s h i p b e t w e e n n o n - p o r p h y r i n m e t a l complexes and p o r p h y r i n s i n crude o i l s and kerogens and t h e i r p o t e n t i a l f o r u s e i n c o r r e l a t i o n s t u d i e s s h o u l d be f u r t h e r i n v e s t i g a t e d . Metal Distributions

i n Exploration

Studies

T h e r e h a v e been a number o f a t t e m p t s t o c l a s s i f y p e t r o l e u m a n d s o u r c e r o c k kerogens by examining e n t i r e m e t a l s u i t e s i n t h e s e m a t e r i a l s . In t h e s e s t u d i e s , p o r p h y r i n c o n t e n t s a r e n o t d e t e r m i n e d . For the m e t a l s o t h e r t h a n n i c k e l a n d v a n a d i u m , i t i s n o t known t h a t t h e chelating ligands are porphyrinic. T h e s e s t u d i e s p a r a l l e l many s i m i l a r i n v e s t i g a t i o n s of c o a l s , from which i t i s u s u a l l y i m p o s s i b l e to e x t r a c t s i g n i f i c a n t amounts o f m e t a l c h e l a t e s , b u t w h i c h o f t e n c o n t a i n s u b s t a n t i a l q u a n t i t i e s o f m e t a l s t h a t a p p e a r t o be a s s o c i a t e d with organic matter (36). Several e a r l y workers attempted to use V/Ni r a t i o s as i n d i c a t o r s o f m a t u r a t i o n ( o r a g e ) o f c r u d e o i l s , b u t many o f t h e c o n c l u s i o n s a r e contradictory. Hodgson (37) measured n i c k e l , vanadium and i r o n i n some W e s t e r n C a n a d a o i l s a n d c o n c l u d e d t h a t t h e V / N i r a t i o d e c r e a s e d w i t h i n c r e a s i n g m a t u r a t i o n from a s p h a l t i c Cretaceous t o l e s s a s p h a l t i c deeper Devonian o i l s . Hodgson (37) a l s o c o n c l u d e d t h a t n i c k e l ,

5.

BRANTHAVER A N D FILBY

91

Exploration Geochemistry

KEROGEN


ι

HYDROCARBONS F i g u r e 1. S c h e m a t i c d i a g r a m o f f o r m a t i o n o f a s p h a l t e n e a g g r e g a t e from kerogen showing N i ( I I ) and VO(II) p o r p h y r i n s and o t h e r m e t a l c o m p l e x e s , ML^, -M-, i n s t r u c t u r e . C o m p l e x e s a r e shown a s s o c i a t e d and bonded t o t h e s t r u c t u r e i n d i f f e r e n t modes.


92


v a n a d i u m , and i r o n were d e r i v e d f r o m t h e o r i g i n a l s o u r c e m a t e r i a l . B a l l et. a l . ( 3 8 ) a n d H y d e n ( 3 9 ) , h o w e v e r , c o n c l u d e d t h a t t h e V / N i r a t i o i n c r e a s e d w i t h r e s e r v o i r r o c k age. Much o f t h i s d i s a g r e e m e n t p r o b a b l y a r i s e s from the i n a b i l i t y to d i s t i n g u i s h between the p o r p h y r i n and n o n - p o r p h y r i n f o r m s o f t h e m e t a l s i n t h e s e o i l s and the p r o b a b l e v a r i a t i o n i n the t r a c e m e t a l assemblages o f the source rocks. Bonham ( 4 0 ) s t u d i e d t h e m e t a l c o n t e n t s o f a n u m b e r o f A m e r i c a n c r u d e o i l s o f v a r i o u s a g e s , w i t h e m p h a s i s on P e n n s y l v a n i a n c r u d e s from the Andarko b a s i n o f Oklahoma. He f o u n d t h a t t h e v a n a d i u m a n d n i c k e l c o n t e n t s o f t h e o i l s d i f f e r e d s i g n i f i c a n t l y f r o m one b a s i n t o another. Bonham c o u l d n o t , o n t h e b a s i s o f m e t a l s u i t e s , c o r r e l a t e b e t w e e n o i l p o o l s i n t h e same p r o d u c i n g s t r a t a o f i n d i v i d u a l b a s i n s o r e v e n d i f f e r e n t i a t e b e t w e e n t h e same p r o d u c i n g s t r a t a . Neverthel e s s , he c l a i m e d t h a t t h e m e t a l s u i t e s p r o v i d e d i n f o r m a t i o n a b o u t t h e p a l e o g e o g r a p h y o f t h e b a s i n s . S e v e r a l a t t e m p t s h a v e b e e n made to c o r r e l a t e t r a c e m e t a l d i s t r i b u t i o n s w i t h t h e a g e s o f r e s e r v o i r r o c k s o r o t h e r geochemical p r o p e r t i e s (41-45) o f R u s s i a n o i l s . T h u s , K o t o v a et_ a^L. ( 4 1 ) s h o w e d that n i c k e l , vanadium, copper, g a l l i u m , and germanium v a r i e d s y s t e m a t i c a l l y w i t h age and d e p t h o f reservoir rocks. I n m o s t o f t h e s e s t u d i e s , l i t t l e a t t e n t i o n was p a i d t o t h e n a t u r e o f t h e m e t a l s p e c i e s i n t h e o i l s (£.£., m i n e r a l forms, e n t r a i n e d aqueous phase, e t c . ) . The s t u d y b y C h a k h m a c h k e v et a l . (43) i s s i g n i f i c a n t b e c a u s e t h e s e a u t h o r s a t t e m p t c o r r e l a t i o n s between s y n g e n e t i c and p a r a a u t o c h t h o n o u s ( s i c ) b i t u m e n s o f J u r a s s i c a n d T r i a s s i c s o u r c e r o c k s a n d o i l s f r o m p r o d u c i n g s t r a t a o f t h e same age. In t h i s study, t r a c e element d i s t r i b u t i o n s were used as p a r a m e t e r s f o r o i l - s o u r c e r o c k and o i l - o i l c o r r e l a t i o n s whereas VO(II) p o r p h y r i n s were used to determine source r o c k m a t u r i t y . The DPEP/etio r a t i o s of VO(II) p o r p h y r i n s i n the bitumen decreased w i t h depth. T r a c e element c o n t e n t s o f o i l s and b i t u m e n s were s i m i l a r f o r s u i t e s o f t h e same a g e , i n d i c a t i n g t h a t t h e o i l s may be s y n g e t i c w i t h t h e T r i a s s i c a n d J u r a s s i c h o s t r o c k s , J L . e _ . , t h a t t h e r e a r e two hydrocarbon sources. M a s t et_ a l . ( 4 6 , 4 7 ) d e t e r m i n e d t h e v a n a d i u m c o n t e n t s o f a l a r g e number o f P a l e o z o i c c r u d e o i l s f r o m I l l i n o i s by n e u t r o n a c t i v a t i o n analysis. L i k e Bonham, t h e s e i n v e s t i g a t o r s f o u n d t h a t v a n a d i u m d i s t r i b u t i o n i n the o i l s provided paleogeographic i n f o r m a t i o n . R e l a t i v e l y h i g h vanadium c o n c e n t r a t i o n s were found i n c r u d e s accumul a t e d i n some d e f o r m a t i o n a l l y h i g h s t r u c t u r a l t r a p s . These t r a p s a r e b e l i e v e d t o h a v e f o r m e d a t a t i m e c l o s e t o when t h e s o u r c e r o c k s o f t h e s t u d y c r u d e s b e g a n g e n e r a t i n g o i l . The a u t h o r s c o n t e n d t h a t t h e i r d a t a s u p p o r t t h e s u g g e s t i o n o f Weeks (48) t h a t h e a v y o i l s a r e formed from s o u r c e r o c k s b e f o r e l i g h t o i l s . I t h a s b e e n shown t h a t the i n i t i a l s t a g e s of kerogen d e c o m p o s i t i o n i n v o l v e a decrease i n oxygen t o c a r b o n , n i t r o g e n t o c a r b o n , and s u l f u r t o c a r b o n r a t i o s (49); hence, carbon-heteroatom bonds of source r o c k kerogens break m o r e r e a d i l y u n d e r t h e r m a l s t r e s s t h a n do c a r b o n - c a r b o n b o n d s . T h u s , o i l s i n i t i a l l y f o r m e d f r o m s o u r c e r o c k s w i l l be r e l a t i v e l y r i c h i n s u l f u r , n i t r o g e n , and oxygen. T h e s e o i l s w o u l d be l e s s e x t e n s i v e l y c r a c k e d than those formed l a t e r i n the o i l g e n e r a t i o n process. These e a r l i e r formed, h e a v i e r o i l s would c o n t a i n most o f the m e t a l complexes, which would accumulate i n those t r a p s e x i s t i n g a t t h e o n s e t o f h e a v y o i l g e n e r a t i o n . The p a u c i t y o f i n f o r m a t i o n o n t h e t r a c e e l e m e n t c o n t e n t s o f b i t u m e n s and k e r o g e n s , h o w e v e r , means a d i s t i n c t i o n between the i n h e r i t a n c e o f a t r a c e element "fingerprint"


5.



93

of t h e kerogen i n t h e heavy bitumen a n d t h e c o m p l e x a t i o n o f m e t a l i o n s f r o m t h e m i n e r a l m a t r i x b y t h e e v o l v i n g b i t u m e n c a n n o t b e made at t h i s time. M c l v e r (50) d e t e r m i n e d t h e n i c k e l a n d vanadium c o n t e n t s o f Wind R i v e r B a s i n , Wyoming, c r u d e s o f v a r y i n g a g e s b y X - r a y f l u o r e s c e n c e . He f o u n d t h a t a l l o f t h e C r e t a c e o u s o i l s h a d V / N i r a t i o s t h a t w e r e d i s t i n c t l y d i f f e r e n t from those o f t h e P a l e o z o i c o i l s t h a t were studied. These d i f f e r e n c e s were a l s o r e f l e c t e d i n o t h e r p r o p e r t i e s of t h e c r u d e s . Mclver interpreted these data t o i n d i c a t e d i f f e r e n c e s i n t h e environments o f d e p o s i t i o n o f t h e source r o c k s o f t h e two petroleum s u i t e s , which i s r e f l e c t e d i nthe composition o f the o i l s . H o d g s o n et_ a l . ( 5 1 ) u s e d t h e v a n a d i u m a n d n i c k e l c o n t e n t s o f A l b e r t a crudes t o determine m i g r a t i o n pathways. Their data indicate that within a given o i l f i e l d , distance o fmigration i s r e f l e c t e d in the metal contents o f an o i l pool. They s u g g e s t a d s o r p t i o n o f m e t a l c h e l a t e s and o t h e r p o l a r m a t e r i a l s on r o c k s d u r i n g m i g r a t i o n as a major determinant o f m e t a l c o n t e n t s o f a p e t r o l e u m d e p o s i t . T h i s c h r o m a t o g r a p h i c e f f e c t may b e s i m i l a r t o t h a t a c t i n g o n t h e porphyrin species ofmigrating o i l s . Radchenko (52) m a i n t a i n e d t h a t vanadium i n crude o i l a n d b i t u mens i s o f s e c o n d a r y o r i g i n . Radchenko i n v o k e d b a c t e r i a l a c t i o n i n r e s e r v o i r s t o a c c o u n t f o r many o f t h e u n u s u a l p r o p e r t i e s o f h e a v y bitumens, i n c l u d i n g h i g h vanadium c o n t e n t s . A c c o r d i n g t o Radchenko, the v a n a d i u m c o n t e n t o f a c r u d e o i l w o u l d t h u s n o t a l w a y s be r e l a t e d to t h e t r a c e element s u i t e o f t h e s o u r c e r o c k o f t h e c r u d e , n o r would m i g r a t i o n e f f e c t s n e c e s s a r i l y be s i g n i f i c a n t . A l - S h a h r i s t a n i and A l - A t y i a (53) measured t h e n i c k e l and vanadium c o n t e n t s o f crudes from t h r e e f i e l d s i n I r a q . Their study was d e s i g n e d t o r e s o l v e a c o n t r o v e r s y o v e r t h e o r i g i n o f t h e o i l s o f northern Iraq. One s c h o o l o f t h o u g h t ( 4 8 ) m a i n t a i n s t h a t t h e s o u r c e r o c k s from which t h e o i l s a r e d e r i v e d a r e contemporaneous w i t h t h e l a t e r Cretaceous and e a r l y T e r t i a r y r e s e r v o i r s i n which they a r e found. Another s c h o o l o f thought (54) contends t h a t t h e o i l s were d e r i v e d from e a r l y Cretaceous r o c k s and i n i t i a l l y accumulated i n middle Cretaceous traps. Later, during extensive f o l d i n g and f r a c t u r i n g d u r i n g t h e T e r t i a r y , m u c h o f t h e o i l m i g r a t e d (i.£., s e c o n d a r y migration) v e r t i c a l l y into Tertiary reservoirs. A l - S h a h r i s t a n i and A l - A t y i a r e a s o n e d t h a t i f a l l t h e o i l s came f r o m t h e same s o u r c e r o c k s , b u td i d n o t m i g r a t e f a r , n i c k e l andvanadium c o n t e n t s and v a n a d i u m t o n i c k e l r a t i o s s h o u l d b e s i m i l a r , r e f l e c t i n g a common source. H o w e v e r , i f e x t e n s i v e v e r t i c a l m i g r a t i o n o f some o f t h e o i l s h a d o c c u r r e d , i t was r e a s o n e d t h a t t h e s e o i l s would have l o w e r m e t a l s c o n t e n t s , b u t s i m i l a r v a n a d i u m t o n i c k e l r a t i o s , when c o m p a r e d with the o i l s remaining i nthe middle Cretaceous traps. The n i c k e l and vanadium d a t a o b t a i n e d b y A l - S h a h r i s t a n i a n d A l - A t y i a were i n t e r p r e t e d b y them t o c o n f i r m t h e t h e o r y o f v e r t i c a l m i g r a t i o n f r o m middle Cretaceous t o l a t e Cretaceous and e a r l y T e r t i a r y traps. A b u - E l g h e i t et_ CLL. ( 5 5 ) c o n c l u d e d t h a t t h r e e G u l f o f S u e z M i o c e n e o i l s could be d i s t i n g u i s h e d from f i v e Western Desert Cretaceous o i l s on the b a s i s o f V/Ni contents and that the V/Ni r a t i o decreased w i t h i n c r e a s i n g age (not given). They a l s o c l a i m e d t h a t t h e V/Sb and N i / S b r a t i o s c o u l d a l s o be used t o d i s t i n g u i s h t h e two g r o u p s o f oils. However, t h e s m a l l number o f samples s t u d i e d a n d t h e l a r g e v a r i a t i o n s i n t h e V/Sb a n d N i / S b r a t i o s i n t h e g r o u p s makes t h e conclusions speculative.


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S a b a n e_t a l _ . ( 5 6 ) i n v e s t i g a t e d t r a c e e l e m e n t s u i t e s o f o i l s o f the P a n n o n i a n B a s i n and c o n c l u d e d t h a t t h e V / N i r a t i o i s r e l i a b l e f o r o i l - o i l correlations. They a l s o e x p r e s s r e s e r v a t i o n s about t h e use of V/Ni f o r d e t e r m i n i n g a b s o l u t e ages o f o i l s , c i t i n g numerous c o n f l i c t i n g s t u d i e s i n the l i t e r a t u r e . Connor and G e r r i l d (57) s t u d i e d t r a c e e l e m e n t d i s t r i b u t i o n s and o t h e r p r o p e r t i e s o f a number o f c r u d e s i n t h e E l k H i l l s , C a l i f o r n i a , field. T h e y w e r e among t h e f i r s t g e o c h e m i s t s t o a n a l y z e o i l - o i l c o r r e l a t i o n d a t a by s t a t i s t i c a l t e c h n i q u e s s u c h as m u l t i p l e discriminant function analysis. They were a b l e t o c l a s s i f y t h e E l k H i l l s o i l s i n t o t h r e e d i s t i n c t types u s i n g these methods. Hitchon e t a l . ( 5 8 ) a n d H i t c h o n a n d F i l b y ( 5 9 ) m e a s u r e d 22 e l e m e n t s i n A l b e r t a B a s i n c r u d e o i l s a n d a p p l i e d Q- a n d R-mode f a c t o r a n a l y s i s to the d a t a . They c o n c l u d e d t h a t t h e t r a c e element d i s t r i b u t i o n s were c o n t r o l l e d by o i l m a t u r a t i o n p r o c e s s e s r a t h e r t h a n by m i g r a t i o n processes. They found t h a t a major f r a c t i o n o f the c u m u l a t i v e v a r i a n c e c o u l d be a s s i g n e d t o s u l f u r , v a n a d i u m , s e l e n i u m , and n i c k e l . H i t c h o n and F i l b y (60) u s e d m u l t i p l e - d i s c r i m i n a n t f u n c t i o n a n a l y s i s to r e - e v a l u a t e t h e A l b e r t a o i l t r a c e element d a t a , and were a b l e t o c l a s s i f y the A l b e r t a crudes i n t o three f a m i l i e s . The e l e m e n t s f o u n d t o be d i s c r i m i n a t i n g w e r e s u l f u r , c o b a l t , v a n a d i u m , s e l e n i u m a n d bromine. S t a t i s t i c a l treatment of the t r a c e element data y i e l d e d c l a s s i f i c a t i o n s of the c r u d e s t h a t were s i m i l a r to t h o s e d e t e r m i n e d by t h e more e x p e n s i v e and t i m e consuming methods o f h y d r o c a r b o n and s u l f u r b i o m a r k e r a n a l y s i s used by Deroo e t a l . ( 6 1 ) . The a d v e n t o f a n a l y t i c a l t e c h n i q u e s s u c h a s I C P s p e c t r o m e t r y permits the convenient q u a n t i t a t i v e a n a l y s i s of t r a c e element s u i t e s of f o s s i l f u e l s . D a t a n e e d no l o n g e r be c o n f i n e d t o t h o s e e l e m e n t s , s u c h as v a n a d i u m and n i c k e l , w h i c h a r e f o u n d i n s u b s t a n t i a l c o n c e n trations. C u r i a l e (62) has l a u n c h e d a c o m p r e h e n s i v e program t o a n a l y z e a l a r g e number o f h e a v y c r u d e o i l s and s o l i d b i t u m e n s f o r several trace elements. The o b j e c t i v e s o f t h e s t u d y a r e t o d e t e r m i n e w h e t h e r o r n o t t r a c e m e t a l d a t a c a n be u s e d t o e s t a b l i s h g e n e t i c r e l a t i o n s h i p s among b i t u m i n o u s s u b s t a n c e s a n d t o d i s c o v e r i n t e r n a l r e l a t i o n s h i p s among e l e m e n t s i n t h e m e t a l s u i t e s . The u l t i m a t e purpose i s to e v a l u a t e the u t i l i t y of metal data i n s o l v i n g problems i n f o s s i l f u e l geochemistry. I n more t h a n a hundred heavy o i l s and s o l i d b i t u m e n s s t u d i e d , C u r i a l e (62) found t h a t a n e g a t i v e r e l a t i o n s h i p e x i s t s between API g r a v i t y and c o n c e n t r a t i o n s o f cadmium, chromium, molybdenum, n i c k e l and v a n a d i u m , and t h a t a p o s i t i v e c o r r e l a t i o n b e t w e e n t h e l a s t f o u r m e t a l s and a s p h a l t e n e c o n t e n t e x i s t s . This suggests that these four m e t a l s a r e a s s o c i a t e d w i t h heavy f r a c t i o n s o f p e t r o l e u m and b i t u m e n s . The same c o r r e l a t i o n s w e r e n o t o b s e r v e d f o r c o b a l t , c o p p e r , i r o n , manganese, and z i n c . T h e s e m e t a l s may h a v e d i f f e r e n t m o d e s o f c o o r d i n a t i o n than the other metals. U s i n g data from t h i s study, C u r i a l e was a b l e t o d e m o n s t r a t e a g e n e t i c r e l a t i o n s h i p b e t w e e n c r u d e o i l s and s o l i d b i t u m e n s . The l a t t e r m a t e r i a l s a r e d e r i v e d f r o m t h e f o r m e r by a p r o c e s s t h a t c o n s e r v e s m e t a l s . S o l i d b i t u m e n s do n o t h a v e a mode o f o r i g i n d i f f e r e n t f r o m p e t r o l e u m . I n t h i s manner, C u r i a l e used metals data to p r o v i d e a s o l u t i o n to a geochemical problem. C u r i a l e (63) r e p o r t s on f u r t h e r s t u d i e s u s i n g t r a c e e l e m e n t data i n t h i s volume. E l l r i c h e_t a l . ( 6 4 ) s t u d i e d t h e c o n c e n t r a t i o n s o f 12 t r a c e e l e m e n t s i n 45 c r u d e o i l s f r o m 17 o i l f i e l d s i n t h e M o l a s s e B a s i n o f

5.



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S. G e r m a n y . They found t h a t t h e y c o u l d c l a s s i f y the o i l s i n t o t h r e e f a m i l i e s on the b a s i s o f n i c k e l , vanadium, and s u l f u r c o n t e n t s . They a l s o showed t h a t t h e i o d i n e c o n t e n t s o f t h e c r u d e s c o u l d b e c o r r e l a t e d w i t h the i o d i n e contents o f the formation waters. Hirner (65), i n t h i s volume, r e p o r t s on a c o n t i n u a t i o n o f t h i s study o f the t r a c e e l e m e n t d i s t r i b u t i o n s i n German o i l s a n d a l s o i n c l u d e s t h e m e t a l contents o f source rock kerogens i n the c o r r e l a t i o n study.


M i g r a t i o n and A l t e r a t i o n Processes: t i o n s o f M e t a l Complexes

T h e i r E f f e c t s on the

Distribu-

The e f f e c t s o f c r u d e o i l m i g r a t i o n o n m e t a l l o p o r p h y r i n o r t r a c e m e t a l a b u n d a n c e s h a v e n o t b e e n f u l l y i n v e s t i g a t e d , a l t h o u g h some o f t h e e a r l y t r a c e m e t a l s t u d i e s a l r e a d y c i t e d have attempted t o c o r r e l a t e V/Ni r a t i o s w i t h m i g r a t i o n process (51-53). C h a k h m a c h k e v «et a l . ( 6 6 ) attempted t o simulate g e o l o g i c m i g r a t i o n o f porphyrins i n t h e laboratory by passing an o i l w i t h high VO(II) porphyrin content through c l a y - s a n d columns. These a u t h o r s found t h a t p o l a r V O ( I I ) p o r p h y r i n s were r e t a i n e d on the column r e l a t i v e t o n o n - p o l a r V O ( I I ) porphyrins (not defined) andthat the DPEP/etio r a t i o i nthe i n i t i a l e f f l u e n t s were lower than the crude o i l r a t i o , a s expected from polarity considerations. B u r k o v a et_ a l . ( 2 2 ) u s e d D P E P / e t i o r a t i o s o f V O ( I I ) p o r p h y r i n s f r o m C r e t a c e o u s - J u r a s s i c W. S u r g u t o i l s t o c o r r e l a t e o i l s that hadmigrated t o d i f f e r e n t degrees. Silverman ( 6 8 ) s h o w e d t h a t p o r p h y r i n c o n t e n t s o f some V e n e z u e l a n o i l s e m p l a c e d at v a r i o u s p o i n t s along a m i g r a t i o n path decreased w i t h d i s t a n c eo f migration. The e f f e c t s o f m i g r a t i o n p r o c e s s e s a r e d i s c u s s e d i n more d e t a i l b y F i l b y a n d V a n B e r k e l (10) i n t h i s v o l u m e . The t r a c e m e t a l a b u n d a n c e s i n s o u r c e r o c k b i t u m e n s a r e u n d o u b t e d l y a f f e c t e d when p e t r o l e u m i s g e n e r a t e d f r o m t h e r o c k s . M i g r a t i o n i s believed t o r e s u l t i n a decrease i n asphaltene and r e s i n content of a m i g r a t e d o i l . Thus t h e abundances o f most m e t a l s w h i c h a r e concentrated i nthe asphaltenes should decrease w i t h d i s t a n c eo f m i g r a t i o n , b u t t h e i r r e l a t i v e c o n c e n t r a t i o n s may b e u n a f f e c t e d . T h i s c o n c l u s i o n w a s r e a c h e d b y L e w a n (9) who s t u d i e d t h e e f f e c t s o f m i g r a t i o n on the n i c k e l a n d vanadium c o n t e n t s o f crude o i l s compared w i t h source rock bitumens. However, i f c h r o m a t o g r a p h i c e f f e c t s do change t h e m e t a l l o p o r p h y r i n o r t r a c e m e t a l d i s t r i b u t i o n s o f m i g r a t e d o i l s , i t s t i l l may be p o s s i b l e t o " r e c o n s t r u c t " t h e p o r p h y r i n o r t r a c e m e t a l d i s t r i b u t i o n s c h a r a c t e r i s t i c o f the bitumen i nthe source rock through a n a l y s i s o f the crude o i l a s p h a l t e n e s . S e v e r a l a u t h o r s h a v e shown t h a t b i o m a r k e r s c a n b e t r a n s p o r t e d a n d p r o t e c t e d f r o m biodégradation a s a consequence o f being i n c o r p o r a t e d asphaltene s t r u c t u r e s i n a crude o i l andc a nbe l i b e r a t e d b y a s p h a l t e n e p y r o l y s i s (70,71). In a s i m i l a r manner, p o r p h y r i n s o r o t h e r t r a c e m e t a l s p e c i e s r e t a i n e d w i t h i n t h o s e a s p h a l t e n e m i c e l l e s w h i c h s u r v i v e m i g r a t i o n may n o t have been s u b j e c t e d t o c h r o m a t o g r a p h i c f r a c t i o n a t i o n d u r i n g m i g r a t i o n . The e f f e c t s o f biodégradation ( a n d a s s o c i a t e d w a t e r w a s h i n g ) o n p o r p h y r i n and t r a c e m e t a l d i s t r i b u t i o n s a l s o have not been f u l l y investigated. A s m e n t i o n e d e a r l i e r , B a r w i s e a n d P a r k (16) c o n c l u d e d that biodegraded o i l s from a m a t u r a t i o n sequence had VO(II) p o r p h y r i n d i s t r i b u t i o n s (e.g., DPEP/etio r a t i o s ) s i m i l a r t o those o f r e l a t e d non-degraded o i l s o f s i m i l a r m a t u r i t y , a l t h o u g h no q u a n t i t a t i v e d a t a were p r e s e n t e d . Palmer (72) s t u d i e d t h e V O ( I I ) p o r p h y r i n s

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from a s e r i e s of g e n e t i c a l l y r e l a t e d o i l s from Colombia c o n s i s t i n g of a h i g h l y d e g r a d e d seep o i l ; a r e s e r v o i r b i o d e g r a d e d o i l ; and n o n degraded o i l s . She f o u n d t h a t t h e D P E P / e t i o r a t i o s , t h e s e r i e s m a x i m a (Cî f o r DPEP, C 2 9 f o r e t i o ) , a n d t h e c a r b o n n u m b e r r a n g e s were v e r y s i m i l a r f o r the o i l s . She d i d n o t i c e , h o w e v e r , t h a t i n t h e most degraded seep o i l t h e V O ( I I ) p o r p h y r i n s were e n r i c h e d r e l a t i v e i n N i ( I I ) p o r p h y r i n s compared t o l e s s degraded o i l s . I t i s not c l e a r , however, whether t h i s enrichment i s a r e s u l t of s e l e c t i v e b i o l o g i c a l processes ( s e l e c t i v e degradation of N i ( I I ) p o r p h y r i n s ) , of s e l e c t i v e d i s s o l u t i o n b y a s s o c i a t e d w a t e r w a s h i n g , o r o f s e l e c t i v e o x i d a t i o n of N i ( I I ) p o r p h y r i n s r e l a t i v e to the VO(II) s p e c i e s . S t r o n g a n d F i l b y ( 2 4 ) h a v e a l s o c o n c l u d e d t h a t biodégradation h a d l i t t l e e f f e c t on p o r p h y r i n d i s t r i b u t i o n s i n t h e h i g h l y d e g r a d e d A l b e r t a o i l sands. I f biodégradation h a s l i t t l e e f f e c t o n p o r p h y r i n o r t r a c e m e t a l d i s t r i b u t i o n s , s u c h d i s t r i b u t i o n s may b e i m p o r t a n t c o r r e l a t i o n p a r a m e t e r s when o t h e r b i o s e n s i t i v e b i o m a r k e r s (ί·β_·, m o s t h y d r o c a r b o n s ) c a n n o t be u s e d . Summary The s t u d y o f p o r p h y r i n a n d t r a c e m e t a l s u i t e s i n c r u d e o i l s i s a promising t o o l of geochemical a n a l y s i s . In order to f u l f i l l t h i s p r o m i s e , i n v e s t i g a t i o n s i n a n u m b e r o f a r e a s w o u l d seem t o be n e c e s sary. R e l a t i o n s h i p s between o r g a n i c a l l y a s s o c i a t e d m e t a l s i n p e t r o l e u m and t h o s e i n s o u r c e r o c k s n e e d t o be a c c u r a t e l y d e t e r m i n e d . This r e q u i r e s i n v e s t i g a t i o n of the nature of minor p o r p h y r i n s u i t e s and any n o n - p o r p h y r i n c o m p l e x e s . Lack of a p p r o p r i a t e a n a l y t i c a l t e c h n i q u e s and t h e i n t r a c t a b i l i t y o f t h e s e m a t e r i a l s has caused r e s e a r c h e f f o r t s t o be f o c u s e d o n t h e m o r e e a s i l y s t u d i e d m a j o r p o r p h y r i n s and t h o s e m e t a l s f o u n d i n h i g h c o n c e n t r a t i o n s . I f t h e e t i o / D P E P r a t i o i s t o be u s e d a s a n y k i n d o f i n d i c a t o r , t h e n t h e o r i g i n o f e t i o - p o r p h y r i n s and t h e mechanisms o f e t i o and DPEP p o r p h y r i n d e g r a d a t i o n ( e . , d e a l k y l a t i o n , i s o c y c l i c r i n g s c i s s i o n ; d e m e t a l l a t i o n , e t c . ) m u s t be u n d e r s t o o d . Are the e t i o p o r p h y r i n s p r o d u c t s o f DPEP c o n v e r s i o n , o r a r e t h e y b e t t e r s u r v i v o r s in c e r t a i n environments than DPEP-porphyrins? Or do t h e y a r i s e i n some o t h e r m a n n e r ? Answers t o the above problems w i l l r e q u i r e a p p l i c a t i o n o f a n a l y t i c a l protocols for geoporphyrin analysis. As Q u i r k e h a s shown i n his overview a r t i c l e i n t h i s volume, s e p a r a t i o n techniques f o r geoporphyrins s t i l l lack standardization. Improvements i n our u n d e r s t a n d i n g of the g e o c h e m i s t r y of m e t a l chelates should r e s u l t i n a b e t t e r understanding of petroleum migration, which i n turn should a s s i s t i n p r o s p e c t i n g f o r petroleum. T h i s a c t i v i t y i s o f c o n s i d e r a b l y more t h a n a c a d e m i c i n t e r e s t . Acknowledgments J . F . B r a n t h a v e r t h a n k s t h e U.S. D e p a r t m e n t o f E n e r g y u n d e r C o n t r a c t Number D E - F C 2 1 - 8 3 F E 6 0 1 7 7 .

f o r support

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Literature Cited 1. 2. 3. 4. 5. 6. 7.


8. 9. 10. 11. 12. 13. 14. 15. 16. 17. 18. 19. 20. 21. 22. 23. 24. 25. 26. 27. 28. 29.

Treibs, A. Ann. Chem. 1934, 509, 103-14. Treibs, A. Ann. Chem. 1934, 510, 42-62. Treibs, A. Ann. Chem. 1934, 517, 172-96. Chicarelli, I.M.; Kaur, S.; Maxwell, J.M. (this volume). Quirke, J.M.E.; Maxwell, J . R . ; Eglinton, G.; Sanders, J.K.M. Tetrahedron Lett. 1980, 21, 2987-90. Fookes, C.J.R. J . Chem. S o c ., Chem. Commun. 1983, 1472-73. Ekstrom, Α.; Fookes, C.J.R.; Hambley, T . ; Loeh, H . J . ; Miller, S.A.; Taylor, J . C . Nature 1983, 206, 173-74. Treibs, A. Angew. Chemie 1936, 49, 682-786. Baker, E.W.; Louda, J.W. In "Biological Markers in the Sedi mentary Record"; Johns, R.B., Ed.; Elsevier: Amsterdam, 1986; pp. 125-225. Filby, R.H. and Van Berkel, G.J. (this volume). Baker, E.W.; Louda, J.W. In "Advances in Organic Geochemistry, 1981"; Bjorøy, M., Ed.; John Wiley: London, 1983; pp. 401-21. Mackenzie, A.S.; Quirke, J.M.E.; Maxwell, J.R. In "Advances in Organic Geochemistry, 1979"; Maxwell, J . R . ; Douglas, A . G . , Eds.; Pergamon Press: Oxford, 1980; pp. 239-48. Barwise, A . J . G . ; Roberts, I. Org. Geochem. 1984, 6, 167-76. Shiobara, M.; Taguchi, K. In "Advances in Organic Geochemistry, 1975"; Campos, R.; Goni, J., Eds.; ENADISMA: Madrid, 1977; pp. 237-51. Moldowan, J . M . ; Sundararaman, P.; Schoell, M. Org. Geochem. 1986, 10, 915-26. Barwise, A . J . G . ; Park, P.J.P. In "Advances in Organic Geochemistry, 1981"; Bjorøy, M., Ed.; John Wiley: London, 1983; pp. 668-74. Barwise, A.J.G. (this volume). Hajibrahim, S.K.; Quirke, J.M.E.; Eglinton, G. Chem. Geol. 1981, 32, 173-88. Sundararaman, P. Anal. Chem. 1985, 57, 2204-06. Barwise, A . J . G . ; Evershed, R.P.; Wolff, G.A.; Eglinton, G.; Maxwell, J.M. J . Chromatography 1986, 368, 1-9. Chicarelli, I.M.; Wolff, G.A.; Maxwell, J.M. J . Chromatography 1986, 368, 11-19. Lewan, M.D. Geochim. Cosmochim. Acta 1984, 48, 2231-38. Van Eggelpoel, A. In "Advances in Organic Geochemistry, 1964"; Hobson, G.D.; Louis, M.C., Eds.; Pergamon: Oxford, 1966; pp. 227-42. Strong, D.; Filby, R.H. (this volume). Goulon, J.; Retournard, Α.; Frient, P.; Goulon-Ginet, C . ; Berthe, C . ; Muller, J.F.; Poncet, J.L.; Guilard, R.; Escalier, J . C . ; Neff, B. J . Chem. Soc. Dalton Trans. 1984, 1095-1103. Gransch, J . Α . ; Eisma, E. In "Advances in Organic Geochemistry, 1966"; Hobson, G.D.; Speers, G.C., Eds.; Pergamon: Oxford, 1970; pp. 69-86. Baker, E.W.; Louda, J.W. Org. Geochem. 1984, 6, 183-92. Quirke, J.M.E.; Yost, R.A.; Britton, E.D.; Trichet, J . In "Geochemical Biomarkers"; Yen, T . F . ; Moldowan, J . M . , Eds.; Gordon and Breach Publishers: London (in press). Yen, T.F. In "Role of Trace Metals in Petroleum"; Yen, T . F . , Ed.; Ann Arbor Science: Ann Arbor, 1975; pp. 1-30.

98


30.


Branthaver, J . F . Ph.D. Thesis, North Dakota State University, Fargo, 1976. 31. Van Berkel, G . J . ; Filby, R.H. In "Geochemical Biomarkers"; Yen, T . F . ; Moldowan, J . M . , Eds.; Gordon and Breach Publishers: London (in press). 32. Van Berkel, G . J . ; Filby, R.H. (this volume). 33. Riley, K.W.; Saxby, J.D. Chem. Geol. 1982, 37, 265-75. 34. Spiro, B.; Dinur, D.; Aizenshtat, Z. Chem. Geol. 1983, 39, 184-214. 35. Tissot, B.P. Bull. Amer. Ass. Petrol. Geol. 1984, 68, 545-63. 36. Finkelman, R.B. Ph.D. Thesis, University of Maryland, 1980. 37. Hodgson, G.W. Bull. Am. Assoc. Petrol. Geol. 1954, 38, 2737-54. 38. Ball, J . S . ; Wagner, W.J.; Hyden, H . J . ; Horr, C.A.; Myers, A.T. J . Chem. Eng. Data 1960, 5, 553-57. 39. Hyden, H.J. U.S. Geol. Surv. Bull. 1100-B, 1961. 40. Bonham, L.C. Bull. Am. Assoc. Petrol. Geol. 1956, 40, 897-908. 41. Kotova, Α.V.; Tokareva, L . N . ; Berkovskii, V.G. Tr. Inst. Khim. Prir. Solei. Aked. Nauk. Kuz. SSR 1970, 21, 83. 42. Gilmanshin, A . F . ; Gazinov, M.G.; Baturina, E.N. Tr. Tat. Neft. Nauk. Issled. Inst. 1971, No. 18, 113. 43. Chakhmachkev, V.A.; Lositskaya, I . F . ; Punanova, S.A.; Semenova, R.A. Geokhimiya 1985, 703-09. 44. Katchenkov, S.M.; Flegentova, E . J . Vest. Akad. Nank. Belarus. SSR. Ser. Khim. Nauk. 1970, 95. 45. Mileshina, A.G.; Punenova, S.A.; Checkhovskitah, N.M. Geol. Neft. Gaza 1971, 15, 41. 46. Mast, R.F.; Ruch, R.R.; Atherton, E. Proc. Symposium on Future Petroleum Potential of NPC Region 9: Illinois Geol. Survey Illinois Petroleum 95 1971, 111, 126. 47. Mast, R.F.; Ruch, R.F.; Meents, W.F. Illinois Geol. Survey Circular 483 1973. 48. Weeks, L.G. In "Habitat of Oil"; Weeks, L . G . , Ed.; Amer. Assoc. Petrol. Geol.: 1958; Tulsa; pp. 1-61. 49. Durand, G. and Monim, J . C . In "Kerogen"; Durand, Β . , Ed.; Edition Technip.: Paris, 1980; pp. 113-42. 50. McIver, R.D. In "Symposium on Early Cretaceous Rocks of Wyoming and Adjacent Areas"; Enyert, R.; Curry, W.H., Eds.; Wyoming Geol. Assoc., 17th Annual Field Conf. 1962, 248-51. 51. Hodgson, G.W.; Fiores, J.; Baker, B.L. Bull. Am. Assoc. Petrol. Geol. 1959, 43, 311-28. 52. Radchenko, O.A. "Geochemical Regularities in the Distribution of the Oil-Bearing Regions of the World"; Israel Program for Scientific Translations: Jerusalem; 1968; pp. 201-2. 53. Al-Shahristani, H . ; Al-Atyia, M.J. Geochim. et Cosmochim. Acta 1972, 36, 929-37. 54. Dunnington, H.V. Inst. Petrol. J . 1967, 53, 129-61. 55. Abu-Elgheit, M.; Khalil, S.O.; Barakat, A.O. Prepr. Div. Petrol. Chem. ACS 1979, 24, 793-97. 56. Saban, M.; Vitorovic, O.; Vitorovic, D. In "Symposium on Characterization of Heavy Crude Oils and Petroleum Residues"; Editions Technip: Paris, 1984; pp. 122-27. 57. Connor, J.J.; Gerrild, P.M. Bull. Am. Assoc. Petrol. Geol. 1971, 55, 1802-13.

5.

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58.


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Hitchon, B.; Filby, R.H.; Shah, K.R. In "The Role of Trace Metals in Petroleum"; Yen, T . F . , Ed.; Ann Arbor Science: Ann Arbor, 1975; pp. 111-22. 59. Hitchon, B.; Filby, R.H. Alberta Research Council Open File Report 1983-02, 144 p. 60. Hitchon, B.; Filby, R.H. Bull. Am. Assoc. Petrol. Geol. 1984, 68, 838-49. 61. Deroo, G.; Powell, T . G . ; Tissot, B.; McCrossan, R.G. Bull. Geol. Soc. Canada 1977, 262, 136 p. 62. Curiale, J.A. In "Exploration for Heavy Oil and Bitumen"; Am. Assoc. Petrol. Geol. Research Conference, Santa Maria, C a l i f . , Oct. 28-Nov. 2, 1984, Vol. 1, pp. 1-39. 63. Curiale, J.A. (this volume). 64. Ellrich, J.; Hirner, A.V.; Stark, H. Chem. Geol. 1985, 48, 313-23. 65. Hirner, A.V. (this volume). 66. Chakhmachkev, V.A.; Burkova, V.N.; Zharkov, N . I . ; Punanova, S.A.; Serebrennikova, O.V.; Titov, V . I . Geokhimiya 1985, 381-86. 67. Burkova, V.N.; Serebrennikova, O.V.; Titov, V . I . Geokhimiya 1978, 945-50. 68. Silverman, S.R. In "Fluids in Subsurface Environments"; Young, Α.; Galley, J.E., Eds.; Am. Assoc. Petrol. Geol., Memoir 4, Tulsa, 1965, 53-65. 69. Lewan, M.D. Ph.D. Thesis, University of Cincinnati, 1980. 70. Rubinstein, I . ; Spyckerelle, C . ; Strausz, O.P. Geochim. Cosmochim. Acta 1979, 43, 1-6. 71. Rubinstein, I . ; Strausz, O.P. Geochim. Cosmochim. Acta 1979, 43, 1887-94. 72. Palmer, S.E. Abstract 186th ACS Meeting, Washington, DC, 1983. 73. Yang, Z . ; Li, Y . ; Cheng, Z . ; Zhang, D. In "Geochemical Biomarkers"; Yen, T . F . ; Moldowan, J . M . , Eds.; Gordon and Breach: London (in press). 74. Shi, J . Y . ; Mackenzie, A.S.; Alexander, R.; Eglinton, G.; Gowar, A.P.; Wolff, G.A.; Maxwell, J.R. Chem. Geol. 1982, 35, 1-31. 75. Hoffman, C.F.; Strausz, O.P. Bull. Amer. Ass. Petrol. Geol. 1986. 70, 1113-28. RECEIVED March 30, 1987

Chapter 6

M e c h a n i s m s Involved

in

Altering

Deoxophyllœrythroetioporphyrin-Etioporphyrin Ratios in Sediments and

Oils

1

A. J. G. Barwise


Exploration and Production Division, BP Research Centre, Sunbury-on-Thames, England

The possible mechanisms which might be involved in causing alteration in DPEP/etio ratios in sediments and o i l s are discussed. Qualitative and quantitative data from a suite of source rock extracts show that several mechanisms may be involved. Data from related oils show that, whatever the mechanism, porphyrin ratios are extremely sensitive parameters for indicating the effects of thermal maturity.

Geochemists are interested in applying biomarker geochemistry to petroleum exploration problems, and many different biomarker reactions have been proposed as potential indicators of the thermal s t r e s s experienced by sediments or o i l s . One of the e a r l i e s t parameters to be investigated as a potential maturity indicator [I) was the ratio of DPEP to etio type porphyrins (see Figure 1 f o r structures). With increasing thermal s t r e s s , the e t i o type becomes r e l a t i v e l y more abundant compared with the DPEP type. The supposed mechanism f o r this reaction i s an intramolecular scission of the i s o c y c l i c ring (I). However, with the advent of new analytical techniques such as high performance l i q u i d chromatography (HPLC 2-4) and the structural elucidation of a number of porphyrin molecules from sediments ( e . g . 5-8), there i s a growing understanding of the diagenetic pathways leading to porphyrin molecules found in sediments and o i l s . This has led to doubts regarding the original simple explanation of the cause of changes in DPEP/etio r a t i o s . (9) In t h i s paper, several alternative mechanisms are discussed and evidence i s presented to show that a simple intramolecular s c i s s i o n is not the only mechanism which could explain the d i s t r i b u t i o n of porphyrins observed in nature. In order to examine the e f f e c t of thermal maturity on porphyrin d i s t r i b u t i o n s , a suite of source rock 'Current address: Standard Oil Production Company, 8404 Esters Boulevard, Irving, TX 75063 0097-6156/87/0344-0100$06.00/0 © 1987 American Chemical Society


6.

BARWISE

Deoxophylloerythroetioporphyrin-Etioporphyrin

Figure 1: Generalised Porphyrin Structures, (b) Etio type (c) B-Unsubstituted type.

101

Ratios

(a)

DPEP

type

102


extracts from a Gulf of Suez Formation were examined. These rocks vary in maturity across the basin and present day depth r e f l e c t s maximum maturity. There is l i t t l e change in source f a c i e s , and thus the effects of maturity can be d i r e c t l y observed. The quantity of vanadyl porphyrins in each sediment was determined using v i s i b l e absorption spectroscopy. Porphyrin d i s t r i b u t i o n s were determined by HPLC a n a l y s i s . Integration of the HPLC d i s t r i b u t i o n s was used to determine DPEP/etio r a t i o s . Oils thought to have been derived from this source rock were also examined. As for the sediments, the separated vanadyl fractions were demetallated and examined by HPLC.


Experimental Rock samples were ground and extracted with dichloromethane. Nickel and vanadyl fractions were separated and quantitated as described previously (10). The fractions were demetallated using hot methane sulphonic acid at 100 C. HPLC analysis of the demetallated fractions was performed as follows. The HPLC system consisted of a Rheodyne 7125 injection valve, three 25cm χ 0.5cm i . d . 5um Spherisorb s i l i c a HPLC columns linked in s e r i e s , a Perkin-Elmer LC55 detector set at 400nm and an HP laboratory data system for integration of the peaks. The s o l v e n t program c o n s i s t e d of a g r a d i e n t system as f o l l o w s . Solvent A was 1% a c e t i c a c i d in hexane. Solvent Β was 4:1 dichloromethane:acetone. A linear gradient elution was used from 20%A:80%B to 80%A:20%B over 30 minutes with the f i n a l composition held for a further 15 minutes. Details of these and similar HPLC conditions have been published elsewhere Q_l). A parameter c a l l e d the porphyrin index was devised from the HPLC measurements which r e f l e c t s the overall DPEP/(DPEP+etio) r a t i o . This is based upon a summation of C32-C28 f u l l y alkylated DPEP components and C32-C28 f u l l y alkylated etioporphyrins. This avoids the inclusion of porphyrins which are not s t r i c t l y DPEP molecules or B-unsubstituted etioporphyrins into the r a t i o . Results and Discussion If the s c i s s i o n of the DPEP i s o c y c l i c ring is the main mechanism for the production of etioporphyrins then one would expect that meso-substituted porphyrins would be the most abundant etioporphyrin type to be found in sediment extracts and o i l s . However examination of many sediment extracts by t h i s author has shown that this is not the case. As an example, Figure 2 shows a porphyrin HPLC distribution from G i l s o n i t e , a natural bitumen. The major etioporphyrin types are a fully alkylated series and a B-unsubstituted s e r i e s . Meso-substituted porphyrins, i f present, are in low abundance in this sample and in a l l of the samples that this author has examined to date. Thus suspicion was raised as to the origin of etioporphyrins in sediments. In order to test where the DPEP/etio ratios were changing in sediments, a series of rock extracts was examined. Figure 3 shows the DPEP/DPEP+etio ratio for the Suez sediments as a function of depth of b u r i a l . These were derived from the demetallated vanadyl fraction and show that a sudden decrease in value occurs at approximately 10,000 f e e t . At c a . 12,000 feet the value reaches


6. BARWISE Deoxophylherythroetwporphyrin-Etioporphyrin Ratios 103

104



1.0

Porphyrin Index

4000

6000

8000

10000

12000

14000

Depth (Feet)

Figure 3: Porphyrin Sediments.

Index

Versus

Depth

of

Burial

for

Suez


6.

BARWISE

Deoxophylloerythwetioporphyrin-Etioporphyrin

Ratios

105

zero, i . e . no DPEP types could be detected. Thus DPEP/etio ratios do r e f l e c t a change in thermal maturity, but whether or not this change i s due to an i n t r a m o l e c u l a r r e a c t i o n i s u n c l e a r . In order to investigate this further, the concentration of vanadyl porphyrins in the sediments was determined and the concentration of etio and DPEP types estimated from HPLC. Figure 4 shows the results expressed as ug porphyrin per gram carbon in the sediment. There are several points of note in this p l o t . F i r s t l y , etioporphyrins were detected in a l l sediments using the HPLC technique. Thus etioporphyrins must be derived from low temperature diagenetic processes. Secondly, a sudden increase in concentration of etioporphyrins is seen to be coincident with the onset of generation of o i l from the source rock. This could imply that etioporphyrins are derived from the thermal decomposition of kerogen. T h i r d l y , at high maturities l i t t l e or no porphyrin i s observed implying that they are thermally destroyed. To complicate matters further, expulsion of o i l from the source rock causes porphyrin concentrations to decrease with o i l expelled in the first part of the window being r e l a t i v e l y enriched in DPEP porphyrins. Thus in nature, there could be a combination of factors which a l t e r DPEP/etio r a t i o s i n sediments and o i l s . These are discussed b r i e f l y below. Oxidative Cleavage. Since etioporphyrins are present in sediments of low thermal maturity, another mechanism must be accountable, at least in part, for t h e i r formation. Oxidative cleavage of the i s o c y c l i c r i n g i s well documented (1_2) and i s a l i k e l y route by which etioporphyrins are generated. Alternate reduction or decarboxylation could produce both the fully alkylated and B-unsubstituted etioporphyrin series observed in geological samples, analogous to the formation of pristane and phytane. Oxidation produces highly functionalised intermediates which could chemically bind onto kerogen via a condensation reaction. Generation From Kerogen. The results shown above suggest that large quantities of etioporphyrins are generated from kerogen under natural burial conditions. Laboratory studies using pyrolysis techniques (13) have also shown that s i g n i f i c a n t quantities of etioporphyrins are released from kerogen during heating. This author now believes that t h i s i s the main mechanism by which DPEP/etio ratios change in sediments and o i l s . The oxidative mechanism probably gives r i s e to highly functionalised etioporphyrin precursors which could readily bond onto kerogen during early diagenesis. Tentative evidence so far suggests that more etioporphyrins are bound onto kerogen than are DPEP types. However, t h i s i s d i f f i c u l t to prove since i t could be argued that the DPEP i s o c y c l i c ring i s cleaved simultaneously during release from kerogen. Thermal Destruction. At high subsurface temperatures, thermal destruction causes a rapid depletion of the concentration of p o r p h y r i n s i n a sediment or an o i l . The r a t i o of DPEP/etio porphyrins may well a l t e r simply because of a difference in thermal s t a b i l i t y of the two types of molecule. It has been reported that etioporphyrins are thermally much more stable than DPEP types (14). A r e l a t i v e l y small difference in thermal s t a b i l i t i e s could e a s i l y



106

Depth(feet)

Figure 4: Data for the Suez sediments showing absolute concentrations of DPEP ( . . · . ) and etioporphyrins ( ) versus depth and also the y i e l d of soluble extract ( ) versus depth. Porphyrin y i e l d s are expressed as ug porphyrin per g. rock. Extract y i e l d s are expressed as ppt. of rock (divided by 4 to f i t s c a l e ) .

6.

BARWISE


Ratios

107


account f o r a rapid change in DPEP/etio ratio during thermal destruction. This i s i l l u s t r a t e d in Figure 5 where a small difference in activation energies (ca. 10kJ/mol.) i s assumed. This diagram shows a theoretical plot of DPEP/(etio+DPEP) ratios as a function of increasing temperature assuming burial under simulated geological conditions (continual burial at a rate of lC/MYr). As can be seen, a molecular intraconversion reaction does not have to be invoked in order to explain changes in r a t i o . How important this mechanism i s compared to the others remains to be seen. Detailed experimental work needs to be c a r r i e d out to measure rates of destruction of both porphyrin types. Expulsion. Since DPEP/etio ratios change over the o i l generation window, the effect of expulsion should be considered. Over t h i s window, material present in the indigenous bitumen (DPEP rich) is diluted with material generated from kerogen (etioporphyrin r i c h ) . Stepwise expulsion leads to the f i r s t products being enriched in DPEP porphyrins whilst l a t e r expulsion products contain r e l a t i v e l y more etioporphyrins. Again, no molecular intraconversion reactions need to be invoked in order to explain changes in DPEP/etio r a t i o s . O v e r a l l , i t appears that there are a number of different factors which affect DPEP/etio ratios in sediments and o i l s . No one single mechanism can be used to d e s c r i b e observed changes i n n a t u r e . However the fact that porphyrin d i s t r i b u t i o n s are so sensitive to generation and expulsion effects makes them p o t e n t i a l l y very useful to geochemists. As an example, Table I shows properties of o i l s derived from the Suez source rock s u i t e . These o i l s vary in property from low API gravity (14 ) to moderately high API gravity (33 ), high sulphur to low sulphur. Examination of t h e i r porphyrin d i s t r i b u t i o n s shows that these changes in bulk property are the effect of thermal maturity. There i s a c l e a r r e l a t i o n s h i p between p h y s i c a l o i l properties and DPEP/etio ratios and this i s probably a r e f l e c t i o n of the temperature at which the o i l s were expelled from the source rock. Comparison of the o i l DPEP/etio ratios with the c a l i b r a t i o n plot for the sediments shows that the o i l s correspond to a temperature range of expulsion of c a . 100-140 C. Without knowing the source rock data i t i s possible to rank the o i l s in order of increasing maturity using porphyrin data a l o n e . In many cases bulk p r o p e r t i e s and other biomarker parameters would not be able to readily rank the o i l s in maturity sequence. Conclusions Data from the f i e l d study have shown that the mechanism for the change in DPEP/etio ratios with increasing thermal stress i s more complex than was previously thought. Etioporphyrins appear to be produced via an oxidative mechanism during early diagenesis. The bulk of etioporphyrins appear to be generated from the decomposition of kerogen during o i l and gas formation. Other mechanisms such as thermal destruction and expulsion effects may also have a role to play. Empirical observations suggest that porphyrin ratios are an extremely sensitive parameter for determining the maturity of an o i l . There i s l i t t l e need to invoke an intramolecular bond s c i s s i o n to account for observed d i s t r i b u t i o n s in nature. Laboratory and f i e l d

108



1

, TOO

j

, 120

,

, 140

,

^

^

^

^

^

160

Temperature (C)

Figure 5: Theoretical plot of DPEP/(DPEP+etio) ratios for sediments heated over a g e o l o g i c a l t i m e s c a l e . It assumes a 10kJ/mol higher activation energy for destruction of etioporphyrin compared to DPEP (E(DPEP) = 200KJ/mol E(etio) = 210kJ/mol).

j 180

6.

BARWISE


Ratios

109

data need to be c o l l e c t e d i n order to i n v e s t i g a t e the p o s s i b l e involvement of the above mechanisms. Table I. DATA FROM GULF OF SUEZ OILS OÏL

Â

B


° A P I GRAVITY 13.7 17.8 SULPHUR (%) 5.2 3.8 NICKEL (ppm) 148 145 VANADIUM (ppm) 190 162 DPEP 0.80 0.66 DPEP + ETIO

C 21.6 3.3 101 100 0.63

D 25.2 2.2 50 54 0.34

Ê 28.6 1.9 23 26 0.54

F 29.1 1.6 28 57 0.52

G 30.5 1.7 23 32 0.26

H

I

31.1 32.7 1.2 1.0 17 4 29 10 0.28 0.11

I would l i k e to thank the management of B r i t i s h Petroleum f o r giving me permission to publish t h i s paper and A l a s t a i r Mann for carrying out some of the analyses.

Literature Cited 1. 2. 3. 4. 5. 6. 7. 8. 9. 10. 11. 12. 13. 14.

Didyk, B.M.; Alturki, Y.I.Α.; Pillinger, C . T . ; and Eglinton, G. Nature 1975, 256, 563-565. Hajibrahim, S.K.; Tibbetts, P.J.C.; Watts, C.D.; Maxwell, J . R . ; Eglinton, G.; Colin, H . ; and Guiochon, G. Anal. Chem. 1978, 50, 549-553. Barwise, A.J.G. and Park, P.J.D. In "Advances in Organic Geochemistry" 1981 (eds. M. Bjoroy et al.) John Wiley and Sons Ltd. 1983; pp. 668-674. Sundararaman, P. Anal. Chem. 1985, 57, 2204-2206. Quirke, J.M.E.; Eglinton, G.; and Maxwell, J.R. J. Amer. Chem. Soc. 1979, 101, 763-769. Ocampo, R.; Callot, H . J . ; and Albrecht, P . J . Chem. Soc., Chem. Commun. 1985, 200-201. Fookes, C.J.R. ibid. 1984, 1472-1473. Chicarelli, M. and Maxwell, J.R. Tetrahedron Lett. 25, 1984, 4701-4704. Barwise, A.J.G. and Roberts, I. 1985 In "Advances in Organic Geochemistry" 1983 (ed. P.A. Schenck et a l . ) Pergamon Press pp. 167-176. Barwise, A.J.G. and Whitehead, E.V. 1981 In "Advances in Organic Geochemistry" 1979 (eds. A.G. Douglas and J.R. Maxwell) Pergamon Press 1980 pp. 181-192. Barwise, A . J . G . ; Evershed, R.P.; Wolff, G.A.; Maxwell, J.R.M.; and Eglinton, G . , J. Chromatogr. 1986, 368, 1-9. Baker, E.W. and Louda, J.W. 1983 In "Advances in Organic Geochemistry" 1981 (ed. M. Bjoroy et al.) Wiley, pp. 401-421. Van Berkel, G. and Filby, R.H. 1986 A.C.S. Meeting. New York. April 13-18. Burkova, U.N.; Ryadnova, O.V.; Serebrennikova, O.W.; and Titov, V.I. 1980, Geokhimiya 9 1417-1421.

RECEIVED January 29, 1987

Chapter 7

Generation of Nickel and Vanadyl Porphyrins from Kerogen During Simulated Catagenesis Gary J. Van Berkel and Royston H. Filby


Department of Chemistry and Nuclear Radiation Center, Washington State University, Pullman, WA 99164-1300

The fate of the Ni and V complexes in Woodford and New Albany oil shale kerogens during simulated catagenesis was studied by laboratory pyrolysis at 100-450°C in toluene. Sequential pyrolysis of the same kerogen aliquot at increasing temperatures allowed a distinction to be made between metal complexes in the pyrolysate which were components of residual bitumen associated with the kerogen (low temperature pyrolysis) and those complexes generated from the kerogen matrix (high temperature pyrolysis). Both Ni(II) porphyrin (NiP) and VO(II) porphyrin (VOP) were generated from the kerogen matrix and in proportion to the amount of organically combined Ni and V in the kerogen. There is no indication that either type of porphyrin is chemically bound to the kerogen matrix, but the porphyrin compositions of the bitumen and pyrolysates are different. The pyrolysate VOP composition shifts to lower carbon number and increases in the amount of etio type porphyrins relative to DPEP type porphyrins as pyrolysis temperature increases. Results also indicate that release of Ni and V complexes from kerogen during catagenesis may substantially alter the Ni and V concentration, porphyrin content, and porphyrin composition of the bitumen accumulating in a source rock. There is increasing evidence that kerogen plays a major role in the geochemistry of biomarker compounds, particularly the porphyrins, in source rocks. Several experimental studies have shown that kerogen liberates a variety of biomarkers upon heating (_l-3), but no data on the porphyrins have been presented. Most of the evidence that indicates a kerogen-porphyrin association is indirect and is based on the analysis of porphyrins from sedimentary rocks, bitumens, and petroleums. For example, high molecular weight geoporphyrins (^33) are hypothesized to originate during catagenesis as thermal cracking 0097-6156/87/0344-0110$07.25/0 © 1987 American Chemical Society


7.

VAN B E R K E L A N D FU BY

Generation

of Nickel and Vanadyl

Porphyrins

111

o f C-C b o n d s r e l e a s e s p o r p h y r i n s c h e m i c a l l y b o u n d t o t h e k e r o g e n m a t r i x (_4,5) . S t u d i e s o f p o r p h y r i n d i s t r i b u t i o n s i n b i t u m e n s f r o m rocks at d i f f e r e n t degrees o f thermal maturation i n sedimentary b a s i n s (6,7_) h a v e b e e n i n t e r p r e t e d t o i n d i c a t e t h a t s u b s t a n t i a l q u a n t i t i e s o f VOP a r e g e n e r a t e d f r o m k e r o g e n d u r i n g c a t a g e n e s i s . A l s o , B a k e r a n d L o u d a ( 8 ) h a v e p o s t u l a t e d t h a t N i P a n d VOP f o r m v i a d i f f e r e n t pathways i n sediments. The N i P i s c o n s i d e r e d t o f o r m p r i m a r i l y a s f r e e o r s o l v e n t e x t r a c t a b l e s p e c i e s , w h e r e a s VOP f o r m s i n a bound, o r n o n - e x t r a c t a b l e , s t a t e l i n k e d t o kerogen and i s o n l y l i b e r a t e d when t h e t h e r m a l s t r e s s b r e a k s t h e k e r o g e n - V O P l i n k a g e . At t h e p r e s e n t t i m e , t h e r e i s no s a t i s f a c t o r y e x p l a n a t i o n f o r the apparent u n i q u e kerogen enhanced c h e l a t i o n and/or a s s o c i a t i o n o f VOP. I n f a c t , r e c e n t s t u d i e s ( 9 - 1 1 ) h a v e shown t h a t some k e r o g e n s may c o n t a i n s i g n i f i c a n t q u a n t i t i e s o f b o t h o r g a n i c a l l y b o u n d N i a n d V. M o r e o v e r , S p i r o et_ a l . ( 1 1 ) f o u n d t h a t t h e N i / V r a t i o i n t h e k e r o g e n o f some I s r a e l i o i l s h a l e s a n d t h e N i P / V O P r a t i o i n t h e a s s o c i a t e d bitumen were p r o p o r t i o n a l (but independent o f t h e N i and V contents of themineral phase), i n d i c a t i n g possible c o r r e l a t i o n between t h e p o r p h y r i n c o n t e n t s o f t h e bitumen and t h e N i and V concentrations i n the kerogen. The c h e m i c a l s t a t e s o f N i a n d V i n kerogen have n o t been d e t e r m i n e d , b u t a major f r a c t i o n o f b o t h metals i sp r o b a b l y present as s t a b l e t e t r a p y r r o l e complexes. Whether t h e s e complexes a r e c h e m i c a l l y bound t o t h e k e r o g e n m a t r i x ( a l k y l bonds, e s t e r bonds, e t c . ) , t r a p p e d i n a m o l e c u l a r s i e v e t y p e network, or s t r o n g l y adsorbed i s u n c e r t a i n . The m e c h a n i s m o f i n c o r p o r a t i o n o f t h e s e m e t a l i o n s and/or m e t a l complexes i n t o t h e k e r o g e n i s unknown, and t h e d i a g e n e t i c s t a g e d u r i n g w h i c h i n c o r p o r a t i o n t a k e s p l a c e a n d the f a t e o f t h e s e complexes d u r i n g c a t a g e n e s i s h a s n o t been i n v e s tigated. I n t h i s p a p e r , l a b o r a t o r y p y r o l y s i s was u s e d t o s t u d y t h e r e l e a s e o f N i and V complexes from o i l s h a l e kerogens d u r i n g simulated catagenesis. The o b j e c t i v e s o f t h i s s t u d y were: (1) t o d e t e r m i n e t h e amount a n d t y p e o f N i a n d V c o m p l e x e s r e l e a s e d f r o m a kerogen d u r i n g s i m u l a t e d c a t a g e n e s i s , and (2) t o determine t h e r e l a t i o n s h i p s among t h e N i a n d V c o m p l e x e s i n t h e k e r o g e n , t h e comp l e x e s r e l e a s e d f r o m t h e k e r o g e n d u r i n g p y r o l y s i s , a n d t h o s e complexes present i n t h e a s s o c i a t e d o i l shale bitumen. Sequential p y r o l y s i s o f t h e same k e r o g e n a l i q u o t a t i n c r e a s i n g t e m p e r a t u r e s w a s used t o d i s t i n g u i s h between m e t a l complexes i n t h e p y r o l y s a t e which were components o f r e s i d u a l bitumen a s s o c i a t e d w i t h t h e kerogen ( o r s o l u b l e o r g a n i c m a t t e r (OM) o r i g i n a l l y p r e s e n t o n t h e r o c k m a t r i x but w h i c h a s s o c i a t e d w i t h t h e kerogen a f t e r d e m i n e r a l i z a t i o n ) and those complexes g e n e r a t e d d u r i n g t h e r m a l breakdown o f t h e k e r o g e n . The c o n c e n t r a t i o n s o f N i a n d V w e r e d e t e r m i n e d b y i n s t r u m e n t a l neutron a c t i v a t i o n a n a l y s i s (INAA). The p o r p h y r i n c o n t e n t s o f t h e bitumen and kerogen p y r o l y s a t e s were determined by U V - v i s i b l e spectrometry and high-performance l i q u i d chromatography (HPLC). Experimental Samples S e l e c t i o n and P r e p a r a t i o n . M i s s i s s i p p i a n New A l b a n y S h a l e ( H e n r y v i l l e Bed O u t c r o p , C l a r k County, IN) and M i s s i s s i p p i a n D e v o n i a n W o o d f o r d S h a l e ( S p r i n g e r O u t c r o p , C a r t e r C o u n t y , OK) w e r e the sources o f t h e kerogens used i n t h i s study. D e t a i l e d g e o l o g i c a l

112



i n f o r m a t i o n o n t h e s e s h a l e s c a n be f o u n d e l s e w h e r e ( 1 2 , 1 3 ) . The s a m p l e p r e p a r a t i o n scheme i s o u t l i n e d i n F i g u r e 1. E a c h s h a l e was g r o u n d t o 200 m e s h a n d t h e n b i t u m e n - I was e x t r a c t e d b y s o n i c a t i o n w i t h t o l u e n e / m e t h a n o l ( 7 : 3 v / v ; 2 mL s o l v e n t / g s h a l e , 6 χ 45 m i n ) a t 40 C. The e x t r a c t s w e r e c o m b i n e d a n d f i l t e r e d ( 0 . 4 5 ym F l u o r o p o r e ) , and t h e s o l v e n t removed u s i n g a r o t a r y e v a p o r a t o r . B i t u m e n - I f r e e s h a l e (BF S h a l e ) was d r i e d i n v a c u o ( 8 0 C) a n d t h e n d e m i n e r a l i z e d u s i n g a p r o c e d u r e s i m i l a r t o t h a t o f D u r a n d and N i c a i s e (14). A f t e r n e u t r a l i z a t i o n o f r e s i d u a l HC1-HF o n t h e k e r o g e n w i t h d i l u t e ΝΉ3 f o l l o w e d b y s e v e r a l w a s h i n g s w i t h d o u b l e d i s t i l l e d H 2 O , t h e k e r o g e n c o n c e n t r a t e was d r i e d i n v a c u o (80°C). The k e r o g e n was t h e n e x t r a c t e d w i t h t o l u e n e / m e t h a n o l ( 7 : 3 v / v ; 2 mL solvent/g k e r o g e n , 6 χ 45 m i n ) t o r e m o v e b i t u m e n ( J L . £ . , b i t u m e n - I I ) l i b e r a t e d d u r i n g t h e a c i d d i g e s t i o n , a n d a g a i n v a c u u m d r i e d (80°C). Bitumen-II was i s o l a t e d u s i n g t h e same p r o c e d u r e a s f o r b i t u m e n - I . Kerogen P y r o l y s i s . The k e r o g e n s w e r e p y r o l y s e d a t c o n s t a n t t e m p e r a t u r e s w i t h i n t h e r a n g e o f 100-450°C i n a 1 L a u t o c l a v e (Autoclave E n g i n e e r s , E r i e , PA) a s shown i n F i g u r e 1. An a l i q u o t o f k e r o g e n t o g e t h e r w i t h 350 mL o f t o l u e n e was a d d e d t o t h e a u t o c l a v e a n d t h e system s e a l e d . The s y s t e m was p u r g e d w i t h n i t r o g e n f o r 5 m i n w i t h c o n s t a n t s t i r r i n g ( 1 0 0 0 r p m ) , p r e s s u r i z e d t o 250 p s i w i t h n i t r o g e n , then brought to the d e s i r e d temperature. The t e m p e r a t u r e o f t h e s y s t e m was a l l o w e d t o e q u i l i b r a t e (~1 h ) , m a i n t a i n e d f o r 5 h , a n d t h e n a l l o w e d t o c o o l t o b e l o w 80°C b e f o r e o p e n i n g t h e s y s t e m . P y r o l y s e d k e r o g e n was i s o l a t e d f r o m t h e p y r o l y s a t e b y c e n t r i f u g a t i o n a n d f i l t r a t i o n ( 0 . 4 5 ym F l u o r o p o r e ) a n d t h e n f u r t h e r e x t r a c t e d b y s o n i c a t i o n w i t h t o l u e n e ( 1 0 0 mL, 3 χ 20 m i n ) a t 40 C ( t o l u e n e / m e t h a n o l (7:3 v/v) i n t h e c a s e o f W o o d f o r d k e r o g e n ) . The filtered e x t r a c t s were c o m b i n e d and e v a p o r a t e d t o d r y n e s s t o y i e l d t h e pyrolysate. The p y r o l y s a t e i n t h i s c a s e i s d e f i n e d a s t h e s o l u b l e o r g a n i c m a t e r i a l l i b e r a t e d from the k e r o g e n w h i c h has a b o i l i n g point greater than that of toluene. The p y r o l y s e d k e r o g e n was vacuum d r i e d (80 C ) , s a m p l e d , and t r a n s f e r r e d t o t h e a u t o c l a v e f o r subsequent p y r o l y s i s at higher temperature. The p y r o l y s i s p r o c e d u r e was t h e n r e p e a t e d . Elemental A n a l y s i s . E l e m e n t a l a n a l y s i s (C,H,N,0) was c a r r i e d o u t C a n a d i a n M i c r o a n a l y t i c a l , LTD ( V a n c o u v e r , BC) u s i n g a C a r l o E r b a M o d e l 1106 E l e m e n t a l Analyzer. X-Ray D i f f r a c t i o n (XRD). XRD p a t t e r n s w e r e o b t a i n e d powder d e f r a c t o m e t e r u s i n g C u - K radiation.

with a

by

Norelco

a

Trace Element A n a l y s i s . C o n c e n t r a t i o n s o f N i and V w e r e d e t e r m i n e d by INAA. Sample a l i q u o t s and a p p r o p r i a t e s t a n d a r d s w e r e w e i g h e d i n t o c l e a n 1.5 mL p o l y v i a l s , r e - e n c a p s u l a t e d i n 7.5 mL p o l y v i a l s , b o t h o f w h i c h w e r e h e a t s e a l e d , and t h e n i r r a d i a t e d i n t h e W a s h i n g t o n S t a t e U n i v e r s i t y TRIGA I I I r e a c t o r . Gamma-ray s p e c t r a w e r e r e c o r d e d u s i n g t h e N u c l e a r D a t a ND 6 7 0 0 G e ( L i ) γ-ray s p e c t r o m e t e r system. The n u c l e a r r e a c t i o n s a n d m e t h o d s u s e d t o r e d u c e γ-ray s p e c t r a t o m e t a l c o n c e n t r a t i o n s were s i m i l a r t o t h o s e o f J a c o b s and F i l b y ( 1 5 ) . C o r r e c t i o n of the kerogen N i or V content to a m i n e r a l - f r e e b a s i s was c a r r i e d o u t i n a m a n n e r s i m i l a r t o t h a t o f V a n B e r k e l a n d F i l b y

(9).

Generation

VAN B E R K E L A N D FILBY


Porphyrins

SHALE 200

I

sonication

mesh toluene/MeOH (7:3v/v)

insoluble

BF

soluble

SHALE

BITUMEN-I

HCL/HF


soluble

insoluble

WASTE

ORGANIC

sonication

RESIDUE

toluene/MeOH (7:3v/v)

insoluble

soluble

KEROGEN

Kerogen

BITUMEN-II

0

> t

v N

Autoclave

N

2

0 C H

2

0 C H

3

Pyrolysate

1

Pyrolysate

pyrolysis

insoluble

marcasite > covellite ~ rutile

68.22 6.71 2.24 4.83 1.17 0.05

a

-18 w t % pyrite > marcasite > ammonium c h l o r i d e

o f o r g a n i c n i t r o g e n content i s u n c e r t a i n because o f ammonium c h l o r i d e ( N H ^ C l ) i n t h e k e r o g e n m a t r i x .

M i n e r a l i m p u r i t y c o n t e n t u n c o r r e c t e d f o r o r g a n i c a l l y bound m e t a l contents. O r g a n i c a l l y combined N i and V a l o n e a c c o u n t f o r -0.3 w t % o f t h e apparent m i n e r a l component.

7. VAN B E R K E L A N D FILBY

Table I I .

Nickel

Generation

of Nickel and Vanadyl Porphyrins

a n d V a n a d i u m C o n t e n t o f New A l b a n y a n d W o o d f o r d Kerogen

Trace Element o r Ratio 3

[Ni]

K

[V] (Ni/V)

K

[Ni]

K

K

[v]

M

F

M F K


(Ni/V)

M F K

115

New

Element Content

Albany Shale Kerogen

(yg/g)

Woodford S h a l e Kerogen

2 5 0 0 ± 34 730 ± 16 3.42 + 0.09

505 ± 1 9 3 2 7 0 ± 62 0.154 ± 0.007

2128 ± 8 1 698 ± 26 3.05 ± 0.16

353 ± 3 3 3 2 6 2 ± 97 0.108 ± 0.01

C o n c e n t r a t i o n s ( y g / g ) o f N i a n d V i n t h e k e r o g e n ([Χ]χ) a n d m i n e r a l - f r e e k e r o g e n ([X]MFK)· M i n e r a l - f r e e kerogen v a l u e s were c a l c u l a t e d i n a manner s i m i l a r t o Van B e r k e l and F i l b y ( 9 ) . Ni/V r a t i o s a r eweight/weight r a t i o s .

polymorph, m a r c a s i t e . I n a d d i t i o n t o t h e s e m i n e r a l s , New A l b a n y kerogen a l s o c o n t a i n e d r u t i l e (T1O2) and c o v e l l i t e (CuS). Rutile was a n e x p e c t e d i m p u r i t y , b u t c o v e l l i t e , w h i c h i s s o l u b l e i n h o t HC1, w a s u n e x p e c t e d . However, because o f t h e h i g h c o n c e n t r a t i o n o f Cu i n t h e s h a l e ( 2 3 6 ppm, 1 3 ) a n d p o s s i b l e i n t e r g r o w t h s o f c o v e l l i t e and p y r i t e , t h e s u r v i v a l o f t h e f o r m e r i n t h e r i g o r o u s a c i d d i g e s tion i s probable. In a d d i t i o n t o p y r i t e and m a r c a s i t e , the Woodford kerogen a l s o c o n t a i n e d ammonium c h l o r i d e ( N H 4 C I ) , w h i c h f o r m e d o n t h e k e r o g e n b y r e a c t i o n o f a d s o r b e d HC1 w i t h d i l u t e N H 3 . The p r e s e n c e o f NH4CI i n the kerogen i m p l i e s t h a t t h e o r g a n i c n i t r o g e n content i n t h i s kerogen is overestimated. The N i a n d V c o n t e n t s o f t h e k e r o g e n s a r e g i v e n i n T a b l e I I . New A l b a n y k e r o g e n i s e n r i c h e d i n N i r e l a t i v e t o V, w h e r e a s f o r Woodford kerogen t h e r e v e r s e i s t r u e . Correction o f t h ekerogen N i o r V c o n t e n t s t o a m i n e r a l - f r e e b a s i s i s s m a l l ( b i t u m e n - I v e r s u s b i t u m e n I + I I ) . Bitumen composition i s a l s o a l t e r e d because o f the d i f f e r e n t compositions o f bitumen-I andbitumen-II , the N i and V concentrations are d i f f e r e n t ) . B i t u m e n - I I i s s o l u b l e OM w h i c h s t r o n g l y a s s o c i a t e s w i t h t h e mineral matrix and i s therefore d i f f i c u l t t o extract before acid digestion. J e o n g a n d K o b y l i n s k i ( 1 9 ) h a v e shown t h a t a s u b s t a n t i a l f r a c t i o n o f s o l u b l e OM i n a s h a l e f o r m s a k e r o g e n - m i n e r a l interf a c i a l l a y e r through chemical bonding o r p h y s i s o r p t i o n t o carbonate and, more s i g n i f i c a n t l y , s i l i c a t e m i n e r a l s . D i s s o l u t i o n o f the mineral matrix i n acid s o l u t i o n r e s u l t s i n i n t e r a c t i o n o f these s o l u b l e p o l a r organic s p e c i e s w i t h the kerogen. S p i r o (20) a l s o s h o w e d t h a t t h e s o l u b l e OM a s s o c i a t e d w i t h t h e m i n e r a l s w a s s y s t e m a t i c a l l y d i f f e r e n t i n composition from the bitumen. This difference was e x p l a i n e d b y t h e p h y s i c a l p r o p e r t i e s o f t h e c o m p o u n d s , a n d b y t h e c a t a l y s i s ( o r i n h i b i t i o n ) o f c e r t a i n r e a c t i o n s o f t h e s e compounds by t h e a s s o c i a t e d m i n e r a l p h a s e s . P y r o l y s i s a t l o w t e m p e r a t u r e (-100 C) r e s u l t s i n f u r t h e r r e m o v a l o f s o l u b l e OM a s s o c i a t e d w i t h t h e k e r o g e n . This m a t e r i a l i s probably s i m i l a r t o bitumen-II. A t t h i s p o i n t , the kerogen i s r e l a t i v e l y f r e e o f a n y s o l u b l e OM o r r e s i d u a l b i t u m e n ( p y r o l y s a t e 1 i s -3.5 w t % a n d -9.0 w t % o f t h e t o t a l s o l u b l e OM e x t r a c t e d f r o m New A l b a n y a n d Woodford s h a l e s , r e s p e c t i v e l y ) . P y r o l y s i s a t higher temperatures begins t o depolymerize the kerogen m a t r i x . T h e s o l u b l e OM p r o d u c e d i s e i t h e r c l e a v e d from t h e k e r o g e n m a t r i x b y bond r u p t u r e o r i s m a t e r i a l so s t r o n g l y adsorbed o r a s s o c i a t e d w i t h the kerogen m a t r i x to be d e f i n e d a s p a r t o f i t ( i n the c o n v e n t i o n a l sense o f s o l u b i l i t y ) , and i s o n l y s o l u b i l i z e d u n d e r t h e s e more d r a s t i c c o n d i t i o n s . Mckay ( 2 1 ) s u g g e s t e d t h a t t h e k e r o g e n o f some s h a l e s i s n o t a n i n s o l u b l e polymer, but m a t e r i a l o f s i m i l a r c o m p o s i t i o n t o the b i t u m e n , w h i c h can o n l y be s o l u b i l i z e d under c o n d i t i o n s d i f f e r e n t than those r e q u i r e d t o e x t r a c t the bitumen component. Neither kerogen produces s u b s t a n t i a l q u a n t i t i e s o f p y r o l y s a t e b e l o w 3 0 0 C. Y i e l d s o f p y r o l y s a t e become s u b s t a n t i a l a t 400°C a n d 4 5 0 C; h o w e v e r , t h e p r e s e n c e o f t o l u e n e p y r o l y s i s p r o d u c t s i n c r e a s e s the p y r o l y s a t e y i e l d . A l s o , a t 450 C the nature o f the p y r o l y s a t e changes from a d a r k , v i s c o u s b i t u m e n t o a n amber, n o n - v i s c o u s material. Other p y r o l y s i s s t u d i e s u s i n g t o l u e n e a s the s o l v e n t have shown l i t t l e e v i d e n c e o f t h e r m a l d e g r a d a t i o n o f t h e p y r o l y s a t e s p r o d u c e d a t 350 C may n o t b e e n t i r e l y

118


representative of the organic composed.

c o n s t i t u e n t s o f which the kerogen i s


E f f e c t o f P y r o l y s i s on t h e K e r o g e n C o m p o s i t i o n . The c h a n g e i n t h e elemental composition o f the kerogens a f t e r p y r o l y s i s i spresented i n T a b l e I V a n d shown g r a p h i c a l l y i n F i g u r e 2 b y p l o t t i n g t h e H/C v e r s u s 0/C r a t i o s o f t h e k e r o g e n a n d p y r o l y s e d k e r o g e n s . For both New A l b a n y a n d W o o d f o r d k e r o g e n s , t h e p y r o l y s i s - i n d u c e d m a t u r a t i o n f o l l o w s t h e t y p i c a l p a t t e r n o f d e c r e a s i n g H/C a n d 0/C r a t i o s a s thermal maturation increases. The anomalous b e h a v i o r o f Woodford k e r o g e n b e t w e e n 103°C a n d 200°C ( 0 / C r a t i o s g r e a t e r t h a n t h e o r i g i n a l k e r o g e n ) may b e t h e r e s u l t o f a d s o r b e d m e t h a n o l w h i c h w a s u s e d w i t h toluene t o e x t r a c t the p y r o l y s a t e s from t h i s kerogen. Pyrolysates f r o m New A l b a n y k e r o g e n w e r e e x t r a c t e d u s i n g o n l y t o l u e n e . Although t h e e l e m e n t a l c o m p o s i t i o n o f t h e kerogen changes a t each p y r o l y s i s t e m p e r a t u r e , t h e l a r g e s t changes o c c u r above 300 C which i s the point at which the kerogens begin t o generate substant i a l quantities of pyrolysate. E f f e c t o f P y r o l y s i s on t h e N i and V C o n t e n t s o f t h e Kerogen and Pyrolysates. T h e N i a n d V c o n t e n t s o f New A l b a n y a n d W o o d f o r d k e r o g e n a n d p y r o l y s e d k e r o g e n s a r e shown i n T a b l e V. B e l o w 4 5 0 C, the ( N i / V ) K r a t i o i s c o n s t a n t ( w i t h i n ± 3 s.d. o f o r i g i n a l k e r o g e n v a l u e ) , b u t d r a m a t i c a l l y i n c r e a s e s a t 450 C i n b o t h s h a l e s . M F

Table IV.

Elemental Composition o f Kerogens

Pyrolysis T e m p e r a t u r e (°C)

Sample

%C

and P y r o l y s e d

Kerogens

%H

%N

%0

5.74 5.82 5.71 5.47 5.29 4.51 3.32

2,.67 2..73 2..72 2..71 2,.75 2..93 3..01

6.87 6.79 5.98 5.64 5.57 5.34 4.45

6.71 6.59 6.12 6.13 6.00 5.07 3.15

2..24 2..04 1 97 2..02 2. ,12 2. ,34 2. ,81

4.83 5.08 5.16 4.46 4.09 3.92 3.07

New A l b a n y Kerogen Kerogen Kerogen Kerogen Kerogen Kerogen Kerogen

1 2 3 4 5 6

110 210 300 350 400 450

67.90 68.62 70.37 70.98 72.15 72.71 73.85 Woodford

Kerogen Kerogen Kerogen Kerogen Kerogen Kerogen Kerogen

0

_

1 2 3 4 5 6

103 200 300 351 400 450

68.22 67.42 64.64 68.17 69.72 69.11 70.87


New

Generation

Albany

(•)

Woodford

(•)


•

Porphyrins

103°C Ο 200°C


35 1°C •

1 1 0 ° C

300 C

/ 210 C 300°C B

/ À nn°r

^

A

e

a 300°c

450°C

0.0

I

«

3.0

«

1

4.0

5.0

O / C x 100

'

"

'

6.0

7.0

8.0

(atomic)

F i g u r e 2. V a r i a t i o n o f t h e e l e m e n t a l kerogens w i t h s e q u e n t i a l p y r o l y s i s .

composition of

120


T a b l e V.

Nickel

and Vanadium C o n c e n t r a t i o n s and N i / V R a t i o s f o r Kerogens and P y r o l y s e d Kerogens

Pyrolysis Temperature

M i n e r a l - F r e e Kerogen Concentration

(yg/g)

u

< c)

Sample

[ N i ]

( N i / V )

MFK

MFK


New A l b a n y Kerogen Kerogen Kerogen Kerogen Kerogen Kerogen Kerogen

0

_

1 2

110 210 300 350 400 450

3 4 5 6

2128 ± 81 2187 2209 2289 2297 2729 3132

6 9 8 ± 26 669 676 730 765 830 851

3.05 ± 0.16 3.27 3.27 3.14

3 2 6 2 ± 97 3357 3663 3609 3513 4541 5479

0.108 ± 0.01 0.115 0.103 0.100 0.115 0.120 0.163

3.00 3.29 3.68

Woodford Kerogen Kerogen Kerogen Kerogen Kerogen Kerogen Kerogen

0

-

1 2 3 4 5 6

103 200 300 350 400 450

353 + 33 385 378 362 403 543 892

C o n c e n t r a t i o n s (yg/g) o f N i and V i n t h e m i n e r a l - f r e e kerogen ([X]MFK)» M i n e r a l - f r e e k e r o g e n v a l u e s were c a l c u l a t e d i n a manner s i m i l a r t o Van B e r k e l and F i l b y ( 9 ) . M i n e r a l - f r e e N i and V c o n t e n t s o f t h e p y r o l y s e d k e r o g e n s were c a l c u l a t e d by m u l t i p l y i n g the measured m e t a l content by t h e percent o f t h e t o t a l m e t a l c o n t e n t w h i c h was o r g a n i c . The o r g a n i c f r a c t i o n o f t h e m e t a l was estimated by a d j u s t i n g t h e o r g a n i c f r a c t i o n o f t h e m e t a l i n k e r o g e n 0 t o a c c o u n t f o r t h e amount o f t h e e l e m e n t e x p e l l e d (organic) w i t h t h e p y r o l y s a t e a t each temperature. Percent r e l a t i v e s t a n d a r d d e v i a t i o n (% RSD) o f t h e p y r o l y s e d k e r o g e n v a l u e s i s .> t h e % RSD o f t h e o r i g i n a l k e r o g e n v a l u e s i n e a c h r e s p e c t i v e column.


7.


Generation


121

A f t e r t h e k e r o g e n s t a r t s t o t h e r m a l l y b r e a k down (~300°C), t h e c o n centration o f both metals i n the residue increases s i g n i f i c a n t l y above t h a t i n t h e o r i g i n a l kerogen. This i n d i c a t e s that as catagenes i s proceeds, themetals p r o g r e s s i v e l y concentrate i n t h e i n s o l u b l e kerogen f r a c t i o n . The p e r c e n t a g e o f t h e N i a n d V o r g a n i c a l l y b o u n d i n t h e k e r o g e n which i sexpelled with the pyrolysates (i-J^., expulsion y i e l d ) i s shown i n T a b l e V I . E x p u l s i o n y i e l d s f o r b o t h e l e m e n t s a r e l o w a t each temperature. T h e maximum e x p u l s i o n y i e l d f o r e a c h k e r o g e n w a s observed f o r t h e element i n h i g h e s t c o n c e n t r a t i o n i n t h a t kerogen ( N i f o r New A l b a n y ; V f o r W o o d f o r d ) . A s s e e n i n F i g u r e 3, t h e e x p u l s i o n y i e l d s o f b o t h e l e m e n t s show a p a r a l l e l b e h a v i o r . In fact, f o r New A l b a n y k e r o g e n t h e e x p u l s i o n y i e l d s f o r N i a n d V a t e a c h t e m p e r a t u r e a r e n o t s t a t i s t i c a l l y d i f f e r e n t (± 3 s . d . ) . F o r Woodford kerogen, however, t h e e x p u l s i o n y i e l d s a r e d i f f e r e n t w i t h g r e a t e r V e x p u l s i o n t h a n N i a t e a c h t e m p e r a t u r e , e x c e p t 4 5 0 C. H o w e v e r , a s p y r o l y s i s temperature i n c r e a s e s , t h e N i e x p u l s i o n y i e l d does i n c r e a s e r e l a t i v e t o t h e V e x p u l s i o n y i e l d (New A l b a n y k e r o g e n a p p e a r s t o show a s i m i l a r t r e n d ) . Since f o r both kerogens t h e e x p u l s i o n r a t e s o f N i and V (yg e l e m e n t / g TOC) a t e a c h t e m p e r a t u r e v a r y , t h e c o n c e n t r a t i o n s o f t h e elements i n t h e p y r o l y s a t e s vary. F o r p y r o l y s i s between 200 C and 4 0 0 C, t h e N i / V r a t i o s o f t h e New A l b a n y p y r o l y s a t e s a r e e q u a l t o t h e corresponding kerogen ( N i / V ) - ^ ^ r a t i o s w i t h i n t h e experimental e r r o r . However, t h e N i / V r a t i o s o f t h e bitumen ( I , I I , o r I + I I ) and t h e p y r o l y s a t e s produced a t these temperatures a r e n o t equal. In the case o f Woodford, t h e N i / Vr a t i o o f t h e p y r o l y s a t e s produced i n t h i s temperature range i s lower than t h e kerogen ( N i / V ) j ^ r a t i o , but equal t o t h e N i / V r a t i o o f bitumen-I. It i spossible that the organic Ni/V r a t i o o f the i n s i t u k e r o g e n i s a l t e r e d b y HC1-HF d e m i n e r a l i z a t i o n o f t h e s h a l e . This e f f e c t may e x p l a i n why t h e r e a p p e a r s t o b e n o s y s t e m a t i c c o r r e l a t i o n among t h e N i / V r a t i o s o f t h e b i t u m e n , p y r o l y s a t e s , a n d k e r o g e n c o n c e n t r a t e b e t w e e n t h e two s a m p l e s . However, i n t h e absence o f a documented model f o r t h e a s s o c i a t i o n o f m e t a l s p e c i e s w i t h t h e k e r o g e n , i t cannot be d e t e r m i n e d g e o c h e m i c a l l y whether t h e N i / V r a t i o o f t h e b i t u m e n , p y r o l y s a t e s , a n d k e r o g e n s h o u l d b e t h e same o r different. F K

Metalloporphyrins. UV-visible s p e c t r a l examination of the pyrolys a t e s r e v e a l e d t h e p r e s e n c e o f N i P a n d VOP. F i g u r e 4 s h o w s t h e s p e c t r a o f b i t u m e n - I a n d t h e p y r o l y s a t e s i n t o l u e n e a t t h e same concentrations. T h e New A l b a n y s a m p l e s c o n t a i n s i g n i f i c a n t q u a n t i t i e s o f b o t h N i P a n d VOP, b u t t h e N i P / V O P r a t i o i n c r e a s e s w i t h i n c r e a s i n g temperature from bitumen-I t o t h e p y r o l y s a t e s a s i n d i c a t e d by t h e a b s o r b a n c e a t t h e N i P a n d VOP S o r e t p e a k s ( 3 9 6 a n d 4 1 0 nm, r e s p e c tively). T h i s same t r e n d i s s e e n i n t h e N i / V r a t i o o f t h e p y r o l y s a t e s , w h i c h s u g g e s t s t h a t t h e NiP/VOP r a t i o and t h e N i / V r a t i o o f the p y r o l y s a t e s a r e p r o p o r t i o n a l . F u r t h e r support f o r t h i s c o n t e n t i o n i s shown i n F i g u r e 5 w h e r e t h e c o m b i n e d N i P a n d VOP Soret peak i n t e g r a t e d absorbance i sp l o t t e d v e r s u s t h e combined c o n c e n t r a t i o n o f N i and V i n the p y r o l y s a t e s . The e x c e l l e n t c o r r e l a t i o n o f S o r e t p e a k a b s o r b a n c e w i t h m e t a l c o n t e n t ( r = 0.98) i n d i c a t e s t h a t t h e NiP/VOP r a t i o o f t h e p y r o l y s a t e s i s p r o p o r t i o n a l

VI.

103 200 300 350 400 450

--

-

96.5

1.63 8.36 9.52 31.45 7.7

16.57 1.50 18.07 1.41

165.1 24.4

-

30.0 126.5 2.96 25.81 115.8

Expulsion yield defined i n the kerogen e x p e l l e d

-

5.19 0.633

0.810 3.69

0.272 0.286 1.43 1.79 5.44 0.98

-

3.34+0.20 7.16+0.33

1.15+0.06 1.69+0.31 1.24+0.07 1.62+0.06 3.20+0.08 3.63+0.19

Ni/V

0. 062+0.008 0. 040+0.003 0. 059+0.006 0.520 0. 057+0.002 0.603 0. 054+0.003 2.38 0. 062+0.004 2.91 0. 062+0.005 8.00 0. 078+0.003 0.95 0. 012+0.02

-

4.67 0.291

0.1774 0.828 3.32

V MFK

-

0.108+0.01 0.115 0.103 0.100 0.115 0.120 0.163

_

3.27 3.14 3.00 3.29 3.68

3.05+0.16 3.27

_

_

( N 1 / V )

i n the Bitumens,

a s w e i g h t p e r c e n t o f t h e o r g a n i c a l l y combined with the p y r o l y s a t e .

N i and V

TOC f o r t h e b i t u m e n s and p e r g k e r o g e n TOC

269 37.66 307 24.85 30.0 134.7 153.8 403.0 62.5

Woodford

-

49.5 3.32

8.08 31.9

0.0946

Albany

New 84.2 17.8 102.0 1.82

Ni

1 0 0

Yield

W

Expulsion (ug X/ug

V

Expulsion rate c a l c u l a t e d per g shale f o r the kerogen samples.

Bitumen-I Bitumen-II Bitumen-I+II Pyrolysate 1 Pyrolysate 2 Pyrolysate 3 Pyrolysate 4 Pyrolysate 5 Pyrolysate 6

400 450

210 300 350

110

Ni

E x p u l s i o n Rate (ug X/g TOC)

R a t e s and Y i e l d s f o r N i c k e l and Vanadium P y r o l y s a t e s , and R e s p e c t i v e Kerogens

Pyrolysis Temperature (°C)

Expulsion

Bitumen-I Bitumen-II Bitumen-I+II Pyrolysate 1 Pyrolysate 2 Pyrolysate 3 Pyrolysate 4 Pyrolysate 5 Pyrolysate 6

Sample

Table


7.


Generation of Nickel and Vanadyl Porphyrins

123


e.o

100

200 300 Pyrolysis Temperature ( C)

400

500

200 300 Pyrolysis Temperature ( C)

400

500

e

8.0

6.0

2.0

0.0

e

F i g u r e 3. W e i g h t p e r c e n t o f o r g a n i c N i a n d V i n New A l b a n y ( A ) and W o o d f o r d (B) k e r o g e n e x p e l l e d w i t h t h e p y r o l y s a t e ( E x p u l s i o n Y i e l d ) a t each p y r o l y s i s temperature ( E r r o r b a r s = ± 1 s.d.).


124 M E T A L C O M P L E X E S IN FOSSIL FUELS


7.


Generation


125

126


t o t h e N i / V r a t i o ; h o w e v e r , t h e [ N i ] a n d [V] n e e d n o t be e q u a l t o t h e [ N i P ] and [VOP], r e s p e c t i v e l y (i.e_. , " n o n - p o r p h y r i n " N i and V may be p r e s e n t , b u t i n t h e same r e l a t i v e p r o p o r t i o n s t o N i P a n d VOP in each sample). The d e v i a t i o n o f t h e b i t u m e n - I p o i n t on t h i s p l o t i n d i c a t e s t h a t t h e f r a c t i o n o f N i and V i n t h e b i t u m e n p r e s e n t as p o r p h y r i n complexes i s l e s s than that i n the p y r o l y s a t e s .


The U V - v i s i b l e s p e c t r a o f W o o d f o r d b i t u m e n - I a n d pyrolysates show t h e p r e s e n c e o f o n l y VOP. H o w e v e r , c o l u m n c h r o m a t o g r a p h y on S1O2 a l l o w s s e p a r a t i o n o f a N i P f r a c t i o n f r o m t h e s a m p l e s . Because the NiP Soret peak i s not d e t e c t a b l e i n the b u l k samples, a v i s u a l c o r r e l a t i o n o f N i P / V O P r a t i o w i t h N i / V r a t i o c a n n o t be made. However, p l o t t i n g Soret peak a b s o r b a n c e v e r s u s m e t a l content of the p y r o l y s a t e s , a s f o r t h e New A l b a n y s a m p l e s , g i v e s a s t r a i g h t l i n e p l o t ( r = 0.96) i n d i c a t i n g t h a t t h e NiP/VOP r a t i o o f the p y r o l y s a t e s i s p r o p o r t i o n a l to the Ni/V r a t i o . In t h i s case, the p l o t i n d i c a t e s t h a t t h e f r a c t i o n o f N i and V i n t h e b i t u m e n p r e s e n t a s p o r p h y r i n complexes i s g r e a t e r than that i n the p y r o l y s a t e s . F o r New A l b a n y k e r o g e n ^ t h e N i / V r a t i o o f t h e p y r o l y s a t e s p r o d u c e d b e t w e e n 200 C a n d 400 C i s a p p r o x i m a t e l y e q u a l t o t h e (Ni/V) ratio. S i n c e t h e N i / V r a t i o and NiP/VOP r a t i o i n t h i s t e m p e r a t u r e r a n g e a r e p r o p o r t i o n a l , t h e k e r o g e n m u s t be generating t h e N i P a n d VOP i n t h e same r a t i o a s t h e i r c o n t e n t s i n t h e k e r o g e n (ji.e:. , ( N I / V ) M F r a t i o ~ N i P / V O P r a t i o o f t h e k e r o g e n ) . Interest i n g l y , t h e s e r a t i o s a r e o v e r 2.5 t i m e s t h a t o f t h e b i t u m e n - I N i / V ratio. Over t h i s t e m p e r a t u r e range, however, the Ni/V r a t i o s of b i t u m e n - I and t h e p y r o l y s a t e s f o r W o o d f o r d a r e e q u a l and p r o p o r t i o n a l t o the NiP/VOP r a t i o o f the p y r o l y s a t e s , but d i f f e r e n t from the (Ni/V)j4pK r a t i o . The r e a s o n f o r t h e d i f f e r e n t b e h a v i o r o f t h e two k e r o g e n s i s n o t o b v i o u s , b u t may r e f l e c t d i f f e r e n c e s i n t h e s p e c i a t i o n a n d m o d e s o f a s s o c i a t i o n f o r t h e N i a n d V i n t h e New A l b a n y a n d Woodford kerogens. M F K

K

The p o r p h y r i n c o m p o s i t i o n s o f b i t u m e n - I a n d t h e p y r o l y s a t e s w e r e i n v e s t i g a t e d u s i n g HPLC ( 1 7 ) . R e l a t i v e abundances of f o u r v a n a d y l p o r p h y r i n s ( C 2 g t i o , C 2 9 e t i o , C 3 1 D P E P , and C 3 2 D P E P ) w e r e measured i n each sample (see T a b l e V I I ) . Porphyrin compositions of b i t u m e n - I and t h e p y r o l y s a t e s a r e d i f f e r e n t and c h a n g e w i t h p y r o l y s i s temperature. The n a t u r e o f t h e c o m p o s i t i o n a l c h a n g e i s s i m i l a r f o r t h e New A l b a n y a n d W o o d f o r d s a m p l e s . As p y r o l y s i s t e m p e r a t u r e i n c r e a s e s , two m a j o r c h a n g e s i n p o r p h y r i n d i s t r i b u t i o n are noted: (1) t h e r e l a t i v e a b u n d a n c e o f t h e l o w e r c a r b o n number p o r p h y r i n i n b o t h p o r p h y r i n s e r i e s i n c r e a s e s , and ( 2 ) t h e a b u n d a n c e o f e t i o p o r p h y r i n i n c r e a s e s r e l a t i v e t o DPEP. I n t e r p r e t a t i o n o f t h e s e changes must t a k e i n t o a c c o u n t not o n l y the p o s s i b l e g e n e r a t i o n of d i f f e r e n t p o r p h y r i n s from the kerogen at d i f f e r e n t t e m p e r a t u r e s , but a l s o t h e r m a l a l t e r a t i o n o f b o t h the s o l v e n t s o l u b l e and k e r o g e n - a s s o c i a t e d porphyrins. e

Discussion The e f f e c t o f HC1-HF d e m i n e r a l i z a t i o n o f t h e s h a l e o n t h e t r a c e element c o n t e n t o f t h e i s o l a t e d k e r o g e n c o n c e n t r a t e has not been assessed. However, b o t h k e r o g e n samples c o n t a i n h i g h concentrations o f o r g a n i c a l l y c o m b i n e d N i a n d V. V a r i a b l e amounts of m i n e r a l i m p u r i t y i n the kerogen samples w i l l cause the c a l c u l a t e d m i n e r a l -

7.

Generation


Table V I I .


R e l a t i v e Abundance of Four V a n a d y l P o r p h y r i n s i n B i t u m e n - I and t h e P y r o l y s a t e s a

R e l a t i v e Abundance C g.etio

Sample

2

C

2 9

etio

C DPEP 3 1

(%) C DPEP 3 2


New A l b a n y Bitumen-I Pyrolysate Pyrolysate Pyrolysate Pyrolysate Pyrolysate Pyrolysate

1 2 3 4 5 6

(110°C) (210°C) ( 3 0 0 C) (350°C) (400°C) ( 4 5 0 C)

13.6 25.0 24.5 40.2 93.2 100 100

21.1 23.7 23.1 43.3 100 68.2 56.5

40.4 62.9 66.4 82.0 83.2 50.9 60.1

100 100 100 100 87.4 34.7 56.5

Woodford Bitumen-I Pyrolysate Pyrolysate Pyrolysate Pyrolysate Pyrolysate Pyrolysate

a

1 2 3 4 5 6

(103°C) (200°C) (300°C) (350°C) (400°C) (450°C)

21.0 26.4 25.9 24.2 35.2 100 100

DPEP = d e o x o p h y l l o e r y t h r o e t i o

29.0 24.4 24.1 32.3 35.8 64.2 37.0

82.3 100 100 96.8 100 90.2

porphyrin; etio

= etio

100 91.4 92.0 100 97.4 57.5

porphyrin.

111

128



f r e e kerogen t r a c e element c o n t e n t s to d i f f e r because as the m i n e r a l i m p u r i t y content of the kerogen i n c r e a s e s , the t r a c e element content of the kerogen i s d i l u t e d . T h i s e f f e c t c a n be o v e r c o m e b y e x p r e s s i n g c o n c e n t r a t i o n s p e r g o f k e r o g e n TOC i n s t e a d o f p e r g o f kerogen. However, i f k e r o g e n t r a c e element d a t a a r e e x p r e s s e d as e l e m e n t a l r a t i o s ( e . j * . , N i / V ) t h e m i n e r a l d i l u t i o n e f f e c t i s o f no consequence. The e f f e c t o f v a r i o u s d e m i n e r a l i z a t i o n p r o c e d u r e s on the t r a c e element content of kerogen i s c u r r e n t l y under i n v e s t i g a t i o n in this laboratory. D u r i n g t h e s i m u l a t e d c a t a g e n e s i s N i P a n d VOP w e r e g e n e r a t e d from the kerogens i m p l y i n g t h a t the concept of s e l e c t i v e kerogen b i n d i n g o f VOP p r o p o s e d b y B a k e r a n d L o u d a (8) n e e d s t o be r e v i s e d . S i n c e b o t h N i P a n d VOP a r e s h o w n t o a s s o c i a t e w i t h t h e k e r o g e n , i t would a p p e a r t h a t t h e d e p o s i t i o n a l e n v i r o n m e n t o f t h e s e d i m e n t and t h e p o s t - d e p o s i t i o n a l e v o l u t i o n o f t h e k e r o g e n a r e more i m p o r t a n t f a c t o r s i n t h e k e r o g e n - p o r p h y r i n a s s o c i a t i o n t h a n any c h e m i c a l p r o p e r t y o f e i t h e r N i P o r VOP f a v o r i n g k e r o g e n e n h a n c e d c h e l a t i o n or association. The d a t a f r o m t h i s s t u d y s u g g e s t t h a t b o t h N i P a n d VOP a s s o c i a t e w i t h t h e k e r o g e n i n a s i m i l a r m a n n e r . The most l i k e l y modes o f a s s o c i a t i o n a r e : - Physisorption of discrete porphyrins - Chemisorption of discrete porphyrins - Molecular sieve trapping of discrete porphyrins - Chemical bonding of p o r p h y r i n s to the kerogen through a l k y l bonds, e s t e r l i n k a g e s , e t c . or t h r o u g h a x i a l bonding to the metal ion. Any " n o n - p o r p h y r i n " N i and V c o m p l e x e s g e n e r a t e d f r o m t h e kerogen are probably part of the asphaltene f r a c t i o n of the p y r o l y s a t e and, t h e r e f o r e , would bear a c l o s e resemblance t o the "nonp o r p h y r i n " complexes t h a t have been d e s c r i b e d i n a s p h a l t e n e s ( 2 4 ) . T h e s e a s p h a l t e n e m e t a l c o m p l e x e s h a v e b e e n c o n s i d e r e d t o be e i t h e r d i s c r e t e complexes ( a d s o r b e d , c h e m i s o r b e d , o r a c t u a l l y bound c h e m i c a l l y to the asphaltenes) or part of the asphaltene s t r u c t u r e . H o w e v e r , t h e y may be p o r p h y r i n s i n o n e o f t h e a s s o c i a t i o n m o d e s a b o v e ( o r y e t a n o t h e r ) w h i c h c a n n o t be l i b e r a t e d f r o m t h e k e r o g e n o r a s p h a l t e n e as a d i s c r e t e p o r p h y r i n s p e c i e s . T o o u l a k o u and F i l b y (25) h a v e shown t h a t t h i s i s t h e c a s e f o r a t l e a s t 2 5 % o f t h e V i n A t h a b a s c a o i l sand a s p h a l t e n e s . A c o m p a r i s o n o f t h e VOP c o m p o s i t i o n o f b i t u m e n - I a n d t h e p y r o l y s a t e s r e v e a l s a g e n e r a l s h i f t t o l o w e r c a r b o n number f o r e t i o and DPEP t y p e p o r p h y r i n s , a n d a n a p p a r e n t i n c r e a s e i n e t i o r e l a t i v e t o DPEP t y p e p o r p h y r i n s a s p y r o l y s i s t e m p e r a t u r e i n c r e a s e s . It is p o s s i b l e t h a t k e r o g e n g e n e r a t e s p o r p h y r i n s o f l o w e r c a r b o n number as p y r o l y s i s t e m p e r a t u r e i n c r e a s e s . Lower c a r b o n number f o r a g i v e n porphyrin type r e s u l t s i n increased p o l a r i t y . Thus, more p o l a r p o r p h y r i n s may be g e n e r a t e d p r e f e r e n t i a l l y a t h i g h e r p y r o l y s i s temperatures because of a s t r o n g e r a s s o c i a t i o n w i t h kerogen than h i g h e r c a r b o n number s p e c i e s . However, d e a l k y l a t i o n o f p o r p h y r i n s d u r i n g t h e r m a l m a t u r a t i o n has been demonstrated i n o t h e r l a b o r a t o r y s t u d i e s (26-29) and i s c o n s i s t e n t w i t h p o r p h y r i n d a t a o b t a i n e d from the a n a l y s i s o f bitumens from sample s u i t e s o f i n c r e a s i n g m a t u r a t i o n (6,7,28). T h e r e f o r e , t h e s h i f t t o l o w e r c a r b o n number p o r p h y r i n s a s p y r o l y s i s t e m p e r a t u r e i n c r e a s e s may be a s e c o n d a r y t h e r m a l e f f e c t which a l t e r s the p o r p h y r i n s as they are generated from the kerogen.


7. VAN B E R K E L A N D FILBY

Generation


129

The a p p a r e n t i n c r e a s e i n e t i o r e l a t i v e t o DPEP t y p e p o r p h y r i n s w i t h i n c r e a s i n g p y r o l y s i s t e m p e r a t u r e ( m a t u r a t i o n ) must be i n t e r p r e t e d w i t h c a u t i o n s i n c e t h i s t r e n d i s based on a n a l y s i s o f o n l y f o u r m e m b e r s o f t h e VOP s e r i e s i n t h e s a m p l e s . The EDPEP/Zetio r a t i o d e t e r m i n e d f r o m t h e DPEP a n d e t i o m a s s s p e c t r a l e n v e l o p e s i s a more r e l i a b l e i n d i c a t o r o f a c o m p o s i t i o n a l change a n d work i s i n progress t o determine t h i s r a t i o f o r both metalloporphyrins. The a p p a r e n t i n c r e a s e i n e t i o r e l a t i v e t o DPEP t y p e p o r p h y r i n s with increasing temperature has several possible explanations: (1) E t i o p o r p h y r i n s a r e p r e f e r e n t i a l l y a s s o c i a t e d w i t h k e r o g e n . Therefore, t h e kerogen p y r o l y s a t e i senriched i n e t i o type p o r p h y r i n s r e l a t i v e t o t h e bitumen. I t h a s been suggested t h a t o x i d a t i v e c l e a v a g e o f t h e DPEP i s o c y c l i c r i n g p r o d u c e s f u n c t i o n a l i z e d e t i o intermediates which could bind t o t h e kerogen m a t r i x (30). ( 2 ) DPEP a n d e t i o t y p e p o r p h y r i n s a r e g e n e r a t e d f r o m t h e k e r o g e n a t t h e same r a t e a t e a c h t e m p e r a t u r e , b u t : ( a ) DPEP p o r p h y r i n s a r e thermally converted t o e t i o porphyrins after being generated, o r ( b ) DPEP p o r p h y r i n s a r e t h e r m a l l y d e g r a d e d a t a f a s t e r r a t e t h a n e t i o porphyrins. Recent work (6,31) i n d i c a t e s t h a t t h e t h e r m a l c o n v e r s i o n o f DPEP t o e t i o i s o n l y a m i n o r s o u r c e o f e t i o t y p e p o r p h y r i n s . P r e f e r e n t i a l t h e r m a l d e g r a d a t i o n o f DPEP v e r s u s e t i o t y p e p o r p h y r i n s h a s b e e n shown i n t h e l a b o r a t o r y (31) a n d i s t h e more p l a u s i b l e e x p l a n a t i o n o f t h e two. ( 3 ) T h e s h i f t t o l o w e r c a r b o n n u m b e r (e._g. , d e a l k y l a t i o n ) o c c u r s m o r e r a p i d l y f o r t h e e t i o r e l a t i v e t o t h e DPEP t y p e p o r p h y r i n s . However, i f t h e e n t i r e homologous s e r i e s e n v e l o p e f o r b o t h p o r p h y r i n t y p e s s h i f t s t o l o w e r c a r b o n number t h e Z D P E P / E e t i o r a t i o w i l l n o t change. Of t h e e x p l a n a t i o n s a b o v e , p r e f e r e n t i a l d e g r a d a t i o n o f k e r o g e n g e n e r a t e d DPEP t y p e p o r p h y r i n s r e l a t i v e t o e t i o t y p e p o r p h y r i n s i s p r o b a b l y t h emajor mechanism p r o d u c i n g t h e changes i n c o m p o s i t i o n . The d a t a i n d i c a t e t h a t b o t h t y p e s o f p o r p h y r i n a r e p r e s e n t i n t h e s a m p l e s up t o a t l e a s t 400°C. N o t u n t i l 200-300°C d o e s t h e r a p i d change i n r e l a t i v e abundance o f t h e two p o r p h y r i n t y p e s a p p e a r . B u r k o v a e t a l . ( 3 1 ) showed t h a t s u b s t a n t i a l c h a n g e s i n D P E P / e t i o r a t i o s t a k e p l a c e w i t h t e m p e r a t u r e s a s l o w a s 200-250 C due t o p r e f e r e n t i a l d e g r a d a t i o n . Another i n d i c a t i o n t h a t t h i s change i s d u e t o t h e r m a l d e g r a d a t i o n comes f r o m t h e r e l a t i v e i n c r e a s e i n N i expulsion yield relative t o V expulsion yield with increasing p y r o l y s i s temperature. R o s s c u p a n d Bowman ( 3 2 ) s h o w e d t h a t VOP w a s more t h e r m a l l y l a b i l e t h a n N i P ; h e n c e , t h e d e c r e a s e i n V e x p u l s i o n y i e l d w i t h i n c r e a s i n g p y r o l y s i s t e m p e r a t u r e may b e d u e t o p r e f e r e n t i a l d e s t r u c t i o n o f l i b e r a t e d VOP r e s u l t i n g i n r e a s s o c i a t i o n o f the " i n o r g a n i c " V w i t h t h e kerogen. The r e l e a s e o f N i a n d V f r o m t h e k e r o g e n d u r i n g p y r o l y s i s o c c u r s a t a r a t e s u c h t h a t t h e t o t a l amount g e n e r a t e d p e r g o f k e r o g e n TOC i s m u c h l a r g e r t h a n t h e a m o u n t o f N i a n d V i n t h e b i t u m e n i s o l a t e d from an e q u i v a l e n t weight o f kerogen i n t h e shale. Theref o r e , t h e e x p u l s i o n o f t h e complexes from t h e kerogen c o u l d s u b s t a n t i a l l y a l t e r ( i g n o r i n g m i g r a t i o n and i n s i t u m a t u r a t i o n ) t h e N i and V c o n t e n t , p o r p h y r i n c o n t e n t , and p o r p h y r i n c o m p o s i t i o n o f t h e bitumen accumulating i n a source rock. Using t h e p y r o l y s a t e y i e l d s and m e t a l e x p u l s i o n r a t e s a t e a c h t e m p e r a t u r e , a n d a s s u m i n g : a) a c l o s e d s y s t e m , b ) a s a m p l e c o n t a i n i n g 1 g k e r o g e n TOC, a n d c ) n o


130


i n s i t u m a t u r a t i o n , t h e N i and V c o n t e n t s o f t h e a c c u m u l a t i n g b i t u mens w e r e e s t i m a t e d . The v a r i a t i o n o f t h e m e t a l c o n t e n t o f t h e accumulating bitumen i s p l o t t e d versus p y r o l y s i s temperature ( m a t u r a t i o n ) i n F i g u r e 6, a n d t h e N i / V r a t i o i s p l o t t e d i n F i g u r e 7. The d a t a a t 4 5 0 C w e r e n o t i n c l u d e d b e c a u s e o f p y r o l y t i c e f f e c t s w h i c h may h a v e s u b s t a n t i a l l y a l t e r e d t h e s a m p l e s . For Woodford, the e x p u l s i o n r a t e of the metals i s such that catagenesis reduces t h e i r c o n c e n t r a t i o n s i n the accumulating bitumen. H o w e v e r , t h e N i / V r a t i o r e m a i n s c o n s t a n t up t o 4 0 0 C, w h e r e i t i n c r e a s e s b y ~12% o v e r t h e o r i g i n a l b i t u m e n . The t r e n d f o r New Albany, however, i s d i f f e r e n t . The V c o n c e n t r a t i o n d e c r e a s e s a s t h e b i t u m e n a c c u m u l a t e s , b u t t h e N i c o n c e n t r a t i o n i n c r e a s e s up t o 300 C then decreases. Therefore, the Ni/V r a t i o of the accumulating b i t u men s h o w s a c o n s i s t e n t i n c r e a s e . The s u b s t a n t i a l q u a n t i t i e s o f p o r p h y r i n l i b e r a t e d f r o m k e r o g e n d u r i n g m a t u r a t i o n w i l l a l t e r t h e p o r p h y r i n c o n t e n t , and p o r p h y r i n c o m p o s i t i o n , of the accumulating bitumen. Although kerogen i s the source of the p o r p h y r i n s , i t i s probably thermal e f f e c t s which cause the c o m p o s i t i o n a l change i n the l i b e r a t e d p o r p h y r i n s r a t h e r than l i b e r a t i o n of c o m p o s i t i o n a l l y d i f f e r e n t porphyrins w i t h i n c r e a s i n g temperature. N o n e t h e l e s s , as m a t u r a t i o n (temperature) i n c r e a s e s , the VOP s e r i e s w i l l s h i f t t o l o w e r c a r b o n n u m b e r a n d e t i o t y p e p o r p h y r i n s w i l l i n c r e a s e r e l a t i v e t o DPEP t y p e p o r p h y r i n s . The b e h a v i o r f o r N i P i s e x p e c t e d t o be s i m i l a r , b u t d i f f e r e n c e s h a v e b e e n n o t i c e d b y o t h e r s ( 7 ) i n t h e r e l a t i v e o f r a t e s o f N i P a n d VOP d e a l k y l a t i o n d u r i n g m a t u r a t i o n , f o r example. Changes i n t h e p o r p h y r i n c o m p o s i t i o n and c o n t e n t o f t h e b i t u m e n s f r o m s a m p l e s u i t e s o f i n c r e a s i n g m a t u r i t y (e.g/? _»]) h a v e b e e n hypothesized to r e s u l t , at l e a s t i n p a r t , from the r e l e a s e of p o r p h y r i n s from the kerogen d u r i n g c a t a g e n e s i s . This study provides e x p e r i m e n t a l e v i d e n c e o f t h e g e n e r a t i o n o f N i P a n d VOP f r o m k e r o g e n . However, the e x a c t n a t u r e o f the changes i n the bitumen w i l l depend on t h e k e r o g e n a n d i t s t h e r m a l h i s t o r y a n d c a n n o t be g e n e r a l i z e d t o a l l sample s u i t e s . Conclusions S e v e r a l c o n c l u s i o n s a b o u t t h e g e o c h e m i s t r y o f N i and V c o m p l e x e s i n k e r o g e n c a n be d r a w n f r o m t h i s s t u d y . (1) The W o o d f o r d a n d New A l b a n y o i l s h a l e k e r o g e n s c o n t a i n s u b s t a n t i a l q u a n t i t i e s o f o r g a n i c a l l y c o m b i n e d N i a n d V. (2) K e r o g e n c a t a g e n e s i s s i m u l a t e d u s i n g l a b o r a t o r y p y r o l y s i s i s e f f e c t i v e i n l i b e r a t i n g o r g a n i c N i and V c o m p l e x e s f r o m k e r o g e n , i n c l u d i n g s u b s t a n t i a l a m o u n t s o f N i P a n d VOP. The r e s p e c t i v e a m o u n t s o f N i P a n d VOP g e n e r a t e d a r e d i r e c t l y p r o p o r t i o n a l t o t h e a m o u n t o f o r g a n i c a l l y combined N i and V i n t h e k e r o g e n . ( 3 ) The c o m p o s i t i o n o f t h e VOP g e n e r a t e d f r o m t h e k e r o g e n changes as a f u n c t i o n of p y r o l y s i s temperature. As p y r o l y s i s temp e r a t u r e i n c r e a s e s , the p o r p h y r i n s e r i e s s h i f t to lower carbon n u m b e r a n d t h e r e i s a n i n c r e a s e i n t h e a b u n d a n c e o f t h e C28 ^ C29 e t i o p o r p h y r i n s r e l a t i v e t o C32 a n d C32 DPEP p o r p h y r i n s . The a p p a r e n t i n c r e a s e i n g e n e r a t i o n o f e t i o r e l a t i v e t o DPEP t y p e p o r p h y r i n s w i t h i n c r e a s i n g p y r o l y s i s t e m p e r a t u r e c a n o n l y be c o n f i r m e d b y d e t e r m i n i n g t h e c a r b o n number d i s t r i b u t i o n s o f e a c h p o r p h y r i n t y p e for both metalloporphyrins. a n

1600

400

• ο = Accumulating Bitumen

£

>> ο ι_

Φ «»

1500

1

Β

1

ι 2500

• Ο

•

200

ι

Γ

400

ι

4500

1

h-- ο — I

(ppm)

3500

[V]

ι

ΚΗ

•

A

m

(ppm)

300

[Ni]

F i g u r e 6. C a l c u l a t e d e f f e c t o f k e r o g e n m a t u r a t i o n o n t h e N i a n d V c o n c e n t r a t i o n o f New A l b a n y ( A ) a n d W o o d f o r d ( B ) accumulating bitumen.

symbols) Α Δ = Bitumen-MI

2000

V (open

(ppm) • • = Bitumen-I

1200 and [ v ]

800

[Ni]

Ni ( s o l i d s y m b o l s )

400

α

Ε 300

200

2 φ

100 h -

ϋ

100


1

τ

1 5500

1

-ι

500

Γ"

3

I

•s,

r

D

>

w

m *> m r

Φ

ε

α

400

300

200

100

1.2

h

_l

I

1.6

I 2.0

Ratio

1.8 Ni/V

L 2.2

2.4

F i g u r e 7. Calculated Ni/V ratio (B) a c c u m u l a t i n g b i t u m e n .

1.4

I

Bitumen-

Ρ

h

h

Ni/V

0.062

0.064 Ratio

(A) and Woodford

0.060

o f New A l b a n y

0.058

400

300

200

ιοο h


0.066

m

G

x m

i

m r η

2

Κ)

7.


Generation


133

(4) G e n e r a t i o n o f N i a n d V c o m p l e x e s from k e r o g e n d u r i n g c a t a genesis can s u b s t a n t i a l l y a l t e r t h eN iand V contents, porphyrin c o n t e n t s , and p o r p h y r i n composition o f t h e bitumen accumulating i n a source rock. The e x a c t n a t u r e o f t h e changes w i l l be dependent o n the p a r t i c u l a r kerogen and i t s p o s t - d e p o s i t i o n a l h i s t o r y . Acknowledgments


The a u t h o r s t h a n k D r . P. S u n d a r a r a m a n ( C h e v r o n O i l F i e l d Research Co.) f o r t h e H P L C a n a l y s e s a n d D r . M.D. L e w a n (Amoco P r o d u c t i o n Company, R e s e a r c h C e n t e r ) a n d D r . R.K. L e i n i n g e r ( I n d i a n a G e o l o g i c a l S u r v e y ) f o r t h e s a m p l e s o f W o o d f o r d a n d New A l b a n y S h a l e , r e s p e c tively. The a s s i s t a n c e o f D r . F.F. F o i t , G e o l o g y Department, Washington State U n i v e r s i t y , i nperforming t h eX-ray d i f f r a c t i o n work i s acknowledged.

Literature Cited 1. 2. 3. 4. 5. 6. 7. 8. 9. 10. 11. 12.

13.

14. 15. 16. 17. 18.

Gallegos, E . J . Anal. Chem. 1975, 47, 1524-28. Seifert, W.K. Geochim. Cosmochim. Acta 1978, 42, 473-84. Burnham, A.K.; Clarkson, J.E.; Singleton, M.F.; Wong, C.M.; Crawford, R.W. Geochim. Cosmochim. Acta 1982, 46, 1243-51. Quirke, J.M.E.; Shaw, G . J . ; Soper, P.D.; Maxwell, J.R. Tetrahedron 1980, 36, 3261-7. Blumer, M.; Rudrum, M. J . Inst. Petrol. 1970, 56, 99-106. Barwise, A . J . G . ; Roberts, I. Org. Geochem. 1984, 6, 167-76. Mackenzie, A.S.; Quirke, J.M.E.; Maxwell, J.R. In "Advances in Organic Geochemistry 1979"; Douglas, A.G.; Maxwell, J . R . , Eds.; Pergamon Press: Oxford, 1980; pp. 239-48. Baker, E.W.; Louda, J.W. In "Advances in Organic Geochemistry 1981"; Bjorøy, M., Ed.; John Wiley: London, 1983; pp. 401-21. Van Berkel, G . J . ; Filby, R.H. In "Geochemical Biomarkers"; Yen, T . F . ; Moldowan, J.M., Eds.; Gordon and Breach Publishers: London (in press). Riley, K.W.; Saxby, J.D. Chem. Geol. 1982, 37, 265-75. Spiro, B.; Dinur, D.; Aizenshtat, Z. Chem. Geol. 1983, 39, 189-214. Ham, W.E.; Amsden, T.W.; Denison, R . E . ; Derby, J . R . ; Fay, R.O.; Graffham, A.A.; Rowland, T . L . ; Squires, R . L . ; Stitt, J . H . ; Wiltse, E.W. "Regional Geology of the Arbuckle Mountains, Oklahoma"; Oklahoma Geological Survey Special Publication 73-3, 1973; 61 p. Hasenmueller, N.R.; Woodward, G.S. "Studies of the New Albany Shale (Devonian and Mississippian) and equivalent strata in Indiana"; Indiana Geological Survey Contract Report to U.S. Department of Energy, Contract DE-AC-21-76MC05204, 1981; 100 p. Durand, B.; Nicaise, G. In "Kerogen: Insoluble Organic Matter from Sedimentary Rocks"; Durand, B . , Ed.; Editions Technip: Paris, 1980; pp. 35-53. Jacobs, F . S . ; Filby, R.H. Anal. Chem. 1982, 55, 74-7. Filby, R.H. In "The Role of Trace Metals in Petroleum"; Yen, T . F . , Ed.; Ann Arbor Science: Ann Arbor, 1975; pp. 31-58. Sundararaman, P. Anal. Chem. 1985, 57, 2204-06. Van Berkel, G . J . , unpublished data.


134


19. Jeong, K.M.; Kobylinski, T.P. In "Geochemistry and Chemistry of Oil Shales"; Miknis, F . P . ; Mckay, J.F., Eds.; ACS SYMPOSIUM SERIES NO. 230, American Chemical Society: Washington, D.C., 1983; pp. 493-512. 20. Spiro, B. Org. Geochem. 1984, 6, 543-59. 21. Mckay, J . F . Energy Sources 1984, 7, 257-70. 22. Compton, L . E . ACS Div. Fuel Chem. Preprints 1983, 28, 205-11. 23. Erdem-Senatalar, Α.; Kadioglu, E . ; Tolay, M.; Bartle, K.D.; Snape, C.E.; Taylor, N. Fuel 1985, 64, 1748-53. 24. Yen, T.F. In "The Role of Trace Metals in Petroleum"; Yen, T . F . , Ed.; Ann Arbor Science: Ann Arbor, 1975; pp. 1-30. 25. Tooulakou, D.; Filby, R.H. In "Geochemical Biomarkers"; Yen, T . F . ; Moldowan, J . M . , Eds.; Gordon and Breach Publishers: London (in press). 26. Casagrande, D . J . ; Hodgson, G.W. Nature 1971, 233, 123-24. 27. Casagrande, D . J . ; Hodgson, G.W. Geochim. Cosmochim. Acta 1974, 38, 1745-58. 28. Didyk, B.M.; Alturki, Y . I . Α . ; Pillinger, C.T.; Eglington, G. Nature 1975, 256, 563-65. 29. Bonnett, R.; Brewer, P.; Noro, K.; Noro, T. Tetrahedron 1978, 34, 379-85. 30. Barwise, A.J.G. (this volume). 31. Burkova, V.N.; Ryadovaya, L . V . ; Serebrennikova, O.V.; Titov, V.I. Geokhimiya 1980, 9, 1417-21. 32. Rosscup, R . J . ; Bowman, D.H. Preprints Div. Pet. Chem. A.C.S. 1967, 12, 77-81. RECEIVED March 11, 1987

Chapter 8 Distribution of Transition Metals in North Alaskan Oils Joseph A. Curiale


Unocal Research, P.O. Box 76, Brea, CA 92621

Copper, iron, manganese, nickel and vanadium distributions have been studied for eleven oils derived from two genetically-distinct source rock sequences on the North Slope of Alaska. Both vanadium-nickel and nickel-API gravity correlations were observed. Each of these oils had been previously classified into a distinct oil family based on isotopic and biological marker data. Cluster analysis was successfully applied to classify the oils according to family, based solely on concentrations of these five transition metals. Canonical discriminant analysis was used to determine the linear combination of metal concentration values which gives (simultaneously) (a) the greatest intra-type similarity, and (b) the greatest inter-type dissimilarity. The derived canonical variable values clearly separate each oil into its respective family. The results of this study suggest that (a) ratios such as V/(V+Ni) and Fe/V are useful as oil type determinants for northern Alaskan o i l s , and (b) these oils can be successfully classified, using only transition metal concentrations and appropriate statistical methods, into source-defined oil families. Knowledge of the occurrence and d i s t r i b u t i o n of t r a n s i t i o n metals in crude o i l s i s important to those engaged in exploring f o r , producing and refining petroleum. Because organometallic compounds are concentrated in the heavy ends of petroleum, t r a n s i t i o n element concentrations and ratios can serve as excellent o i l - o i l correlation parameters. An understanding of the occurrence of these metals i s also helpful to refining chemists seeking to minimize catalyst poisoning during o i l upgrading. Recognizing the importance of trace metal information, both organic geochemists and petroleum chemists have examined numerous o i l s worldwide in an e f f o r t to establish common t r a n s i t i o n element characteristics among them, and therefore 0097-6156/87/0344-0135$06.00/0 © 1987 American Chemical Society


136


better understand the reasons for metal concentration variations from o i l to o i l . Metals in crude o i l s arise from several sources. Produced o i l w i l l contain metal contributions from original source rock organic matter, from minerals leached during migration and after emplacement in r e s e r v o i r s , and from contamination during production and s h i p ment. Nevertheless, studies of t r a n s i t i o n elements in o i l usually presume that the d i s t r i b u t i o n of these elements r e f l e c t s t h e i r d i s t r i b u t i o n in the source rock, ignoring both contamination and secondary gain or loss of metal during migration. Such complica tions are obviated to some degree by s p e c i f i c a l l y studying organometallic compounds. However, such an approach introduces a proce dural bias to the resulting data, insomuch as current organometallic i s o l a t i o n methods are not completely quantitative (_1). An alternative approach, in l i e u of a complete understanding of the molecular association of transition elements in crude o i l s , is to study their concentration distributions in a selected suite of crude o i l s . This paper presents the results of such a study, involving a group of well-characterized o i l s from northern Alaska. The d i s t r i b u t i o n s of copper, i r o n , manganese, nickel and vanadium in two North Slope o i l families are presented in an e f f o r t to assess the usefulness of trace metal data as a determinant of o i l type. Background The presence of t r a n s i t i o n elements in crude o i l was i n i t i a l l y established over f i f t y years ago (2). Several recent summaries on the subject are available (3-5). ft review of studies on the f i r s t series metals, including those discussed in the present paper, i s given elsewhere (Curiale, J . Α . , AAPG Studies in Geology No. 23, in press). The reader is referred to these papers for d e t a i l s . Certain t r a n s i t i o n metal (vanadium and nickel) concentration data have recently been used as type determinants for crude o i l families on the North Slope of Alaska (6). These o i l s are commonly grouped into two source-controlled groups based on biological marker distributions (Curiale, J . Α . , SEPM Special Publication, in press) and element concentrations and isotope ratios (7). TïïTs two-family concept for North Slope o i l s has wide support, as i s suggested by recent summaries of a multi-group study of North Slope o i l composition (8). Type A o i l s are characterized by o i l s from Prudhoe Bay and Kuparuk F i e l d s , while type Β o i l s , currently non-commercial, are characterized by o i l s from the Umiat and Simpson areas. Oils in the type A family, r e l a t i v e to those in the type Β family, are higher in heteroatom concentrations, V/(V+Ni) ratios and t r i c y c l i c / p e n t a c y c l i c terpane r a t i o s , and have d i s t i n c t i v e trisnorhopane d i s t r i b u t i o n s . While the type A o i l s are usually found in reservoirs in Cretaceous and older rocks, the type Β o i l s are more often found in reservoirs in Cretaceous and younger rocks. The d i s t i n c t i o n between o i l types based on vanadium and nickel concentrations and ratios suggests that other t r a n s i t i o n elements may also serve as family determinants. In the present study, concentrations of f i v e t r a n s i t i o n metals (copper, i r o n , manganese, nickel and vanadium) in eleven North Slope o i l s were examined; some data represent duplicate analyses of samples discussed in prior

8.

CURIALE

Distribution

of Transition

Metals in North Alaskan

Oils

137

publications (6). Eight of these o i l s have been c l a s s i f i e d by isotopic and bTomarker data as type A o i l s ; three are type Β (Curiale, J . Α . , SEPM Special Publication, in press). The purpose of the present paper is to demonstrate the potential u t i l i t y of transition metal concentrations and distributions as a parameter of d i s t i n c t i o n for o i l types on the North Slope, and for worldwide source-related o i l families in general.


The Sample Suite Eleven o i l s , ranging in API gravity from 13.6 to 27.8 degrees (at 6 0 ° F ) , were examined. Sample i d e n t i f i c a t i o n s and pre-assigned o i l types (based largely on whole o i l stable carbon isotope ratios and biological marker distributions) are given in Table I. The o i l s examined range in production depth from the surface to almost 13,000 f t , and cover an area of about 20,000 square miles. Sample l o c a tions are presented elsewhere (6). A l l samples were analyzed as aqueous solutions of ashes, by "inductively coupled plasma atomic emission spectrometry. Detection l i m i t s varied, depending upon sample s i z e . Limited f i l t r a t i o n experiments suggest that a l l metal-containing species in these o i l s w i l l pass a five micron filter. Further details of the analytical procedures have been given previously (Appendix I of C u r i a l e , J . Α . , AAPG Studies in Geology No. 23, in press). Table I.

North Slope Oil Sample Identification

Sample ID AA0085-1 AA0085-3 AB0097-11 AI7251-5 AI7251-8 AI7288 AI7291 AJ0031R AJ0032 AJ6013-1 AK7467

and Type Assignment

Description Put River No. 1; 8720-9260 f t . Sag River State No. 1; 8540-9020 f t . Well 10, East of Prudhoe Field Simpson Core Test O i l ; less than 400 f t . Oil from Simpson area shot hole; B19,SP53 Well 20, West of Prudhoe Field Well 30, West of Prudhoe Field Well 40, East of Prudhoe Field Well 50, East of Prudhoe Field Well 60, East of Prudhoe Field Umiat No. 5

Type A A A Β Β A A A A A Β

In the remainder of this paper, I w i l l f i r s t present the metal concentrations and other relevant geochemical data, then discuss potential s t a t i s t i c a l separation of the o i l s into genetic types, using only t r a n s i t i o n element data. A f i n a l discussion w i l l pursue potential application of trace metal data as an o i l family deter minant for other o i l s worldwide. Transition Metal Concentrations Transition metal concentration data (in parts per m i l l i o n by weight) and API gravities are presented in Table II for each of the eleven

138


o i l s . An detection values of V) ranges


asterisk (*) indicates that concentrations were below l i m i t s ; concentrations less than 0.1 ppm are assigned 0.0. Total metal concentration (Cu + Fe + Mn + Ni + from less than 1.0 ppm to over 180 ppm.

Table II.

Element Concentrations (ppm) and Canonical Variables

Sample ID

Cu

AA0085-1 AA0085-3 AB0097-11 AI7251-5 AI7251-8 AI7288 AI7291 AJ0031R AJ0032 AJ6013-1 AK7467

0.3 1.1 0.0 1.6 7.4 13.0 2.6 28.0 0.1 4.7 1.2 6.2 0.7 1.2 3.3 66.0 0.3 4.8 1.8 6.4 0.1 0.4

Fe

Mn

Ni

3.0 9.6 8.0 10.0 * 16.0 0.1 0.9 0.0 0.9 6.0 11.0 • 23.0 1.2 34.0 0.0 10.0 0.1 15.0 0.0 0.2

V

Total

19.0 33.0 20.0 39.7 30.0 66.4 0.8 32.4 1.9 7.6 29.0 53.4 66.0 90.9 81.0 185.5 26.0 41.1 61.0 84.3 0.0 0.7

V/V+Ni 0.66 0.67 0.65 0.47 0.68 0.73 0.74 0.70 0.72 0.80 0.17

API 27.8 25.2 22.3 21.0 20.2 26.6 21.3 13.6 26.1 36.8

Type

(CV) CV

A 3.48 A 2.08 A Β •-6.25 Β •-5.49 A 3.34 A A 3.14 A 0.94 A 2.88 Β •-4.12

It is apparent from the data that (a) few internal correlations exist in the concentration data, (b) type A o i l s generally show higher total metal concentrations (predominantly vanadium and nickel) than type Β o i l s , and (c) there appears to be a general relationship between API gravity and t r a n s i t i o n metal content. The only s i g n i f i c a n t inter-metal correlation i s present between concen trations of vanadium and nickel (r=0.95; Figure 1). The data in this figure also show major concentration differences between type A and type Β o i l s . Note p a r t i c u l a r l y that, while type A o i l s show a large range of vanadium and nickel concentrations, the V/(V+Ni) ratio stays r e l a t i v e l y constant, between 0.65 and 0.80. This ratio is often invoked as an o i l - o i l correlation parameter, because i t s value appears to remain r e l a t i v e l y constant despite subsequent in-reservoir alteration of crude o i l (9, and references cited therein). On this basis i t would appear that the type A o i l s are derived from a single source rock s u i t e , and that the differences in vanadium and nickel concentrations for these o i l s are caused by post-migration a l t e r a t i o n . This i s consistent with current thinking about this o i l type (6). It has been noted repeatedly that heavy o i l s contain unusually large amounts of t r a n s i t i o n metals (10-12). Thus i t is plausible that the variation of vanadium and nickel concentrations within the type A o i l s shown in Figure 1 results from differences in API gravity (Curiale, J . Α . , SEPM Special Publication, in press). Figure 2 shows the relationship between API gravity and metal (vanadium and nickel) concentration of the type A o i l s . Both API gravity vs Ni and API gravity vs V show trends of increasing metal concentration with decreasing API gravity. Figure 2 shows the best f i t line for Ni vs API gravity; the second l i n e in the diagram is inferred for vanadium, based on an average V/(V+Ni) r a t i o for type A o i l s of 0.71 (see Table II). The difference in line f i t s for these


8.

CURIALE

Distribution

o.oH? 0.0

of Transition Metals in North Alaskan

,

,

20.0

40.0

, 60.0

Oils

139

, 80.0

V A N A D I U M ppm (w/w)

Figure 1. Concentration of nickel (ppm) _vs vanadium (ppm) f o r types A and Β North Slope o i l s . Type A o i l s f a l l within or very close to a V/(V+Ni) r a t i o envelope between 0.65 and 0.80.

140



30.0

1 o.o

4,

,

,

,

,

,

0.0

20.0

40.0

60.0

80.0

100.0

N I C K E L (ppm, ο ) VANADIUM (ppm, · )

Figure 2. API gravity vs nickel and vanadium concentrations (ppm) in type A North Slope o i l s . Best-fit l i n e f o r API gravity vs Ni is shown. The other l i n e is inferred as an ideal f i t f o r API gravity vs V, using an average V/(V+Ni) r a t i o of 0.71 f o r type A o i l s "(Table II).

8.

CURIALE

Distribution

of Transition


Oils

141

two metals may suggest that, in type A o i l s , the molecular species of nickel i s d i f f e r e n t from that of vanadium. A l t e r n a t i v e l y , the d i f f e r i n g source inputs to the type A o i l family (6,13) may supply d i f f e r i n g vanadium concentrations, but similar nickel concentrations.


Statistical

Discrimination Between Oil Types. Using Metal Data

Efforts at o i l - o i l correlations using metal data from a group of o i l s comprising more than one source family are i m p l i c i t attempts at either cluster or discriminant a n a l y s i s . Such e f f o r t s commonly involve only two or three metals, usually presented as ratios (14-16). In the present study, concentrations of f i v e t r a n s i t i o n metals have been determined (Table II), and both cluster and d i s c r i minant analysis techniques have been applied. Figure 3 shows clustering results using a model with these five metals as variables; data were read in the order l i s t e d in Table II, and distances were calculated using Bray-Curtis (BC) indices (17). Note that clustering using only eleven o i l s i s capable of d i s t i n g u i shing two groups at the 1.0 BC l e v e l , and that these groups corres pond exactly to the A and Β o i l types of the North Slope. Neverthe l e s s , considerable variety within the groups is evident. Note p a r t i c u l a r l y that geographically proximate o i l s do not necessarily c l u s t e r at low BC values ( e . g . , AI7288 and AI7291). Cluster analysis has i t s greatest u t i l i t y when o i l types have not yet been established by other methods. For the o i l s l i s t e d in Table I however, the typing specifications are c l e a r . In such s i t u a t i o n s , discriminant analysis can provide greater u t i l i t y as a type determinant for c l a s s i f i c a t i o n of future samples (18). In the present study, canonical discriminant analysis has ïïêen used to determine the linear combination of the f i v e t r a n s i t i o n elements that provides the greatest intra-type correlation within each o i l type, while simultaneously providing maximum discrimination between types (19·). The a n a l y s i s , subject to a data l i m i t a t i o n of only eleven o i l s comprising two c l a s s e s , provides a single canonical variable (CV) capable of separating the o i l s according to type based solely on concentrations of copper, i r o n , manganese, nickel and vanadium (note that the strong correlation between nickel and vanadium shown in Figure 1 makes the addition of vanadium p a r t i a l l y superfluous). The raw c o e f f i c i e n t s derived by the analysis are: Cu = 3.486; Fe = -0.419; Mn = -0.117; Ni = 1.340; V = -0.266 (residual = -4.562). The canonical variables for nine of the eleven o i l s are l i s t e d in Table II. A strong discrimination has been established between o i l types A (CV = -6.25 to -4.12) and Β (CV = 0.94 to 3.48). Thus each of these nine o i l s are e a s i l y c l a s s i f i e d using this technique into the two pre-determined o i l types, indicating that t r a n s i t i o n metal data are useful as o i l typing parameters indepen dently of other geochemical data. Mahalanobis' distances provide a measure of the extent of class separation achieved by the canonical variable discriminant a n a l y s i s , and allow an estimate of the contribution of parameter pairs to the total separation (19). In the present case, the Mahalanobis' distance using C u , T e , Mn, Ni and V i s 7.93, of which Fe and Ni



Figure 3. Results of cluster analysis using Bray-Curtis distance for type A and Β North Slope o i l s . Concentrations of copper, i r o n , manganese, nickel and vanadium are used as clustering variables. Note the d i s t i n c t separation between types A and B.


8.

CURIALE

Distribution

of Transition


OUs

143

comprise 56.3% of the total separation. That i s , the concentrations of iron and nickel in North Slope o i l s account for over half of the difference in the d i s t r i b u t i o n of these five metals in the o i l s l i s t e d in Table I. Although the intent of this study is to determine the capa b i l i t y of distinguishing North Slope o i l s based solely upon t r a n s i tion metal data, the addition of the API gravity (Table II) to the discriminant analysis provides an interesting r e s u l t . The addition of this variable necessitates deleting three of the eleven samples (in addition to the two data gaps in Table II, sample AJ0032 drops out of the a n a l y s i s , because API data are unavailable). The Mahalanobis distance resulting solely from the addition of API gravity increases from 7.93 to 23.58, suggesting that gravity differences between o i l types are indeed s i g n i f i c a n t . This was previously noted for non-biodegraded North Slope o i l s (_7). The unstandardized canonical c o e f f i c i e n t s noted above are useful in deriving unique ratios for defining North Slope o i l types. For example, note that the CV's of type Β o i l s (Table II) are s i g n i f i c a n t l y more negative than those for type A o i l s , while at the same time iron has the most negative canonical c o e f f i c i e n t (as noted above). These two observations suggest that r e l a t i v e iron content may be a c o n t r o l l i n g factor in recognizing type Β o i l s . Indeed, the Fe/V ratio is consistently greater than 1.0 for type Β o i l s , and less than 1.0 for type A o i l s . Discussion While metal concentration data have been used in the past to d i s t i n guish North Slope o i l types, they have been limited to vanadium and nickel (Curiale, J . Α . , SEPM Special Publication, in press). The present study demonstrates that other f i r s t series t r a n s i t i o n elements, p a r t i c u l a r l y i r o n , are also useful indicators of o i l type. Further, the u t i l i t y of cluster and discriminant analyses as deter minants of o i l type appears to transcend certain post-migration o i l alteration e f f e c t s , such as biodégradation and extreme thermal maturation. For example, sample AI7251-8, a heavily biodegraded type Β o i l , clusters consistently with AI7251-5, a r e l a t i v e l y unaltered type Β o i l (Figure 3). Further, discriminant analysis separates these two o i l s by only one CV unit. In a d d i t i o n , sample AK7467, a very mature (API = 36.8) o i l , also is c l e a r l y grouped by cluster analysis and force-grouped by discriminant analysis into type Β o i l , in agreement with other conclusions for Umiat o i l s (_7). It can be concluded that t r a n s i t i o n metal data provide excellent supporting data for o i l type c l a s s i f i c a t i o n on the North Slope. Although t r a n s i t i o n metals successfully support a dual c l a s s i f i c a t i o n , i t is unclear whether each o i l type is necessarily sourcedistinctive. Published data appear to support multiple sourcing for type A (Prudhoe) o i l s (6,13), and the concept of a single source unit for type Β o i l s is also subject to some question (Curiale, J . Α . , SEPM Special Publication, in press). Future e f f o r t s at e s t a b l i s h ! ng~trirn?Trroir^ in kerogens and bitumens of North Slope source units could potentially provide a d i s t i n c t i v e c l a s s i f i c a t i o n for each o i l l i s t e d in Table I. If successful, direct matching of a single o i l to a series of source rocks w i l l be


144


possible, allowing one to assign percentage contributions from each source to the mixed o i l . The successful application of t r a n s i t i o n metal data as an o i l type indicator on the North Slope of Alaska suggests that these data could be applicable as o i l family determinants elsewhere. Analyti cal developments over the past two decades have made i t possible to determine a large number of t r a n s i t i o n elements r a p i d l y , with constantly improving p r e c i s i o n . In a d d i t i o n , improvements in f i l t r a t i o n techniques allow e f f i c i e n t separation of mineral matter from the indigenous organic matter of crude o i l , greatly increasing the accuracy of metals-in-oil determinations. Such advances now make the routine analysis of organically-associated trace metals in crude o i l s a r e a l i t y ; such data are no longer limited to determina tions of vanadium and nickel concentration. The future applications of trace metal geochemistry to o i l typing and petroleum exploration in general appear to be extensive (3,4). As analytical methods f o r analysis of hydrocarbons in crude oTTs mature, research directions w i l l begin to emphasize the heteroatom-containing molecules. Of these, organometallic compounds w i l l undoubtedly provide a s i g n i f i c a n t amount of information concerning the genesis and c l a s s i f i c a t i o n of o i l . Acknowledgments Drs. G. H. Smith, J . R. Fox, S. R. Larter, R. E. Sweeney, R. J . Lukasiewicz and F. G. Dewalt, a l l of Unocal's Science & Technology D i v i s i o n , provided needed advice and expertise. S. A. Bharvani and M. Jacob assisted in the laboratory. Special thanks goes to Mary MacDonald for preparing the f i n a l manuscript. I also thank Unocal management f o r providing an environment where this type of work can continue, and f o r giving permission to publish the r e s u l t s . Literature Cited 1. 2. 3.

4. 5. 6.

7. 8.

Fish, R. H . ; Komlenic, J. J.; Wines, Β. K. Anal. Chem. 1984, 56, 2452-2460. Treibs, A. Annal. Chem. 1934, 510, 42-62. Barwise, A. J . G . ; Whitehead, Ε. V. In The Significance of Trace Elements in Solving Petrogenic Problems and Controversies; Augustithis, S. S., Ed.; Theophrastus: Athens, 1983; p. 599-643. Jones, P. In Forum on Oil and Ore in Sediments; Imperial College of Science and Technology: London, 1977; p. 40-53. Hitchon, B.; Filby, R. H. Bull. Amer. Assoc. Petr. Geol. 1984, 68, 838-849. Curiale, J . A. In Oil/Rock Correlation Study on North Slope of Alaska; Magoon, L . B . ; Claypool, G . E . , Eds.; AAPG Studies in Geology Series No. 20; Amer. Assoc. Petr. Geol.: Tulsa, 1986; p. 203-232. Magoon, L. B.; Claypool, G. E. Bull. Amer. Assoc. Petr. Geol. 1981, 65, 644-652. Claypool, G. E . ; Magoon, L. B. In Oil/Rock Correlation Study on North Slope of Alaska; Magoon, L. B.; Claypool, G. Ε . , Eds.; AAPG Studies in Geology Series No. 20; Amer. Assoc. Petr. Geol.: Tulsa, 1986; p. 49-81.

8. CURIALE

Distribution of Transition Metals in North Alaskan OUs145


9. Lewan, M. D. Geochim. Cosmochim. Acta 1984, 48, 2231-2238. 10. Skinner, D. A. Ind. Eng. Chem. 1952, 44, 1159-1165. 11. Erickson, R. L.; Myers, A. T . ; Horr, C. A. Bull. Amer. Assoc. Petr. Geol. 1954, 38, 2211-2218. 12. Breger, I. A. In The Future of Heavy Crude Oils and Tar Sands; Barnea, J.; Bowman, C. W., Eds.; UNITAR: New York, 1977; p. 163-167. 13. Seifert, W. K.; Moldowan, J . M.; Jones, R. W. Proc. 10th World Petr. Cong., 1979, p. 425-440. 14. Bonham, L. C. Bull. Amer. Assoc. Petr. Geol. 1956, 40, 897-908. 15. Curiale, J . A. Ph.D. Thesis, University of Oklahoma, 1981. 16. Saban, M.; Vitorovic, O.; Vitorovic, D. In Characterization of Heavy Crude Oils and Petroleum Residues; Editions Technip: Paris, 1984; p. 122-127. 17. Seber, G. A. F. Multivariate Observations, John Wiley & Sons: New York, 1984. 18. O'Connor, J . T. In USGS Research on Energy Resources -- 1986 Program and Abstracts; Carter, L. M. H., Ed.; USGS Circular 974; USGS: Washington, D.C., 1984; p. 46. 19. Davis, J . C. Statistics and Data Analysis in Geology; John Wiley & Sons, Inc.: New York, 1973. RECEIVED October 16, 1986

Chapter 9 Metals

in

Crude

Oils,

Asphaltenes,

Bitumen,

and

Kerogen in Molasse Basin, Southern Germany Alfred V. Hirner


Mineralogisch-Petrographisches Institut der Universität, Theresienstrasse 41, D-8000 München 2, Federal Republic of Germany

In the course of organic geochemical investigations in the Southern German Molasse Basin, the use of trace element studies on maltene, asphaltene and kerogen fractions of crude oils, bitumens and potential source rocks for o i l - o i l and oil-source rock correlations has been tested. The Ni, V and Co contents of crude oil-maltenes and -asphaltenes enabled the differentiation of two o i l families to be made in conjunction with other geochemical analyses. Elemental concentrations in the asphaltene fraction of bitumen and in the kerogen of potential source rocks are similar to those in the corresponding crudes. However, these correlations are not true for Zn and I. It could be shown that Ni in kerogen is associated with the organic phase, whereas Ti is derived from the mineral matrix. Organic substances p l a y a dominant r o l e i n geochemical c y c l i n g , e s p e c i a l l y i nthe l o c a l c o n c e n t r a t i o n o f t r a c e metals (1-3). Metalo r g a n i c a n d o r g a n o m e t a l l i c s p e c i e s i n s e d i m e n t s may o r i g i n a t e f r o m t h e b i o m a s s w i t h o u t m a j o r c h e m i c a l c h a n g e s , o r t h e y may b e f o r m e d d u r i n g sedimentation and/or d i a g e n e s i s from o r g a n i c molecules and metal ions d e r i v e d from d i f f e r e n t b i o g e n i c (biomass) and a b i o g e n i c sources (weathering o f m i n e r a l s ) . T h u s , i n many o f t h e s e g e o chemical cycles i n o r g a n i c as w e l l as organic a s s o c i a t i o n s o f t h e metals are i n v o l v e d , and o f t e n they d i r e c t l y o r i n d i r e c t l y i n t e r a c t w i t h each o t h e r . Complex s i t u a t i o n s r e s u l t , and c o r r e l a t i o n s between metal c o n c e n t r a t i o n s and e i t h e r i n o r g a n i c o r o r g a n i c sediment f r a c t i o n s may n o t a l w a y s b e f o u n d . For example, i n A u s t r a l i a no i l s h a l e s n i c k e l i s a s s o c i a t e d w i t h the o r g a n i c as w e l l as t h e i n o r g a n i c f r a c t i o n s w i t h no a p p a r e n t p r e f e r e n c e ( 4 ) . In o r g a n i c geochemical e x p l o r a t i o n however, o n l y those metals a r e o f s i g n i f i c a n c e , whose c o n c e n t r a t i o n s a r e c l o s e l y a s s o c i a t e d w i t h the o r g a n i c matter. The c o o r d i n a t i o n c h e m i s t r y a n d abundance o f these metals i n crude o i l s p r o v i d e u s e f u l i n f o r m a t i o n on the o r i g i n , m i g r a t i o n , and m a t u r a t i o n o f p e t r o l e u m ( 5 ) .


9.

HIRNER

Metab in Mo fasse Basin, Southern

Germany

147

In t h i s s t u d y , f o r m e r i n v e s t i g a t i o n s (6) a r e e x t e n d e d t o t h e m a l t e n e a n d a s p h a l t e n e f r a c t i o n s o f S o u t h e r n German c r u d e o i l s a s w e l l as t h e b i t u m e n and k e r o g e n f r a c t i o n s o f p o t e n t i a l s o u r c e r o c k s of these crudes.


Samples and

Methods

S e v e r a l geochemical i n v e s t i g a t i o n s o f crude o i l s have r e v e a l e d the e x i s t e n c e o f o n l y two o i l f a m i l i e s i n t h e S o u t h German M o l a s s e B a s i n (6-8) . A l l c r u d e s f o u n d a t t h e s t r a t i g r a p h i e base o f t h e T e r t i a r y b e l o n g t o one g r o u p . The o i l s i n M e s o z o i c r e s e r v o i r s i n t h e w e s t e r n p a r t o f t h e b a s i n a r e s u p p o s e d t o be o f a d i f f e r e n t o r i g i n . Based on t h e s e r e s u l t s , r e p r e s e n t a t i v e samples f r o m each o i l f a m i l y have been s e l e c t e d : M e s o z o i c o i l s : F r o n h o f e n 12, P f u l l e n d o r f 6, O s t r a c h 8 T e r t i a r y b a s e o i l s : M o n c h s r o t , A r l e s r i e d , D a r c h i n g 1, H o h e n r a i n 4. C a r b o n i s o t o p i c s t u d i e s g a v e some e v i d e n c e f o r S a n n o i s i a n a n d R u p e l i a n s e d i m e n t s as p o t e n t i a l s o u r c e r o c k s f o r t h e T e r t i a r y base o i l s (9), a l t h o u g h the samples i n v e s t i g a t e d were s t i l l immature. T h e r e f o r e , t h e b o r e c o r e samples T e i s i n g 1 and H o h e n r a i n 2 have been included i n t h i s study. The c o n c e n t r a t i o n s o f V, C r , F e , Co, N i , Z n , S e , B r , A g a n d I were d e t e r m i n e d b y i n s t r u m e n t a l n e u t r o n a c t i v a t i o n a n a l y s i s as a l r e a d y d e s c r i b e d ( 6 ) ; T i i n k e r o g e n was d e t e r m i n e d b y X - r a y s p e c t r o metry. The a s p h a l t e n e s w e r e s e p a r a t e d b y p r e c i p i t a t i o n w i t h p e t r o l e u m e t h e r 40/60. Trace element c o n c e n t r a t i o n s o f the maltenes (= d e a s p h a l t e d o i l s ) w e r e c a l c u l a t e d b y d i f f e r e n c e , u s i n g t h e a n a l y t i c a l r e s u l t s o f t h e t o t a l o i l and t h e a s p h a l t e n e f r a c t i o n . The c o r e samples were e x t r a c t e d w i t h c h l o r o f o r m / m e t h a n o l (2:1 v/v) f o r t h r e e days. The m a l t e n e a n d t h e a s p h a l t e n e f r a c t i o n s o f t h e e x t r a c t s w e r e analysed separately. Trace element c o n c e n t r a t i o n s To i n d i c a t e t h e c o n c e n t r a t i o n r a n g e s o f t r a c e e l e m e n t s i n S o u t h e r n G e r m a n o i l s a n d k e r o g e n s , p r e v i o u s d a t a (6_, JLO) h a v e b e e n c o m p i l e d a s s h o w n i n F i g u r e 1. T r a c e e l e m e n t c o n c e n t r a t i o n s r a n g e o v e r more t h a n s i x o r d e r s o f magnitude, i . e . from s e v e r a l p a r t s per b i l l i o n to s e v e r a l weight percent. With the e x c e p t i o n o f I, the elements are e n r i c h e d i n the a s p h a l t e n e f r a c t i o n b y a b o u t one o r d e r o f m a g n i t u d e o n t h e a v e r a g e , i n d i c a t i n g an i n c r e a s e o f the m e t a l - b i n d i n g c a p a c i t y w i t h i n c r e a s i n g p o l a r i t y and m o l e c u l a r w e i g h t o f the o r g a n i c m o l e c u l e o r , a l t e r n a t i v e l y , an i n c r e a s e i n m e t a l - t r a p p i n g c a p a c i t y o f a s p h a l t e n e s . Se, Zn, Fe a n d C r a r e e n r i c h e d i n t h e k e r o g e n f r a c t i o n c o m p a r e d t o t h e asphaltenes. W i t h r e s p e c t t o N i , V a n d Co, h o w e v e r , t h e s e two f r a c t i o n s o v e r l a p , a r g u i n g f o r a common o r i g i n o f t h e s e e l e m e n t s i n both f r a c t i o n s . I t must be c o n s i d e r e d , h o w e v e r , t h a t t h e k e r o g e n f r a c t i o n c a n n e v e r be c o m p l e t e l y f r e e o f i n o r g a n i c c o n t r i b u t i o n s .

American Chemical Society,

Library 1155 16th St., N.W. Washington, O.C. 2003S

148


001 -τη

0-1 ,

I

ppm 10

1 ' • • • • mi

I

100 ι

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ι — ι crude oils ββιββ^ΕΕΕίίΕΕΕΕ^Ηΐί^ββ

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w////Aàw//AwmmM»A

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0 01

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.

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(n = 49)

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F i g u r e 1. Ranges o f t r a c e e l e m e n t c o n c e n t r a t i o n s i n c r u d e a s p h a l t e n e s a n d k e r o g e n f r o m S o u t h e r n G e r m a n y (6_, ICQ .

oils,

9.

HIRNER

Meîab

in Molasse Basin, Southern


Results o f correlation

Germany

149

studies

C o m p a r e d t o t h e T e r t i a r y - b a s e o i l s , t h e M e s o z o i c c r u d e o i l s show s i g n i f i c a n t l y l o w e r c o n t e n t s o f N i , V a n d Co i n t h e m a l t e n e a s w e l l as i n t h e a s p h a l t e n e f r a c t i o n ( F i g u r e 2 ) . This r e s u l t i s i n accordance w i t h t h e presumed a s s o c i a t i o n o f these elements w i t h t h e o r i g i n a l source m a t e r i a l (biomass). However, o v e r l a p p i n g ranges a r e o b s e r v e d i n t h e c a s e o f Zn a n d I , i n d i c a t i n g a n u n k n o w n a s s o c i a t i o n b e t w e e n compounds o f t h e s e e l e m e n t s o r j u s t a c o n t r i b u t i o n f r o m i n o r g a n i c matter ( m i n e r a l s ) . Other arguments f o r t h e l a t t e r h y p o t h e s i s a r e t h e s t r o n g e n r i c h m e n t ( 7 - t o 1 5 - f o l d ) o f Zn i n t h e m a l t e n e s a n d a s p h a l t e n e s o f t h e e x t r a c t e d b i t u m e n , w h e r e a s N i a n d Co i n t h e a s p h a l t e n e f r a c t i o n o f t h e b i t u m e n show s i m i l a r a b u n d a n c e s a s i n t h e crude o i l asphaltenes. B e c a u s e o f t h e e n r i c h m e n t o f t h e p o l a r compounds i n t h e n o n - m i g r a t e d bitumen compared t o t h e m i g r a t e d c r u d e s , a n d b e c a u s e N i a n d Co a r e c o n c e n t r a t e d i n t h e p e t r o l e u m h e a v y e n d s , the observed enrichment (2- t o 6-fold) o f these elements i n t h e bitumen maltenes compared t o t h e o i l maltenes i s u n d e r s t a n d a b l e . I n F i g u r e 2, d a t a f o r Co a n d Zn o b t a i n e d f r o m p r e v i o u s s t u d i e s are i n c l u d e d f o r comparison. T h i s c o u l d n o t be done f o r N i a n d V i n the f i g u r e s used because t h e u s u a l low c o n c e n t r a t i o n s o f these e l e m e n t s i n S o u t h e r n German c r u d e o i l s p r e c l u d e d s h o w i n g b o t h d a t a s e t s o n t h e same g r a p h . Concerning Cr c o n c e n t r a t i o n s , a l l bitumen f r a c t i o n s (1.2 t o 11.1 ppm) l i e w i t h i n t h e r a n g e o f o i l a s p h a l t e n e s ( 0 . 9 t o 2 2 . 7 p p m ) . A l s o , t h e Ag contents o f bitumen maltenes a r e w i t h i n t h e crude o i l r a n g e ( 0 . 0 2 t o 0.32 ppm). Whereas Fe i n b i t u m e n m a l t e n e s (35 t o 38 ppm) i s a s a b u n d a n t as i n crudes, t h e bitumen a s p h a l t e n e s (700 t o 2100 ppm) a r e e n r i c h e d c o m p a r e d t o t h e o i l a s p h a l t e n e s ( n-pentane e x t r a c t > methanol-acetone e x t r a c t T h i s t r e n d s h o w s c l e a r l y t h a t t h e v a n a d y l e t i o a n d DPEP p o r p h y r i n s d i s t r i b u t e d i f f e r e n t l y between t h e l e s s p o l a r m a l t e n e s a n d t h e more p o l a r f r a c t i o n s o f t h e b i t u m e n , i_.e_. , t h e n - p e n t a n e a n d m e t h a n o l acetone e x t r a c t s o f the asphaltenes. The f a c t o r s w h i c h c o n t r o l t h e d i s t r i b u t i o n o f o r g a n i c c o n s t i t u ents i n the m i c e l l a r s t r u c t u r e o f the bitumen are not w e l l understood, but p r o b a b l y the most i m p o r t a n t a r e p o l a r i t y ( d e t e r m i n e d l a r g e l y b y f u n c t i o n a l i t y ) and m o l e c u l a r w e i g h t ( 1 , 2 0 ) . The m e t a l l o p o r p h y r i n s i n a n o i l - s a n d b i t u m e n w i l l b e d i s t r i b u t e d among c o m p o n e n t s o f t h e m i c r o s t r u c t u r e and thus the d i f f e r e n c e s i n the a s s o c i a t i o n between t h e DPEP a n d e t i o s e r i e s i n t h e m a l t e n e s a n d i n t h e a s p h a l t e n e e x t r a c t s may b e e x p l a i n e d i n t e r m s o f d i f f e r e n c e s i n p o r p h y r i n polarity. I n g e n e r a l , the p o l a r i t y o f each vanadyl p o r p h y r i n c l a s s ( D P E P , e t i o , b e n z o - e t i o , b e n z o - D P E P , THBD) i s i n v e r s e l y p r o p o r t i o n a l to c a r b o n number a s has been o b s e r v e d d u r i n g chromatographic s e p a r a t i o n o f p o r p h y r i n mixtures (21,22). Thus, the h i g h e r carbon n u m b e r h o m o l o g u e s o f b o t h t h e e t i o a n d t h e DPEP a r e r e l a t i v e l y m o r e abundant i n t h e mass s p e c t r a o f t h e l e s s p o l a r m a l t e n e s compared t o the methanol-acetone e x t r a c t s o f the asphaltenes. I n the Athabasca m a l t e n e s , t h e DPEP p o r p h y r i n s w i t h c a r b o n n u m b e r g r e a t e r t h a n 32 c o m p r i s e 3 0 % o f t h e t o t a l i n t e n s i t y o f t h e DPEP s e r i e s , w h e r e a s i n the m e t h a n o l - a c e t o n e e x t r a c t they account f o r o n l y 12% o f the t o t a l DPEP i n t e n s i t y . Porphyrins with i s o c y c l i c rings, i n general,a r e a l s o more p o l a r t h a n p o r p h y r i n s w i t h o u t i s o c y c l i c r i n g s o f s i m i l a r c a r b o n number. H e n c e , t h e D P E P , t h e THBD, a n d t h e b e n z o p o r p h y r i n s o f t h e same c a r b o n n u m b e r a r e m o r e p o l a r t h a n t h e c o r r e s p o n d i n g e t i o porphyrins. Thus, the r a t i o o f etio/DPEP which decreases from maltenes t omethanol-acetone e x t r a c t (Table I ) i s c o n s i s t e n t w i t h an a s s o c i a t i o n o f the m e t a l l o p o r p h y r i n s w i t h the asphaltenes and other bitumen components based on p o l a r i t y . The etio/THBD, e t i o / b e n z o e t i o andetio/benzo-DPEP porphyrin r a t i o s are highest i n the maltenes of each o i l sand bitumen, and a l s o decrease i n the o r d e r : maltenes > n-pentane e x t r a c t > methanol-acetone e x t r a c t T h u s t h i s t r e n d i s a l s o c o n s i s t e n t w i t h p o l a r i t y d i f f e r e n c e s among these porphyrins. The d i s t r i b u t i o n o f t h e v a n a d y l p o r p h y r i n s among b i t u m e n compon e n t s i s i n a g r e e m e n t w i t h p r e v i o u s w o r k ( 1 7 ) i n w h i c h i t w a s shown the p o r p h y r i n s are a c t u a l l y d i s t r i b u t e d between the maltenes and t h e a s p h a l t e n e s i n t h e b i t u m e n a n d do n o t f r a c t i o n a t e d u r i n g a s p h a l t e n e

166



precipitation. Thus t h e r e i s a decrease i n t h e p o l a r / l e s s p o l a r p o r p h y r i n r a t i o s from t h e p o l a r core o f t h e a s p h a l t e n e m i c e l l e through the intermediate p o l a r i t y r e s i n s that " p e p t i z e " t h e m i c e l l e s i n the maltenes t o the r e l a t i v e l y non-polar maltenes i n which the l e s s p o l a r porphyrins predominate. No e v i d e n c e h a s b e e n f o u n d f o r the u n u s u a l l y h i g h molecular weight p o r p h y r i n s i n t h e a s p h a l t e n e s , suggested by Blumer and Snyder (23), o r f o r t h e v e r y complex, a r o m a t i c t y p e p o r p h y r i n s ( a p a r t f r o m THBD a n d b e n z o ) a s s u g g e s t e d b y Y e n ( 2 4 ) o r J a c o b s ( 2 5 ) . H o w e v e r , s u c h p o r p h y r i n s may b e s t r o n g l y a s s o c i a t e d w i t h t h e a s p h a l t e n e s and a r e n o t e x t r a c t a b l e w i t h methanol-acetone, and thus a r e c l a s s i f i e d w i t h t h e "non-porphyrin" vanadium. The m e t h a n o l - a c e t o n e e x t r a c t o f t h e w h o l e b i t u m e n ( s i m i l a r t o the p o r p h y r i n aggregate o b t a i n e d from c o n v e n t i o n a l o i l s ) has v a l u e s f o r e t i o / o t h e r p o r p h y r i n r a t i o s t h a t a r e i n t e r m e d i a t e between t h e maltenes and t h e methanol-acetone e x t r a c t o f t h e asphaltenes. I t i s c l e a r , however, t h a t t h e p o r p h y r i n abundances i n t h e p o r p h y r i n aggreg a t e s o f o i l s o f s i m i l a r o r i g i n a n d t h e r m a l h i s t o r y may b e i n f l u e n c e d by t h e amount a n d p o l a r i t y o f t h e a s p h a l t e n e s ( o r p o l a r c o m p o n e n t s o f the r e s i n s ) . A l s o , t h e degree o f e x t r a c t i o n i s important because i t i s n o t known what f r a c t i o n o f t h e v a n a d i u m r e m a i n i n g i n t h e t e r t i a r y a s p h a l t e n e s (between 52.8-63.9% o f t o t a l ) (17) i s v a n a d y l p o r p h y r i n , a n d w h a t t h e n a t u r e o f t h e s e v a n a d y l p o r p h y r i n s m i g h t b e . T h e UV s p e c t r u m o f t h e e x t r a c t e d t e r t i a r y a s p h a l t e n e s t i l l shows a S o r e t a b s o r b a n c e a t 4 0 8 nm. Based on t h e e x t r a c t i o n d a t a , i t w o u l d be expected that the vanadyl porphyrins remaining i n t h e e x t r a c t e d a s p h a l t e n e s w o u l d c o n t a i n a h i g h e r p r o p o r t i o n o f THBD a n d b e n z o , a n d possibly other species. P o r p h y r i n R a t i o s as Geochemical

Correlation

Parameters

The s t r o n g a s s o c i a t i o n o f t h e p o r p h y r i n s w i t h t h e a s p h a l t e n e s i n t h e o i l - s a n d bitumens has i m p l i c a t i o n s regarding t h e i r f a t e during the m i g r a t i o n o f t h e o r i g i n a l o i l and subsequent a l t e r a t i o n processes i n the r e s e r v o i r . R u b i n s t e i n e t ad. ( 2 6 , 2 7 ) h a v e shown t h a t g e o c h e m i c a l b i o m a r k e r s c a n be l i b e r a t e d from t h e a s p h a l t e n e s d u r i n g p y r o l y s i s . T h i s i n v e s t i g a t i o n shows t h a t m e t a l l o p o r p h y r i n s c a n a l s o be i s o l a t e d from t h e a s p h a l t e n e s and t h a t t h e d i s t r i b u t i o n s o f p o r p h y r i n t y p e s a s s o c i a t e d w i t h t h e a s p h a l t e n e s a r e d i f f e r e n t from those i n t h e maltenes. I t h a s a l s o b e e n shown t h a t i t i s n o t n e c e s s a r y t o pyrolyze the asphaltenes t o extract a substantial f r a c t i o n ofthe vanadium a s vanadyl p o r p h y r i n s . The e t i o / o t h e r p o r p h y r i n r a t i o s o f t h e t h r e e o i l s a n d s a r e shown g r a p h i c a l l y i n F i g u r e 8 a n d g e o c h e m i c a l d a t a a r e g i v e n i n T a b l e I I . The e t i o / D P E P r a t i o i n c r e a s e s i n t h e o r d e r Athabasca < Peace R i v e r < Cold Lake T h i s t r e n d i s seen i n each o f t h e bitumen components. T h e same t r e n d i s e x h i b i t e d by t h e etio/THBD, and t h e e t i o / b e n z o p o r p h y r i n r a t i o s i n the bitumen components. T h e e t i o / D P E P r a t i o s may b e i n t e r p r e t e d t o r e p r e s e n t a m a t u r a t i o n s e q u e n c e among t h e t h r e e b i t u m e n s , although the A t h a b a s c a , Peace R i v e r , and C o l d Lake o i l sand samples were a l l r e s e r v o i r e d a t l e s s t h a n 3 0 0 m; t h u s , i n s i t u m a t u r a t i o n c a n n o t explain the porphyrin distributions. The o i l sands have been subj e c t e d a l s o t o extensive biodegradation/water washing (13,14), but

F i g u r e 8. Etio/DPEP ( # ) , etio/THBD ( Ο ) , e t i o / b e n z o - e t i o (·) and e t i o / b e n z o - D P E P ( e ) r a t i o s f o r b i t u m e n components o f A t h a b a s c a ( A ) , P e a c e R i v e r ( P R ) , and C o l d L a k e (CL) o i l s a n d s .


ON -J

168


T a b l e I I . G e o c h e m i c a l , V, N i a n d V a n a d y l P o r p h y r i n D a t a A t h a b a s c a , Peace R i v e r and C o l d Lake O i l Sands

f o r the

Property

Lake

Athabasca

Present depth reservoir

of

0


D e g r e e o f biodégradation V

Very

concentration

(us/e) Ni

V/Ni VOP

Cold

444

169

high

196 +

Very

3

high

180 ±

High

3

191 ±

3

74.8

±

2.6

±

3

62.4

±

2.9

±

1

62.6+5

a

a

(yg

V/g)

Extractable

b

V0P

b , C

DPEP/(DPEP +

etio)

0.1

0.2

47.2%

51.1%

40.1%

1.80

1.64

1.39

0.64

0.62

0.58

Taken from S t r o n g

(17); V/Ni r a t i o contents

m u l t i p l i e d by Roberts (9).

±

76.8

d

"Expressed as p e r c e n t

3.1

92.0

Vanadyl

porphyrin

0.1

92.5

DPEP/etio

Wen and

River

a

concentration

(yg/g)

Peace

of t o t a l

100,

i s demetal weight

estimated

ratio.

t o have r e l a t i v e

V i n bitumen

e r r o r ^10-15%.

(17).

e q u i v a l e n t t o %DPEP c a l c u l a t e d

by

Barwise


10.

STRONG A N D FILBY

Vanadyl Porphyrin Distribution in Alberta

169

p r e v i o u s w o r k b y P a l m e r ( 1 2 ) a n d B a r w i s e ( 2 ) h a s shown t h a t biodégradation has l i t t l e e f f e c t on the vanadyl p o r p h y r i n d i s t r i b u t i o n s o f heavy o i l s . The t o t a l v a n a d y l p o r p h y r i n c o n t e n t s o f t h e o i l - s a n d b i t u m e n s ( A : 9 2 . 5 y g V / g ; PR: 9 2 . 0 y g V / g ; C L : 7 6 . 8 y g V / g ) a r e h i g h a n d n o t s t a t i s t i c a l l y d i f f e r e n t among t h e t h r e e s a m p l e s , c o n firming the r e l a t i v e l y l i t t l e , i f any, e f f e c t o f biodegradation/water washing. The e t i o / D P E P a n d e t i o / o t h e r p o r p h y r i n r a t i o s thus p r o b a b l y r e f l e c t the depth (temperature) o f formation o f t h e o r i g i n a l crude o i l s p r i o r t o m i g r a t i o n t o t h e present r e s e r v o i r s , because i n r e s e r v o i r m a t u r a t i o n h a s been s m a l l (assuming s i m i l a r m i g r a t i o n pathways). The o r i g i n o f t h e b i t u m e n i n t h e o i l sands h a s been d e b a t e d , b u t most t h e o r i e s i n v o l v e l o n g - r a n g e m i g r a t i o n o f c o n v e n t i o n a l o i l s from down-dip Lower Cretaceous source r o c k s (13,14,28), a l t h o u g h r e c e n t r e s e a r c h (16,29) i n d i c a t e s p o s s i b l e Devonian c o n t r i butions. Thus i f t h e t h e o r e t i c a l DPEP/(DPEP + e t i o ) v e r s u s e x p u l s i o n t e m p e r a t u r e c u r v e o f B a r w i s e (8) i s u s e d (assumes 10 KJ/mole d i f f e r e n c e s i n a c t i v a t i o n e n e r g y f o r e t i o a n d DPEP d e g r a d a t i o n ) , e x p u l s i o n t e m p e r a t u r e s o f 145-150 C a r e computed. Although these t e m p e r a t u r e s a r e p r o b a b l y t o o h i g h , t h e y do c o n f i r m t h e f o r m a t i o n , or e x p u l s i o n , o f t h e o r i g i n a l crude o i l s a t depths g r e a t e r than t h e present r e s e r v o i r s and i n d i c a t e a depth o f o r i g i n a l o i l formation i n the sequence Athabasca < Peace R i v e r < Cold Lake. The e f f e c t o f l o n g r a n g e m i g r a t i o n o f c r u d e o i l s o n t h e v a n a d y l p o r p h y r i n d i s t r i b u t i o n s h a s n o t b e e n a s s e s s e d b u t may b e o f s i g n i ficance given the d i f f e r e n t p o l a r i t i e s o f d i f f e r e n t porphyrin types. Burkova e t a l . (30) examined t h e v a n a d y l p o r p h y r i n s from t h e Surgut, W. S i b e r i a n o i l f i e l d a n d c o n c l u d e d t h a t t h e p r o p o r t i o n o f n o n - p o l a r v a n a d y l p o r p h y r i n s ( d e f i n e d b y TLC Rf v a l u e s ) i n c r e a s e d w i t h i n c r e a s e d migration distance. I ft h e o r i g i n a l o i l migrated from deeper source rocks a s a s i n g l e phase, t h e d i f f e r e n t a s s o c i a t i o n o f m e t a l l o p o r p h y r i n s i n t h e b u l k hydrocarbon phase (maltenes) and i n t h e a s p h a l t e n e s may h a v e a f f e c t e d t h e e t i o / D P E P , e t i o / T H B D , a n d e t i o / b e n z o d i s t r i b u t i o n s d u r i n g t h e m i g r a t i o n from t h e source rock t o r e s e r v o i r . The " f r e e " p o r p h y r i n s w h i c h a r e p r e s e n t i n t h e h y d r o c a r b o n o r m a l t e n e s f r a c t i o n o f t h e o i l may h a v e b e e n m o r e s u b j e c t t o d i f f e r e n t i a l chromatographic r e t e n t i o n o f the rock matrix than the porphyrins present w i t h i n t h e a s p h a l t e n e m i c e l l e s . These a s p h a l t e n e - a s s o c i a t e d p o r p h y r i n s were p r o b a b l y p r o t e c t e d d u r i n g m i g r a t i o n much l i k e b i o s e n s i t i v e m a r k e r compounds a r e p r o t e c t e d w i t h i n t h e a s p h a l t e n e d u r i n g biodégradation ( 2 6 , 2 7 ) . The e t i o / o t h e r p o r p h y r i n r a t i o s f o r t h e m e t h a n o l - a c e t o n e e x t r a c t o f t h e a s p h a l t e n e s ( F i g u r e 8 ) show s i m i l a r t r e n d s among t h e t h r e e o i l s a n d s , b u t t h e r e a r e q u a l i t a t i v e d i f f e r e n c e s i n t h e m e t h a n o l - a c e t o n e e x t r a c t s compared t o t h e r a t i o s f o r t h e o t h e r bitumen components. T h e s e d i f f e r e n c e s may r e f l e c t the e f f e c t s o f m i g r a t i o n , w h i c h need t o be f u r t h e r e v a l u a t e d . The e t i o / o t h e r p o r p h y r i n r a t i o s f o r c o m p o n e n t s o f t h e t h r e e o i l s a n d b i t u m e n s s h o w n i n F i g u r e 8 show t h a t t h e t r e n d s f o r t h e e t i o / THBD a n d e t i o / b e n z o p o r p h y r i n r a t i o s a r e s i m i l a r t o t h a t o b s e r v e d for t h e etio/DPEP r a t i o . H o w e v e r , d i f f e r e n c e s among t h e e t i o / T H B D a n d e t i o / b e n z o r a t i o s f o r t h e t h r e e o i l s a n d s a r e g r e a t e r t h a n among the etio/DPEP r a t i o s , p a r t i c u l a r l y f o r t h e p o r p h y r i n aggregate and the methanol e x t r a c t o f t h e asphaltenes. I f t h e d i f f e r e n c e s among the etio/THBD a n d e t i o / b e n z o r a t i o s a r e due t o m a t u r a t i o n e f f e c t s , t h e n t h e s e p o r p h y r i n r a t i o s may b e m o r e s e n s i t i v e i n d i c a t o r s o f


170


maturation effects. However, u n t i l t h e o r i g i n o f t h e s e s p e c i e s h a s been determined and t h e e f f e c t s o f m i g r a t i o n a s s e s s e d , u s e o f these r a t i o s i sunwarranted. The p o r p h y r i n f r a c t i o n a t i o n d a t a a l s o i n d i c a t e t h a t t h e change i n etio/DPEP r a t i o i n t h e o i l sand bitumens i s n o t a r e s u l t o f a DPEP t o e t i o c o n v e r s i o n d u r i n g b i t u m e n m a t u r a t i o n . T h e r e i s n o o b v i o u s g e n e t i c r e l a t i o n s h i p among t h e e t i o a n d t h e TH3D a n d b e n z o p o r p h y r i n s , b u t t h e same t r e n d i n t h e e t i o / o t h e r p o r p h y r i n r a t i o s as f o r the etio/DPEP r a t i o s i s observed. R e c e n t l y K a u r e t a l . ( 3 1 ) h a v e shown t h a t t h e b e n z o - D P E P p o r p h y r i n s c o n t a i n t h e a r o m a t i c r i n g o n t h e C-7 a n d C-8 p o s i t i o n s (B r i n g ) r a t h e r t h a n t h e C-17 a n d C-18 p o s i t i o n s (D r i n g ) p r o p o s e d b y B a r w i s e a n d R o b e r t s (9) who a l s o p r o p o s e d t h a t t h e 6-membered r i n g i n THBD w a s o n t h e D r i n g . T h i s would i m p l y no g e n e t i c r e l a t i o n s h i p b e t w e e n b e n z o - D P E P a n d THBD p o r p h y r i n s u n l e s s t h e s t r u c t u r e o f THBD p r o p o s e d b y B a r w i s e a n d R o b e r t s (9) i s i n c o r r e c t . I f , however, t h e 6-membered r i n g i n THBD a n d b e n z o - D P E P p o r p h y r i n s a r e b o t h o n t h e Β r i n g , t h e n t h e b e n z o - D P E P may a r i s e b y d e h y d r o g e n a t i o n o f THBD during maturation. I f t h i s i s t h e c a s e , t h e THBD/benzo-DPEP r a t i o should decrease during maturation. The THBD/benzo-DPEP r a t i o s shown i n T a b l e I show no o b v i o u s p a t t e r n ; f o r t h e p o r p h y r i n a g g r e g a t e , t h e r e v e r s e o r d e r i s s e e n , jL.<e., THBD/benzo-DPEPT A t h a b a s c a < P e a c e R i v e r < C o l d L a k e Thus t h e s e l i m i t e d d a t a c a n n o t be u s e d t o s u p p o r t a g e n e t i c r e l a t i o n s h i p b e t w e e n THBD a n d b e n z o - D P E P , a l t h o u g h a r e - e x a m i n a t i o n o f t h e s t r u c t u r e o f THBD p r o p o s e d b y B a r w i s e a n d R o b e r t s (9) i s w a r r a n t e d . Conclusions The v a n a d y l e t i o , D P E P , THBD, b e n z o - e t i o a n d b e n z o - D P E P p o r p h y r i n s d i s t r i b u t e among t h e c o m p o n e n t s o f o i l - s a n d b i t u m e n s o n t h e b a s i s o f porphyrin polarity. T h i s e f f e c t i s demonstrated by t h e p r o g r e s s i o n to a s m a l l e r c a r b o n number r a n g e , a n d t o a l o w e r b a s e - p e a k c a r b o n n u m b e r f o r e t i o a n d DPEP t y p e s f r o m t h e l e s s p o l a r m a l t e n e s t o t h e most p o l a r m e t h a n o l - a c e t o n e e x t r a c t o f t h e a s p h a l t e n e s . The A t h a b a s c a , P e a c e R i v e r , a n d C o l d L a k e o i l - s a n d b i t u m e n s s h o w a consistent increase i n a l l etio/other porphyrin ratios i n the sequence Athabasca < Peace R i v e r < Cold Lake T h i s sequence i s observed f o rt h e p o r p h y r i n aggregate as w e l l as t h e maltenes, n-pentane e x t r a c t , and methanol-acetone e x t r a c t o f t h e asphaltene. The p o r p h y r i n d i s t r i b u t i o n d a t a c a n b e i n t e r p r e t e d t o s h o w t h a t the o i l - s a n d bitumens a r e degraded c o n v e n t i o n a l crude o i l s t h a t formed a t depths g r e a t e r than t h e i r c u r r e n t r e s e r v o i r s and t h a t t h e s o u r c e r o c k d e p t h s e q u e n c e was p r o b a b l y Athabasca < Peace R i v e r < Cold Lake a n d / o r p o s t - g e n e r a t i o n m a t u r a t i o n f o l l o w e d t h e same s e q u e n c e . The e t i o / T H B D a n d e t i o / b e n z o p o r p h y r i n r a t i o s a p p e a r t o b e m o r e s e n s i t i v e i n d i c e s of thermal m a t u r i t y than t h e etio/DPEP r a t i o s . A l t e r n a t i v e l y , t h e b e n z o a n d THBD s e r i e s may b e s e l e c t i v e l y r e m o v e d during migration. However, t h e i r u s e a s t h e r m a l m a t u r i t y i n d i c e s i s r e s t r i c t e d b y l a c k o f i n f o r m a t i o n o n t h e o r i g i n o f t h e THBD a n d benzo p o r p h y r i n s .

10.

STRONG A N D FILBY

Vanadyl Porphyrin

Distribution

in Alberta

171

Acknowledgments The a u t h o r s would l i k e t o thank Mr. F. D o o l i t t l e , Department o f C h e m i s t r y , f o r a s s i s t a n c e i n mass s p e c t r o m e t r i c a n a l y s e s .

Literature Cited 1. 2.


3. 4. 5. 6. 7. 8. 9. 10. 11. 12. 13. 14. 15. 16. 17. 18. 19. 20. 21. 22. 23. 24. 25. 26.

Tissot, B.P.; Welte, D.H. "Petroleum Formation and Occurrence"; 2nd Ed.; Springer-Verlag: New York, 1984. Barwise, A . J . G . ; Park, P.S.D. In "Advances in Organic Geochemistry 1981"; Bjorøy, M. et al., Eds.; John Wiley: London, 1983; 668. Treibs, A. Ann. Chem. 1934, 517, 103. Baker, E.W. J . Amer. Chem. Soc. 1966, 88, 2311. Baker, E.W.; Yen, T . F . ; Dickie, J . P . ; Rhodes, R . E . ; Clark, L . F . J . Amer. Chem. Soc. 1967, 89, 3631. Didyk, B.M.; Alturki, Y . I . Α . ; Pillinger, C.T.; Eglinton, G. Nature 1975, 256, 563-65. Burkova, V.N.; Ryadovaya, L . V . ; Serebrennikova, O.V.; Titov, V . I . Geokhimiya 1980, 1417-21. Barwise, A.J.G. (this volume). Barwise, A . J . G . ; Roberts, I. Org. Geochem. 1984, 167-176. Van Berkel, G . J . ; Filby, R.H. (this volume). Chakhmachkev, V.A.; Burkova, V.N.; Eharkov, N.I.; Punarova, S.A.; Serebrennekova, O.V.; Titov, V . I . Geokhimiya 1985, 381-386. Palmer, S.E. Amer. Chem. Soc. Annual Meeting, Washington, DC, Abstract, August 28-September 2, 1983. Vigrass, L.W. Bull. Amer. Ass. Petrol. Geol. 1968, 52, 1984-99. Deroo, G.; Powell, T . G . ; Tissot, B.; McCrossan, R.G. Geol. Survey Canada Bull. 262 1977, 136 p. Moshier, S.O.; Waples, D.W. Bull. Amer. Ass. Petrol. Geol. 1985, 69, 161-72. Hitchon, B.; Filby, R.H. Bull. Amer. Ass. Petrol. Geol. 1984, 68, 838-49. Strong, D. Ph.D. Thesis, Department of Chemistry, Washington State University, Pullman, WA, 1986. Spencer, W.A.; Galobardes, J . F . ; Curtis, M.A.; Rogers, B.L. Separation Sci. Technol. 1982, 17, 797. Baker, E.W.; Palmer, S.E. In "The Porphyrins"; Dolphin, D., Ed.; Academic Press: New York, 1978; pp. 486-552. Speight, S.G.; Long, R.B. In "Atomic and Nuclear Methods in Fossil Energy Research"; Filby, R.H.; Carpenter, B.S.; Ragaini, R.C., Eds.; Plenum Press: New York; pp. 295-321. Quirke, J.M.E.; Eglinton, G.; Maxwell, J.R. J . Amer. Chem. Soc. 1978, 101, 7693. Hajibrahim, S.K.; Quirke, J.M.E.; Eglinton, G. Chem. Geol. 1982, 35, 69. Blumer, M.; Snyder, W.D. Chem. Geol. 1967, 2, 35. Yen, T.F. In "The Role of Trace Metals in Petroleum"; Yen, T . F . , Ed.; Ann Arbor: Ann Arbor, 1975; pp. 1-30. Jacobs, F.S. Ph.D. Thesis, Department of Chemistry, Washington State University, Pullman, WA, 1982. Rubinstein, I . ; Spyckerelle, C . ; Strausz, O.P. Geochim. Cosmo chim. Acta 1979, 43, 1.

172


27. Rubinstein, I . ; Strausz, O.P. Geochim. Cosmochim. Acta 1979, 43, 1887. 28. Jones, R.W. Bull. Amer. Ass. Petrol. Geol. 1981, 65, 103-22. 29. Hoffman, C.F.; Strausz, O.P. Amer. Ass. Pet. Geol. 1986, 70(9), 1113. 30. Burkova, V.N.; Serebrennikova, O.V.; Titov, V . I . Geokhimiya 1978, 945-50. 31. Kaur, S.; Chicarelli, M.I.; Maxwell, J.R. J . Am. Chem. Soc. 1986, 108, 1347-48. 32. Ocampo, R.; Callot, H . J . ; Albrecht, P. (this volume). 33. Chicarelli, I.M.; Kaur, S.; Maxwell, J.R. (this volume).


RECEIVED March 11, 1987

C h a p t e r 11 Metalloporphyrins in Lignite, Coal, and Calcite Raymond Bonnett, Philip J. Burke, and Franciszek Czechowski


Department of Chemistry, Queen Mary College, Mile End Road, London E1 4NS, United Kingdom

The present understanding of work on porphyrins and metalloporphyrins in coals and lignites is summarised. New results are described on the isolation of individual porphyrins from the heme fraction of Colorado coal, from which two crystalline porphyrins have been obtained, and on the examination of iron and gallium porphyrins in the lithotypes (vitrain, durain) from a Polish sub bituminous coal (Janina). Gallium mesoporphyrin IX has been identified in a pink calcite from a hydrothermal region (Deutsch-Altenburg) in Austria.

The o c c u r r e n c e o f m e t a l s , i n c l u d i n g some r a t h e r r a r e m e t a l s , i n c o a l s i s w e l l known Ο ) · That some o f these m e t a l s a r e p r e s e n t i n p a r t a s t e t r a p y r r o l e complexes might, perhaps, have been i n f e r r e d from e a r l y o b s e r v a t i o n s on pigmented l e a f compressions i n brown c o a l ( M i d d l e Eocene) ( 2 ) , but i t was T r e i b s , i n h i s p i o n e e r i n g papers on o r g a n i c g e o c h e m i s t r y , who f i r s t r e p o r t e d i r o n and v a n a d y l p o r p h y r i n s i n c o a l s (3, _4). I n h i s s t u d i e s on f o s s i l f u e l s , T r e i b s c o n c e n t r a t e d on crude o i l and i t s r e l a t i v e s , p o s s i b l y because i n c e r t a i n o f t h e s e m a t e r i a l s the p o r p h y r i n c o n t e n t was l a r g e r and more amenable t o e x t r a c t i o n . Subsequent workers have f o l l o w e d T r e i b s i n t h i s p r e d i l e c t i o n a s i s i l l u s t r a t e d by t h e programme o f the p r e s e n t m e e t i n g : o f 14 o r so s c h e d u l e d papers on p o r p h y r i n s i n r e l a t i o n t o t h e g e o s p h e r e , t h i s i s the o n l y one t o have c o a l i n t h e t i t l e . The r e n a i s s a n c e o f t h e s u b j e c t o c c u r r e d i n t h e l a t e 1 9 7 0 s , w i t h the d i s c o v e r y o f g a l l i u m p o r p h y r i n s i n bituminous c o a l s ( 5 , _6). Subsequently i r o n p o r p h y r i n s , manganese p o r p h y r i n s (one example) and m e t a l - f r e e p o r p h y r i n s were a l s o d e t e c t e d ( 7 ) . Vanadyl and n i c k e l p o r p h y r i n s , which a r e commonly encountered i n c r u d e o i l and i t s r e l a t i v e s ( 8 ) , have not as y e t been found i n l i g n i t e and c o a l . Using e x t r a c t i o n p r o c e d u r e s which cause d e m e t a l l a t i o n , Palmer and coworkers (9) r e p o r t e d p o r p h y r i n s i n a number o f US humic c o a l s , and, more r e c e n t l y , Bonnett and Burke (10) demonstrated t h e o c c u r r e n c e o f i r o n p o r p h y r i n s i n seven such samples, i n some o f which m e t a l - f r e e and g a l l i u m p o r p h y r i n s were a l s o d e t e c t e d ( T a b l e I ) . f


174


T a b l e I.

Coal C l a s s (Rank) Bituminous (HVA) Bituminous (HVC) Bituminous (HVC) Sub-bituminous


Lignite

Pennsylvania

Tetrapyrroles

i n C o a l s from the

3

Origin (Code) W. V i r g i n i a (PSOC-1001)

Age Penns y l v a n i a n

2H

Pennsylvanian

—

Cretaceous

—

Washington Eocene (PSOC-230A3) Montana Cretaceous (PSOC-833)

—

Indiana (PSOC-677) Colorado (PSOC-850)

State

—

U.S.A.

P o r p h y r i n s μg/g (duplicate) Ga Fe 0.07 0.35 (0.34) (0.09) 0.22 0.38 (0.50) (0.25) 0.20 12.9 (13.1) (0.18)

0.14 (0.15)

0.82 (0.89) 1.05 (1.03)

— —

University Collection

The but

c o a l p o r p h y r i n s t o r y i s s t i l l a t an e a r l y stage of development, i t i s u s e f u l t o summarise the main r e s u l t s so f a r .

1.

Metalloporphyrins (Ga, Fe, Mn) and m e t a l - f r e e p o r p h y r i n s and c h l o r i n s have been d e t e c t e d i n l i g n i t e s and b i t u m i n o u s c o a l s i n amounts from 0 t o 20 μg/g. The major group of t e t r a p y r r o l e s c o n s i s t s of a m i x t u r e of homologous p o l y a l k y l p o r p h y r i n s i n a p p r o x i m a t e l y the C 2 6 - C 3 2 range, the Qo and C32 members o f t e n b e i n g dominant (6, _7, 9>, 11). The C32 compound has not been d i s t i n g u i s h e d from e t i o p o r p h y r i n ( t y p e I I I isomer shown a t 1). The ^-H spectrum of the mixed homologues shows the p r e s e n c e o f u n s u b s t i t u t e d β-positions, presumably o c c u r r i n g i n lower homologues as a r e s u l t of a c i d c a t a l y s e d d e a l k y l a t i o n p r o c e s s e s (_7), o r a r i s i n g a t C-13 (as i n 2) from c h l o r o p h y l l p r e c u r s o r s .

2.

3.

4.

5.

Sub-bituminous c o a l s and, e s p e c i a l l y , l i g n i t e s o f t e n c o n t a i n e t i o p o r p h y r i n mono- and d i - c a r b o x y l i c a c i d s ( m e t a l l a t e d and metal-free). P u r i f i c a t i o n o f the i r o n e t i o p o r p h y r i n d i c a r b o x y l i c a c i d (Fe C32 diCOOH) f r a c t i o n from an A u s t r a l i a n l i g n i t e g i v e s a component (as the d i e s t e r ) which i s i d e n t i c a l w i t h m e s o p o r p h y r i n IX (3, as the d i e s t e r ) on the b a s i s of t i c and h p l c comparisons w i t h the a u t h e n t i c r e f e r e n c e samples, and on the b a s i s o f nmr s p e c t r o s c o p y (11, 12). The f o l l o w i n g g e n e r a l i s a t i o n s appear to h o l d . As c o a l rank i n c r e a s e s , l e s s p o r p h y r i n can be e x t r a c t e d ( a n t h r a c i t e s y i e l d o n l y t r a c e s of t e t r a p y r r o l e : _6, 7); carboxylic acid derivatives d e c r e a s e and v a n i s h ; the FeP/GaP r a t i o d e c r e a s e s (7); and t h e w e i g h t e d mean of the p o r p h y r i n m o l e c u l a r masses moves to lower v a l u e s (_9, 12). I t has been suggested t h a t the l a t t e r parameter has some m e r i t i n p r o v i d i n g an independent s c i e n t i f i c a l l y - b a s e d assessment of c o a l rank ( P o r p h y r i n Index of C o a l i f i c a t i o n : 12). The g e n e r a t i o n of lower homologues of a C 3 2 - p o r p h y r i n accords w i t h the g e o c h e m i c a l t r a n s f o r m a t i o n o f the c h l o r o p h y l l s : however, the o b s e r v a t i o n of m e s o p o r p h y r i n IX s u g g e s t s t h a t an a d d i t i o n a l pathway from m i c r o b i a l heme p r o t e i n s may a l s o be s i g n i f i c a n t ( 1 1 ) .


11.

BONNETT ET A L .

Metalloporphyrins

in Lignite, Coal, and

Calcite

175


176 Iron Porphyrins

i n Colorado

Coal

I t has r e c e n t l y been shown (10) t h a t a Cretaceous c o a l from C o l o r a d o i s p a r t i c u l a r l y r i c h i n i r o n p o r p h y r i n s ( c a . 12 μg/g, T a b l e I ) . T h i s c o a l was k i n d l y s u p p l i e d from the P e n n s y l v a n i a S t a t e U n i v e r s i t y C o l l e c t i o n through the c o u r t e s y o f P r o f e s s o r P.H. G i v e n , and some c h a r a c t e r i s t i c s of the c o a l are p r o v i d e d i n T a b l e I I . Petrog r a p h i c a l l y the c o a l i s o f i n t e r e s t i n b e i n g p a r t i c u l a r l y r i c h i n vitrinite.

Table


Age:

II.

Characteristics

Cretaceous

Proximate a n a l y s i s Ash (d) 6.197o V o l a t i l e m a t t e r ( d a f ) 35.72%

Macérai c o m p o s i t i o n (dmmf, v o l . %) Vitrinite Fusinite 91.5 2.3 Source/Code

of C o l o r a d o Rank:

Coal

HVC

Ultimate analysis (daf) C 78.92% H 5.49% Ν 1.72% S 0.43%

Semi-fusinite 4.0

Micrinite 1.4

PSOC-850, Seam D

Mass s p e c t r o m e t r y has shown a range o f lower homologues o f etioheme ( a c c u r a t e m o l e c u l a r i o n measurements f o r the i r o n complexes o f C28, C 2 9 , C 3 0 > C 3 1 and C 3 2 p o r p h y r i n s ) : no p o r p h y r i n c a r b o x y l i c a c i d s were d e t e c t e d ( 1 0 ) . The s e p a r a t i o n of the components of t h i s homologous s e r i e s i s now i n hand, the aim b e i n g t o produce adequate q u a n t i t i e s o f c r y s t a l l i n e s i n g l e components f o r X-ray c r y s t a l l o g r a p h y . The s e p a r a t i o n i s a l e n g t h y p r o c e s s , and i s summarised i n F i g u r e 1. It has not yet proved p o s s i b l e to f r a c t i o n a t e i r o n p o r p h y r i n s by h i g h p r e s s u r e l i q u i d chromatography ( h p l c ) i n a s a t i s f a c t o r y manner, so the m i x t u r e i s d e m e t a l l a t e d . S t a r t i n g w i t h 4 Kg of the powdered c o a l , and f o l l o w i n g the u s u a l e x t r a c t i o n (_6, JJ_) w i t h 7% H2S0i+/Me0H and r e p e a t e d s e p a r a t i o n by t i c , an i r o n p o r p h y r i n c o n c e n t r a t e (36 mg) was o b t a i n e d . D e m e t a l l a t i o n gave a m i x t u r e o f p o r p h y r i n s the components of which c o u l d be a n a l y s e d by r e v e r s e phase h p l c , as shown i n F i g u r e 2. T h i s showed t h a t the m i x t u r e was v e r y complex, b u t , e n c o u r a g i n g l y , t h e r e were a p p a r e n t l y o n l y f o u r p r i n c i p a l components. For f u r t h e r s e p a r a t i o n , the m i x t u r e was m e t a l l a t e d w i t h z i n c , and t h e product was s u b j e c t e d to f u r t h e r stages of s e p a r a t i o n u s i n g semip r e p a r a t i v e hplc to give f o u r f r a c t i o n s , a l l four s t i l l being mixtures. These are l a b e l l e d A-D i n F i g u r e 1, where A i s the most p o l a r , and D i s the l e a s t s o . Repeated f r a c t i o n a t i o n u s i n g the same procedure showed t h a t A was o b t a i n e d i n o n l y minor amount, Β gave two components, B4B and B4C, which have not as yet been c r y s t a l l i s e d ; C gave C3B as a major c r y s t a l l i n e product (2.8 mg); w h i l e D gave D4C as a c r y s t a l l i n e

11.

BONNETT ET A L .

Metalloporphyrins


Calcite

177

Colorado c o a l (4 Kg)

1 I r o n porphyrins

(3 6 mg)

jdemetallate

M e t a l - f r e e porphyrins

a n a l y t i c a l hplc (Figure 2 )


insert zinc

Zinc(II)

porphyrins

[preparative hplc more polar i

less polar

semipreparative hplc

A1-A5 (minor)

B1-B6

ι

C1-C4

i

D1-D4

I

B4B

C3B

DMC

BMC

major

major

major not yet crystalline

2.8 mg

1.1 mg

crystals

crystals Zinc E t i o porphyrin I I I

F i g u r e 1. I s o l a t i o n o f m e t a l l o p o r p h y r i n s from C o l o r a d o c o a l (PSOC-850). Note t h a t t h e i r o n p o r p h y r i n s a r e d e m e t a l l a t e d and then c o n v e r t e d t o z i n c complexes t o a i d s e p a r a t i o n and identification.


178


F i g u r e 2. A n a l y t i c a l h p l c o f p o r p h y r i n s o b t a i n e d by d e m e t a l l a t i o n o f i r o n p o r p h y r i n f r a c t i o n from C o l o r a d o c o a l (see F i g u r e 1, Apex ODS, 3% MeOH/CH3CN).

11.

BONNETT ET A L .

MetaUoporphyrins


Calcite

179

product (1.4 mg). The l a t t e r compound i s indistinguishable chromatographically from etioporphyrin I I I : but X-ray and nOe effect results on this sample, and on f r a c t i o n C3B are awaited before secure conclusions can be drawn.


Porphyrins i n Relation to Pétrographie Components Up to the present time there has been no information on the v a r i a t i o n of porphyrin content i n r e l a t i o n to pétrographie composition. An experiment has now been carried out to examine this question, a subbituminous coal from Janina C o l l i e r y (East High S i l e s i a n Coal Basin, Poland) being selected. The separation into pétrographie constituent samples, v i t r a i n and durain, and the pétrographie analyses of these, was carried out with the help of Dr. H. Kidawa (Wroclaw): the r e s u l t s are shown i n Table I I I . While the composition of the "durain" lithotype does not precisely f i t the international d e f i n i t i o n f o r the durite microlithotype ( 95% i n e r t i n i t e + exinite, 5% v i t r i n i t e ) (13) i t does represent a considerable enrichment of i n e r t i n i t e and exinite over that of the raw coal (and a corresponding reduction i n vitrinite).

Table III.

Chemical and Pétrographie Analyses of Janina Raw i t s V i t r a i n and Durain Lithotypes Vitrain

Durain

5.76 40.6 77.0 4.9 1.30

3.30 36.5 74.7 4.6 0.92

7.69 38.0 77.6 4.5 1.47

61.1 14.7 1.7 21.5 0.9 0.1

96.9 0.9 0.2 1.8 0.1 0.1

17.2 28.1 9.8 44.6 0.2 0.1

Raw Chemical Analysis Ash (d) % V o l a t i l e matter (daf) % C (daf) % H (daf) % Ν (daf) % Maceral Composition Vitrinite Exinite Micrinite Fusinite Minerals Pyrite

Coal and

Coal

Janina coal contains appreciable amounts of both iron and gallium porphyrins: these were extracted and separated by t i c and estimated using the standard conventions which we have employed throughout ( v i z . a molecular weight of 600 i s assumed, and the molar extinction of the Soret band i s taken as 105,000 for iron porphyrins and as 400,000 for gallium porphyrins). The results are shown i n Table IV.

180


Table

IV.

Raw c o a l Vitrain Durain

M e t a l l o p o r p h y r i n Contents L i t h o t y p e s (\ig/g) FeP 5.83 1.03 0.24

of J a n i n a C o a l and i t s

GaP 0.67 0.96 0.27

The c o m p o s i t i o n s of the s i x m e t a l l o p o r p h y r i n s f r a c t i o n s were e s t i m a t e d by mass s p e c t r o m e t r y , w i t h the r e s u l t s shown i n F i g u r e 3. The p o r p h y r i n m i x t u r e comprises m a i n l y p o l y a l k y l p o r p h y r i n s i n the C 2 7 - C 3 2 range, w i t h a s m a l l amount o f m o n o c a r b o x y l i c a c i d ( l a b e l l e d C3 2 ) b e i n g d e t e c t e d i n the heme s p e c t r a . Three p r e l i m i n a r y c o n c l u s i o n s emerge from t h e s e r e s u l t s . F i r s t l y , f o r these t h r e e samples t h e r e i s a p a r a l l e l between the v i t r i n i t e c o n t e n t and the amount o f g a l l i u m p o r p h y r i n d e t e c t e d . Secondly, i r o n p o r p h y r i n seems to have been l o s t i n p r e p a r i n g the lithotypes. T h i s has l e d to the s u p p o s i t i o n t h a t i r o n p o r p h y r i n s a r e c o n c e n t r a t e d i n boundary r e g i o n s between maceral components, and we now have e x p e r i m e n t a l e v i d e n c e s u p p o r t i n g t h i s view. Thirdly, a l t h o u g h the homologue c o m p o s i t i o n s of the i r o n and g a l l i u m p o r p h y r i n s ( F i g u r e 3) a r e not i d e n t i c a l , t h e y a r e r a t h e r s i m i l a r . T h i s suggests to us t h a t they have s i m i l a r o r i g i n s . S i n c e the g a l l i u m p o r p h y r i n s a r e assumed t o a r i s e by m e t a l l a t i o n ( s i n c e s u c h complexes have not been d e t e c t e d i n the b i o s p h e r e ) t h i s i m p l i e s t h a t the i r o n p o r p h y r i n s a r i s e i n the same way. In o t h e r words t h i s e v i d e n c e , a l t h o u g h i n d i r e c t , suggests t h a t the i r o n p r e s e n t i n the hemes o b t a i n e d from c o a l i s not the o r i g i n a l i r o n p r e s e n t i n p o s s i b l e b i o l o g i c a l heme p r e c u r s o r s . However, we emphasise t h a t these are the f i r s t r e s u l t s o f t h i s s o r t t h a t have been o b t a i n e d , and f u r t h e r examples are c l e a r l y needed b e f o r e g e n e r a l i s a t i o n s can be made.


m

C a l c i u m c a r b o n a t e i s not i n f r e q u e n t l y a s s o c i a t e d w i t h c o a l , and i t i s of i n t e r e s t i n the c o n t e x t of c o a l microcomponents to draw a t t e n t i o n t o a r a r e p i n k c a l c i t e from a h y d r o t h e r m a l a r e a i n A u s t r i a ( D e u t s c h - A l t e n b u r g ) which was i d e n t i f i e d as c o n t a i n i n g a g a l l i u m p o r p h y r i n by H a b e r l a n d t (14) i n 1944. We have o b t a i n e d a s m a l l amount of t h i s m i n e r a l which f l u o r e s c e s red i n u l t r a v i o l e t l i g h t . The e m i s s i o n spectrum o f the m i n e r a l i s shown i n F i g u r e 4, and i s t y p i c a l of a m e t a l l o p o r p h y r i n where the metal has a f i l l e d ( o r c o m p l e t e l y empty) d_ s h e l l . E x t r a c t i o n and chromatography r e v e a l m e t a l - f r e e p o r p h y r i n and a m e t a l l o p o r p h y r i n , which i s the major pigment component. The m e t a l l o p o r p h y r i n i s not a s i n g l e s u b s t a n c e , but i s p r e d o m i n a n t l y g a l l i u m ( I I I ) m e s o p o r p h y r i n IX ( t h e a x i a l l i g a n d i n the m i n e r a l i s not known) as shown by m e t a l s a n a l y s i s , t i c and h p l c comparisons, and mass s p e c t r o m e t r y . The comparison w i t h a u t h e n t i c c h l o r o g a l l i u m ( I I I ) m e s o p o r p h y r i n IX by h p l c - i n c l u d i n g c o i n j e c t i o n - i s shown i n F i g u r e 5. The o r i g i n of the m e s o p o r p h y r i n i s not known, but i n our view a b a c t e r i a l o r i g i n a s s o c i a t e d w i t h t h e h y d r o t h e r m a l n a t u r e o f the d e p o s i t deserves a t t e n t i o n . The s e q u e s t r a t i o n o f g a l l i u m i s a l s o not u n d e r s t o o d , but s t u d y o f t h i s type of d e p o s i t may i n the f u t u r e throw some l i g h t on the o c c u r r e n c e of g a l l i u m p o r p h y r i n s i n c o a l and l i g n i t e .

Metalloporphyrins

BONNETT ET A L .

Iron


Porphyrins c

Calcite

Gallium Janina

32

raw

181

Porphyrins

coal.

•30

L

29

C

31


C2I

i-ttrtUrf Vitrain

separated

from Janina

coat.

11 π ιι ιι ι g 111 Durain

100 η

separated

from Janina

i

coal

30Η

60'

40'

20Η

450

500

ii| n m m n 550

600

III l l l l l l

400

I | I I I I I M

4 50

ιριπιπιη'ΜιιιιΐΊΐιιιη 500 550 600

m/ζ

F i g u r e 3. Mass s p e c t r a o f m e t a l l o p o r p h y r i n s from J a n i n a c o a l and i t s v i t r a i n and d u r a i n l i t h o t y p e s (MS902, d i r e c t i n s e r t i o n , 3 0 0 ° C ) .



688

628

640

668

688

7ΘΘ

FLUORESCENCE

720

748

768

788

WAVELENGTH 10 ppm) a m o u n t s (J_). Some h i g h - s u l f u r crudes have t o t a l vanadium and n i c k e l c o n t e n t s e x c e e d i n g 1000 ppm ( 2 ) . S u b s t a n t i a l amounts o f i r o n h a v e b e e n d e t e c t e d i n some c r u d e s , b u t i t i s n o t c e r t a i n t o w h a t e x t e n t i r o n c o m p o u n d s a r e n a t i v e o r become i n c o r p o r a t e d i n t o c r u d e s as a r e s u l t o f h a n d l i n g . Other metals occur i n i n o r g a n i c s a l t s i n b r i n e s a s s o c i a t e d w i t h crude o i l s , but these s a l t s a r e not t r u e components o f p e t r o l e u m . I t i s k n o w n t h a t some f r a c t i o n o f t h e m e t a l c o m p l e x e s f o u n d i n petroleum a r e p o r p h y r i n complexes o f such d i v a l e n t i o n s as n i c k e l and v a n a d y l . The s t r u c t u r e s o f t h e p o r p h y r i n s f o u n d i n p e t r o l e u m h a v e b e e n s t u d i e d i n some d e t a i l ( 3-4 ; F i l b y a n d V a n B e r k e l , this volume). I n most c r u d e s , p o r p h y r i n s c o n s i s t o f homologous s e r i e s of d e s o x o p h y l l o e r y t h r o e t i o (DPEP), e t i o , and rhodo types (Figure 1). The n a t u r e o f n o n - p o r p h y r i n m e t a l c h e l a t e s i n p e t r o l e u m i s still a matter o f some c o n t r o v e r s y . T h i s i s because no such compounds have been i s o l a t e d and c h a r a c t e r i z e d w i t h t h e r i g o r t h a t has been the case with metalloporphyrins. Indeed, some investigators q u e s t i o n whether non-porphyrin metal chelates are present i n petroleum. O r i g i n a l l y , the existence of non-porphyrin complexes i n petroleum was i n f e r r e d from the fact that metal c o n t e n t s o f many c r u d e s a r e o b s e r v e d t o e x c e e d p o r p h y r i n c o n t e n t s , as measured by U V - v i s i b l e s p e c t r o m e t r y . Because the h e a v i e r crudes which contain relatively large amounts o f m e t a l s a r e c o l l o i d a l systems i n v o l v i n g d i s p e r s e d m o l e c u l a r a g g r e g a t i o n s , i t has been argued that UV-visible s p e c t r o m e t r y u n d e r s t a t e s t h e amounts o f porphyrins i n such systems (5) , a n d t h a t t h e e x i s t e n c e o f n o n porphyrinic species i s only apparent. Other i n v e s t i g a t o r s (6-12) have unearthed a v a r i e t y o f e v i d e n c e t o i n d i c a t e t h a t a s u b s t a n t i a l f r a c t i o n o f metals i n p e t r o l e u m a r e complexed w i t h l i g a n d s t h a t a r e not c l a s s i c a l porphyrins. I t has been suggested that thenonporphyrin coordination sites are part of large aromatic sheets ( 13). T h e r e i s some e v i d e n c e t h a t n o n - p o r p h y r i n m e t a l c o m p l e x e s o f p e t r o l e u m may n o t i n v o l v e c o o r d i n a t i o n w i t h f o u r n i t r o g e n atoms (14-15 ; F i s h , e t a l . ; t h i s volume). The n a t u r e o f t h e l i g a n d s c h e l a t e d w i t h m e t a l s o t h e r than vanadium and n i c k e l i s n o t w e l l known, a l t h o u g h t h e e x i s t e n c e o f i r o n p o r p h y r i n s i n a heavy c r u d e has been r e p o r t e d ( 1 6 ) . M e t a l complexes o f vanadium and n i c k e l a r e c o n c e n t r a t e d i n asphaltene and r e s i n fractions of petroleum. A s p h a l t e n e s and r e s i n s c o n s t i t u t e t h e most p o l a r and a r o m a t i c p o r t i o n o f a c r u d e . A s p h a l t e n e s a r e p r e c i p i t a t e d as b l a c k s o l i d s by t r e a t i n g a c r u d e w i t h l a r g e volumes o f an a l k a n e s o l v e n t , u s u a l l y n-pentane o r nheptane. Materials soluble i n the alkane solvent are referred t o as m a l t e n e s or petrolenes. The r e s i n fraction i s o b t a i n e d by chromatographic treatment of maltenes. The m o s t p o l a r c o m p o n e n t s of the maltenes become c o n c e n t r a t e d i n t h e r e s i n s . Therefore r e s i d u a l f r a c t i o n s from d i s t i l l a t i o n p r o c e s s e s w i l l c o n t a i n almost a l l metals o r i g i n a l l y present i n a crude. Metalloporphyrins are s l i g h t l y v o l a t i l e a t h i g h e r t e m p e r a t u r e s , a n d t h e r e f o r e t h e y may b e present i n higher d i s t i l l a t i o n fractions.


190


Figure

1.

a. b. c. d.

S t r u c t u r e s o f P o r p h y r i a s and a C h l o r i n . M = M e t a l ( N i , V = 0, e t c . ) Meta11ated E t i o p o r p h y r i n Metallated Deoxophylloerythroetioporphyrin M e t a l l a t e d Rhodoporphyrin Metallated Chlorin

(DPEP)

12.

BRANTHAVER


Refining

Influence

of Metal Complexes

on Industrial

Operations

191

o f Heavy Crudes

The energy c r i s e s of the 1970's w i t h the accompanying i n c r e a s e s i n the p r i c e of petroleum r e s u l t e d i n the p r o c e s s i n g of g r e a t e r amounts of heavy crudes by refineries. Heavy crudes are c h a r a c t e r i z e d by low API g r a v i t y (

( 1 2

^

Experimental evidence for this r e s u l t i n the case of hydrodesulfurization of heavy crudes i s presented i n Table I I , which summarizes the various k i n e t i c orders obtained for both hydrodesulfurization and hydrodemetallization over a wide range of operating conditions i n d i f f e r e n t reactor systems.

15.

Modes of Operation in Hydrodemetallization 243

DAUTZENBERG AND DE DEKEN

Table I I . Kinetic Orders for Hydrodesulfurization and Hydrodemetallization i n Plug-Flow and Back-mixed Flow Reactor Systems HDM

HDS PFR

2.0

(21,34-36)

1 .5

(22,27)

BMR

1 .5

(22,37)

1.0

(22,27,37)

n

n


Deviation from r e l a t i o n 1 2 i n the case of hydrodemetallization i s not well understood, but could be due to a deviation from f i r s t - o r d e r k i n e t i c s f o r the i n d i v i d u a l metal-containing species. F r a c t i o n a l k i n e t i c orders have indeed been reported for several vanadyl- and nickel-containing compounds (J_6) · Catalyst S e l e c t i v i t y and Reactor Volume Requirements The concept of an averaged r e a c t i v i t y for contaminant removal appears useful i n that a single parameter s u f f i c e s to describe the s e l e c t i v i t y of a given catalyst toward hydrodemetallization or hydrodesulfurization. Taking the nominal orders of Table II for a plug-flow, e.g., trickle-bed (28), reactor into account, continuity equation 6 can also be stated as:

(13)

2F PFR

k

(1

0.5

(14)

1

X ) m

i f demetallization and desulfurization are considered to occur independently. Elimination of the reactor volume from the above equations then yields the following unique r e l a t i o n between the demetallization and desulfurization conversions:

χ

m

= 1-

(15)

1 +

i n which the single parameter k / k constitutes a convenient measure for the s e l e c t i v i t y of the c a t a l y s t considered. The s e l e c t i v i t y behavior shown i n Figure 6 for d i f f e r e n t values of k / k i s indeed t y p i c a l for the i n d u s t r i a l catalysts reported i n reference 8 . I t has been argued elsewhere ( 3 9 , 4 0 ) that the c a t a l y s t s e l e c t i v i t y can be altered by varying the pore size to m

m

s

s

244


p a r t i c l e diameter r a t i o and by adding Co (Ni)/Mo sulfides instead of Ni/V subsulfides as active catalyst components. The above equations can also be used to estimate the tolerable amount of metals i n a feedstock that would give, at a required degree of desulfurization, a minimum desired c a t a l y s t l i f e t i m e . The minimum catalyst volume required for a specified l i f e t i m e i s given by: (16)

mL / VO(TPP) > H (TPP) > Ni(OEP) 2

Previous work showed the same r e a c t i v i t y order for the tetraphenylporphyrin compounds when exposed to hydrogen s u l f i d e (JL). However, Ni(OEP) was as stable to attack by hydrogen s u l f i d e as Ni(TPP). The lack of oxidative s t a b i l i t y of Ni(OEP) may be due to the ease of o x i dation of the ethyl groups. Arabian Heavy Crude A i r Oxidation. The degree of a i r oxidation undergone by Arabian Heavy crude o i l depends upon pressure, tempera ture, l i q u i d hourly space v e l o c i t y (LHSV), and oxidation catalyst (Table I I ) . For instance, a i r oxidation at 500 p s i g , 392°F and 2 LHSV (Run 1) increases the oxygen content of the processed o i l to 1.55% oxygen (Table I I ) , while lower pressure (Run 3 at 200 psig) and higher temperature (464°F) give 1.28% oxygen i n the o i l . At the same temperature of 464°F, 2 LHSV (Run 2) incorporates 1.77% oxygen while 4 LHSV (Run 4) has 1.34% oxygen. V2O5 catalyst also improved oxida tion (see Runs 2 and 3). A i r versus He gas during thermal treatment gives marked differences i n oxygen content (compare Runs 3 and 5 ) .

260


2.0

Ni(TPP) Feed

1.50 1.0 0.50 0.0 -0.50 -1.0 -1.50

b = 0.03 cm

-2.0 3(

350

Τ

1.0

550

400 450 500 Wavelength (nm)

0.80

1

1

600

1

Ni(TPP) 24 Hours

0.60 0.40


0.20 0.0 -0.20 -0.40 -0.60 -0.80 -1.0 I 300

_J

350

b = 0.005 cm ι t 1 1— 550 600 400 450 500 Wavelength (nm)

F i g u r e 1. A i r o x i d a t i o n o f N i ( T P P ) a t 464°F 1-methylnaphthalene.

•ur

»

300

350

ι

ι

400 450 500 Wavelength (nm)

•

>

550

F i g u r e 2. A i r o x i d a t i o n o f Ni(OEP) 1-methylnaphthalene.

i n refluxing

d 600

a t 464°F i n r e f l u x i n g

16.

RANKEL

Degradation of Metalloporphyrins in Heavy Oils

261

Table I I . A i r Oxidation or Thermal Treatment of Arabian Heavy Crude Run i n 5/8 i n tubular reactor (15 c c / v o l ) ; Reactor Packing: (1) V2O5= V2O5/alumina 10% V2O5 (12/20 mesh), (2) Vycor 12/20 mesh sized; Flow: 100 cc/min Run Number


Reaction temp., °F LHSV (hrs.-l) Reactor packing Gas used Pressure, psig Tig P/g o i l % Oxygen i n o i l

Feed

1

400 >0.1

392 2 Vycor Air 500 28.4 1.55

2 464 2 V 0 Air 200 21.3 1.77 2

5

3

4

5

464 2 Vycor Air 200

464 4

752 2 Vycor He 500 44.4 0.84

1.28

vo 2

5

Air 200 30.5 1.34

As the degree of crude oxidation increases, more petroporphyrins are degraded. A half hour exposure of Arabian Heavy crude o i l to a i r at 392°F, 500 psig a i r reduces the petroporphyrin content from 400 yg porphyrin/gram of o i l to 28.4 yg porphyrin/g o i l (Run 1). C a t a l y t i c oxidation reduces the petroporphyrin content even more (Run 2). Vanadyl porphyrins are known to promote asphalt oxidation, part i c u l a r l y as measured by increases i n ketone content (4). Oxygenation can also cause polymerization reactions and molecular weight increases. As more higher metals crudes and resids become refinery feeds, oxidation during handling could present more d i f f i c u l t i e s for refiners. Thermal Treatment of Arabian Heavy Crude and Resid. A 752°F thermal treatment of Arabian Heavy crude f o r a half hour reduces the petroporphyrin content by 90% (Table I I , Run 5). Additional heating at t h i s temperature would degrade more petroporphyrins. During a vacuum d i s t i l l a t i o n to produce r e s i d , the heavy f r a c t i o n of o i l i s exposed to temperatures around 800°F for about 15 minutes. This thermal exposure can degrade as much as 90% of the petroporphyrins. Arabian Heavy resid (Table III) contains 36.4 yg porphyrin/g o i l while i t s parent Arabian Heavy crude has 400 yg/g o i l (Table I I ) . Thus, the thermal h i s t o r y of crudes and resids can markedly change the amount of petroporphyrins present. In addition, thermal treatment can remove Ni and V and cause s i z e reduction i n the metal containing compounds (5) . Effects of Hydrogen and Hydrogen + Hydrogen Sulfide on Resid. Comparisons between thermal treatment with hydrogen and hydrogen + hydrogen s u l f i d e showed that hydrogen s u l f i d e accelerates petroporphyrin degradation (Table I I I ) . This enhanced degradation by hydrogen s u l f i d e i s more pronounced at low space v e l o c i t i e s and 750°F (Table I I I , LHSV=0.3). At 750°F thermal reactions are slower than at 850°F and the effects of hydrogen s u l f i d e can be seen. Hydrogen s u l f i d e at atmospheric pressure also causes decomposition of model compound porphyrins and metalloporphyrins under mild conditions (464°F, r e f l u x i n g 1-methylnaphthalene) (1).

262

METAL COMPLEXES IN FOSSIL FUELS Table I I I . Micrograms Petroporphyrin Per Gram Of O i l Assumed M.W.


Arabian Heavy 1075°F+ Resid C5~soluble C5~insoluble

yg Porphyrin/ g oil

455 432 520

36.4 13.8 73.0

LHSV

Processed O i l :

5.5

H2, 850°F C5-soluble C5-insoluble

455

29.0 00.0 35.6

5.5

H

455 520

27.0 00.0 35.6

1.0

H,

455

21.0

1.0

H

455

20.0

455

35.1

455

24.7

2

2

2

0.3

H,

0.3

H

2

2

+ H S (20%), 850°F C5~soluble C5-insoluble 2

850°F + H S, 2

850°F

750°F + H S, 2

750°F

Demetallation of metalloporphyrins occurs through sequential hydrogénation of the peripheral double bonds followed by f i n a l fragmentation of the ring and metal removal (1,6-8). Hydrogen s u l f i d e can also add to double bonds and therefore aid i n ring saturation (9) (Figure 4). Acid cracking of the ring and metal s u l f i d e formation can occur as well (1). Processing O i l s Exposed to A i r , H2S, H or Heat. Metal containing petroporphyrins degraded to polypyrroles by a i r , hydrogen s u l f i d e , hydrogen, or thermal exposure would probably be easier to hydrodemetallate with a catalyst (1,6-8). Depending upon the percentage of metal coordinated by the petroporphyrins, this could be s i g n i f i c a n t for hydrodemetallation processing. Estimates for petroporphyrin coordinated metal range from 10 to 60% (10). O i l molecules that have undergone a i r oxidation, hydrogen and/or hydrogen s u l f i d e addition, or thermal cracking may be easier to crack but oxygen or sulfur added to the resids by the above treatments w i l l cause processing problems. 2

Summary The model compound porphyrins Ni(TPP), VO(TPP), Ni(OEP), and H (TPP) are many times more stable to a i r oxidation, hydrogen s u l f i d e , hydrogen or heat than petroporphyrins. A i r oxidation at 464°F converts the model compounds into polypyrrolics within 24 hours while >90% of Arabian Heavy crude petroporphyrins degrade i n one half hour with a i r oxidation or are >95% degraded on V 05. At 464°F, model compound porphyrins are stable for many hours while Arabian Heavy r e s i d 2

2


16.

RANKEL

Degradation of Metalloporphyrins in Heavy Oib

Figure 3.

A i r oxidation of model compound porphyrins.

HX

HX a d d i t i o n loads to t h e r m a l c l e a v a g e of s a t u r a t e d b o n d s with polypyrrohc formation

Metal Removal

Figure 4.

Routes f o r porphyrin ring degradation by H2 or H2S.

263

264

METAL COMPLEXES

IN F O S S I L F U E L S

petroporphyrins are s i g n i f i c a n t l y decomposed i n one-half hour. When Arabian Heavy r e s i d i s exposed to a mixture of H and H S, acceler ated decomposition of the petroporphyrins i n the resid takes place. Thus petroporphyrins i n resids can be markedly decomposed by thermal treatment and exposure to reactive gases. A i r , hydrogen s u l f i d e , hydrogen or heat degraded petroporphyrins would probably be easier to c a t a l y t i c a l l y demetallate because the aromatic porphyrin ring has been disrupted. However, oxygen or s u l fur introduced into the o i l during processing might cause molecular weight increases and other problems i n r e f i n i n g these treated resids. 2

2

Literature Cited


1. 2. 3. 4. 5. 6. 7. 8. 9. 10.

Rankel, L. A. Preprints, Div. P e t r o l . Chem., ACS 1981, 26, 689. Baker, E. W.; Yen T. F.; et al J . Amer. Chem. Soc. 1967, 89, 3631. Erdman, J . G. U.S. Patent 3 190 829, 1965. Branthaver, J . F.; Nazir, M.; et al L i q . Fuels Tech. 1984, 2, 67. Reynolds, J . G.; Biggs, W. R. Preprints, Div. P e t r o l . Chem., ACS 1985, 30, 679. Ware, R. Α.; Wei, J . J . Catalysis 1985, 93, 100. Ware, R. Α.; Wei, J . J . Catalysis 1985, 93, 122. Ware, R. Α.; Wei, J . J . Catalysis 1985, 93, 135. Khimmi, U. Russ. Chem. Rev. 1963, 32, 399. F i l b y , R. H. "The Role of Trace Metals i n Petroleum"; Yen, T. F., Ed.; Ann Arbor Science, Ann Arbor, MI, 1975; Chap. 2.

RECEIVED

October 16, 1986

Chapter 17

Hydrodemetallization with Phosphorus Compounds over

Aluminas

in

a

Trickle-Bed

Reactor

S. G. Kukes, A. W. Aldag, and S. L. Parrott


Phillips Petroleum Company, Bartlesville, OK 74004

Oil soluble phosphorous compounds were found to be active and selective for vanadium removal i n hydroprocessing resids over either high or low surface area aluminas. The phosphorus compounds preferent i a l l y reacted with the low molecular weight species in the resin fraction of the oil resulting i n the i n t e r s t i t i a l deposition of a vanadium - phosphorus material. No effect was observed on the rate of nickel removal and the HDS a c t i v i t y was actually inhibited by phosphorus.

E a r l i e r we r e p o r t e d e x t e n s i v e s t u d i e s i n the a r e a o f c h e m i c a l d e m e t a l l i z a t i o n o f heavy o i l s and r e s i d s (_1_, 2_). A v a r i e t y o f c h e m i c a l r e a g e n t s , such as s t r o n g i n o r g a n i c a c i d s , c h l o r i n a t i n g compounds, c h e l a t i n g a g e n t s , s t r o n g o x i d a n t s , e t c . , e x h i b i t e d some a c t i v i t y f o r m e t a l s and heteroatom removal. Most of these reagents were o i l s o l u b l e c h e m i c a l s which were heated w i t h o i l i n a b a t c h reactor without c a t a l y s t present. U n f o r t u n a t e l y , the most a c t i v e of these c h e m i c a l s a l s o produced s i d e r e a c t i o n s i n c l u d i n g element i n c o r p o r a t i o n , c r a c k i n g , p o l y m e r i z a t i o n , e t c . , and i n f a c t r e s u l t e d i n a degraded o i l . Phosphorous compounds were unique i n showing h i g h a c t i v i t y f o r vanadium removal w i t h r e l a t i v e l y low l e v e l o f s i d e r e a c t i o n s (_3, 4 ) . I t was found that both o r g a n i c and some i n o r g a n i c phosphorous compounds were e f f e c t i v e f o r vanadium removal from heavy o i l s and r e s i d s at temperatures i n excess o f 370 C (Table I ) . Vanadium removal c a n occur a t lower temperatures a t lower a s p h a l t e n e c o n c e n t r a t i o n ( T a b l e I I ) as t y p i c a l l y seen i n heavy o i l e x t r a c t s .


266


Table I


E f f e c t o f Phosphorous Compounds on M e t a l Removal From Monagas Pipe L i n e O i l ( B a t c h R e a c t o r )

Run

A d d i t i v e and Concentration

1 2 3 4 5 6 7 8 9 10 11

None 3.0% Pi^S 3.0% P S 3.0 Red Ρ 3.0% ( P h O ) P ( 0 ) H 1.0% (CH 0) P None 1.0% ( C H 0 ) P 0.7% ( P h 0 ) P ( 0 ) H 3.0% P S 1.0% ( P h 0 ) P ( 0 ) H 3

2

5

2

3

3

3

3

2

i+

3

2

% N i Removed

% V Removed

Temp C

64 90 80 59 71 58 10 12 20 18 8

71 99 99 97 99 99 15 84 69 90 65

417 417 417 417 417 417 400 400 400 400 388

Residence Time: 1 hour

Table I I E f f e c t o f Phosphorous Compounds on Vanadium Removal From Heavy O i l E x t r a c t ( B a t c h R e a c t o r ) Additive

None 10% 2% 2% 11% 11% 2% 10% 10% 2%

(CH (CH (CH (CH (CH (CH (CH (CH (CH

3

3

3

3

3

3

3

3

3

0) 0) 0) 0) 0) 0) 0) 0) 0)

Temp C

3

3

3

3

3

3

3

3

3

0 83 50 32 54 45 21 82 79 61

60 60 60 20 60 20 20 60 20 20

360 360 360 360 317 317 317 317 317 317

P0 PO P0 PO PO PO P P P

% Removal Ni V

Residence Time (min)

0 0 2 0 0 0 0 0 0 0

The s o l u b i l i t y o f the phosphorous compounds and p a r t i c u l a r l y the s t e r i c e f f e c t s o f groups a t t a c h e d to the phosphorous a r e v e r y i m p o r t a n t p a r a m e t e r s . The e f f e c t i v e n e s s o f the a d d i t i v e s d e c l i n e d i n the f o l l o w i n g o r d e r : ( RO) P>( ArO) P ( 0) H>( ArO) P>Ar P0>( N H ^ H P 0 3

2

where R - a l k y l and Ar - p h e n y l .

3

3

2

H

17.

Hydrodemetallization with Phosphorus Compounds

KUKES ET AL.

267

I n i t i a l studies also indicated that phosphorous compounds were effective in a t r i c k l e bed reactor packed with alundum (low surface area alumina

750 ppm Ρ Ο

% Vanadium Removed

90 80 ο

:

70

°

0

•

Ο

°

60

Ο

50

Ο ++

+

+

+

• • +

+

° +

+

α

ο

0

++

+

+

40 30 20

+ -

•

+D

10 0]

100

200

300

400

500

600

700

Time on Stream (Hours) Maya 400F+, 2250 pel. 2500 SCF/Bbl, 1 LHSV, 400C

Figure 4. E f f e c t of Ρ on Vanadium Removal (Alumina Packing)


KUKES ET AL.

No Ρ ο

750 ppm Ρ +

% Nickel Removed


30

200

300

400

500

Time on Stream (Hours) Maya 400F+, 2250 pel, 2500 SCF/Bbl, 1 LHSV, 400C Figure 5.

E f f e c t of Ρ on Nickel Removal (Alundum Packing) No Ρ •

Λ Λ

20

750 ppm Ρ +

% Sulfur Removed

200 300 400 Time on Stream (Hours) Maya 400F+. 2250 pel, 2500 SCF/Bbl, 1 LHSV, 400C Figure 6.

500

E f f e c t of Ρ on Sulfur Removal (Alundum Packing)

272


Table IV % Vanadium Removed Alumina

Alundum Hours on stream


0 ppm phosphorus 750 ppm phosphorus

0

30

0 30

8 42

150

0

30

150

10 80

0 30

11 42

50 80

As these d a t a show, the h y d r o d e m e t a l l i z a t i o n (HDM) a c t i v i t y o f the h i g h s u r f a c e area alumina i n c r e a s e s w i t h time much f a s t e r than t h a t o f alundum i n the absence o f phosphorus. However, the HDM a c t i v i t y f o r both systems i s remarkably s i m i l a r and i n c r e a s e s w i t h time i n the presence o f l a r g e phosphorus c o n c e n t r a t i o n s . This i s a p p a r e n t l y due t o the development o f heterogeneous a c t i v i t y on vanadium s p e c i e s which have d e p o s i t e d i n t e r s t i t i a l l y . In b o t h cases severe p l u g g i n g problems o c c u r r e d a f t e r 200 - 300 hundred hours on stream. E l e c t r o n microprobe d a t a c o n f i r m e d t h a t o n l y a s m a l l f r a c t i o n o f the vanadium d e p o s i t e d i n the alumina p e l l e t s . A n a l y s i s o f the i n t e r s t i t i a l d e p o s i t s r e v e a l e d the presence o f h i g h c o n c e n t r a t i o n s o f phosphorus, vanadium, and c a r b o n . Low l e v e l s o f phosphorus i n the feed (20 ppm) d i d not a f f e c t the HDM a c t i v i t i e s o f alumina o r alundum even a f t e r 600 hours on stream and no p r e s s u r e drop was observed a t the end o f the r u n . The e f f e c t o f phosphorus c o n c e n t r a t i o n on the HDM a c t i v i t y o f the h i g h s u r f a c e area alumina a f t e r the heterogeneous r a t e became relatively constant (600 hours on stream, 10 wt.% m e t a l s accumulated) was i n v e s t i g a t e d ( F i g u r e 8 ) . N e i t h e r 135 nor 275 ppm phosphorus showed any e f f e c t on the r a t e o f vanadium r e m o v a l ; however, a f t e r 500 hours o f c o n t i n u o u s phosphorus a d d i t i o n , the r e a c t o r plugged. These r e s u l t s support the proposed mechanism o f a homogeneous r e a c t i o n o f t h e phosphorous compounds w i t h t h e low m o l e c u l a r weight vanadium s p e c i e s . These vanadium s p e c i e s are more r e a c t i v e than the c o r r e s p o n d i n g h i g h m o l e c u l a r weight vanadium s p e c i e s even under heterogeneous r e a c t i o n c o n d i t i o n s (6)· When the r a t e o f the heterogeneous r e a c t i o n i s h i g h and most o f t h e low molecular weight vanadium compounds a r e removed, phosphorus a d d i t i o n does not a f f e c t the r a t e o f vanadium removal. However, the p h o s p h o r y l a t i o n o f a s p h a l t e n e s was s t i l l observed a t these c o n d i t i o n s which r e s u l t e d i n a s p h a l t e n e p r e c i p i t a t i o n , and an e x c e s s i v e r e a c t o r p r e s s u r e drop. LC-ICP a n a l y s e s o f p r e c i p i t a t e showed presence o f phosphorous i n a h i g h m o l e c u l a r weight s p e c i e s (more than 5000 by p o l y s t y r e n e c a l i b r a t i o n ) . Conclusions Phosphorus promotes the r a t e o f vanadium removal d u r i n g h y d r o p r o c e s s i n g over h i g h and low s u r f a c e area a l u m i n a s . T h i s r e a c t i o n o c c u r s homogeneously and r e s u l t s i n the i n t e r s t i t i a l d e p o s i t i o n o f

17.

273


KUKES ET AL.

750 ppm Ρ +

NoP •


» % Vanadium Removed

400 200 300 Time on Stream (Hours) Maya 400F+, 2250 psi. 2500 SCF/Bbl, 1 LHSV. 400C

100

Figure 7.

E f f e c t of Ρ on Vanadium Removal (Alundum Packing) NoP •

100,

500

135 ppm Ρ +

275 ppm Ρ Ο

% Vanadium Removed

908070 6050-

•

•

4030 c

2010 ^ D D

D

° °

200

mLm

600 800 1000 Time on Stream (Hours) Blended feed (see text), 2250 psi, 2500 SCF/Bbl. 1 LHSV, 400C

Figure 8.

400

1200

E f f e c t of Ρ on Vanadium Removal (Alumina Packing)

274


a vanadium - phosphorous species which results in heterogeneous activity. Phosphorus preferentially removes low molecular weight vanadium species in the resin fraction. Phosphorus was found to have no effect on the rate of nickel removal and actually inhibits the HDS activity. Acknowledgments The authors would like to acknowledge the assistance of M. D. Phillips for electron microprobe analysis.


Literature Cited (1)

Kukes, S. G. 34th Can. Chem. Eng. Conf., Quebec, 1984, p. 146.

(2)

Kukes, S. G.; Aldag, A. W. Preprints, Div. of Petrol. Chem., ACS, 1985, 30 (1), 119.

(3)

Kukes, S. G. U. S. patent 4,529,503, 1985.

(4)

Kukes, S. G. et a l . U. S. Patents Nos. 4,419,225, 4,421,638, 1983; 4,522,702, 1985.

(5)

Hausler, D. W.; Carlson, R. S. Preprints, Div. of Petrol. Chem., ACS, 1985, 30 (1), 28.

(6)

Bridge, A. G.; Green, D. C. "Diffusional Considerations in Residium Hydrodemetallization", Chem Tech '80, Symposium 5.

RECEIVED October 30, 1986

1983;

Chapter

18

Characteristics of Vanadium Complexes in Petroleum Before and After Hydrotreating S. Asaoka, S. Nakata, Y. Shiroto, and C. Takeuchi


Chiyoda Chemical Engineering and Construction Company, R&D Center, 3-13 Moriya-cho, Kanagawa-Ku, Yokohama, 221 Japan

Vanadium removal from asphaltenes plays an important role i n hydrotreating of heavy o i l s . Vanadium i s mainly concentrated i n asphaltenes as vanadyl porphyrins involved i n associations with other large hydrocarbon molecules to form asphaltene micelles, which cause d i f f i c u l t i e s i n hydrodemetallization. Dissociation of asphaltene micelles enhances metal removal. Vanadyl porphyrins i n the non-asphaltene portion of heavy o i l s are less associated and are r e a d i l y removed. Vanadium removed during hydrotreatment of heavy o i l s i s deposited on catalysts initially as four-sulfur coordinated vanadyl compounds, which react further to form vanadium sulfide. Remaining vanadium complexes i n treated o i l s are involved i n smaller associations than the asphaltene micelles of the feed. During the hydrotreating of heavy oils, hydrodemetallization depends significantly on catalyst pore structure, which changes with hours-on-stream and depends on the molecular sizes of the reacting materials. The preferable catalyst pore structure for hydrotreating reactions i s determined by the nature of metal deposition on catalysts. I t also has been shown that vanadium s u l f i d e deposited on a catalyst during hydrotreating not only causes catalyst pore structure changes, but has autocatalytic a c t i v i t y . A hydrodemetallization mechanism on catalysts i s proposed which considers this autocatalytic a c t i v i t y derived from the deposited vanadium s u l f i d e . As i s generally known, i t i s not easy to h y d r o c a t a l y t i c a l l y upgrade heavy petroleum residues. This i s because they contain large quantities of metals, mainly vanadium, which are complexed with porphyrins and possibly with other large molecules containing condensed polyaromatic r i n g s . Much fundamental research on the c h a r a c t e r i s t i c s of metal complexes i n heavy o i l s has been carried


276


out to study hydrotreating behavior. Petroleum residues are mixtures of asphaltene micelles containing r e s i n components c o l l o i d a l l y dispersed i n maltenes (non-asphaltenes) as the dispersing medium (1). Asphaltenes are r i c h i n heteroatom compounds, and vanadium compounds also are concentrated i n asphaltenes. Vanadium compounds play a s i g n i f i c a n t role i n hydrotreating (,2) and this role may be c l a r i f i e d by examination of the nature of hydrodemetallized vanadium deposited on catalysts and the changes observed i n non-demetallized vanadium complexes. In this paper, extensive studies done during the develop ment of hydrotreating catalysts and processes for heavy o i l upgrading are described.


f

Experimental A main feedstock used for the hydrotreating tests i s Boscan crude produced i n Venezuela. Other feedstocks used are Bachaquero atmospheric residue, Khafji vacuum residue, Gach Saran vacuum residue, Basrah Heavy vacuum residue, Athabasca t a r sand bitumen, etc. The hydrotreating tests were carried out by a high-temperature, high-pressure, flow-type unit. The feed o i l and hydrogen passed by the once-through upflow mode through a fixed-bed reactor, and the catalyst bed was maintained isothermally. The reactions were carried out under the following conditions: pressure, ^90 to 180 kg/cm ; temperature, 360 to 430°C; LHSV, 0.2 to 1.5 h~ ; and hydrogen to l i q u i d r a t i o i n volume, 600 to 1000 NL/L. The thermal treatments were done without catalyst i n a similar way. The catalysts, especially prepared for the t e s t s , were a l l of the cobalt-molybdenum type, supported on a c a r r i e r of an oxide. The sizes and shapes of these catalysts were the same, cylinders 0.8mm i n diameter and about 3mm i n length. A n a l y t i c a l gel permeation chromatograms (GPC) were obtained by means of a Japan Anal. Ind. LC-08 chromatograph, equipped with four columns of 600mm length and 20mm diameter i n series, f i l l e d with Shodex A-802 χ 1, A-803 χ 2 and A-804 χ 1, respectively. Molecular weight d i s t r i b u t i o n s were calibrated by the use of polystyrene. After fractionation by GPC, each f r a c t i o n was subjected to elemental analysis by radiation method so that the d i s t r i b u t i o n s of heteroatom compounds were obtained. ESR spectra were obtained using a JEOL EF-1 spectrometer operat ing at X-band frequency (9.2 GHz) with 100 kHz f i e l d modulation. The microwave cavity for measurements at high temperature was equipped with a hot-air blower. The ESR spectra were obtained at temperatures between 20 and 270°C. The ESR techniques and a n a l y t i c a l procedures used i n t h i s study were according to Tynan et a l . (4) The a n a l y t i c a l methods used for characterization of deposited vanadium were common ones c h a r a c t e r i s t i c of each a n a l y t i c a l i n s t r u ment: Spark Source Mass Spectrometer (JEOL, 01BM, ED-01), X-ray Diffractometer (Rigaku Denki), X-Ray Fluorescence Spectrometer (Philips, PW-1400), Fourier Transform Infrared Spectrometer (JEOL, JIR-100) , Transmission Electron Microscope (JEOL), Scanning Electron Microscope (Hitachi, S-650), Energy Dispersive X-Ray Spectrometer (Philips, EDAX), Electron Probe Micro Analyzer (Shimadzu, EMX-SM&7), X-Ray Photoelectron Spectrometer (Shimadzu, ESCA-750).


18.

ASAOKA ET AL.

Characteristics of Vanadium Complexes in Petroleum

Molecular Weight D i s t r i b u t i o n of Vanadium Containing Compounds When a heavy o i l such as Boscan crude i s analyzed by gel permeation chromatography (GPC), vanadium i s concentrated i n the heavy fractions, as i l l u s t r a t e d i n Figure l a . Asphaltenes, which are demetallized with d i f f i c u l t y , are of greater molecular weight than most of the sulfur and some of the vanadium compounds i n the nonasphaltene portion of Boscan crude. In a previous report (3) i t has been indicated that cracking of asphaltenes i s very important i n the hydroprocessing of heavy o i l s . Both hydrodemetallization and hydrodesulfurization are closely related to asphaltene cracking. I t i s observed that the number-average molecular weights of asphaltenes and of s u l f u r - and vanadium-containing components change as a r e s u l t of hydrotreating. However, the changes of the number-average molecular weights of the sulfur and vanadium compounds, which decrease from 1200 to 1100 and 1700 to 1500 respectively, i s small compared to the change observed for the asphaltenes, which are reduced from 4600 to 2200 (Figure 1). In addition, the molecular weight d i s t r i b u t i o n s of the aphsltenes and the sulfur and vanadium complexes become narrower. These facts i l l u s t r a t e that under the hydrotreating conditions we employed, the larger molecules are more e a s i l y cracked as the molecular weights of vanadium compounds are reduced. ESR Spectra of Vanadyl Ion i n Asphaltenes and Maltenes Vanadium compounds i n asphaltenes mainly exist as vanadyl porphyrins, which interact with other molecules to form large associations. Electron Spin Resonance (ESR) has been used to study the environment of vanadium i n petroporphyrins and other complexes (4). The behavior of vanadyl compounds i n asphaltene cracking reactions and i n hydrodemetallization has been described (3) . The c h a r a c t e r i s t i c changes in vanadyl porphyrins during hydrotreating and thermal treating have been further studied using ESR. In general, vanadyl groups i n petroleum exhibit two types of ESR signals. One i s a 16-line anisotropic spectrum due to "bound" vanadyl groups. The other i s an 8-line i s o t r o p i c spectrum due to "free" vanadyl groups. Asphaltenes dissolved i n a solvent have anisotropic ESR spectra s i m i l a r to asphaltenes i n the s o l i d state (Figure 2). Therefore vanadium compounds i n asphaltenes are considered to be involved i n very large molecular associations. When asphaltenes obtained from hydrotreated Boscan crude are examined by ESR, i s o t r o p i c spectral l i n e s are observed i n addition to the anisotropic spectrum. The i s o t r o p i c peaks are quite small. Maltenes of the parent crude dissolved i n a solvent exhibit anisotropic and i s o t r o p i c spectra of equal magnitude. Maltenes of hydrotreated Boscan crude have ESR spectra i n which the i s o t r o p i c peaks are larger than anisotropic peaks. Therefore, the r e l a t i v e sizes of the molecular associations involving vanadium are: free asphaltenes > product asphaltenes >> feed maltenes > product maltenes The degree of association of vanadium i n the hydrotreated product i s not greatly changed from that of the parent crude, although the number-average molecular weight of the asphaltenes of the product i s greatly changed. There also i s l i t t l e change i n association of vanadium remaining i n maltenes after hydrotreating. This suggests

277


278


Figure 1. Molecular Weight Distributions of S-, V-compound and Asphaltenes (a)before and (b)after Hydrotreating (Boscan Crude).

feed

100 gauss

Figure 2. Crude).

ESR

Spectra

of Asphaltenes

and Maltenes

(Boscan

18.

ASAOKA ET AL.

279


that maltene and asphaltene associations containing vanadium are not cracked without demetallization. Indeed, i t should be noted that those molecules that are cracked are almost free of vanadium. A model of t h i s behavior i s shown i n Figure 3. Characteristic Changes of Vanadyls i n Asphaltenes During Hydrotreating As shown i n Figure 2, the vanadium i n asphaltenes from both the feed and product o i l s give the same anisotropic ESR spectra. This i s a 16-line spectrum and i s c h a r a c t e r i s t i c of vanadyl ion i n petroleum asphaltenes at low temperatures. At higher temperatures, an 8-line i s o t r o p i c spectrum i s observed. This i s o t r o p i c spectrum has been quantitatively studied over a range of temperatures i n order to understand the e f f e c t s of hydrotreating on vanadyl coordination. This analysis has been described i n d e t a i l previously (_3) · analysis centers on the r a t i o of the magnitude of the No. 5 l i n e i n the i s o t r o p i c spectrum to that of the No. 6 l i n e i n the anisotropic spectrum. This r a t i o i s temperature dependent, and d i s s o c i a t i o n energies of ligands a x i a l l y coordinated to vanadyl groups may be calculated from the r a t i o by means of Arrhenius p l o t s . The r e l a t i v e amounts of "bound" and "free" vanadyl species present at a given temperature can be calculated from the r a t i o . Dissociation energies of vanadyl complexes i n asphaltenes from various feeds are calculated to be about 15 to 18 kcal/mol using the above method, whereas the vanadyl complexes i n the asphaltenes of the hydrotreated crudes have d i s s o c i a t i o n energies of 8 to 10 kcal/mol (Figure 4). I f d i s s o c i a t i o n energies and the amount of vanadyl i n the "bound" state r e f l e c t strengths and quantities of binding respectively, i t may be inferred that vanadyls i n feed o i l asphaltenes are associated with heteroatom-containing species. In the product o i l asphaltenes, many heteroatoms have been removed, and vanadyl a x i a l coordination i f believed to be involved with aromatic sheets. This analysis i s supported by results reported by Tynan, et a l . (4). These investigators report the energy of dimerization of formic acid to be 14 kcal/mol, and the energy of association of ethanol tetramer to be 23 kcal/mol. The energy of association between aromatic layers i n asphaltenes i s about 1 kcal/mol, while the energy of hydrogen bonding between aromatic sheets i s 2 to 8 kcal/mol. I t may be inferred that some asphaltene micelles are broken up during hydrotreating and that some vanadium i n them i s removed. The remaining vanadium compounds form new asphaltene associations by interaction with stacked aromatic sheets. Asphaltenes are not readily demetallized thermally, but undergo hydrodemetallization i n catalyst pores as a r e s u l t of o v e r a l l reduction i n molecular weight of asphaltenes i n c a t a l y t i c hydrotreating.


T

n

e

Thermal Treatment (Visbreaking and Hydrovisbreaking), Hydrotreating, and Their Combination Many processes are known to accomplish heavy o i l upgrading. Among these are visbreaking and hydrovisbreaking. Visbreaking i s a simple thermal treatment, whereas hydrovisbreaking i s a thermal treatment under hydrogen pressure. A combination of the thermal treatment and a hydrotreatment has been proposed (5^) . The c h a r a c t e r i s t i c changes i n vanadyl coordination were examined


280


Figure 3 . Model of Hydrotreating Analysis for Boscan Crude.

ô ε

20 ο

(Asphaltene Cracking)

from ESR

Jeed— ο Q ο; i hydrotreating

£

10 product

5h

ΙΟ

Figure 4. Change Hydrotreating.

10 10 vanadium in asphaltenes ,wt-ppm

of

Characteristics

for

Vanadyls

during

18.

ASAOKA ET AL.



for an o i l subjected to these processes. As shown i n Figure 5, there i s only a small change i n vanadyl coordination i n products from the two thermal processes compared with the feed, and l i t t l e vanadium i s l o s t . Hydrotreating causes loss of vanadium, and that vanadium which survives i s i n a more "bound" state and has a lower d i s s o c i a t i o n energy. When hydrotreating follows a thermal process, the surviving vanadium i s converted almost e n t i r e l y into a "bound" state with a d i s s o c i a t i o n energy intermediate between the vanadium i n the feed and when the feed i s hydrotreated without a p r i o r thermal treatment. Obviously, the e f f e c t of a combination of processes on vanadium i s not additive (5). Vanadium i n Catalyst Pores The bonding of vanadyl compounds to the inner surface of catalyst pores also was studied by ESR. Large- and small-pore catalysts with sharp pore d i s t r i b u t i o n s were prepared. These pore diameters were completely d i f f e r e n t from each other. Each catalyst was contacted with solutions of asphaltenes from a feedstock and asphaltenes from a hydrotreated feedstock at room temperature. Vanadyl compounds from these solutions diffused into the catalyst pores. ESR spectra of these vanadyl complexes were taken at 100°C. As shown i n Figure 6, the vanadyl complexes from the feed asphaltenes which d i f f u s e into the small-pore catalyst are "free" when compared with the vanadyl complexes that diffused into the large-pore c a t a l y s t . The pore size i n the large-pore catalyst i s believed to approximate the size of asphaltene micelles. These micelles are dissociated when heated to 100°C, and some smaller vanadyl complexes become strongly adsorbed on the catalyst surface. These adsorbed vanadyl complexes are not reintegrated into micelle structures on cooling. A second increase i n temperature results i n vanadyl complexes having the same degree of freedom f o r feed asphaltenes i n both the small- and large-pore c a t a l y s t . Asphaltenes from the hydrotreated product do not have micellar aggregations. The vanadyl complexes i n these asphaltenes are strongly bound to the surface of the catalyst and would be expected to be reactive i n any subsequent c a t a l y t i c demetallization. Therefore i n c a t a l y t i c hydrodemetallization, i t i s important to consider molecular sizes of feed vanadyl complexes. I t must be remembered i n the design of hydrotreating catalysts for heavy o i l upgrading that the molecules to be treated can e x i s t i n large associations. Dependence of C a t a l y t i c A c t i v i t i e s on Pore Structure and Changes Due to Metal Deposition I t i s well known that pore structure (volume, diameter, surface area, etc. ) i s one of the most important properties of hydrotreating catalysts for heavy o i l s (6). For example, r e a c t i v i t i e s of catalysts with similar pore volumes depend on pore diameters. As i l l u s t r a t e d i n Figure 7, hydrodemetallization (HDM) a c t i v i t y depends on pore diameter. The pore diameter giving maximum a c t i v i t y i s about 25 nm for a fresh catalyst. As metals deposit, r e a c t i v i t y becomes maximized at larger pore diameters. Hydrodeasphaltening (HDA) a c t i v i t y shows a similar tendency to HDM a c t i v i t y . On the other hand, hydrodesulfurization (HDS) shows a maximum a c t i v i t y at pore diameters of about 10 nm. This means that the HDS a c t i v i t y i s d i s t i n c t l y d i f f e r e n t from HDM or HDA a c t i v i t y . HDA i s also affected by metal deposition.

281

282


20

hydrovisbreaking Q i visbreaking Ο feed A hydrovisbreaking /hydrotreating

10

hydrotreating

hydrovisbreaking '-fc visbreaking Ο feed


10

] [^hydrotreating hydrovisbreaking • /hydrotreating _J I I I I I I I 1 I L 10' ΚΓ vanadium in asphaltenes,wt-ppm Figure 5. Vanadyls i n Combination of Those.

hydrotreating,

catalyst pore size 30 r

Ο lOnm

Thermal-treating

• 20nm

Ε

^ 25 S

r

feed

2 15

a>

\•o

product .2 10 .2 ο 5 ~

2nd elevation of temperature

(Λ «Λ

*

ο ο 1 st elevation of temperature

0

10'

;

,-2 10"'

m-'

ι

to

10

2

ratio of No.5 iso/No.6xaniso (at 100°C) Figure

6.

Vanadyls i n C a t a l y s t Pores.

and

18.


ASAOKA ET AL.

283


Changes i n pore structure due to metal deposition are determined by the amount of metal deposited and i t s d i s t r i b u t i o n i n the catalyst particle. Theoretical studies of metal deposition and d i s t r i b u t i o n have been reported (7) . The characterization of deposited vanadium i s important to the understanding of catalyst a c t i v i t y , especially HDM a c t i v i t y . Characterization of Vanadium Deposited on Catalysts Vanadium deposits onto catalysts with a s p e c i f i c d i s t r i b u t i o n . As shown i n Figure 8, t h i s d i s t r i b u t i o n occurs along the reactor a x i a l length and along the radius of individual catalyst p a r t i c l e s . These p a r t i c l e s were examined by X-ray microanalysis (XMA). Vanadium deposits were found to be concentrated near the reactor i n l e t and near the outer surfaces of catalyst p a r t i c l e s . Metal deposits decrease along the reactor axis and toward the center of catalyst particles. At the reactor inlet itself, vanadium i s less concentrated. There i s also less vanadium i n a very thin layer at the outside of catalyst p a r t i c l e s . This phenomenon indicates that the HDM process requires hydrogen s u l f i d e . As shown i n the broken lines in Figure 8, the phenomenon disappears i f HDM i s performed with added hydrogen s u l f i d e . Deposited metals exist as sulfides and show X-ray d i f f r a c t i o n (XRD) patterns attributable to a c r y s t a l l i n e V^S phase (8) , as shown in Figure 9. In t h i s V^S^ phase, vanadium may be substituted by other t r a n s i t i o n metals such as n i c k e l . 4 ^ non-stoichiometric compound i n which the atomic r a t i o of sulfur to vanadium can vary from 1.2 to 1.5. When vanadium s u l f i d e deposits over catalyst outer surfaces, the p o l y c r y s t a l l i n e state can be observed by scanning electron microscopy (SEM), as shown i n Figure 10a. In catalyst pores, vanadium s u l f i d e forms rod-shaped deposits several tens of nanometers thick and hundreds of nanometers i n length, as determined by transmission electron microscopy (TEM) on an u l t r a - t h i n sample (Figure 10b). Electron d i f f r a c t i o n (ED) studies also were performed (Figure 10c). Since the deposited vanadium has been i d e n t i f i e d as ^^4 information about the surface of the vanadium s u l f i d e has been obtained by X-ray photoelectron spectroscopy (XPS) and ESR. The XPS spectra are shown i n Figure 11. The vanadium i n the V S^ exists p a r t l y as V , and on the outer surface of catalyst p a r t i c l e s partly as V . C a t a l y t i c a c t i v i t i e s of the surface thus w i l l vary with the makeup of the V^S metal cluster compound. ESR spectra (Figure 12) show that some vanadium dispersed on catalyst surfaces exists as vanadyl (V=0) i o n . 4

V

S

s a

3

r

+4

4

The Change of Vanadyl Coordination As reported previously (3) , the nature of the ligands involved i n chelation with vanadium may be determined by ESR spectra. This i s done by examining the i s o t r o p i c parameters g and A (the hyperfine constant). Ligand systems of vanadyl ion remaining i n treated crudes are of the four-nitrogen donor type ( ) (Figure 13). Vanadyl ion deposited on catalysts i s complexed with sulfur (VOS^). V 0 N

4

C a t a l y t i c A c t i v i t y of Vanadium Sulfide I t has been shown that vanadium sulfide deposits grow i n a d i r e c t i o n a l l y selective manner as the V S phase builds up. This growing

284


θ h

0.3 0.4 0.5 I

[

Ο

ι

ι

200

,

I

400

[

1

600

Average Pore Diameter Based on Fresh Catalyst ( Â ) θ : Loss in pore volume due to metal sulfides deposition


Figure 7 . Diameter.

Hydrodemetallization

inlet

Activity

Reactor Axial Length

with

Average

outlet

outer surface center Catalyst Particle Radius

Figure

8.

D i s t r i b u t i o n of Deposited Vanadium.

V3S4

10

20

30

40 2Θ ( )

50

60

e

Figure

9.

X-ray D i f f r a c t i o n Pattern.

Pore


18.

ASAOKA ET AL.

Figure 10. and TEM.


Observation

of Deposited

Vanadium Surfide with SEM

sputtering time

(min) U s e d Catalyst

Surface

1

?m 520

285

0 1

513

Binding Energy (eV)

Figure 11. Oxidation State of Vanadium.


286


Figure 12.

ESR Spectra of Vanadiums.

160 products

-supported

140

(ΗΤ,ΤΤ)

V0S04

feeds

7"—

spent catalyst

V0(N4K^-

V0S4

N

Ζ 120

ο
4000 daltons), are removed. Low molecular weight components, and any s a l t s present are retarded. The advantage of GPC as a preliminary step i s that i t reduces aberrant chromatographic behavior i n l a t e r separations owing to the presence of asphaltenes. An alternative approach i s to remove the asphaltenes by p r e c i p i t a t i o n with hexane, and study these substances separately. Column chromatography using either alumina or s i l i c a gel i s by far the most common p u r i f i c a t i o n technique.(7) Generally i t i s advisable to purify on both alumina and s i l i c a columns. It i s not clear whether there i s any advantage to be gained using s i l i c a as the i n i t i a l column followed by alumina or vice versa. A wide range of solvent gradients have been used i n s i l i c a gel chromatography, (e.g.4,5,7,13-17) A gradient elution of a s i l i c a gel column (100-200 mesh, packed i n hexane) from hexane to chloroform i s usually a very e f f e c t i v e system. Most of the n i c k e l porphyrins should elute i n ca. 10-20% CHC1-. The vanadyl porphyrins should elute i n ca. 30-50% CHC1 . There i s s u f f i c i e n t variation between samples, and i n the a c t i v i t y of the s i l i c a gel and humidity that careful monitoring of the eluant by v i s i b l e spectrosopy i s e s s e n t i a l . The vanadyl or n i c k e l geoporphyrin mixtures themselves may be p a r t i a l l y resolved on the s i l i c a gel columns, but the fractions may be recombined i f necessary. It i s important to carry out the separations f a i r l y rapidly as there i s the p o s s i b i l i t y of generating a r t i f a c t s . DPEP porphyrins can undergo hydroxylation at the i s o c y c l i c ring during chromatography on s i l i c a gel.(^8) Usually this i s not a major process, but i t should be considered i f polar geoporphyrins are isolated. Ekstrom and co-workers have p u r i f i e d vanadyl porphyrins using Kieselgel 60 (Merck) eluting with a gradient of chloroform and carbon tetrachloride. (4^) Barwise and co-workers have chromatographed vanadyl porphyrins over "functionalized" s i l i c a . ( 1 9 ) The sulphonic acid groups attached to the s i l i c a help to remove i n t e r f e r i n g nitrogenous bases. Using such columns, i t i s possible to obtain very clean samples; however, both nickel and metal- free porphyrins are lost on the column. In addition, i t i s possible that a r t i f a c t s are generated, therefore residence times on the column should be minimised. There were substantial alterations i n the daughter 3


312


spectra of molecular ions of high carbon number (> Coo) vanadyl porphyrins p u r i f i e d on functionalized s i l i c a compared with those of the untreated vanadyl porphyrin f r a c t i o n . In both cases the background on the mass spectra was low.(20) Alumina columns (grade I I , Brockmann) are developed by gradient elution using a variety of solvent mixtures, and are monitored by v i s i b l e spectroscopy.(e.g.5,8,13-15,21,22) A gradient elution from hexane to dichloromethane v i a toluene i s an e f f e c t i v e system. The n i c k e l geoporphyrins are l i k e l y to elute i n 30-50% toluene i n hexane and the vanadyl porphyrins i n 30-60% dichloromethane i n toluene. There i s a possibility of p a r t i a l decomposition of the geoporphyrins, p a r t i c u l a r l y the nickel complexes, on alumina columns thus i t i s advisable to effect the chromatography as rapidly as possible. There have been recent developments i n the role of low and medium pressure l i q u i d chromatography (LPLC and MPLC). Thus Baker and co-workers purify n i c k e l geoporphrin mixtures on alumina columns, eluting with acetone-petroleum ether mixtures. The porphyrins elute i n 3.5-5.0% acetone-petroleum ether.(5) Barwise and Roberts used MPLC on s i l i c a i n their study of the porphyrins of E l Lajun shale; however, the eluting solvents were not divulged.(23) Thin layer chromatography (TLC) i s also very useful i n the f i n a l stages of p u r i f i c a t i o n of t o t a l mixtures. Nickel geoporphyrins have been p u r i f i e d on s i l i c a gel plates either carbon tetrachloride (24) or heptane-dichloromethane (7:3, vol:vol) as eluant. S i m i l a r l y , vanadyl porphyrins may be p u r i f i e d using heptane-tetrahydrofuran (5:1, vol:vol).(25) The separated geoporphyrin mixtures are often demetallated prior to further analysis. (e_.£. 1,1,19,23,26,27) Typically the geoporphyrin mixtures are demetallated by the Erdman procedure using methanesulfonic acid at 100°C (4 hours).(28) The harsh conditions are required to demetallate the vanadyl components, but n i c k e l porphyrins are demetallated i n less than an hour. Yields vary, and there i s the p o s s i b i l i t y of p r e f e r e n t i a l decomposition of geoporphyrin species. Demetallation of n i c k e l porphyrins using either t r i f l u o r o a c e t i c acid (TFA) and 1,2 ethanedithiol (29) or 10% sulphuric acid-TFA at ambient temperature may replace the Erdman demetallation process.(30) Vanadyl porphyrins are demetallated by anhydrous hydrofluoric acid at 0 C.(31) Extensive chromatography of the demetallated porphyrins should be avoided i f the objective of the analysis i s the study of the intact porphyrin mixtures. A good p u r i f i c a t i o n process for i s o l a t i n g the metal-free porphyrins i s described subsequently. A summary of a reasonably e f f i c i e n t p u r i f i c a t i o n procedure for the i s o l a t i o n of intact n i c k e l and/or vanadyl geoporphyrin mixtures i s shown i n figure 2. P u r i f i c a t i o n of Individual Geoporphyrin Components. The initial chromatographic stages of i s o l a t i o n are e s s e n t i a l l y the same as those described previously. The p u r i f i e d metalloporphyrin fractions are e f f i c i e n t l y separated on TLC. The n i c k e l complexes may be separated using hexane-toluene (3:2, v o l : v o l ) , and the vanadyl porphyrins using hexane-tetrahydrofuran (5:1, vol:vol).(25) The resolution may be improved by multiple elutions or by the continuous

20.

Geoporphyrins and Chlorins

QUIRKE

313

Total Porphyrin Extract 1.

Ni

GPC LH-20 Tetrahydrofuran

and VO P o r p h y r i n s A1 0 2

3

(Grade I I ) Column

Hexane/Toluene/CH Cl


2

Ni

Porphyrins

2

*1

Gradient

VO P o r p h y r i n s

Si0 Column

*1

*1

2

Si0

Hexane/CHCl^ G r a d i e n t 2.

TLC

Hexane/CHC1

(Silica)

2.

Heptane/CH C1 2

Column

2

2

3

Gradient

Functionalised

(7:3)

Tol/Tol-EtOAc TLC

Si0

2

Column

Gradient

(Silica)

Heptane-THF (5:1) Pure N i P o r p h y r i n

Mixture

CF C0 H/H S0 3

2

4

(9:1)

or

1.

C F C 0 H / HSCH CH SH

or

1.

CH S0 H,

Demetallated

Toi

2

Pure VO P o r p h y r i n

3

3

Ni

2

3

2

2

or

Mixture

1.

HF 0 C

1.

CH S0 H, 3

3

100°C, 4h

100°C

Porphyrins

Demetallated

VO

Porphyrins

= T o l u e n e ; EtOAc = E t h y l A c e t a t e ; THF = T e t r a h y d r o f u r a n

1. C o n v e n t i o n a l Columns may be r e p l a c e d by MPLC.

2. Chromatograph r a p i d l y

to prevent

unnecessary generation of a r t i f a c t s .

Figure 2. P u r i f i c a t i o n scheme f o r the study of t o t a l n i c k e l and vanadyl a l k y l geoporphyrin mixtures.

*

2



314

elution method. (_14) Nickel geoporphyrins may be partially fractionated on calcium carbonate columns developing the chromatogram i n benzene-petroleum ether (4:1, v o l : v o l ) . (32) Usually i t i s necessary to demetallate the mixtures to effect the i s o l a t i o n of individual porphyrin components. The range of p o l a r i t i e s of the metal-free geoporphyrins i s greater than those of the metalloporphyrins. It i s often possible to i s o l a t e individual metal free porphyrins from metalloporphyrin fractions by preparative TLC on silica gel. (£«Jl/A>!>i^>iZ>H»!^ Toluene-dichloromethane (1:1, vol:vol) i s an e f f e c t i v e solvent system. The mode of separation seems to be as follows :(14,35) 1) Porphyrins bearing i s o c y c l i c rings are more polar than e t i o porphyrins similar carbon number. 2) The p o l a r i t y of each s k e l e t a l class of porphyrin i s inversely proportional to the carbon number. 3) An unsubstituted Β-position causes a reduction i n p o l a r i t y equivalent to an additional 2-3 methylene units. Thus a C^Q e t i o porphyrin with 1 unsubstituted 3-position i s intermediate i n p o l a r i t y between f u l l y β-alkylated C ^ and C ^ etio porphyrins. The separation i s greatly f a c i l i t a t e d by carrying out Friedel-Crafts acetylations on the geoporphyrin mixtures. The reaction s p e c i f i c a l l y converts unsubstituted β-positions on the porphyrin macrocycle into acetyl moieties. The reaction may be carried out on the nickel geoporphyrin mixtures themselves. Vanadyl porphyrin must be demetallated, and converted to the n i c k e l , copper or iron porphyrins before acetylation. The metalloporphyrin i n dichloromethane i s treated at 0°C with anhydrous tin(IV) chloride and acetic anhydride. After standing for a short time, the solution i s neutralized, and the porphyrins are extracted. The acetylated porphyrins are readily separated by TLC from the f u l l y β-alkylated geoporphyrins. The i n d i v i d u a l acetylated porphyrins may then be isolated, and characterized by nuclear magnetic resonance spectroscopy.(36) The method has yet to be employed i n the study of geoporphyrins bearing > 2 unsubstituted β-positions. Isolation of i n d i v i d u a l porphyrins by High Performance Liquid Chromatography (HPLC) - the best f i n a l p u r i f i c a t i o n technique- i s discussed below. A summary of useful i s o l a t i o n procedures i s shown i n Figure 3. The Isolation and Geological Sources.

Purification

of

Geoporphyrins

from

Other

There have been few studies on the geoporphyrins i n coals and kerogens. The i s o l a t i o n methods employed i n these cases are very different from those described i n the previous sections because of the d i f f e r e n t nature of the samples and the geoporphyrins themselves. The i s o l a t i o n of Porphyrins from Coals. The p r i n c i p a l recent work done i n this area i s that of the Bonnett group, and that of Palmer and co-workers. Neither group use the method of Treibs, who carried out an i n i t i a l extraction of the coal with pyridine.(37,38) The approach of Palmer involved extraction of ground coal p a r t i c l e s (20-mesh) with MSA (100°C, 3 h). The porphyrins were then

20.


QUIRKE

Porphyrin

Extract GPC

Ni

AÔ^

Column

Si0

Column

o

Porphyrins 1.

TLC

*1

VO P o r p h y r i n s

(Silica)

1.

Hexane-Tol (3:2) -Ni

Porphyrin


1.

VO

i : t

Porphyrin

Fractions

(0Ac), 1.

Ac 0/SnCl. 2 4 TLC CH C1

HF 0 C

o

2.

2

*

(Silica)

^Hexane-THF (5:1)

Fractions

Ni

I TLC

or 1.

C H S 0 H , 100°C, 4h 3

3

2

Metal-Free

Porphyrins

2

Alkyl Ni Porphyrins

Ni A c e t y l Porphyrins

TLC Tol/CH Cl 2

TFA/H S0. 2 4

TFA/H S0. 2 4

o

Metal-Free Acetyl Porphyrins 1.

2

(1:1)

HPLC

Metal-Free Alkyl Porphyrins 1.

TLC CHC1

or 1.

or 1

o

TLC

(Silica)

Tol/CH Cl

3

2

or 1.

HPLC

Individual Acetyl Porphyrins

*

2

(1:1)

HPLC

Individual Alkyl Porphyrins -

T o i = Toluene; ΤFA = T r i f l u o r o a c e t i c A c i d ; THF = T e t r a h y d r o f u r a n ; A c 0 = A c e t i c Anhydride. 2

1. See F i g u r e 2.

k 2.

Demetallate

and s e p a r a t e on HPLC

Figure 3. Procedures f o r the i s o l a t i o n of i n d i v i d u a l porphyrins from n i c k e l and vanadyl a l k y l geoporphyrin mixtures.


316


p u r i f i e d using GPC on Sephadex LH-20, before mass spectrometric analyses. (39) The Bonnett approach of an i n i t i a l treatment of the f i n e l y ground coal with 7% H^SO.-CHÔH for 12 hours at room temperature yields the metalloporphyrins intact. The porphyrins were extracted with chloroform, and neutralized. Using these methods, gallium ( I I I ) , iron (III), and manganese (IT) porphyrins were detected i n coals. Gallium porphyrins were isolated and p u r i f i e d by column chromatography on silica gel using gradient elution of benzene-methanol, i n the presence of 0.02-0.03 molar anhydrous ammonia. The porphyrin extracts are further p u r i f i e d on s i l i c a gel TLC p l a t e s , eluting with benzene-methanol (4:1) i n the presence of ca. 0.1 molar anhydrous ammonia and then rechromatographed i n 4.15 molar methanolic ammonia. The gallium porphyrins may be analysed on reverse phase HPLC using a Waters Bondapak column C ^ / P o r a s i l eluting with methanol:water (17:3).(40,41) Gallium porphyrin methyl esters may be analysed on Techsil 5C 18 columns eluting with methanol-water (4:1).(42) Iron porphyrins are isolated somewhat d i f f e r e n t l y . After the i n i t i a l extraction with 7% sulphuric acid-methanol, the porphyrins are chromatographed on s i l i c a gel TLC plates eluting with 15% 1 molar ammoniacal methanol-toluene.(43) Any porphyrin acids should be converted into their methyl esters. The porphyrins may then be demetallated, and analysed by HPLC using Apex ODS columns and eluting with 3% methanol-acetonitrile.(42) The Isolation of Porphyrins from Kerogens. There i s very l i t t l e information on the generation of porphyrins from kerogens even though there have been many hypotheses on the nature of the porphyrins within the kerogen matrix. Van Berkel and F i l b y have made a detailed study on the subject, and their approach to the problem i s summarized here.(44) The bitumen i s removed from the f i n e l y ground shale. The kerogen concentrate i s prepared by a method similar to that of Durand.(45) The concentrate i s sonicated to remove organic solubles associated with the minerals which associate with the kerogen after treatment with hydrofluoric acid. Then the kerogen i s pyrolysed i n toluene at the selected temperature under an atmosphere of nitrogen. The pyrolysed kerogen i s isolated by centrifugation, and then sonicated with toluene or toluene-methanol, and the organic extract i s combined with the f i l t r a t e from the pyrolysis. The porphyrins may be isolated using the methodologies described e a r l i e r . The kerogen may then be pyrolysed again at a higher temperature. Tygically, the pyrolyses temperatures are selected i n the range 100-450 C. Using this method i t i s possible to distinguish the bituminous porphyrins from those porphyrins associated with inorganic mineralsbut not intimately bound into the kerogen matrix- and from the porphyrins associated with the kerogen. It i s also possible to obtain information on the order i n which the geoporphyrins are liberated from the kerogen. The studies indicate that the majority of the porphyrins are liberated at 300°C.

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The i s o l a t i o n of Unusual C y c l i c Tetrapyrroles. With the exception of coals, nickel and vanadyl alkyl porphyrins are the dominant porphyrin species i n sedimentary rocks and petroleums. Nevertheless, other porphyrin species have also been i s o l a t e d . The methodology for the i s o l a t i o n of these components w i l l be discussed.


Copper Geoporphyrins. Copper Porphyrins have very similar chromatographic and chemical properties to n i c k e l porphyrins. Thus they are isolated i n the same manner as described previously. They may be demetallated i n the same way as the n i c k e l porphyrins. In a l l i s o l a t i o n procedures, i t i s p a r t i c u l a r l y important to rigorously exclude copper s a l t s , because metal free porphyrins chelate with copper (II) ions very readily.(46) Metal-Free Geoporphyrins. Metal-free porphyrins occur rarely i n geological samples; however, they are perhaps the easiest species to i s o l a t e . The simplest i s o l a t i o n procedure i s to treat the t o t a l organic extract i n ethereal solution with fresh d i l u t e (III>II>l IV>II,I>III IV>II>111>I III>IV>II>I

C

(14) (14) (54) (55)

See Figure I. UV data f o r pure metal free benzo e t i o , and DPEP-7 (5) porphyrins are unavailable. The intensity of band I I I i s diminished i n the 3-unsubstituted e t i o porphyrins compared to the f u l l y substituted components. C

The isomeric DPEP-5 (3) i s similar.


320

Table I I I . Molecular Ions of Geoporphyrins


C No.

20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 a

Etio Ni VO FB

Porphyrin Molecular ions Isocyclic Benzo Benzo D. Ni VO FB Ni VO FB Ni VO FB

366 380 394 408 422 436 450 464 478 492 506 520 534 548 562 576 590 604 618 632 646

392 406 420 434 448 462 476 490 504 518 532 546 560 574 588 602 616 630 644

375 389 403 417 431 445 459 473 487 501 515 529 543 557 571 585 599 613 627 641 655

310 324 338 352 366 380 394 408 422 436 450 464 478 492 506 520 534 548 562 576 590

401 415 429 443 457 471 485 499 513 527 541 555 569 583 597 611 625 639 653

336 350 364 378 392 406 420 434 448 462 476 490 504 518 532 546 560 574 588

416 430 444 458 472 486 500 514 528 542 556 570 584 598 612 626 640

425 439 453 467 481 495 509 523 537 551 565 579 593 607 621 635 649

360 374 388 402 416 430 444 458 472 486 500 514 528 542 556 570 584

414 428 442 456 470 484 498 512 526 540 554 568 582 596 610 624 638

423 437 451 465 479 493 507 521 535 549 563 577 591 605 619 633 647

358 372 386 400 414 428 442 456 470 484 498 512 526 540 554 568 582

Ni

TetraBD VO FB

-

-

446 460 474 488 502 516 530 544 558 572 586 600 614 628 642

455 469 483 497 511 525 539 553 567 581 595 609 623 637 651

-

390 404 418 432 446 460 474 488 502 516 530 544 558 572 586

The molecular ions are based on C, ^N, "^Ni. Higher carbon number porphyrins may be observed at 1 dalton above the calculated value owing to rounding up the p a r t i a l mass to the next integer. I s o c y c l i c = Molecular ions for a l l porphyrins bearing an i s o c y c l i c ring, and tetrahydrobenzo porphyrins (2-6, Figure 1.) Benzo = Benzo porphyrins (8, Figure 1.) Benzo D. = Benzo DPEP porphyrins (9, Figure 1.) TetraBD = Tetrahydrobenzo DPEP porphyrins (7, Figure 1.) FB = Free Base; Ni = Nickel; VO = vanadyl porphyrin.


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(3) Jj: i s esggntial to correct for isotopic contributions from C, Ν and Ni (where appropriate) i n quantitation to d i s t i n g u i s h between molecular ions and coincident isotope peaks from other components. Such correction procedures have been described. (_7) Chemical Ionisation Mass Spectrometry (CIMS) may provide a better solution to the quantitation problem once the problem of r e p r o d u c i b i l i t y i s overcome. In CIMS using hydrogen or methane as reagent gases, porphyrins may either fragment to form their individual pyrrole rings or y i e l d the desired molecular ion without any major fragments.(57,58) The mode of fragmentation appears to be dependent on the temperature of the source. Analysis of geoporphyrins mixtures using Fast Atom Bombardment (FAB) methods may prove valuable, although the technique may not be s u f f i c i e n t l y sensitive for quantitative work. The techniques of GC-MS and HPLC-MS are both methods of great potential. The developments i n GLC using s i l y l a t e d s i l i c o n porphyrin derivatives by Eglinton and co-workers are p a r t i c u l a r l y exciting. McFadden et a l . , have carried out HPLC-MS analysis on geoporphyrin mixtures. The data confirm the potential of the method. The only impediment l i e s i n the e f f i c i e n t interfacing of the HPLC and the MS.(59) Mass spectrometric analyses of t o t a l mixtures gives only limited structural data. Analyses of metastable ions gives information on the nature of the substituents on the porphyrin macrocycle. In this way, Titov and co-workers were able to confirm the presence of geoporphyrins with extended a l k y l substituents «C ).(60) Tandem mass spectrometric (MS/MS) i s another valuable a n a l y t i c a l t o o l . (6J[,62) Using this technique i n the EI mode i t i s possible to obtain daughter ions and neutral losses from the molecular ions of the porphyrin components without prior separation of the mixture. These data provide information on the type of the substituents on a l l the porphyrins of single carbon number. The predominant mode of cleavage of the molecular ions i s 3-cleavage of the substituents. The data indicate that high carbon number O C 3 3 ) geoporphyrins have more than one s i t e of extended alkylation, and there may be several isomeric porphyrinic species present. (63-65) The daughter spectra of the molecular ions may prove to be valuable "fingerprints" i n correlation studies. The technique of CIMS/MS has great p o t e n t i a l for the analysis of geoporphyrin mixtures also, but there are problems of reproducibility at present.(20) 12

Chromatographic Methods. HPLC i s the most valuable a n a l y t i c a l technique. The porphyrins eluting from the various columns are monitored by v i s i b l e spectrophotometry. The choice of detecting wavelength i s dependent on the nature of porphyrin species being studied. (Tables 1,11). Demetallated porphyrin mixtures are usually analysed using normal phase s i l i c a columns. Maxwell, Barwise and co-workers have achieved the best separations of such mixtures to date. (e_._g 23). F i n a l l y , after over four years since the o r i g i n a l publications, the chromatographic conditions are to be published i n "Journal of Chromatography". Sundaraman and co-workers have succeeded i n the e f f i c i e n t separation of vanadyl porphyrin mixtures; unfortunately the precise


322


conditions employed have not been divulged.(66) Nickel porphyrins are not usually analysed i n the metallated state; however, Fookes reported the separation of the n i c k e l porphyrins of J u l i a Creek o i l shale into 30 fractions on a C-18 column eluting with methanol.(24) Eglinton and co-workers have made notable advances i n the GLC and GC-MS analyses of porphyrins.(e.g. 67-70) Although i t i s possible to chromatograph several metalloporphyrin species inluding gallium, aluminium and rhodium (III) complexes, analysis of the s i l i c o n ( I V ) derivatives i s the preferred method.(68) The procedure i s summarized below. The demetallated porphyrins i n dry toluene are converted into their s i l i c o n derivatives by treatment with hexachlorodisilane, for 2 hours at ambient temperature. The porphyrins are p u r i f i e d on alumina TLC, eluting with dichloromethane, and the hydroxy ligands are s i l y l a t e d using BSTFA-pyridine. The chromatography i s carried out on either OV-1 or CPSil 5 c a p i l l a r y columns, using helium as the c a r r i e r gas (50-120 cm sec flow rate). The i n i t i a l oven temperature i s 60 C, and the temperature i s increased l i n e a r l y to ca. 300°C. The advantages of GC-MS analysis of geoporphyrins f o r fingerprinting of crude o i l s and correlation studies are obvious. Clearly, GC-MS-MS would be a yet more powerful a n a l y t i c a l t o o l . In addition to i t s role as a p u r i f i c a t i o n technique, GPC has been used i n the study of the molecular weight d i s t r i b u t i o n s of geoporphyrin mixtures. Blumer and co-workers studied the porphyrins of the Serpiano shale, and obtained evidence for very high molecular weight porphyrin species, and even dimeric porphyrins.(71,72) More recently, Fish and co-workers have used size exclusion HPLC to investigate the nature of the nickel and vanadium compounds i n petroleums. The eluates from the 50-100 u Spherogel column were analysed by graphite furnace atomic absorbtion. Using this technique i t i s possible to deduce the molecular weight range of such species.(73) Degradative Methods. The degradation of porphyrin mixtures to maleimides (2,5-pyrrolediones) using chromic acid gives valuable information on the substituent patterns of the geoporphyrins. (9^,74,75) Each p y r r o l i c subunit i s converted to a maleimide bearing the o r i g i n a l pair of substituents. The i s o c y c l i c ring-bearing pyrroles are converted to maleimide carboxylic acids.(76) The method compliments chromatographic and mass spectrometric analyses of such geoporphyrin mixtures. An e f f i c i e n t procedure i s outlined below. (9^) Treatment of the demetallated porphyrin mixture i n t r i f l u o r o a c e t i c acid with chromium trioxide i n sulphuric acid at 0 C for 2 hours yields the maleimides. These compounds may be analysed by GLC or GC-MS using OV-1 or carbowax c a p i l l a r y columns programmed from 60°C to 260°C at 4°C miη . The maleimides usually show molecular ions, and a c h a r a c t e r i s t i c fragment ion, m/z 125. To obtain better peak shapes, the maleimides may be s i l y l a t e d p r i o r to analysis. There are three other degradative techniques, which may be used for the analysis of geoporphyrin mixtures. Oxidation of porphyrins using lead (IV) dioxide (4h, ambient temperature) to the corresponding 5,10,15,20-tetraoxoporphyrinogens i s a potentially

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valuable method. These compounds fragment i n EIMS to give the individual p y r r o l i c species, together with d i - and t r i - p y r r o l i c fragments from the t e t r a p y r r o l i c macrocycle.(77) Treatment of the porphyrins with hydriodic acid gives the i n d i v i d u a l pyrroles, which may then be analysed by GC-MS. The method has been superceded by the developments i n CIMS.(78) The oxidative degradation of porphyrins by potassium permanganate to form 2,5-pyrrole dicarboxylic acids could be used for geoporphyrin analyses, but i t too has been supercedeed by CIMS.(79) Characterisation of Individual Porphyrin Components. This i s the area of geoporphyrin chemistry i n which the greatest advances have been made. The developments i n NMR i n p a r t i c u l a r have resulted i n a c l a r i f i c a t i o n of the T r e i b s hypothesis on the o r i g i n of the geoporphyrins, and confirmed that these compounds are derived from naturally-occurring chlorophylls. In addition, i t i s possible to determine i n some cases the precise precursor of s p e c i f i c geoporphyrins.(51,80)


1

Spectrophotometric Methods. UV/Visible spectrophotometry provide information on the s k e l e t a l type of porphyrin present. Otherwise i t is of l i t t l e value i n s t r u c t u r a l elucidation. The most important role f o r this technique i s i n the characterisation of the geochlorins.(12) Mass Spectrometric Methods. High resolution EIMS yields the molecular formula of a porphyrin. The primary mode of fragmentation of the porphyrins i n the EIMS i s cleavage 3 to the porphyrin ring. Thus determination of the daughter ions of the molecular ion provides limited s t r u c t u r a l information.(56,63,64) The CIMS analysis of porphyrins using hydrogen as reagent gas and a source temperature of 200°C reveals pyrrole, dipyrrole and t r i p y r r o l e fragments, which can be used to sequence the pyrrole units within the porphyrin macrocycle, and requires very little sample (ca. 1 yg). (58,80 More reproducible results are obtained by using ammonia as reagent gas.(82) This i s usually the best a n a l y t i c a l technique when working such small quantities of porphyrin that NMR i s i n f e a s i b l e . The method w i l l probably be further improved by using CIMS-MS with ammonia as the reagent gas. Nuclear Magnetic Resonance Methods. The use of NMR has revolutionized the study of the geoporphyrins. In fact i t i s by far the most important method currently employed for the analysis of individual geoporphyrins. The technique i s i d e a l for such studies as i t can be effected on f a i r l y small samples (C«) substituents. The chemical s h i f t of the water peak may be varied by a l t e r i n g the pyridine concentration. Porphyrins bearing i s o c y c l i c rings are i d e a l l y suited for nOe analysis. Geochlorins w i l l also be readily analysed by the nOe technique because these compounds bear a reduced p y r r o l i c ring which ensures that the meso protons are well resolved. In addition the substituents on the reduced p y r r o l i c ring are very readily assigned which w i l l greatly f a c i l i t a t e such studies. Porphyrins bearing an unsubstituted 3-position may be analysed d i r e c t l y by the nOe method, but better results are obtained i f the porphyrins are initially acetylated by the Friedel-Crafts acylation reaction.(86,87) Usually the technique i s of l i t t l e value for the characterisation of f u l l y B-alkylated etio porphyrins as the meso protons coincide. There have been two other approaches to the analysis of porphyrins by NMR. A etio porphyrin i n Gilsonite was i d e n t i f i e d as etioporphyrin-III \Ia) by converting the porphyrin into i t s "mercury sandwich" complex i n which two porphyrin macrocycles are interspersed between three mercury ions. The mercury sandwich complex of each of the four porphyrin type isomers has a different H NMR spectrum. These metal-free type isomers have v i r t u a l l y i d e n t i c a l NMR spectra.(L7) The method i s limited because i t i s essential to obtain spectra of a l l the possible isomers for comparison. Also the complex readily decomposes to the 1:1 complex; hence, the CDCl^ solvent should be passed through alumina to remove traces of acid. Krane and co-workers used aggregation studies to assign the structure of the C~ etioporphyrin i n Marl slate as etioporphyrin-III.(91) This approach i s l i k e l y to be the method of choice for the analysis of porphyrins which are not amenable to nOe analysis. The chemical s h i f t s of some important geoporphyrinic substituents are shown i n F i g . 4. Degradative Techniques. The maleimide degradation may be used to confirm the NMR data. ( 14,1_7,82) Otherwise, the method i s of l i t t l e value for precise structure determination.

2

The

3

1

o f v a l u e s i s a approximate.

3.1-3.5 M e t a l and m e t a l

f r e e s p e c i e s have s i m i l a r

δ-value.

Figure 4. H NMR chemical shift data for common geoporphyrin substituents and exocyclic rings.

CH C=0

range

3

CH CH

1.6-1.9

9.0-10.5

3.7-4.3

3

CH CH

2

Meso-H


to LA

326



Synthetic and Chromatographic Methods. The method of structure elucidation by comparison of the isolated compound with a l l the possible s t r u c t u r a l isomers i s impractical except for research groups s p e c i a l i s i n g i n porphyrin synthesis. (91-96) A t y p i c a l t o t a l synthesis w i l l take over twenty steps from readily available starting materials, and involves a moderate y i e l d cyclisation step.(91-96) The method was successfully used to determine the structure of the desethyl C~Q etio porphyrin (1 b).(97) Four isomers of the compounds were synthesized, and separated by HPLC on 10 y ODS-HC-Sil-XI eluting with a c e t o n i t r i l e , and the structure of the geoporphyrin was assigned by co-injection. The only occcassion when i t i s essential to employ this strategy i s i f the structure determination of porphyrins cannot be readily determined by other techniques. Crystallographic Methods. The major d i f f i c u l t y i n using the technique i s that i t i s very d i f f i c u l t to grow crystals of s u f f i c i e n t quality, when working with small amounts (< 1 mg) of sample. Nevertheless the nickel complexes of deoxophylloerythroetioporphyrin and deoxophylloerythrin (2a, 2b) have been characterized by X-ray crystallography.(4 98^ χ

Characterisation of Bound Porphyrins. There have been very few studies on the nature of the porphyrins within the organic substances or inorganic mineral matrix. The techniques available for such studies have been mainly applied to model compounds. Bergaya and van Damme have studied the s t a b i l i t y of metalloporphyrins adsorbed onto a clay surface.(99) The porphyrin species were investigated by using UV-visible diffuse reflectance and diffuse transmission spectra. The diffuse transmittance spectra were i d e n t i c a l with conventional transmission spectra. Provided that the sample i s a highly dispersed suspension, i t i s also possible to obtain quantitative data. The diffuse reflectance spectra are not as e a s i l y compared; however a direct comparison gives enough information for distinguishing the nature of the porphyrin species present. For rigorous work the two parameters are correlated through the Kubelka-Munk function: (l-R ) /2R = k/s Z

O0

0o

Roo = the reflectance of a layer s u f f i c i e n t l y thick that further concentration does not change the reflectance, k = absorption c o e f f i c i e n t (molar extinction times concentration) s = scattering c o e f f i c i e n t . Cady and Pinnavaia used a similar approach; however the v i s i b l e spectroscopic data were obtained by dispersing the m i c a - s i l i c a t e bearing the porphyrin i n a nujol mull. Infra red studies were effected by running the spectra of the s o l i d material as thin films supported between KBr plates.(100) Electron spin resonance spectroscopy (ESR) i s a powerful technique for the study of bound vanadyl porphyrins. T y p i c a l l y , the spectra show eight weak p a r a l l e l lines (three may be hidden) and

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eight perpendicular l i n e s , which are readily recognized. The basic methodology, and interpretation of the data has been reviewed recently by Lin.(101) Using the method, evidence has been obtained for the presence of non-porphyrinic vanadyl compounds i n petroleums and tar sands.(102,103) Goulon e_t a l . have reported x-ray absorption spectroscopic analysis on asphaltenes which indicated that the vanadium was associated with porphyrins, and that the porphyrin content may be greater than indicated by v i s i b l e spectroscopy.(104,105)


Summary There i s s t i l l no one scheme which i s i d e a l for the i s o l a t i o n of porphyrins from a l l types of geological samples. This i s not surprising because of the substantial variations i n the sedimentary environment. The development of HPLC, and the advances i n mass spectrometry have been major assets i n the characterisation of t o t a l geoporphyrin mixtures. In the future, GC, ÇC-MS, HPLC-MS w i l l y i e l d even more information. The advent of H NMR has provided the geochemist with by f a r the most important tool f o r ^ t h e s t r u c t u r a l elucidation of i n d i v i d u a l geoporphyrins. No doubt, C NMR studies w i l l become feasible as the s e n s i t i v i t y of the instruments i s improved. MS-MS w i l l also be a valuable technique for the study of i n d i v i d u a l components within intact geoporphyrin mixtures. The major area of the f i e l d which i s yet to be thoroughly investigated i s the study of the bound geoporphyrins. It i s e s s e n t i a l that there are more studies i n t h i s area i f the chemistry of the geoporphyrins i s to be f u l l y understood. Acknowledgments I am g r a t e f u l to Dr. J.F. Branthaver (Western Research I n s t i t u t e , Laramie), Dr. R.H. F i l b y and Mr. G.J. van Berkel (Washington State University, Pullman), Dr. K.M. Smith and his students (University of C a l i f o r n i a , Davis) for useful discussions i n the preparation of t h i s manuscript. References 1. F i l b y , R.H.; Van Berkel, G.J., t h i s volume. 2. Branthaver, J.F., this volume. 3. Thomas, D.W.; Blumer, Μ., Geochim. Cosmochim. Acta 1964, 28, 1147-1154. 4. Ekstrom, Α.; Fookes, C.J.R.; Hambley, T.; Loeh, H.J.; Miller, S.A.; Taylor, J.C. Nature 1983, 306, 173-174. 5. Louda, J.W.; Baker, E.W. In " I n i t i a l Reports of the Deep Sea D r i l l i n g Project "; Yeats, R.S.; Haq, B.U. et al., Eds.; U.S. Government Printing Office: Washington, 1981; Vol.LXIII, pp.785-818. 6. Quirke, J.M.E.; Dale, T.; Britton, E.D.; Yost, R.A.; Trichet, J.; Belayoumi, H. Org. Geochem. submitted. 7. Baker, E.W.; Palmer, S.E. In "The Porphyrins"; Dolphin, D., Ed.; Academic: New York, 1978; Vol.I, pp. 485-622. 8. Baker, E.W. J . Am. Chem. Soc. 1966, 88, 2311-2315.


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9. Quirke, J.M.E.; Shaw, G.J.; Soper, P.D.; Maxwell, J.R. Tetrahedron 1980, 36, 3261-3267. 10. HajIbrahim, S.K.; Tibbetts, P.J.C.; Watts, C.D.; Maxwell, J.R.; Eglinton, G.; Colin, H; Guichon, G. Anal. Chem. 1978, 50, 549-553. 11. Quirke, J.M.E.; Abedi, V., unpublished data. 12. Baker, E.W. and Louda, J.W. In "Advances i n Organic Geochemistry" Bjorøy, M. et al., Eds.; Wiley: Chichester, 1983, pp. 401-421, and references therein. 13. Kowanko, N.; Branthaver, J.F.; Sugihara, J.M. Fuel 1978, 57, 769-775. 14. Quirke, J.M.E.; Eglinton, G.; Maxwell, J.R. J . Am. Chem. Soc. 1978, 101, 7693-7697. 15. Dunning, H.N.; Rabon, N.A. Ind. Eng. Chem. 1956, 48, 951-955. 16. Baker, E.W.; Louda, J.W., Org. Geochem. 1984, 6, 183-192. 17. Quirke, J.M.E.; Maxwell, J.R. Tetrahedron 1980,36, 3453-3458. 18. Ponomarev, G.V.; Shul'ga, A.M. Khim. G r e t e r t s i k l . Soedin. 1984, 19, 485-489. 19. Barwise, A.J.G.; Whitehead, E.V. In "Advances i n Organic Geochemistry 1979" Douglas, A.J.; Maxwell, J.R., Eds.; Pergamon: Oxford, 1980, pp. 181-192. 20 B r i t t o n , E.D., M.Sc. Thesis, University of F l o r i d a , Gainesville, 1985. 21. Branthaver, J.F.; Trudell, L.G.; Heppner, R.A. Org. Geochem. 1982, 4, 1-7. 22. Branthaver, J.F.; Storm, C.B.; Baker, E.W. Org. Geochem. 1983, 4, 121-134. 23. Barwise, A.J.G.; Roberts, I. Organic Geochemistry In "Advances i n Organic Geochemistry, 1983" Schenck, P.A. and De Leeuw, J.W. Eds.; Pergamon Oxford 24. Fookes, C.J.R. J . Chem. Soc., Chem. Comm. 1983, 1472-1473. 25. Van Berkel, G.J.; F i l b y , R.H.; Quirke, J.M.E., unpublished data. 26. Baker, E.W.; Yen, T.F.; Dickie, J.P.; Rhodes, R.E.; Clark, L.F. J. Am. Chem. Soc. 1967, 89, 3631-3639. 27. Aizenshtat, Z.; Dinur, D.; Nissenbaum, A. Chem. Geol. 1979, 24, 161-174. 28. Erdman, G.J. U.S. Patent 3 190 829, 1965. 29. Battersby, A.R.; Jones, Κ., Snow, R.J. Angew. Chem., Int. Ed. 1983, 22, 734-736. 30. K. Snow, personal communication. 31. Branthaver, J.F. Ph.D. Thesis, North Dakota State University, Fargo, 1976. 32. Sugihara, J.M. and McGee, L.R. J . Org. Chem. 1957, 22, 795-798. 33. Blumer, M. An. Acad. B r a s i l . Cienc. 1974, 46, 77-81. 34. A l t u r k i , Y.I.Α.; Eglinton, G. and P i l l i n g e r , C.T. In "Advances i n Organic Geochemistry 1971" von Gaertner, H.R.; Wehner, Η., Eds.; Pergamon: Oxford, 1972, pp.135-150. 35. HajIbrahim, S.K.; Quirke, J.M.E.; Eglinton, G. Chem. Geol. 1982, 35, 69-85. 36. Quirke, J.M.E. In "Advances i n Organic Geochemistry, 1981" Bjorøy et al,. Eds.; Wiley: Chichester, 1983, pp.733-737. 37. Treibs, A. Ann. Chem. 1935, 517, 172-196. 38. Treibs, A. Ann. Chem. 1935, 520, 144-151.

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46. 47. 48. 49. 50. 51. 52.

53. 54. 55. 56. 57. 58. 59. 60. 61. 62. 63. 64. 65. 66.

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67. Alexander, R.; Eglinton, G.; Gill, J.P.; Volkman, J.K. J . High Resol. Chromat. Chromat. Comm. 1980, 3, 521-522. 68. Marriott, P.J.; Gill, J.P.; Eglinton, G.; J . Chromatogr. 1982, 249, 291-310. 69. Marriott, P.J.; Gill, J.P.; Eglinton, G.; J . Chromatogr. 1984, 107-128. 70. Eglinton, G.; Marriott, P.J.; Evershed, R.P.; Gill, J.P. Org. Geochem. 1984, 6, 157-165. 71. Blumer, M.; Rudrum, M. J . Inst. Pet. 1970, 56, 99-106. 72. Blumer, M.; Snyder, W.D. Chem. Geol. 1967, 2,. 35-45. 73. Fish, R.H.; Komlenic, J.J. Anal. Chem. 1984, 56, 510-517. 74. Didyk, B.; A l t u r k i , Y.I.Α.; P i l l i n g e r , C.T.; Eglinton , G. Chem. Geol. 1975, 15, 193-208. 75. Hodgson G.W.; Strosher, M.; Casagrande, D.J. (1972) In "Advances i n Organic Geochemistry, 1971"; von Gaertner, H.R. Wehner, Η., Eds.; Pergamon:Oxford, 1972, pp.151-161 76. Brockmann, H.; Tacke-Karimdadian, R. Ann. Chem. 1979, 419-430. 77. Boylan, D.B. Org. Mass Spectrom. 1970, 3, 339-351. 78. Chapman, R.A.; Roomi, M.W.; Morton, T.C.; Krajcarski, D.T.; MacDonald, S.F. Canad. J . Chem. 1971, 49, 3544-3564. 79. Nicolaus, R.A.; Mangoni; L. C a g l i o t i , L. Ann. Chim. (Rome) 1956, 46, 793-805 80. C h i c a r e l l i , M.I.; Kaur, S.; Maxwell, J.R., this volume. 81. Wolff, G.A.; C h i c a r e l l i , M.I.; Shaw, G.J.; Evershed, R.P.; Quirke, J.M.E.; Maxwell, J.R. Tetrahedron 1984, 40, 3777-3786. 82. T o l f , B.-R.; Jiang, X.-Y.; Wegmann-Szente, Α.; Kehres, L.A.; Bunnenbergh, E.; Djerassi, C. J.Am. Chem. Soc. 1986, 108, 1363-1374. 83. Quirke, J.M.E.; Maxwell, J.R.; Eglinton, G.;Sanders, J.K.M. Tetrahedron Lett. 1980, 21, 2987-2990. 84. Fookes, C.J.R. J . Chem. Soc., Chem. Comm. 1983, 1474-1476. 85. Fookes, C.J.R. J . Chem. Soc., Chem. Comm. 1985, 706-708. 86. C h i c a r e l l i , M.I.; J.R. Maxwell Tetrahedron Lett. 1984, 25, 4701-4704. 87. C h i c a r e l l i , M.I.; Wolff, G.A.; Maxwell, J.R. J . Chem. Soc., Chem. Comm. 1985, 723-724. 88. Wolff, G.A.; Murray, M.; Maxwell, J.R.; Hunter, B.; Sanders, J.K.M. J . Chem.Soc.,Chem. Commun. 1983, 922-924. 89. Ocampo, R.; C a l l o t , H.J.; Albrecht, P. J . Chem Soc., Chem. Comm. 1985, 198-200. 90. Storm, C.B.; Krane, J . ; Skjetne, T.; Telnaes, N.; Branthaver, J.F.; Baker, E.W. Science 1984, 223, 1075-1076. 91. Krane, J . ; Skjetne, T.; Telnaes, N.; Bjoroy, M. S o l l i , H. Tetrahedron 1983, 39, 4109-4119. 92. Baker, E.W.; Corwin, E.W.; Klesper, E.; Wei, P.E.; J . Org. Chem. 1968, 33, 3144-3148. 93. Flaugh, M.E.; Rapoport, H. J . Am. Chem. Soc. 1968, 90, 6877-6879. 94. Smith, K.M.; Langry, K.C.; Minnetian, O.M. J . Org. Chem. 1984, 49, 4602-4609. 95. Clezy, P.S.; Mizra, A.H. Aust. J . Chem. 1982, 35, 197-209. 96. Morgan, A.R.; Pangka, V.S.; Dolphin, D. J . Chem. Soc., Chem. Comm. 1984, 1047-1048.


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97. Clewlow, P.J.; Jackson, A.H.; Roberts, I. J . Chem Soc., Chem. Comm. 1985, 724-726. 98. Habermehl; G.G.; Springer, G.; Frank, M.H Naturwissenschaften 1984, 71, 261-263. 99. Bergaya, F.; van Damme, H. Geochim. Cosmochim. Acta 1982, 46, 349-360. 100. Cady, S.S.; Pinnavaia, T.J. Inorg. Chem. 1978, 17, 1501-1507. 101. L i n , W.C. In "The Porphyrins"; Dolphin, D., Ed.; Academic: New York, 1978; Vol IV, pp.355-377. 102. Malhotra, V.M.; Buckmaster, H.A.; Fuel 1985, 64,335-341. 103. Reynolds, J.G.; Biggs, W.R.; Fetzer, J.C. L i q . Fuels Technol. 1985, 3, 423-448. 104. Goulon, J . ; E s s e l i n , C.; Friant, P.; Berthe, C.; Muller, J.F.; Poncet, J.L.; Guilard, R.; E s c a l i e r , J.C.; Neff, B. C o l l e c t . Colloq. Semin. (Inst. Fr. Pet.) 1984, 40, 158-163. 105. Goulon, J . ; Retournard, P.F.; Goulon-Ginet, C.; Berthe, C.; Muller, J.F.; Poncet, J.C., Guilard, R.,Escalier, J.C.; Neff, B. J . Chem. S o c ., Dalton Trans. 1984, 1095-1103. RECEIVED March 11, 1987

Chapter 21 Molecular Characterization of Nickel and Vanadium Nonporphyrin Compounds Found in Heavy Crude Petroleums and Bitumens 1

2

2

Richard H. Fish , John G.Reynolds ,and Emilio J. Gallegos 1

Lawrence Berkeley Laboratory, University of California—Berkeley, Berkeley, CA 94720 Chevron Research Company, Richmond, CA 94802


2

Pyridine/water extracts of selected crude petroleums were separated by polarity on a high performance liquid chromatography (HPLC) octadecylsilane column (ODS) into three fractions; low, moderate, and high polar. The moderate and low polar fractions were examined by electron impact mass spectroscopy (EIMS) to elucidate structural and behavioral characteristics of vanadyl petroporphyrin and metallo-nonporphyrin compounds. The EIMS results indicated vanadyl petroporphyrins in Cerro Negro and Wilmington moderate polar fractions and possibly in the Wilmington low polar fraction. These EIMS results showed the presence of petroporphyrins in the above-mentioned fractions, but no discrete information about the metallo-nonporphyrins. A highly polar nickel fraction from a Wilmington crude petroleum pyridine/water extract, separated on the ODS column, was further purified on a cyano normal phase column. This fraction had a nickel concentration of approximately 15,000 wppm, and was examined by EIMS mass spectroscopy. The spectral results indicated several homologous series structures possible for the binding sites of nickel. Further examination of the same fraction by positive ion fast atom bombardment (FAB+) mass spectroscopy, using a metal ion exchange technique, showed a substantially simplified spectrum and indicated the possibility of the nickel binding sites being small molecular weight naphthenic (carboxylic) acid salts. Gilsonite, a bitumen, was analyzed by reversed-phase HPLC with graphite furnace atomic absorption (RP-HPLC-GFAA) element specific detection, which indicated that the nickel is predominantly bound as metallopetroporphyrin, while a small portion eluted as a highly polar metallo-nonporphyrin fraction. These results are important in the identification of nonporphyrin metal-containing compounds in heavy crude petroleums and residua and could be beneficial for future petroleum exploration as metallobiomarkers. We have extensively examined various crude petroleums and separated fractions to determine the characteristics of the metal-containing compounds, particularly the metallononporphyrins. Recently, we reported the molecular weights (MW) of the vanadium and nickel compounds found in selected heavy crude petroleums — Boscan, Cerro Negro,



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Characterization of Nickel and Vanadium Nonporphyrins

333

Wilmington, and Prudhoe Bay ~ and their extracts (1,2) by size exclusion chromatography in conjunction with graphite furnace atomic absorption selective metal detection (SECH P L C - G F A A ) . The metals distribution was found to be unique for each petroleum, while the histogrammic metals profiles may have utility for fingerprinting the heavy crude petroleums. In the case of vanadium, the majority of the metal-containing compounds falls into the 2,000 to 9,000 dalton M W range, while 3 to 7% was found in the M W range > 9,000 daltons. The low M W range was calibrated by vanadyl and nickel model compounds, with 23 to 30% having a M W range of 2,000 daltons. The extract consists predominantly of very small M W compounds with an average M W of approximately 350 daltons. By comparison with nickel and vanadyl model compounds of similar M W , we also feel this further substantiates metallo-nonporphyrin coordination spheres. These pyridine/water extracts were separated by R P - H P L C into three fractions based on polarity, and the fractions were monitored by element specific detection (GFAA) and UV-vis spectroscopy (2). Most of the nickel-containing compounds eluted in the most polar fractions. Comparison with model compound retention times indicated these compounds are nonporphyrin bound. Most of the vanadium-containing compounds were found in the moderate polar fractions. Rapid scan (RS) UV-vis data showed a prominent Soret band in this fraction for Boscan and Cerro Negro indicating at least some of the vanadium is bound as petroporphyrin. This was not the case for Wilmington and Prudhoe Bay moderate polar fractions where the RS-UV-vis exhibited little or no Soret. A t this time, we have no adequate model compounds that co-elute in this fraction. The least polar fraction also contained vanadium (up to 30% of total in crude). Model compound retention times showed the model porphyrins eluted in this fraction, but the absence of a prominent Soret in this fraction for most of the crudes suggests nonporphyrins. The moderate and low polar R P - H P L C fractions from Boscan, Cerro Negro, Wilmington, and Prudhoe Bay crude petroleums, were examined by electron paramagnetic resonance (EPR) spectroscopy to further elucidate the structure of the average coordination sphere around the vanadium-containing molecules (5). Several nonporphyrin coordination spheres for the vanadyl ion were observed: 1) Boscan moderate polar and Prudhoe Bay moderate and low polar fractions exhibited N S coordination. 2) Cerro Negro and Wilmington moderate polar fractions showed S coordination. 3) Boscan low polar fraction showed N coordination. 4) Cerro Negro had distinctively different parameters showing a N O S coordination. We have also examined the R P - H P L C fractions by EIMS to further identify the metallo-nonporphyrin components. Unfortunately, the EIMS spectral studies only revealed the presence of metallopetroporphyrins in certain fractions. The metallo-nonporphyrins remained undifferentiated in the organic matrix. We have attempted to elucidate the structure of nickel-containing molecules in the high polar R P - H P L C fractions by using C-18 ODS reversed-phase and cyano normal phase chromatography techniques to purify the pyridine/water extract of Wilmington crude petroleum. We have examined the resulting purified fractions with EIMS, F A B + , and metal replacement F A B + mass spectroscopies. We have also attempted to verify the existence of these highly polar nickel components in other carbonaceous materials. For example, we examined Gilsonite by R P - H P L C - G F A A and found this highly polar nickel complexes may also be present in this petroleum precursor. Results and Discussion 2

2

4

4

2

Spectral Analyses of the Moderate and Low Polar RP-HPLC Fractions. In efforts to identify the elusive nonporphyrin metal-containing species, the moderate and low polar fractions,

334



obtained by the R P - H P L C separation of the pyridine/water extracts of Boscan, Cerro Negro, Prudhoe Bay and Wilmington crude petroleums, were examined by E P R , EIMS, and RS-UV-vis spectroscopies. The E P R techniques employed utilize vanadyl square pyramidal model compounds to elucidate the average first coordination sphere of the vanadiumcontaining compounds in the sample studied (6-10). The E P R (5) and RS-UV-vis (1,2) results have been reported elsewhere. The EIMS of the R P - H P L C fractions, in general, identified the existence of vanadyl petroporphyrins when present. Figure 1 shows the EIMS for Cerro Negro moderate polar fraction for m/z of 200 to 800. Although some individual peaks stand out, the vanadyl etio homologous series is evident from m/z of 473 to 557. The vanadyl deoxophylloerythroetio (DPEP) homologous series, although less prominent, is evident from m/z of 499 to 575. The same spectral characteristics were observed in the Wilmington moderate polar fraction indicating vanadyl petroporphyrins. RS-UV-vis examination of these moderate polar fractions also indicated the presence of vanadyl petroporphyrins by the appearance of the distinctive 408 nm Soret band (1,2). The vanadyl porphyrin model compounds elute in the low polar fraction. We do not have model compounds with a Soret at 408 nm which co-elute in the moderate polar fraction. These could represent metallopetroporphyrins with a carboxylic acid functionality, (11,12) dimers of petroporphyrins (13,14), petroporphyrins of much higher molecular weight (15). These EIMS results do not necessarily conflict with the E P R data for these fractions which showed N S average first coordination sphere around the vanadyl ion (5). The E P R techniques are average parameter techniques and would not necessarily be able to resolve a minor percentage of the N coordination sphere. The EIMS method also only detects the petroporphyrins, but does not quantitate them. The EIMS spectrum of Prudhoe Bay low polar fraction, Figure 2, shows no metallopetroporphyrin homologous series. This spectrum is very typical of those fractions which contained no discernible petroporphyrins. As can be seen by Figure 2, any individual homologous series are overwhelmed by the organic matrix. The same spectral characteristics were observed for Boscan and Cerro Negro low polar fractions indicating very low levels or no petroporphyrins. This is corroborated by only a weak 408 nm Soret found by RS-UVvis. o

2

r

2

4

The E P R of these fractions indicated N coordination for the Boscan and Prudhoe Bay low polar fractions and N O S coordination for the Cerro Negro low polar fraction. The N nonporphyrin coordination sphere has been seen before in the E P R studies and suggests a variety of nonporphyrin ligand structures (5,16,17). 4

2

4

Purification of the Highly Polar Nickel Compounds Found in Wilmington Heavy Crude Petroleum. R P - H P L C - G F A A examination of the pyridine/water extracts of several heavy crude petroleums indicated the majority of the nickel-containing compounds eluted in the high polar fraction. The lack of EIMS spectral identification of these fractions suggested the need for further purification. Wilmington crude petroleum was extracted with pyridine/water and the extract was separated on the ODS column into a highly polar fraction (methanol eluted) and a less polar fraction (methylene chloride eluted). The highly polar fraction was re-chromatographed on the ODS column, and was found to increase its nickel concentration from 8000 to 11000 wppm. Table I shows the concentrations of these fractions. Further purification was performed on a cyano column using a methylene chloride to methanol solvent gradient. The use of bonded phase H P L C separations, either reversedphase or cyano columns, offer several unique advantages over the more conventional silica columns (18). Because polar solvents can be used, bonded packings are capable of separating highly polar metal-containing complexes. These highly polar complexes would be irreversibly bonded to silica, because silica packings rapidly degrade in polar solvents. Reversed-phase packings allow for partition separations where the more polar components elute first. Cyano columns can be operated in normal or reversed-phase modes providing increased flexibility over silica columns


21. FISH ET AL.


335


336 METAL COMPLEXES IN FOSSIL FUELS

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FISH ET AL.


337

Table I: Nickel Concentrations of Preparatively Collected Fractions from the Wilmington Petroleum Extract


Ni, (ppm) Wt. of Collected fraction, (mg) Nickel Complexes, (wt %)

ODS I

ODS II

8,040 60 4.1

11,000 25.2 5.7

2

Cyano Peak Γ

14,250 4.0 7.4

Concentrations Determined Using Aqua Regia Conditions and Standards Plots jRechromatography of ODS I Using ODS Column Rechromatography of ODS II Using Cyano Column Assumed Molecular Weight of Complexes 300 - Daltons

Figure 3 shows the elution profile for this separation with the effluent monitored for both UV-vis wavelength of 254 nm, and G F A A wavelength of 232 nm. Organic impurities eluted quickly at approximately 3 minutes. Two fractions of nickel complexes eluted; the first in the 50% methylene chloride solvent mixture. This corresponded to several sharp maxima in the UV-vis monitor. A second fraction eluted shortly after the solvent system was changed to 100% methanol. This fraction corresponded to a broader maximum in the UV-vis monitor. These nickel compounds are more polar than the nickel nonporphyrin model complexes which eluted at approximately 10 percent methanol. In contrast, nickel (II) chloride eluted at approximately 28 minutes, which is substantially longer than the second nickel fraction in Figure 3 and precludes the possibility of inorganic nickel. Table I shows the further concentration of the nickel fraction by chromatography on a cyano column and this corresponds to 7.4 wt % nickel complex in the sample (assuming an average molecular weight of 300 daltons based on model compound elution times from S E C - H P L C - G F A A studies). Mass Spectral Analyses of the Cyano Column Separated Nickel Fraction. In order to inter pret the mass spectral results of the fraction derived from the cyano column separation, we examined in detail, the mass spectral (19) behavior of several nickel and vanadium model compounds by EIMS, F A B , field ionization and field desorption (FI/FD), and chemical ioni zation (CI) in positive or negative ionization modes. Figure 4 shows nickel (II) bis(diethyldithiocarbamate), nickel (II) tetramethyldibenzotetraaza-[14]-annulene (TADA), and nickel (II) bis(dipivaloylmethane) (DPM) by EIMS. A l l three parent ions are observable at m/z 354, 400, and 424 respectively. Even though the parent ion is the dominant ion, for the dithiocarbamate complex, the spectrum is complicated by substantial fragmentation. This extensive fragmentation is not evident for the other model compounds, but the Ni(DPM)n spectrum shows a fragment ion to be the dominant peak. While these spectra give identifiable patterns, they do not exhibit any sys tematic behavior. Interpretation of unknown species can be substantially complicated by the lack of systematic behavior, and we do not necessarily expect to identify the metallononporphyrin compounds by this method. Thin layer and R P - H P L C chromatography indicated that nickel carboxylate model compounds have a very similar polarity behavior, when compared to these concentrated nickel fractions. Because this is the case, nickel carboxylates were selected as model com-

338


uv ( 2 5 4 nm) — *

Nickel Complexes


HPLC Conditions With a Cyano Normal Phase Column Organic Contaminents I

Solvent (%)

Time (min)

CH CI 2

2

Duration (min)

-

100 95 90 50 0

0 3 7 10 15

Nickel Α Δ ( 2 3 2 nm)

0

2 2 2 3

(remainder MeOH)

I— L

10

20

30

E l u t i o n T i m e (min)

Figure 3. H P L C - G F A A Profile for the Nickel Complexes from the Cyano Column Separation of the High Polar Reversed-Phase Fraction of Wilmington Crude Petroleum Extract.

FISH ET AL.



21.

Figure 4. Electron Impact Mass Spectra of Selected Nickel Model Compounds,

339


340


pounds. Carboxylic acids are appropriate choices because they have been detected and characterized in carbonaceous materials and can constitute up to 3 wt % of the crude petroleum (20). We also examined nickel acetate, nickel bis(2-ethylhexanoate), and a naphthenic acid extract from crude petroleum in which the nickel was synthetically placed. Figure 5 shows the Ε IMS of the nickel naphthenates. Clearly, the parent ion homologous series is evident in the spectrum. The naphthenates show even mass molecular ions extending from about m/z 426 to 582. Note, though, the intensity of the molecular ions is substantially less than that of the major fragments. The presence of impurities would easily overwhelm the parent ions, causing substantial interpretation problem in mixtures. The cyano column purified nickel fractions of the Wilmington crude petroleum extract were combined and examined by Ε IMS and compared to the spectra of the nickel model compounds. The spectrum of the purified nickel fraction is shown in Figure 6. Unfor tunately, as expected from the complicated spectrum of the nickel naphthenates, no clearly defined metallo-nonporphyrin species are identifiable. Several homologous series are discer nible, but their association with nickel is tenuous. The cyano column purified nickel fraction was also examined by Ε IMS for metallopetroporphyrins at m/z values where porphyrins should be detected (not shown). A t the concentration of nickel in this sample, the petroporphyrins would be overwhelmingly evi dent; however, no porphyrins were detected. Thus, it is evident that these compounds are not metallopetroporphyrins. Positive Ion Fast Atom Bombardment (FAB+) Mass Spectroscopic Analyses of the Cyano Column HPLC Fractions. F A B + is a particularly efficient method for examining polar components in hydrocarbon mixtures. The technique allows the observation of the polar portion of a sample without the complication of the neutral organic components (these are not observed by the F A B + technique), and greatly simplifies analyses of the spectra. In addition, only certain ionic species are observable, i.e., vanadium and nickel complexes do not show ligand-metal ions, while calcium, magnesium, silver, and iron do show these ions. In addition, only certain metal complexes are also seen, e.g., porphyrins and acetylacetonates are not necessarily observed, while carboxylic acid complexes are observed. Several carboxylic acid model compounds were examined by F A B + . Nickel (II) bis(2ethylhexanoate) was examined using triethanolamine (TEA) as the hydrogen source. Although some fragments of the acid are apparent in the spectrum (not shown), the parent ions necessary for identification of the model compound are not present in high enough con centration to be evident. Fragments of Ni + T E A are also evident. In the FAB4- spectrum, the metal ion fragments from the complex are detected, but the ligands are not apparent. Figure 7 shows the F A B + spectrum of nickel naphthenates and T E A , which also gave rea sonable Ε IMS spectra (Figure 5). The metal-ligand parent ions are not obvious; however, Ni + T E A ions are evident. Although the technique is not viable for ligand identification, it may have utility for metal ion identification. Recent developments (21) have shown, using calcium compounds with a F A B + ion source, well resolved spectra of naphthenic (carboxylic) acids. This technique exchanges the metal ion of the complex with calcium and gives a calcium naphthenate ion spectrum. Fig ure 8 shows the F A B + spectrum of the nickel naphthenate mixture with T E A and calcium acetate. Several homologous series of carboxylic acids + Ca + T E A are apparent in the spectrum. (FAB- shows the naphthenic acid series with a maximum at m/z of 251.) These match identically to F A B + spectra of calcium naphthenates synthetically prepared from the same naphthenic acid source. The F A B + results of several carboxylic acid model com pounds of different metals also responded similarly with calcium compounds and T E A . The results of these experiments and the development of the technique will be published else where (21). The cyano column purified nickel fraction from the Wilmington crude petroleum extract was examined by the F A B + metal exchange technique. The F A B + spectrum of the fraction with just T E A shows no apparent parent ions, just the N i J T E A ^ ion. This feature was also common to model compound spectra. Figure 9 shows the corresponding F A B +


21. FISH ET AL.


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FISH ET AL.


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A||sua|U|

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spectrum with Ca and T E A . Apparently, there are several homologous series of nickel com pounds that are thought to be carboxylic acids complexes. In addition, detailed examina tion of the spectrum further shows that carboxylic acids are possible binding sites for the nickel, when compared to the Ε IMS spectrum of the same material (Figure 6). Reactions 1 through 8 are presumed to take place as the calcium and T E A doped with the nickel fraction is bombarded with krypton neutral atoms in the fast atom bombardment process. These reactions explain most of the ions observed in the metal atom exchange technique. The mechanism of this exchange has not been elucidated, but the nickel appears to be removed, and the calcium complex is formed with only one carboxylic acid ligand. The other coordination site on the calcium is taken with a T E A fragment (this adds m/z of 189 to the free acid parent fragment). (RC0 ) Ni + T E A + C a 2

2

2 +

—

[RC0 CaTEA]

—


+

(l)

2

JRC0 Ca2TEA ] 2

(2)

[(NiTEA) ]+

(3)

2

-

2

+

m/z 411

->

[(CaTEA) ]+ 2

(4)

m/ζ 375

-

+

(5)

+

(6)

[NiTEA ] 2

m/z 355 -*

[caTEA ] 2

m/ζ 337

—

[NÎTEA]

+

(7)

+

(8)

m/z 206

—

|CaTEAJ

m/z 188 The acid molecular weight can be ascertained from the EIMS of the sample. In the ELMS, the intensity of the metal-containing molecular ion is about 1/200 of the fragments. As a result, when comparing the F A B + spectrum to the EIMS spectrum of the same material, one must look for the acid anion in the EIMS spectrum, not the nickel complex. In Figure 9, three homologous series are clearly indicated with the possibility of several more. The corresponding carboxylic acid fragment, as observed in the EIMS spectrum (Figure 6) of the sample, are indicated in parentheses above the corresponding metal-ligand peak. The homologous series in the FAB-f spectrum starting at m/z 422 could correspond to the EIMS series starting at m/z 233. This series is apparent in the EIMS figure on the lower right side of the massive peak ( m/z 373 and 359). This could be attributed to four ring saturated naphthenic acids. Likewise, the homologous series starting at m/z 410 in the

21. FISH ET AL.


341


F A B + spectrum possibly correlates with three ring saturated naphthenic acids, and the series starting at m/z 440 corresponds to two ring saturated naphthenic acids. The two most intense peaks in Figure 9 correspond to the C20 four ring saturated acid at m/z 506 and the C15 four ring saturated acid at m/z 436 and can be related by an isoprene unit (C5). This suggests the two, three, four, and five ring components are due to bicyclic sesquiterpanoic, tricyclic diterpanoic, and four and five ring triterpanoic (steranoic and hopanoic) acids. Figure 10 shows generalized structures of these acid ligands. Model compound data, by the metal replacement technique, also indicates replacement reactions as shown in reaction 2. This reaction adds another 187 mass units to the molecule. Although, peaks corresponding to the homologous series formed by reaction 2 can be located in the F A B + spectrum (not shown), the noise inhibits any clear identification of these species. RP-HPLC-GFAA Studies on Gilsonite. Gilsonite, a bitumen (Eocene, Unita Basin, Utah), has a high concentration of nickel (100 wppm), but a low concentration of vanadium. We chose Gilsonite as another possible source of the highly polar nickel compounds, because it already had been examined for petroporphyrins (22). In addition, Gilsonite is associated with the Green River Formation and has petroporphyrins which should have experienced mild thermal alterations. Thus, we wanted to ascertain whether the presumed nickel carboxylates in Wilmington crude petroleum were present in Gilsonite. Gilsonite was dissolved in T H F and separated on the C-18 ODS column and the effluent monitored by G F A A . Figure 11 shows the nickel R P - H P L C - G F A A profile of the column effluent, which was also monitored at 320 and 408 nm. Three different component classes containing nickel were separated: compounds eluting at 1) the solvent front, 2) 24 minutes (80% THF), and 3) 36 minutes (100% THF). The most polar nickel components eluted at the solvent front, but are in minor amounts compared to other bands. The middle fraction eluted at the same time as nickel etioporphyrin. The 408 nm response also indi cates that at least some of these compounds are porphyrins. We did not have standards which elute at the same time as the third fraction (36 min). The prominent Soret indicates these are petroporphyrin components. Unfortunately, we have not been able to obtain the needed concentrations of this highly polar nickel compound fraction to verify the metalcontaining components by F A B + as nickel carboxylates. However, we speculate that these are small amounts of nickel carboxylates in Gilsonite, which are potential conduits for nickelation of porphyrin ligands during fossilization. Conclusion We have separated pyridine/water extracts of selected crude petroleums by reversed-phase chromatography, and examined the vanadium-containing compounds in the moderate and low polar fractions by mass spectroscopy. The EIMS results indicated vanadyl petropor phyrins in Cerro Negro and Wilmington moderate polar fraction and possibly in the Wilm ington low polar fraction. The EIMS results provided no additional information on the metallo-nonporphyrins. By further purification of the highly polar fraction from the ODS separation of the Wilmington crude petroleum extract, we have seen evidence of bonding for at least one type of nickel-containing nonporphyrin compound. EIMS and FAB-f with metal exchange indi cates this nickel is bound as carboxylates (naphthenates). We are continuing our molecular characterization studies in order to further determine the highly polar nickel compounds as carboxylic salts and as well in our attempts to iden tify the vanadyl nonporphyrin compounds found in heavy crude petroleums and their pre cursors. Experimental The reversed-phase separations were performed by methods and on equipment described previously (1,2). EIMS were obtained on equipment described previously (23). The vana dyl etio and D P E P petroporphyrins were observed, when present, around m/z of 500. In addition, a plethora of peaks is also evident. This overwhelming continuum was charac teristic of all fractions studied, and prevented us from using EIMS for any metal characteri zation other than vanadium p^t^r^yyr^^||inQJj^?|^ρ tJ^gj^-^PLC fractions.

Library 1155 16th St., N.W. Washington. D.C 20036

348


Triterpanes Steranes

Diterpanes


ÔH

Sesquiterpenes

Figure 10. Possible Carboxylic Acid Ligands for Nickel Complexes in the Cyano H P L C Column Purified Nickel Fraction from Wilmington Crude Petroleum.

UV, λ = 320 η m

Nickel AA

232 nm — γ 2.5

10.5

18.5

27.5

35.5

43.5

Min

Figure 11. RP-HPLC-GFAA Nickel Profile for a Gilsonite Sample Dissolved in THF.

21.

FISH ET AL.


349

The separation procedures for the nickel carboxylate fraction isolated from Wilmington crude petroleum utilized both reversed-phase (ODS) and cyano normal phase H P L C techniques and details will be published elsewhere (24)· The F A B + mass spectral methods will also be discussed elsewhere (21). Model compounds for the studies were either purchased from Alfa Chemical Company, or synthesized by literature methods. The Gilsonite sample was separated by R P - H P L C - G F A A techniques and details will be reported elsewhere (2\). Acknowledgments We thank John J. Komlenic and Alejandro Izquierdo for experimental assistance, Dr. Geoffrey Eglinton of the University of Bristol for helpful suggestions, and Dr. Robert M . Carlson of Chevron Oil Field Research for the Gilsonite sample. The Lawrence Berkeley Laboratory studies were support by the Assistant Secretary of Fossil Energy, Division of Oil, Gas, and Shale technology, and the Bartlesville Project Office of the U.S. Department of Energy under contract DE-AC03-765F00098.


Literature Cited (1) Fish, R.H.; Komlenic, J.J. Anal. Chem. 1984, 56, 510. (2) Fish, R.H.; Komlenic, J.J.; Wines, B.K. Anal. Chem. 1984, 56, 2452. (3) Boduszynski, M.M.; McKay, J.F.; Latham, D.R. Assoc. of Asphalt Paving Tech. 1980, 49, 123. (4) Boduszynski, M.M. In "Chemistry of Asphaltenes." J.W. Bunger (ed.), Adv. in Chem. Ser. 1981, 195, 119. (5) Reynolds, J.G.; Gallegos, E.J.; Fish, R.H.; Komlenic, J.J. Submitted to Energy and Fuels 1986. (6) Dickson, F.E.; Kunesh, C.J.; McGinnis, E.L.; Petrakis, L. Anal. Chem. 1972, 44, 978. (7) Dickson, F.E.; Petrakis, L. Anal. Chem. 1974, 44, 1129. (8) Yen, T.F.; Boucher, L.J.; Dickie, J.P.; Tynan E.C.; Vaughan, G.B. J. Inst. Petrol. 1969, 55, 87. (9) Yen, T.F. In "The Role of Trace Metals in Petroleum." T.F. Yen (ed.), Ann Arbor Sci., 1975, Ann Arbor, MI. Chap. 1, 1. (10) McCormick, B.J.; Bellott, E.M. Inorg. Chem. 1970, 9, 1779. (11) More, K.M.; Eaton, S.S.; Eaton, G.R. J. Amer. Chem. Soc. 1981, 103, 1087. (12) Ocampo, R.; Callot, H.J.; Albrecht, P. J. Chem.Soc.,Chem. Comm. 1985, 198. (13) Blumer, M.; Synder, W.D. Chem. Geol. 1967, 2, 35. (14) Blumer, M.; Rudrum, R. J.Inst.of Petrol. 1970, 56(548), 99. (15) Johnson, J.V.; Britton, E.D.; Yost, R.A.; Quirke, J.M.E.; Cuesta, L.L. Anal. Chem. 1986, 58, 1325. (16) Reynolds, J.G. Liq. Fuels Tech. 1985, 3(1), 73. (17) Reynolds, J.G.; Biggs, W.R.; Fetzer, J.C. Liq. Fuels Tech. 1985, 3(4), 423. (18) O'Laughlin, J.W. J. of Liq. Chrom. 1984, 7, 127. (19) Reynolds, J.G.; Gallegos, E.J.; Fish, R.H. Manuscript in preparation, 1986. (20) Seifert, W.K. Progress in Chem. Org. Nat. Products 1975, 32, 1. (21) Gallegos, E.J.; Reynolds, J.G.; Fish, R.H. 33rd Annual Conference on Mass Spectrometry and Allied Topics, San Diego, 1985. (22) Quirke, J.M.E.; Eglinton, G.; Maxwell, J.R. J. Amer. Chem. Soc. 1979, 101, 7693. (23) Sundararaman, P.; Gallegos, E.J.; Baker, E.W.; Slayback, J.R.B.; Johnston, M.R. Anal. Chem. 1984, 56, 2552. (24) Fish, R.H.; Reynolds, J.G.; Gallegos, E.J. Manuscript in preparation, 1986. RECEIVED November 13, 1986

C h a p t e r 22 Gel of

Permeation Metalloporphyrins

Chromatographic from

a

Rock

Behavior Extract

G. Šebor


Department of Petroleum Technology and Petrochemistry, Institute of Chemical Technology, 166 28 Prague 6, Czechoslovakia

The number of carbon atoms present in the porphine substituents and mainly the d i f f e r e n t geometry of n i c k e l and vanadyl ions i n the molecule of metalloporphyrins were found to be the main factors i n fluencing the GPC separation of these e t i o and deoxophylloerythroetio type complexes. This chromatographic technique provided an e f f e c t i v e separation of n i c k e l from vanadyl porphyrins present i n a rock extract from the vicinity of petroleum dep o s i t i n the Persian Gulf area. Both met a l l o p o r p h y r i n s were i s o l a t e d by the comb i n a t i o n of adsorption chromatography on silica gel and GPC on s t y r e n e - d i v i n y l b e n zene copolymer. In order to study the GPC behavior of these complexes, GPC f r a c t i o n s were c o l l e c t e d and and analyzed by mass spectrometry. For many y e a r s a l r e a d y , c o n s i d e r a b l e a t t e n t i o n has b e e n p a i d t o t h e c h a r a c t e r o f n i c k e l and v a n a d y l p e t r o p o r p h y r i n s found i n f o s s i l f u e l s and b o t h a n c i e n t and r e c e n t sediments. The knowledge o f t h e type o f p e t r o p o r p h y r i n s found i n f o s s i l f u e l s i s s i g n i f i c a n t b o t h f o r g e o c h e m i c a l c o r r e l a t i o n s and f o r t h e s t u d y o f t h e b e h a v i o r o f b o t h types of the r e l e v a n t m e t a l l o p o r p h y r i n s d u r i n g f o s s i l fuels processing. An e f f e c t i v e s e p a r a t i o n o f p e t r o p o r p h y r i n s from t h e sample i s a n e c e s s a r y p r e r e q u i s i t e f o r t h e i r d e t a i l e d characterization. The methods used f o r t h e s e p a r a t i o n o f p e t r o p o r p h y r i n s may be d i v i d e d i n t o two b a s i c g r o u p s , v i z . e x t r a c t i o n methods and c h r o m a t o g r a p h i c methods. An a p p r o p r i a t e c o m b i n a t i o n o f b o t h t y p e s o f methods i s a l s o applied very f r e q u e n t l y . Numerous o r g a n i c s o l v e n t s and b o t h o r g a n i c and m i n e r a l a c i d s have been used as e x t r a c t i o n r e a g e n t s (J_). I t i s e s p e c i a l l y the e x t r a c t i o n



22.

SEBOR

Gel Permeation Chromatographic Behavior of Metalloporphyrins

351

of p e t r o p o r p h y r i n s w i t h an a c i d , w h i c h s t a r t s as a demet a l a t i o n o f the m e t a l l o p o r p h y r i n s p r e s e n t , and i s f r e q u e n t l y used as the f i r s t s t e p i n the i s o l a t i o n o f the r e l e v a n t compounds (2_) . T h e r e i s a d i s a d v a n t a g e however, i n t h a t changes i n the o r i g i n a l s t r u c t u r e o f the com pounds may o c c u r d u r i n g d e m e t a l a t i o n and the s u b s e q u e n t e x t r a c t i o n of f r e e p o r p h y r i n s ( 3_~6_) . The b a s i c a s s u m p t i o n made i s t h a t e v e r y compound decomposes to the same e x t e n t , e.g. the r e l a t i v e amounts of the v a r i o u s compounds p r e s e n t a r e unchanged a f t e r d e m e t a l a t i o n (2). In the f i e l d o f c h r o m a t o g r a p h i c methods, h i g h - p e r formance l i q u i d c h r o m a t o g r a p h y has r e c e n t l y been c o n s i d e r e d an e x t r e m e l y p r o m i s i n g t e c h n i q u e (7_~J_2 ) . This chromatographic t e c h n i q u e e n a b l e s s e p a r a t i o n of homolo gous s e r i e s and t y p e s o f m e t a l l o p o r p h y r i n s as w e l l as s t r u c t u r a l i s o m e r s ( j j O . W i t h the e x c e p t i o n of i o n - e x change c h r o m a t o g r a p h y , o t h e r l i q u i d c h r o m a t o g r a p h y t e c h n i q u e s have been employed f o r p e t r o p o r p h y r i n s s e p a r a t i o n s , v i z . a d s o r p t i o n column c h r o m a t o g r a p h y , t h i n l a y e r c h r o m a t o g r a p h y , p a p e r c h r o m a t o g r a p h y , and g e l permeation chromatography (2). The l a s t method has been used by some a u t h o r s f o r s e p a r a t i o n of n i c k e l and v a n a d y l p o r p h y r i n s ( J_3^, Jj_4_ ) . To d a t e however the mechanism o f GPC s e p a r a t i o n of t h e s e compounds has not been d i s c u s s e d i n a d e t a i l e d manner. In the p r e s e n t p a p e r , the c h a r a c t e r i s t i c s o f n i c k e l and v a n a d y l p o r p h y r i n s , found i n the r o c k e x t r a c t o b t a i n e d i n the v i c i n i t y of c r u d e o i l d e p o s i t s , a r e presented. The r e l e v a n t m e t a l l o p o r p h y r i n s have been s e p a r a t e d by a c o m b i n a t i o n o f a d s o r p t i o n c h r o m a t o g r a p h y on s i l i c a g e l and GPC on a s t y r e n e - d i v i n y l b e n z e n e c o p o lymer. Gel permeation chromatographic b e h a v i o r of n i c k e l and v a n a d y l m e t a l l o p o r p h y r i n s has been s t u d i e d i n a d e t a i l e d manner. Experimental Sample P r e p a r a t i o n . D r i l l i n g s were made to a d e p t h of 6 m i n the v i c i n i t y of c r u d e o i l d e p o s i t s i n the P e r s i a n Gulf area. The r o c k e x t r a c t s o b t a i n e d from the b o r e h o l e were c r u s h e d ; 450 g were e x t r a c t e d w i t h benzene i n a S o x h l e t e x t r a c t o r and the e x t r a c t s were w e i g h e d . The y i e l d s of e x t r a c t a b l e mass were w i t h i n the range of 0.1-15 wt%, u s u a l l y about 0.15 wt% . E x t r a c t samples marked KB6a, KB7a, and KB9b were s u p p l i e d by P r o f e s s o r W. D. Gill. The o r i g i n a l e x t r a c t s were c h a r a c t e r i z e d by means of t h e i r c o n t e n t of n i c k e l , vanadium, and m e t a l l o p o r p h y r i n s ; the r e s u l t s have been p u b l i s h e d p r e v i o u s l y (j_5_) . F o r the p r e s e n t s t u d y , the KB6a sample has been chosen. A d s o r p t i o n Chromatography. A d s o r p t i o n chromatography of the e x t r a c t was c a r r i e d out on a g l a s s column C60 cm χ 8 mm i . d . ) p a c k e d w i t h s i l i c a g e l (Woelm Eschwege)


352


d e a c t i v a t e d by a d d i t i o n o f 3 wt% w a t e r . Saturated hydro c a r b o n s and a r o m a t i c s were e l u t e d w i t h 50% e t h e r i n pentane. The m e t a l l o p o r p h y r i n s were e l u t e d w i t h e t h e r . The e l u e n t was d e l i v e r e d w i t h a MC 300_micropump ( M i c r o t e c h n a , P r a g u e ) a t a f l o w r a t e o f 1 mL min and m o n i t o r e d w i t h a UV-VIS d e t e c t o r (KNAUER) f o r q u a n t i t a t i v e i s o l a t i o n of metalloporphyrins. The d e t e c t o r was s e t a t 400 nm. Gel Permeation Chromatography. Gel permeation chromato g r a p h y of the m e t a l l o p o r p h y r i n s c o n c e n t r a t e was performed on a g l a s s column (150 cm χ 14 mm i . d . ) p a c k e d w i t h a s t y r e n e - d i v i n y l b e n z e n e c o p o l y m e r c o n t a i n i n g 3 wt% o f d i v i n y l b e n z e n e C t h e g e l was p r e p a r e d at the I n s t i t u t e o f Macromolecular C h e m i s t r y , C z e c h o s l o v a k Academy o f S c i e n ces, Prague). The g e l was c h a r a c t e r i z e d by p a r t i c l e s i z e of 40-120 ,um and an e x c l u s i o n l i m i t of about 2000. It was s w e l l e d i n a methano1-benzene m i x t u r e c o n t a i n i n g 10% methanol. The column was c l o s e d a t b o t h ends w i t h b r a s s s t o p p e r s e q u i p p e d w i t h T e f l o n s e a l s , and the g e l was f i x e d on b o t h ends by a g l a s s wool l a y e r . The m e t h a n o l -benzene m o b i l e phase was d e l i v e r e d by means o f a d e v i c e w o r k i n g on_îjIar i o 11 i s p r i n c i p l e ; a c o n s t a n t f l o w r a t e of 1.5 mL min was m a i n t a i n e d . A s i x way s t o p cock w i t h a s a m p l i n g l o o p was used f o r the i n j e c t i o n o f the m e t a l l o p o r p h y r i n s c o n c e n t r a t e p r e p a r e d by a d s o r p t i o n c h r o m a t o graphy. The e l u e n t was c o n s t a n t l y m o n i t o r e d w i t h a UV-VIS d e t e c t o r (KNAUER) s e t at 550 and 572 nm, respectively . -

Mass S p e c t r o m e t r y . Mass s p e c t r a were r e c o r d e d on an A . E . I . MS 902 s p e c t r o m e t e r at an i o n i z a t i o n e n e r g y o f 70 eV. The samples were i n t r o d u c e d by means o f a d i r e c t i n s e r t i o n probe. The mass s c a l e was c a l i b r a t e d w i t h the use of p e r f l u o r o t r i b u t y l a m i n e . S p e c t r a were measured w i t h a r e s o l u t i o n o f 3000 on a 10% v a l l e y . Results

and

Discussion

By means of a d s o r p t i o n c h r o m a t o g r a p h y of the r o c k e x t r a c t , about 100 mg o f a c o n c e n t r a t e o f n i c k e l and v a n a d y l p o r p h y r i n s was o b t a i n e d . The c o u r s e o f GPC a n a l y s i s o f the c o n c e n t r a t e i s shown i n F i g u r e 1. It i s evident that g e l c h r o m a t o g r a p h y r e s u l t e d i n an e f f e c t i v e s e p a r a t i o n o f n i c k e l and v a n a d y l p o r p h y r i n s p r e s e n t i n the above mentioned c o n c e n t r a t e . The f a c t t h a t v a n a d y l p o r p h y r i n s are e l u t e d from the column e a r l i e r t h a n n i c k e l p o r p h y r i n s means t h a t the s e p a r a t i o n of b o t h m e t a l l o p o r p h y r i n s i s p r o b a b l y c o n t r o l l e d by the s t e r i c f a c t o r to a c o n s i d e r a b l e d e g r e e . The c o o r d i n a t i o n s p h e r e geometry o f n i c k e l p o r p h y r i n s i s p l a n a r , the n i c k e l atom b e i n g l o c a t e d i n the p l a n e formed by the n i t r o g e n atoms of the f o u r p y r r o l e r i n g s t h a t form the b a s i c p o r p h y r i n s k e l e t o n . Vanadyl p o r p h y r i n s are complex compounds w i t h t e t r a g o n a l p y r a m i d a l g e o m e t r y ,

22.


SEBOR

Fractions

1


τ

I

100

2 1

3 1

4 1

5 1

6 ι

1

150

7 1

Γ

ι

I

200 Elution

250 volume

(mL)

F i g u r e 1. Chromatogram of m e t a l l o p o r p h y r i n s i s o l a t e d from a r o c k sample on s t y r e n e - d i v i n y l b e n z e n e c o p o l y m e r ( a - t h e e l u t i o n c u r v e of v a n a d y l p o r p h y r i n s , b - t h e e l u t i o n c u r v e of n i c k e l p o r p h y r i n s )

353


354


w i t h the oxygen atom o c c u p y i n g the apex of the p y r a m i d and the v a n a d y l group l y i n g o u t s i d e the p l a n e formed by the f o u r n i t r o g e n atoms. A l s o , i t may be d e r i v e d from the c o u r s e o f e l u t i o n o f b o t h m e t a l l o p o r p h y r i n s o b s e r v e d t h a t the a n a l y z e d c o n c e n t r a t e of m e t a l l o p o r p h y r i n s i s a complex m i x t u r e of the r e l e v a n t compounds. In o r d e r to s t u d y the GPC b e h a v i o r of b o t h t y p e s of m e t a l l o p o r p h y r i n s on the s t y r e n e - d i v i n y l b e n z e n e c o p o l y m e r , s e v e n f r a c t i o n s were c o l l e c t e d C s e e F i g u r e 1] and a n a l y zed by mass s p e c t r o m e t r y . T a b l e s I and I I p r e s e n t a summary of the mass s p e c t r o m e t r i c d a t a o b t a i n e d . In f r a c t i o n s 1, 2, and 3, the f o l l o w i n g i o n s have been i d e n t i f i e d ( s e e T a b l e I ) : i o n s of the homologous s e r i e s of v a n a d y l p o r p h y r i n s o f the e t i o t y p e (M=375+14n, where η i s an i n t e g e r ) , and i o n s of the homologous s e r i e s of v a n a d y l p o r p h y r i n s of the d e o x o p h y l l o e r y t h r o e t i o t y p e (the mass of w h i c h i s M=373+14m, where m i s an i n t e g e r £ 2). With r e s p e c t to the i d e n t i f i e d members of homolo gous s e r i e s of b o t h t y p e s of v a n a d y l p o r p h y r i n s i n GPC f r a c t i o n s ( T a b l e I ) , i t may be d e m o n s t r a t e d t h a t GPC b e h a v i o r of t h e s e compounds i s a f f e c t e d by the m o l e c u l a r sieve e f f e c t , i . e . , t h e i r separation c o r r e l a t e s roughly w i t h the number of c a r b o n atoms i n t h e i r p o r p h i n e substituents. In f r a c t i o n no. 4, two s e r i e s of i o n s have been i d e n t i f i e d : M =371+14n, M =379+14n; f o r b o t h s e r i e s , η l i e s i n the range of 7-11. From the t h e o r e t i c a l p o i n t of v i e w , any of the f o l l o w i n g s t r u c t u r e s may be a s c r i b e d (16) to the M.j s e r i e s of mass l i n e s : p o r p h i n e d e r i v a t i v e s w i t h two i s o c y c l i c r i n g s i n t h e i r m o l e c u l e s (12)» c h l o r i n s w i t h one b enzo s ub s t i t uent on p y r r o l e i n f>, (> p o s i t i o n (Η Β ^ ) , c h l o r i n s w i t h t h r e e i s o c y c l i c r i n g s ( H J I ^ ) , or p o r p h y r i n s w i t h t h r e e b e n z o s u b s t i t u e n t s on p y r r o l e r i n g s i n f>, β' p o s i t i o n s (Ββ)· case of the s e r i e s of mass l i n e s , the f o l l o w i n g s t r u c t u r e s may be c o n s i d e r e d (j_6): c h l o r i n s i n w h i c h the (>, f! d o u b l e bond on a n o t h e r p y r r o l e i s a l s o h y d r o g e n a t e d , i . e . tetrahydroporphyrins ( l ^ ) , hexahydroporphyrins w i t h one i s o c y c l i c r i n g ( H ^ I j ) , p o r p h y r i n s w i t h two i s o c y c l i c r i n g s and one b e n z o - s u b s t i t u e n t (B 1 ^ ) , or t e t r a b e n z o p o r p h y r i n s ( B , ) . E x a c t mass measurements have not been c a r r i e d o u t . A d e t a i l e d a n a l y s i s of f r a c t i o n 4 was beyond the s c o p e of the p r e s e n t s t u d y . 1

I

n

F r a c t i o n s 5, 6, and 7 c o n t a i n e d n i c k e l p o r p h y r i n s . As i n the c a s e of v a n a d y l p o r p h y r i n a n a l y s i s , members of the homologous s e r i e s of DPEP and e t i o p o r p h y r i n s have been i d e n t i f i e d i n t h e s e f r a c t i o n s ( s e e T a b l e I I ) . In t h i s c a s e , the e v a l u a t i o n of mass s p e c t r a o b t a i n e d i s somewhat more c o m p l i c a t e d due to the f a c t t h a t n i c k e l has several natural isotopes ( N i 67.88%; N i , 26.23%; N i , 1.19%; N i , 3.66%; and N i , 1.08%). The e v a l u a t e d i n t e n s i t i e s may be used f o r d e t e r m i n a t i o n of Ι^_,_ 60 . i n t e n s i t i e s as f o l l o w s : DPEP Ni 26.23 DPEP °Ni DPEP Ni 67 .88 b Z

η

6 4

Λ7

I

6

= I

5 8

detected

Data

Spectrometric

atoms s u b s t i t u t e d on

porphine

from

GPC

f r o m GPC

DPEP r a n g e Maximum Molecular nC Molecular nC ions ion 574-504 15-10 518 1 1 546-476 13- 8 490 9 518-434 11-5 462 4

F r a c t i o n s Trapped

DPEP r a n g e Maximum Molecular nC Mo 1 e c u l a r nC ions ion 639-541 19-12 541 1 2 597-485 16- 8 10 513 555-457 13- 6 485 8 n.d.

P o r p h y r i n s F r a c t i o n s Trapped

f o r Nickel Porphyrins

Maximum M o l e c u l a r nC ion 520 1 1 492 9 464 7

Data

porphine

Maximum M o l e c u l a r nC ion 543 1 2 515 10 487 8

f o r Vanadyl

atoms s u b s t i t u t e d on

E t i o range^ Molecular nC ions 576-506 15-10 548-478 13- 8 520-436 11-5

Mass

of carbon

Figure 1

number

see

5 6 7

3

Table I I .

not

Spectrometric

E t i o range^ Molecular nC ions 641-543 19-12 599-487 16- 8 557-459 13- 6 η .d.

Mass

number o f c a r b o n

Fractions

a

3

I.

see F i g u r e 1

1 2 3 4

Fractions

Table



356

I t i s a l s o p o s s i b l e to i d e n t i f y i n the s p e c t r a a s e r i e s of i o n s f o r w h i c h M= 366+1 4m. T h e i r i n t e n s i t i e s may be e x p r e s s e d as


1=1

DPEP

6C\ .+I · 58 . Ni etio Ni 7

XT

Consequently, I . may be o b t a i n e d v i a s u b t r a c t i o n from I. As seen from èfie mass s p e c t r o m e t r i e d a t a shown i n T a b l e I I , the GPC b e h a v i o r of n i c k e l p o r p h y r i n s i s a l s o a f f e c t e d by the m o l e c u l a r s i e v e e f f e c t . On the b a s i s of the c o u r s e of e l u t i o n o b s e r v e d f o r n i c k e l and v a n a d y l p o r p h y r i n s ( F i g u r e 1) and mass s p e c t r o m e t r i c d a t a ( T a b l e s I and I I ) , the f o l l o w i n g c o n c l u s i o n s are d e r i v e d : The p r i m a r y f a c t o r a f f e c t i n g GPC b e h a v i o r of b o t h m e t a l l o p o r p h y r i n s i s the geometry of the n i c k e l i o n or the v a n a d y l i o n i n the m é t a l l o porphyrin molecule. To a l e s s e r e x t e n t , t h i s b e h a v i o r a l s o depends upon the number of c a r b o n atoms i n p o r p h i n e sub s t i t u e n t s . These c o n c l u s i o n s a r e c o n f i r m e d by the f a c t t h a t , i n f r a c t i o n no. 3 f o r example ( e l u t i o n volume 141-164 mL), v a n a d y l p o r p h y r i n s w i t h the f o l l o w i n g v a l u e s of m o l e c u l a r mass have been i d e n t i f i e d : 457, 459, 471, 473, 485, and 487. On the o t h e r hand, i n f r a c t i o n 6, w i t h a h i g h e r e l u t i o n volume (175-200 mL), n i c k e l p o r p h y r i n s of m o l e c u l a r mass between 504 and 576 have been i d e n t i f i e d . Gel permeation chromatography enables e f f e c t i v e s e p a r a t i o n s of n i c k e l and v a n a d y l p o r p h y r i n s . Its a p p l i c a t i o n i s a d v a n t a g e o u s p a r t i c u l a r l y as the f i r s t step i n q u a n t i t a t i v e i s o l a t i o n of m e t a l l o p o r p h y r i n s found i n a s p h a l t e n e s from v a r i o u s t y p e s of f o s s i l f u e l s . In c o n t r a s t to the commonly a p p l i e d e x t r a c t i o n of m e t a l l o p o r p h y r i n s w i t h an a c i d , GPC s e p a r a t i o n of the r e l e v a n t compounds i s n o n - d e s t r u c t i v e and e n a b l e s to o b t a i n a r e p r e s e n t a t i v e c o n c e n t r a t e of m e t a l l o p o r p h y r i n s p r e s e n t i n an a n a l y z e d sample. Acknowledgments I would l i k e to thank P r o f e s s o r W. D. G i l l , I m p e r i a l C o l l e g e , London f o r p r o v i d i n g the r o c k e x t r a c t s t u d i e d and Dr. V. K u b e l k a , Department of Mass S p e c t r o m e t r y , I n s t i t u t e of C h e m i c a l T e c h n o l o g y , P r a g u e f o r m e a s u r i n g the mass s p e c t r a . Literature Cited 1.

2. 3. 4.

B a k e r , E. W. i n " O r g a n i c G e o c h e m i s t r y " ; Eglinton, G.; Murphy, M. T. J . , E d s . ; S p r i n g e r - V e r l a g : Berlin- H e i d e l b e r g - N e w Y o r k , 1969; p. 464. Š e b o r , G.; W e i s s e r , O.; Novák, M. Chem. listy 1979, 73, 23. Howe, W. W.; B l u m e r , M. A n a l . Chem. 1961, 33, 1288. M i l l s o n , M. F.; Montgomery, D. S.; Brown, S. R. Geochim. Cosmochim. A c t a 1966, 30, 207.

22.

SEBOR

5.

6. 7.

8. 9. 10.


11.

12. 13. 14. 15. 16.


S u g i h a r a , J. M.; B r a n t h a v e r , J. F.; Wu, G. Y.; W e a t h e r b e e , C. D i v . o f Petrol. Chem., ACS 1970, 15, C5. Chang, Y.; C l e z y , P. S.; Morell, D. B. Australian J . Chem. 1967, 20, 959. H a j i b r a h i m , S. K.; Tibbetts, P. J. C.; W a t t s , C. D.; M a x w e l l , J . R.; Eglinton, G.; Colin, H.; G u i o c h o n , G. A n a l . Chem. 1978, 50, 549. E k s t r o m , Α.; L o e h , Η.; D a l e , L. D i v . o f Petrol. Chem., ACS 1983, 28, 166. F i s h , R. H.; K o m l e n i c , J. J. A n a l . Chem. 1984, 56, 510. F i s h , R. H.; K o m l e n i c , J. J.; Wines, Β . K. Anal. Chem. 1984, 56, 2452. Vásquez, Y.; C e b a l l o , C.; Sánchez, V.; C a r b o g n a n i , L.; S u c r e , L.; L u b k o w i t z , J. P r o c . Int. Symposium on "Characterization o f Heavy Crude O i l s and P e t r o l e u m R e s i d u e s " : L y o n , 1984; p. 62. Sundararaman, P. A n a l . Chem. 1985, 57, 2204. R o s s c u p , R. J.; Pohlmann, H. P. D i v . o f Petrol. Chem., ACS 1967, 12, A103. Šebor, G.; W e i s s e r , O.; Šešulka, V. R i v . Combust. 1975, 29, 380. P o p l , M.; Dolanský, V.; Šebor, G.; Stejskal, M. F u e l 1978, 57, 565. Yen, T. F.; B o u c h e r , L. J.; Dickie, J . P.; Tynam, E. C.; Vaughan, G. B. J . Inst. Petrol. 1969, 55, 87.

RECEIVED

November 10, 1986

357

Chapter 23

Analysis of Metal Species in Petroleum and Tar Sands Using the Electron Paramagnetic Resonance and Fourier Transform Infrared Techniques W. R. M. Graham


Department of Physics, Texas Christian University, Fort Worth, TX 76129

The results are reviewed from studies carried out to demonstrate the versatility of the electron paramagnetic resonance (EPR) technique supplemented by Fourier transform infrared (FTIR) spectroscopy in characterizing the metals in crude oils and tar sands. Application of the highly sensitive, but nondestructive, EPR technique can provide detailed information on the occurrence of metals in metalloporphyrins, in other organic complexes, or in associated mineral matter. The vanadyl ion has been identified bound to a porphyrin and associated with clay in tar sand samples. Examples of manganese in bitumen and in carbonate minerals, and the origin of ferric iron are also discussed. The identification of metal species in crude oils, source rocks, tar sands, and oil shales is of fundamental interest in understanding the geochemical origin of petroleum, and has important implications for the extraction, processing, and upgrading of petroleum and synfuels. Just as significant as the identification of the metal elements present, which can be done by standard analytical techniques, is the determination of the site of the metal species. Whether they occur in metalloporphyrins, in other organic complexes in the bitumen, or are associated with minerals or clays, has important consequences for their behavior and influence in processing. Electron paramagnetic resonance (EPR) has several unique advantages over more commonly used analytical techniques. It is extremely sensitive, with the capability of detecting concentrations of metal ions as low as a few ppm. At the same time it is nondestructive, which means that EPR analysis can be carried out without altering the original environment, site, or complex containing the metal species. This is an important advantage since the magnetic constants derived from standard EPR measurements, particularly the g-value and hyperfine splitting constants, are extremely sensitive to the chemical bonding to the paramagnetic ion and the structure in which it is located, and thus they provide an extremely useful probe for the characterization of metals in organic complexes and minerals. 0097-6156/87/0344-0358$06.00/0 © 1987 American Chemical Society


23.

GRAHAM

Metal Species in Petroleum and Tar Sands

359

The purpose o f t h i s paper i s t o demonstrate the k i n d o f i n f o r m a t i o n about m e t a l s p e c i e s i n p e t r o l e u m and s y n f u e l s which can be drawn from the a p p l i c a t i o n o f EPR, supplemented t o some e x t e n t by F o u r i e r t r a n s f o r m i n f r a r e d (FTIR) s p e c t r o s c o p y . Examples are d i s c u s s e d from the r e s u l t s o f work c a r r i e d out i n t h i s l a b o r a t o r y ( 1 - 6 ) , p r i n c i p a l l y on t a r sands, but a l s o on c o a l and p e t r o l e u m . The p r i n c i p l e s i n v o l v e d are g e n e r a l l y a p p l i c a b l e t o p e t r o l e u m and s y n f u e l s . An i n t r i n s i c l i m i t a t i o n o f the t e c h n i q u e which s h o u l d be acknowledged, i s t h a t the m e t a l s p e c i e s i n v e s t i g a t e d must be e i t h e r p a r a m a g n e t i c , f e r r o m a g n e t i c , or f e r r i m a g n e t i c i n o r d e r t o be d e t e c t a b l e u s i n g an EPR s p e c t r o m e t e r ; however, a l a r g e p e r c e n t a g e o f the m e t a l s o f i n t e r e s t such as i r o n , vanadium, and manganese f a l l i n t o these c a t e g o r i e s . B e f o r e a d i s c u s s i o n o f some examples o f the a p p l i c a t i o n o f the EPR t e c h n i q u e to m e t a l s i n p e t r o l e u m and t a r sands, a b r i e f o u t l i n e o f the p r i n c i p l e s o f EPR s p e c t r o s c o p y i s p r e s e n t e d i n the next s e c t i o n . D e t a i l e d t r e a t m e n t s o f EPR t h e o r y at both the i n t r o d u c t o r y (7) and advanced (8) l e v e l s are a v a i l a b l e e l s e w h e r e . H a l l (9,10) has r e viewed the a p p l i c a t i o n o f EPR to s t u d i e s o f c l a y m i n e r a l s . P r i n c i p l e s o f EPR

Spectroscopy

The EPR phenomenon depends on the p r o p e r t y t h a t any atomic or molecu l a r system w i t h one or more u n p a i r e d e l e c t r o n s p o s s e s s e s a magnetic moment which i n t e r a c t s w i t h an a p p l i e d magnetic f i e l d , H. Of p r i n c i p a l i n t e r e s t i n the case o f f o s s i l f u e l s are the t r a n s i t i o n m e t a l i o n s , such as V , M n , or F e , and f r e e r a d i c a l s , which are f r a g ments o f o r g a n i c m o l e c u l e s . In the s i m p l e s t case o f one u n p a i r e d e l e c t r o n ( t o t a l s p i n S = 1/2) the magnetic moment i s a l i g n e d e i t h e r p a r a l l e l or a n t i p a r a l l e l to the e x t e r n a l magnetic f i e l d , c o r r e s p o n d ing to the two s p i n s t a t e s M = -1/2 and +1/2. The d i f f e r e n c e i n energy between these two s p i n s t a t e s i s z e r o i n the absence o f the magnetic f i e l d , but e q u a l t o ggH ( t h e Zeeman s p l i t t i n g ) i n i t s p r e s ence, where $ i Bohr magneton and g i s the g f a c t o r . Thus, as shown i n F i g u r e 1, the energy d i f f e r e n c e i n c r e a s e s w i t h H. A transit i o n can be i n d u c e d between the two s t a t e s by r a d i a t i o n o f f r e q u e n c y V , p r o v i d i n g the resonance c o n d i t i o n H +

2 +

s t

n

3 +

e

hv=

g$H

(1)

is f u l f i l l e d . For an x-band EPR s p e c t r o m e t e r the r e q u i r e d microwave energy i s o f f r e q u e n c y v = 9.2 GHz, and i s f i x e d . The EPR spectrum i s then o b t a i n e d by v a r y i n g the magnetic f i e l d u n t i l the resonance c o n d i t i o n g i v e n by E q u a t i o n 1 i s met. For a f r e e e l e c t r o n g = 2.0023 and the t r a n s i t i o n o c c u r s at -330 mT ( c e n t e r f i e l d ) . The t r a n s i t i o n i s r e c o r d e d as the f i r s t d e r i v a t i v e o f the a b s o r p t i o n c u r v e . C o m p l e x i t y i s i n t r o d u c e d t o the spectrum when the paramagnetic ion p o s s e s s e s a nonzero n u c l e a r s p i n I, which i n t e r a c t s w i t h the e l e c t r o n s p i n S. T h i s i n t e r a c t i o n causes h y p e r f i n e s p l i t t i n g o f the s p i n l e v e l s and, t h e r e f o r e , o f the EPR l i n e s i n t o 2 1 + 1 components. Thus f o r an i o n w i t h I = 1/2 the o r i g i n a l EPR l i n e i s s p l i t i n t o a d o u b l e t as shown i n F i g u r e 1. The magnitude o f the h y p e r f i n e s p l i t t i n g , A, r e f l e c t s the c h a r a c t e r o f the m e t a l l i g a n d bonds. In the more g e n e r a l case o f more than one u n p a i r e d e l e c t r o n , the e x t e r n a l magnetic f i e l d produces 2S + 1 s p i n l e v e l s , and t r a n s i t i o n s


360


H

F i g u r e 1. Energy l e v e l s and a l l o w e d EPR t r a n s i t i o n s f o r a s y s tem w i t h : ( t o p ) a s i n g l e u n p a i r e d e l e c t r o n , S = 1/2; ( m i d d l e ) n u c l e a r s p i n I = 1/2 and S = 1/2, showing the h y p e r f i n e s p l i t t i n g , A; and (bottom) S = 3/2, showing the z e r o - f i e l d s p l i t t i n g , D.

23.

GRAHAM


361


are induced between a d j a c e n t l e v e l s a c c o r d i n g t o the s e l e c t i o n r u l e AM = +1. When the paramagnetic i o n o c c u r s i n a c r y s t a l ( f o r example, i n a m i n e r a l ) the c r y s t a l l i n e f i e l d may be s u f f i c i e n t t o s p l i t the s p i n l e v e l s ( z e r o - f i e l d s p l i t t i n g ) , even i n t h e absence o f an e x t e r n a l f i e l d , as shown i n F i g u r e 1 f o r S = 3/2. S i n c e the c r y s t a l l i n e f i e l d i s determined by the e l e c t r i c charge on n e i g h b o r i n g atoms, the z e r o - f i e l d s p l i t t i n g parameter, D, measured from the EPR spectrum r e f l e c t s the environment o f the paramagnetic i o n . In g e n e r a l , the r e l e v a n t magnetic parameters a r e o b t a i n e d by s o l v i n g the a p p r o p r i a t e s p i n H a m i l t o n i a n H, f o r the r e q u i r e d sym metry : H = 3H.£-S + S-A-I + SvD.S (2) In E q u a t i o n 2, A i s the h y p e r f i n e s p l i t t i n g c o n s t a n t , and D, the z e r o - f i e l d s p l i t t i n g c o n s t a n t . I t i s the e v a l u a t i o n o f g, A, and D which can l e a d unambiguously t o the i d e n t i f i c a t i o n o f both the m e t a l i o n , and the m i n e r a l c r y s t a l o r o r g a n i c m o l e c u l a r s t r u c t u r e i n which i t occurs. Procedure The EPR measurements i n t h i s work were a l l made u s i n g a V a r i a n V-4500 s p e c t r o m e t e r o p e r a t i n g a t 9.2 GHz w i t h 100 kHz magnetic f i e l d modula tion. Samples were p l a c e d i n 3 mm O.D. q u a r t z t u b e s , and the temper a t u r e was c o n t i n u o u s l y m o n i t o r e d w i t h a c h r o m e l - c o n s t a n t a n thermo c o u p l e . A V a r i a n V-4557 v a r i a b l e temperature a c c e s s o r y was used i n r e c o r d i n g s p e c t r a a t temperatures down t o 80 K. The supplementary i n f r a r e d s p e c t r a were r e c o r d e d on a N i c o l e t 5DXE FTIR s p e c t r o m e t e r . Samples were u s u a l l y made f o l l o w i n g p r o c e dures d i s c u s s e d elsewhere (5) i n the form o f p r e s s e d p e l l e t s o f mix t u r e s o f m i n e r a l i n KBr i n a 1:100 r a t i o by w e i g h t . In the case o f the t a r sand samples d i s c u s s e d h e r e , v a r i o u s f r a c t i o n s were o b t a i n e d u s i n g e x t r a c t i o n t e c h n i q u e s which have been p r e v i o u s l y reported i n d e t a i l (3,11). R e s u l t s and D i s c u s s i o n Vanadium. Vanadium i n d i v a l e n t and t e t r a v a l e n t o x i d a t i o n s t a t e s w i t h c o n f i g u r a t i o n s 3 d and 3d , r e s p e c t i v e l y , i s r e a d i l y o b s e r v a b l e by EPR ( 7 , 8 ) . I n c o n t r a s t t o V + and V**"", V + would o n l y be o b s e r v a b l e under s p e c i a l c i r c u m s t a n c e s (7) a t low t e m p e r a t u r e s , and i s l e s s l i k e l y t o be i m p o r t a n t i n f o s s i l f u e l s . I n p e t r o l e u m o r t a r sands V Ή- i s expected t o o c c u r most commonly i n the form o f the v a n a d y l c a t i o n , V 0 + . I t s EPR spectrum i s c h a r a c t e r i z e d by an 8 - l i n e p a t t e r n a r i s i n g from the s p l i t t i n g i n t o 2 1 + 1 components which i s produced by the h y p e r f i n e i n t e r a c t i o n between the S = 1/2 s p i n o f the u n p a i r e d e l e c t r o n and the I = 7/2 s p i n o f the vanadium n u c l e u s a c c o r d i n g t o the second term i n the s p i n H a m i l t o n i a n g i v e n above ( E q u a t i o n 2 ) . F i g u r e 2 i s the c e n t r a l p o r t i o n o f the EPR spectrum r e c o r d e d f o r the a s p h a l t e n e f r a c t i o n o f C i r c l e C l i f f s t a r sand ( 4 ) . Two s e t s o f f e a t u r e s each show the 8 - l i n e p a t t e r n c h a r a c t e r i s t i c o f vanadium. The EPR spectrum o f a x i a l l y symmetric paramagnetic systems which a r e randomly o r i e n t e d i n a powder e x h i b i t s two c h a r a c t e r i s t i c l i n e com ponents c o r r e s p o n d i n g t o the o r i e n t a t i o n o f the symmetry a x i s p a r a l 3

1

2

2

1

3

362


BOSCAN ASPHALTENE


IN ι ι ι ι I PERPENDICULAR LINES CIRCLE

CLIFFS

ASPHALTENE

PARALLEL LINES I

I

I L n ι 11 l i t PERPENDICULAR LINES

P.R.

SPRING

MINERAL FINES

2 +

Figure 2. EPR spectra of V 0 observed for Boscan asphaltene, C i r c l e C l i f f s tar sand asphaltene, and mineral fines extracted from P.R. Spring bitumen.

23.

TABLE I .

Comparison o f EPR

Sample

gx

Parameters f o r V02+

g//

A//( mT)

mT)

Ref.

1..986

1..962

6. 08

17. 20

4

1..9861

1,.9598

5. 93

17. 30

3

Vanadyl e t i o p o r p h y r i n

1,.9862

1..9629

6. 01

17. 13

12

Vanadyl t e t r a b e n z o porphyrin

1..985

1,.962

5. 0

15. 0

13

1,.9928

1,.9432

7. 26

18. 51

7. 1

19. 4

14

Circle Cliffs Boscan

P.R. Publication Date: July 6, 1987 | doi: 10.1021/bk-1987-0344.ch023

363


GRAHAM

asphaltene

Spring mineral

2 +

Mg -hectorite γ-Α1 0 2

Si0

asphaltene

(2% V 0 ) 2 +

2

2 +

(5% V 0 ) 2 +

3

(2% V 0 )

fines

3

1 .989

1 .916

7. 08

18. 12

15

1 .982

1 .922

7. 72

19. 51

15

l e i and p e r p e n d i c u l a r t o the magnetic f i e l d . The t y p i c a l , p a r a l l e l and p e r p e n d i c u l a r l i n e shapes observed i n F i g u r e 2 i n d i c a t e t h a t V** + o c c u r s at an a x i a l l y symmetric s i t e . A v e r y s i m i l a r spectrum i s ob served f o r Boscan petroleum a s p h a l t e n e s . In Table I , an e x a m i n a t i o n o f the p e r p e n d i c u l a r and p a r a l l e l components o f the magnetic con s t a n t s g and A (lmT = 10 g a u s s ) , f o r the C i r c l e C l i f f s and Boscan a s p h a l t e n e s r e a d i l y c o n f i r m s t h a t the vanadium p r e s e n t i n b o t h samples i s i n the form of v a n a d y l e t i o p o r p h y r i n . Table I a l s o g i v e s the magnetic c o n s t a n t s measured f o r a v a n a d y l spectrum which was observed f o r m i n e r a l f i n e s w h i c h remained i n P.R. S p r i n g t a r sand bitumen a f t e r c o n v e n t i o n a l S o x h l e t e x t r a c t i o n t e c h n i q u e s had been a p p l i e d ( 3 ) . Subsequent e x t r a c t i o n (11) o f these f i n e s from the bitumen was accomplished by c e n t r i f u g i n g the m i x t u r e , which had been r e d i s s o l v e d i n benzene, at 8000 r e v m i n " f o r 35 min at 4° C, d e c a n t i n g the l i q u i d , and then r e p e a t e d l y washing the r e maining c l a y p a r t i c l e s w i t h benzene u n t i l the s o l v e n t was c o l o r l e s s . Even though the c l a y p a r t i c l e s were e x h a u s t i v e l y t r e a t e d to remove a l l o r g a n i c m a t e r i a l , the p o s s i b i l i t y e x i s t s , o f c o u r s e , t h a t the v a n a d y l i n t h i s case o r i g i n a t e s from p o r p h y r i n i n bitumen which had been adsorbed onto the s u r f a c e s o f the m i n e r a l f i n e s . Table I I shows the r e s u l t s o f an FTIR a n a l y s i s o f the b u l k o f the P.R. S p r i n g t a r sand m i n e r a l m a t t e r o b t a i n e d by the s p e c t r a l s u b t r a c t i o n method and d i s c u s s e d i n d e t a i l elsewhere ( 5 ) . As can be seen, the b u l k m i n e r a l m a t t e r , which was o b t a i n e d by the c o n v e n t i o n a l S o x h l e t e x t r a c t i o n method to remove the bitumen, c o n t a i n s 50%) o f t h e n i c k e l c o n t e n t o f t h e a s p h a l t e n e s may be n o n - p o r p h y r i n complexes. The mode o f a s s o c i a t i o n o f N i ( I I ) o r V O ( I I ) p o r p h y r i n s w i t h a s p h a l t e n e s has n o t been s t u d i e d , a l t h o u g h i t has been shown t h a t t h e s p e c t r o s c o p i c p r o p e r t i e s o f m e t a l l o p o r p h y r i n s (e.£., molar a b s o r p t i v i t i e s ) a r e m o d i f i e d s i g n i f i c a n t l y i n t h e p r e s e n c e o f a s p h a l t e n e s (12), presumably a s a r e s u l t o f c h e m i c a l interactions.


+

Lewan and Maynard (15) have shown t h a t t h e vanadium and n i c k e l i n c r u d e o i l s p r o b a b l y have been d e r i v e d from m e t a l i o n s i n t h e water column d u r i n g sediment d e p o s i t i o n o r d u r i n g subsequent sediment compaction and d i a g e n e s i s . A l t h o u g h t h i s may be t h e s o u r c e o f n i c k e l

386


i n N i ( I I ) p o r p h y r i n s w h i c h o c c u r i n immature sediments, i t i s p o s s i b l e t h a t n o n - p o r p h y r i n N i ( I I ) s p e c i e s i n crude o i l s form l a t e r i n the geochemical e v o l u t i o n o f t h e sediment. A s p h a l t e n e s may complex N i ( I I ) i o n s from m i n e r a l s u r f a c e s d u r i n g f o r m a t i o n o f bitumen from m a t u r i n g kerogens i n source r o c k s , d u r i n g m i g r a t i o n o f a crude o i l , or d u r i n g m a t u r a t i o n and a l t e r a t i o n o f the o i l i n a r e s e r v o i r . A l t e r n a t i v e l y , p o l a r N i ( I I ) n o n - p o r p h y r i n complexes may d i s s o l v e , o r be formed, i n the bitumen a t some stage d u r i n g i t s geochemical e v o l u t i o n and may s t r o n g l y a s s o c i a t e w i t h components o f the a s p h a l tene m i c e l l e s . The c o m p l e x a t i o n o f m e t a l c a t i o n s , such a s V O ( I I ) , N i ( I I ) , C u ( I I ) , C o ( I I ) , Z n ( I I ) , and M g ( I I ) from c o l l o i d a l s i l i c a t e s by p e t r o l e u m a s p h a l t e n e s (16) has been demonstrated. A l s o , Erdman and H a r j u (17) showed t h a t some crude o i l a s p h a l t e n e s were u n d e r s a t u r a t e d w i t h r e s p e c t t o m e t a l c o n t e n t and t h a t the vanadium c o n t e n t c o u l d be i n c r e a s e d by r e a c t i o n w i t h V 0 ( a c a c ) 2 i n benzene s o l u t i o n . T h e i r d a t a , however, do not a l l o w a d i s t i n c t i o n t o be made between c o m p l e x a t i o n o f V 0 ^ by l i g a n d groups i n the a s p h a l t e n e s o r some form of a s s o c i a t i o n o f the V 0 ( a c a c ) 2 complex w i t h the a s p h a l t e n e s . In t h i s s t u d y , the r e a c t i o n s o f the n o n - p o r p h y r i n N i ( I I ) complex, N i ( a c a c ) 2 , and the N i ( I I ) p o r p h y r i n complexes (NiOEP and NiDME) w i t h Athabasca o i l - s a n d a s p h a l t e n e s were s t u d i e d i n c h l o r o f o r m s o l u t i o n .


+

Experimental

Procedures

A s p h a l t e n e S e p a r a t i o n P r o c e d u r e . A t h a b a s c a bitumen was s e p a r a t e d i n t o m a l t e n e s and a s p h a l t e n e s by p r e c i p i t a t i o n w i t h 40:1 volume r a t i o o f n-pentane t o bitumen. The n-pentane a s p h a l t e n e s were d i s s o l v e d i n t o l u e n e and r e p r e c i p i t a t e d w i t h a 20:1 volume r a t i o o f methanol t o t o l u e n e . The a s p h a l t e n e s were then S o x h l e t - e x t r a c t e d w i t h 12:88 v/v methanol-acetone u n t i l the s o l v e n t r e t u r n t o t h e s o l v e n t r e s e r v o i r was c o l o r l e s s . S y n t h e s i s o f L a b e l e d Compounds. The N i ( I I ) and C u ( I I ) a c e t y l a c e t o n a t e s were s y n t h e s i z e d a c c o r d i n g t o the method o f C h a r l e s e t a l . (18). The N i ( a c a c ) 2 was s y n t h e s i z e d e i t h e r w i t h 6 % i o r w i t h l ^ C l a b e l e d 2,4-l^C a c e t y l a c e t o n e ( a c a c ) . The Cu(acac)2 was s y n t h e s i z e d using C u labeled Cu(N0 ) . N i c k e l o c t a e t h y l p o r p h y r i n (NiOEP) and n i c k e l m e s o p o r p h y r i n I X d i m e t h y l e s t e r (NiDME) were s y n t h e s i z e d w i t h 6 % i l a b e l s u s i n g t h e a c e t a t e method d e s c r i b e d by Bucher ( 1 9 ) . 6 4

3

2

R e a c t i o n o f M e t a l Complexes w i t h A s p h a l t e n e s . The m e t a l complexes l a b e l e d e i t h e r w i t h r a d i o a c t i v e m e t a l i o n o r -^C-acac and 50 mg o f a s p h a l t e n e s were r e a c t e d i n 30 mL o f c h l o r o f o r m i n c l o s e d g l a s s r e a c t i o n v e s s e l s f o r p e r i o d s o f up t o 1440 m i n u t e s depending on t h e r e a c t i o n . F o r the a c e t y l a c e t o n a t e complexes, 30 mL o f methanol was added a t the end o f the r e a c t i o n t o c o n v e r t the e x c e s s u n r e a c t e d N i ( a c a c ) 2 (or C u ( a c a c ) 2 ) i n the s o l u t i o n t o i t s u n r e a c t i v e p o l y m e r i c form. An a d d i t i o n a l 100 mL methanol was added t o complete t h e p r e c i p i t a t i o n o f the a s p h a l t e n e s and the s o l u t i o n was then f i l t e r e d through a 0.45 um Nucleopore PTFE f i l t e r . The s o l i d a s p h a l t e n e s were washed w i t h 50 mL o f methanol t o remove e x c e s s m e t a l complex. To d e t e r m i n e the a d s o r p t i o n o f N i ( a c a c ) 2 on s o l i d a s p h a l t e n e s , the a s p h a l t e n e s were shaken w i t h a methanol s o l u t i o n o f N i ( a c a c ) 2 o f

25.

Ni(II) Complexes and Athabasca Asphaltenes

NGUYEN AND FILBY

387

d i f f e r e n t concentrations. The asphaltenes were then f i l t e r e d and washed as described above. The reactions of NiDME and NiOEP with asphaltenes were studied in chloroform solutions under experimental conditions similar to those for the acetylacetonates. The asphaltenes were precipitated with 1:1 v/v methanol-acetone mixture for these experiments because of the higher s o l u b i l i t y of NiDME and NiOEP i n methanol-acetone versus methanol. Size Exclusion Chromatography (SEC). Asphaltenes were separated into molecular-weight fractions by SEC on Bio-Beads SX-1 (nominal molecular-weight exclusion l i m i t , 14,000 daltons) using tetrahydrofuran at 1 mL/min as the mobile phase. Polystyrene molecular-weight standards and rubrene, C42H28» were used for column c a l i b r a t i o n . Determination of ^ 3 ^ j 14ç^ j 64ç Liquid s c i n t i l l a t i o n counting (LSC) was used to measure °3Ni and a c t i v i t i e s i n the reacted asphaltenes. Because of the low energy of 63$i beta p a r t i c l e s (Emax = 66 keV), oxidation techniques were used to eliminate color quenching by asphaltenes i n the LSC c o c k t a i l . An aliquot of the asphaltenes was wet-ashed with 2 mL H2SO4 i n a 20 mL LSC v i a l at 100°C for 6 hr. The solution was evaporated to dryness and then ashed i n a i r i n a muffle furnace at 450°C for 6 hr. The residue was dissolved i n 0.2 mL6MHCl, 1 mL double d i s t i l l e d water added and then 18.8 mL of AQUAS0L-2 c o c k t a i l solution was added to the v i a l . Because color quenching was not as severe for C as for ^^Ni, samples and standards were adjusted to contain the same amount of asphaltenes by the addition of unlabeled asphaltenes to the l^C standard solutions. The -^C was determined using 0.2 mg of l ^ C containing asphaltenes, dissolved i n 1 mL chloroform, plus 19 mL Scintilene c o c k t a i l . The ^^Cu a c t i v i t i e s of asphaltenes were measured using the 511 keV a n n i h i l a t i o n peak with a 3" χ 3" Nal(Tl) detector interfaced to a single channel analyzer (SCA).


?

a

n

(

Ut

Results Reaction of Asphaltenes with Ni(II) and Cu(II) Acetylacetonates. U l t r a v i o l e t - v i s i b l e spectroscopic examination of chloroform solu tions of Ni(acac)2 showed that both the monomeric and a trimeric species, [Ni(acac)2]3, were present. When s o l i d Ni(acac)2 was dissolved i n chloroform at 25°C, equilibrium between the monomer and the trimer was established only after 8 hours, as can be seen from Figure 1. In Figure 1, the absorbance r a t i o (A265 monomer)/(A295 trimer) i s shown as a function of time a f t e r s o l i d d i s s o l u t i o n . The monomer-trimer equilibrium was found to be very sensitive to other compounds ( p a r t i c u l a r l y oxygenated compounds) i n solution and less than 1 percent methanol shifted the equilibrium completely to the trimeric species. However, the rate of reaction of Athabasca asphaltenes with previously equilibrated chloroform solutions of Ni(acac)2 was very rapid as shown i n Table I. The reaction between Ni(acac)2 and asphaltenes was e s s e n t i a l l y complete i n less than 5 minutes, although i t i s not clear whether true equilibrium was reached. The influence of the Ni(acac)2 s o l u t i o n - e q u i l i b r a t i o n time on the Ni(acac)2-asphaltenes reaction can be seen from Figure 2, i n

388



200

100 C

300

(ug Ni/ml solution)

63 . F i g u r e 2. V a r i a t i o n o f N i c o n t e n t o f a s p h a l t e n e s w i t h c o n c e n t r a tion of 6 3 N i ( ) 2 i n s o l u t i o n f o r e q u i l i b r a t i o n times o f a) 1 h r ( o ) ; b) 12 h r ( · ) . w

a c a c

Λ

25.

NGUYEN AND FILBY


389

Table I. Uptake of Ni by Asphaltenes from Ni(acac)2 i n Chloroform Solution as a Function of Reaction Time a

Ni


Reaction Time (min)

Content

as yg Ni/g asphaltenes

as ymole Ni/g asphaltenes 43.3 + 1.2

5

2540 + 69

15

2570 + 85

43.8 + 1.5

30

2400 + 72

40.8 + 1.2

60

2640 + 109

45.0 + 1.9

120

2650 + 179

45.2 + 3.0

240

2610

+ 95

44.5 + 1.6

480

2640 + 79

45.0 + 1.3

2390 + 59

40.7 + 1.0

2550 + 214

43.5 + 3.6

720 1440

b

Concentration of Ni(acac)2 i n i n i t i a l solution = 0.32 mM; asphaltenes = 50 mg; volume of solution = 30 mL. 'Error terms are + one standard deviation from counting

b

mass of

statistics.

which data for 1 hr and 12 hr monomer-trimer e q u i l i b r a t i o n times are presented. It i s apparent that the reacting species of Ni(acac)2 i s the square planar monomer rather than the octahedral trimer. This i s inferred from a) the lower Ni(II) uptake by asphaltenes at the 1 hr e q u i l i b r a t i o n time compared to 12 hr, and b) the uptake of Ni(II) by asphaltenes from equilibrated solutions of Ni(acac)2 does not increase with reaction time (Table I ) . The monomer/polymer r a t i o could not be measured spectroscopically i n the asphaltene-Ni(acac)2 solutions because of the very high asphaltene absorbance i n the 250-300 nm range. However, i t i s l i k e l y that components of the asphaltenes (e. g^., phenols, a c i d i c species, etc. ) s h i f t the Ni(acac)2 species equilibrium to the trimer, as does methanol and other oxygenated compounds. Thus, the asphaltenes react rapidly with the monomeric complex and unreacted Ni(acac)2 i n the solution i s converted to the unreactive trimeric form. The monomer i s expected to be more reactive with asphaltene components because a x i a l bond formation between the N i ^ ion and heteroatom-containing ligands i n asphaltenes i s possible. The octahedral geometry of the N i ^ ion i n the trimeric species requires breaking a Ni-0 bond i n the complex i n order for bonding of N i ^ to another ligand to occur. Figure 2 demonstrates that there i s substantial uptake of n i c k e l by asphaltenes from Ni(acac)2 i n chloroform solution and that a saturation concentration i s not reached below 10,000 yg Ni/g asphaltenes. However, i t i s not possible to distinguish between association (e.g^., chemisorption) of the Ni(acac)2 complex with asphaltenes or a chemical reaction involving ligand replacement on +

+

+

390

METAL COMPLEXES IN FOSSIL FUELS b J

14

Table I I . Total N i , C - N i ( a c a c ) , and N i Athabasca Asphaltenes Function of Ni(acac)2 as i n Chloroform

Z +

Uptake by Concentration

2

3

14

J

Total Ni Uptake [Ni(acac)2] (mM)


b

[Nilasp (ymole/g)

sol

0.24

a

C-Ni(acac)2 Uptake [Ni(acac) ] (ymole/g) 2

a s p

2+ Ni

Complexed [Ni

2 +

]

a S

r,

(ymole/g) 30.8 +

4.3°

45.4 + 3.0°

14.6 +

3.1

19.3 +

3.1

39.8 +

4.8 4.6 4.4

C

0.55

59.1 + 3.6

1.16

82.5 +

3.4

20.5 +

3.1

62.0 +

1.80

90.5 +

3.1

17.3 +

3.1

73.2 +

2.41

111 + 3.6

16.9 + 3.1

94.1 +

4.8

3.04

119 + 4.1

21.2 +

3.1

97.8 +

5.1

3.65

142 +

3.2

22.7 +

3.1

119 + 4.5

4.27

165 +

2.4

20.8 +

3.1

144

+3.9

4.58

174 + 3.5

18.0 +

3.1

156

+4.7

Reaction conditions: mass of asphaltenes = 50 mg; = 30 mL; reaction time = 4 hr.

solution volume

k-^C-Ni(acac)2 content corrected for l^C-acac uptake by asphaltenes. c Error terms are + one standard deviation from counting s t a t i s t i c s . the metal complex. To d i s t i n g u i s h between the reaction mechanisms, Ni(i^C-acac)2 was synthesized and reacted with asphaltenes under conditions i d e n t i c a l to those used for ^^Ni-Ni(acac)2» Retention of C by asphaltenes after reaction could r e s u l t from the uptake of discrete Ni(l^C-acac)2 molecules or from association of l^C-acac liberated by ligand exchange with the asphaltenes. Hence, the reaction of -^C-acac with asphaltenes was studied under experimental conditions similar to those of the metal complex-asphaltene system. Table II l i s t s uptake data for the asphaltenes-Ni(acac)2 reaction as a function of i n i t i a l Ni(acac>2 solution concentration. The n i c k e l uptake (measured by ^ % i a c t i v i t y ) i s expressed as ymole Ni(II)/g asphaltenes and the -^C content of the asphaltenes i s expressed as [(ymoles acac)x2]/g asphaltenes. Both concentrations are thus equivalent to ymoles Ni(acac)2/g asphaltenes. Column 3 of Table II l i s t s the 14

C

uptake data corrected for l^C-acac incorporation i n the asphaltenes, JL.e^., the concentration of N i i ^ C - a c a c ^ molecules in the asphaltenes. The difference between the t o t a l Ni(II) content (from the 63fli data) and the Ni(acac)2 content (from the data) i s the amount of n i c k e l incorporated into the asphaltenes by ligand replacement, [ N i ] (Column 4). The v a r i a t i o n of t o t a l n i c k e l taken up by the asphaltenes, [ N i ] p , and that of the molecular complex, [Ni(acac)2] sp> with solution concentration of Ni(acac)2 at equilibrium, [ N i ( a c a c ) 2 ] l > i s shown i n Figure 3. This figure shows 2 +

a s p

a S

a

so


25. NGUYEN AND FILBY


391

Figure 3. Variation of t o t a l Ni (·), Ni(acac>2 (o), and t o t a l Cu (®) concentrations i n asphaltenes, C , as a function of concentration of Ni(acac)2 or Cu(acac)2 i n chloroform solution, C . a s p

g

392

METAL COMPLEXES IN FOSSIL FUELS T a b l e I I I . E l e m e n t a l Composition

Element:

Η

0

Ν

S

80.31

7.80

1.18

2.47

8.24

^ N i determined

Asphaltenes

a

C

S u l f u r o b t a i n e d by d i f f e r e n c e from


(wt%) of Athabasca

Ni 0.0317

100%.

by n e u t r o n a c t i v a t i o n a n a l y s i s (_4) .

t h a t a t l e a s t two r e a c t i o n mechanisms a r e i n v o l v e d i n the r e a c t i o n of N i ( a c a c ) 2 w i t h a s p h a l t e n e s : a) a c h e m i c a l r e a c t i o n between N i ( a c a c ) 2 and a s p h a l t e n e s l e a d i n g to l i g a n d (acac) r e p l a c e m e n t , which i s a f u n c t i o n of the c o n c e n t r a t i o n of N i ( a c a c ) 2 i n s o l u t i o n , and b) an a s s o c i a t i o n of m o l e c u l a r N i ( a c a c ) 2 w i t h a s p h a l t e n e s (19.1 + 2.5 ymole/g) t h a t i s independent o f s o l u t i o n c o n c e n t r a t i o n w i t h i n e x p e r i m e n t a l e r r o r a t the 95% c o n f i d e n c e l i m i t s . The c o n c e n t r a t i o n independent uptake o f N i ( a c a c ) 2 i m p l i e s an a s s o c i a t i o n w i t h c o n c e n t r a t i o n l i m i t i n g s p e c i f i c s i t e s i n the a s p h a l t e n e s . A d i s t r i b u t i o n of N i ( a c a c ) 2 between a s p h a l t e n e s and the c h l o r o f o r m s o l u t i o n , o r p a r t i t i o n of the complex between s o l i d a s p h a l t e n e s and the m e t h a n o l - c h l o r o f o r m s o l u t i o n d u r i n g p r e c i p i t a t i o n would l e a d , i n b o t h c a s e s , t o a c o n c e n t r a t i o n - d e p e n d e n t b e h a v i o r . The v a r i a t i o n o f n i c k e l i n c o r p o r a t e d i n t o the a s p h a l t e n e s by l i g a n d replacement, [ N i ] , with [Ni(acac)2]sol f° 2 +

i s

o f

t n e

r m :

a s p

2 +

[Ni ]

where

= K. [ N i ( a c a c ) J -+b asp Ni 2 sol b = 23.0 ymole N i / g a s p h a l t e n e s (1350 yg K = 26.1 mL/g; r = 0.99

Ni/g)

N ±

The i n t e r c e p t o f 23.0 ymole N i / g shows t h a t the r e a c t i o n between N i ( a c a c ) 2 and a s p h a l t e n e s may i n v o l v e more than one l i g a n d exchange mechanism. A p o s s i b l e e x p l a n a t i o n o f the e x t r a p o l a t e d zero s o l u t i o n c o n c e n t r a t i o n of 23.0 ymole N i / g i s t h a t t h e r e i s a s p e c i f i c f u n c t i o n a l group ( o r groups) i n the a s p h a l t e n e s t h a t i s p r e s e n t a t a c o n c e n t r a t i o n e q u i v a l e n t to 23.0 ymole N i / g and w h i c h has a v e r y h i g h a f f i n i t y for N i ion. The n a t u r e o f the f u n c t i o n a l groups, or m o l e c u l a r s p e c i e s , i n the a s p h a l t e n e s t r u c t u r e t h a t r e a c t w i t h N i ( a c a c ) 2 , has not been determined but undoubtedly i n v o l v e s f u n c t i o n a l groups c o n t a i n i n g n i t r o g e n , oxygen, and p o s s i b l y s u l f u r . The e l e m e n t a l c o m p o s i t i o n o f the a s p h a l t e n e s used i n t h i s s t u d y i s shown i n T a b l e I I I . Although oxygen i s the l e a s t abundant heteroatom, i t may be most i m p o r t a n t i n terms of r e a c t i v e f u n c t i o n a l groups t h a t complex N i i o n . Ketone, p h e n o l , quinone, and e s t e r groups have been i d e n t i f i e d i n a s p h a l t e n e s , but p h e n o l i c groups have been shown (20) t o account f o r more than 60 p e r c e n t of the oxygen i n Athabasca a s p h a l t e n e s . Specific f u n c t i o n a l g r o u p i n g s such as d i p h e n o l s , α-hydroxy N - h e t e r o c y c l i c s , e t c . may a l s o be i m p o r t a n t i n complexing N i ( I I ) s i n c e such compounds (Ë-'UL* ' h y d r o x y q u i n o l i n e s , p o l y p h e n o l s ) form s t r o n g complexes w i t h Ni(II). The p o s s i b i l i t y t h a t the r e t e n t i o n of n i c k e l by the a s p h a l t e n e s i n v o l v e s the s u r f a c e a d s o r p t i o n o f N i ( a c a c ) 2 on a s p h a l t e n e s d u r i n g 2 +

2 +

25.

NGUYEN AND FILBY

Ni(H) Complexes and Athabasca Asphaltenes

393

63 Table IV. Concentration of Ni (as Ni) i n Asphaltenes after Reaction of N i ( a c a c ) i n Methanol (Heterogeneous System) a

2

b [Ni(acac)2] ol (mM)

Total Ni Uptake

[Ni]

a s p


S

yg Ni/g

ymole Ni/g

1.3

2.12 + 0.20

36.1 + 3.4

2.6

1.79 + 0.20

30.5 + 3.4

3.9

1.99 + 0.17

33.9 + 2.9

5.2

2.45 + 0.21

41.7 + 3.6

6.5

2.67 + 0.20

45.5 + 3.4

7.8

2.13 + 0.20

36.3 + 3.4

9.1

2.30 + 0.20

39.2

10.4

1.89 + 0.18

32.2 + 3.1

13.0

2.07

0.20

35.3 + 3.4

>s of asphaltenes = 50 reaction time = 4 hr.

±

3.4

mg; volume of reaction medium = 30 ι

^Concentration of Ni(acac)2 i n i n i t i a l C

±

solution.

E r r o r terms are + one standard deviation from counting s t a t i s t i c s .

p r e c i p i t a t i o n by methanol was studied by measuring the adsorption of 63Ni(acac)2 on s o l i d asphaltenes i n methanol medium. The data, shown i n Table IV, indicate that adsorption or surface complexation of N i or adsorption of Ni(acac)2 i s extremely small (30.5-45.5 nmole Ni/g) and i s independent of concentration. If this minor adsorption results from adsorption of trimeric Ni(acac)2 (form of the complex i n methanol) or a reaction involving ligand exchange on the surface, the number of active s i t e s must be very small and concentration l i m i t i n g . The factors which determine the occurrence of Ni(II) and VO(II) porphyrins to the exclusion of other metalloporphyrins i n crude o i l s and oil-sand bitumens have been discussed by several authors (21,22). Nickel and vanadium are normally the most abundant metals i n petroleum asphaltenes (1_,4^,6) and t h i s may be the result of incor poration of the metalloporphyrins. However, the enrichment of asphaltenes i n Ni(II) and VO(II) non-porphyrin complexes due to a p r e f e r e n t i a l reaction of Ni(II) and VO(II) complexes with s p e c i f i c binding s i t e s i n the asphaltenes should also be considered. Thus the reaction of other metal complexes, e_.£., Cu(acac)2 with asphal tenes should be less s i g n i f i c a n t . The reaction between asphaltenes and ^^Cu(acac)2 was therefore studied i n chloroform solution under the same conditions used for Ni (acac ^-asphaltene reaction. Copper was chosen because stable Cu(II) porphyrins are found i n immature sediments, although not i n crude o i l s . Thus, non-porphyrin complexes of Cu(II) may be formed i n these sediments and they eventually associate with asphaltenes i n the source-rock bitumen. The ^Cu 2 +

394


c o n t e n t was determined by gamma-ray s p e c t r o m e t r y and t h e uptake d a t a are compared w i t h t h e N i ( a c a c ) 2 d a t a i n F i g u r e 3. F i g u r e 3 shows t h a t C u ( I I ) was taken up by t h e a s p h a l t e n e s t o a much s m a l l e r e x t e n t than N i ( I I ) , a l t h o u g h a l i n e a r r e l a t i o n s h i p was a l s o o b s e r v e d . The r e a c t i o n o f Cu(acac)2 w i t h a s p h a l t e n e s i n c h l o r o f o r m f o l l o w s t h e equation: [Cu] = Κ [Cu(acac) ] - + b asp Cu 2 sol 0

where

Κ

= 3.47 mL/g Cu b r

= 20.1 ymole/g = 0.98

The i n t e r c e p t v a l u e o f 20.1 ymole/g i n d i c a t e s t h a t e i t h e r Cu(acac)2 a s s o c i a t e s (e.£., a d s o r b s ) w i t h t h e a s p h a l t e n e s t o a s i m i l a r degree as N i ( a c a c ) 2 (19.1 ymole/g) o r t h a t a s i m i l a r mechanism o p e r a t e s f o r the r e a c t i o n o f C u v i a l i g a n d replacement a s f o r t h e c o n c e n t r a t i o n independent r e a c t i o n o f N i w i t h t h e a s p h a l t e n e s (23.0 ymole/g). The v a l u e o f 3.47 f o r Kq i n d i c a t e s t h a t t h e a s p h a l t e n e s r e a c t t o a much s m a l l e r e x t e n t w i t h C u than w i t h N i ( K ^ = 26.1).


2 +

2 +

u

2 +

2 +

N

R e a c t i o n o f A s p h a l t e n e s w i t h t h e N i c k e l P o r p h y r i n s , NiOEP and NiDME. The r e a c t i o n s o f a s p h a l t e n e s w i t h NiOEP and NiDME were s t u d i e d t o determine the r e l a t i v e a f f i n i t y o f N i ( I I ) porphyrins f o r asphaltenes and t o compare t h e degree o f a s s o c i a t i o n w i t h t h e i n c o r p o r a t i o n o f non-porphyrin N i ( I I ) species i n the asphaltenes. For both porphyrins, a l i g a n d - e x c h a n g e r e a c t i o n i s i m p r o b a b l e because o f t h e d i f f i c u l t y of d e m e t a l l a t i o n o f N i p o r p h y r i n s under t h e c o n d i t i o n s used i n t h i s e x p e r i m e n t ; hence c h e m i c a l r e a c t i o n i s u n l i k e l y . The u p t a k e o f NiOEP and NiDME by a s p h a l t e n e s i s shown i n T a b l e V. F o r b o t h p o r p h y r i n s t h e r e i s a l i n e a r dependence o f c o n c e n t r a t i o n i n t h e a s p h a l tenes, [ N i P ] p , w i t h e q u i l i b r i u m s o l u t i o n c o n c e n t r a t i o n , [ N i P ] ^ . The e q u a t i o n s e x p r e s s i n g t h e N i ( I I ) p o r p h y r i n u p t a k e a r e : a S

NiOEP: NiDME: where

K

Q E p

K

D M E

s o

[NiP]

a s p

= K

0 E p

[NiP]

s o l

[NiP]

a s p

= K

D M E

[NiP]

s o

- 0.036 ( r = 0.97)

i - 0.48 ( r = 0.99)

= 1.65 mL/g =42.7mL/g

For b o t h p o r p h y r i n s , t h e d a t a can be a p p r o x i m a t e d by: [NiP] asp _ [NiP]. " sol The p o s s i b i l i t y t h a t NiOEP and NiDME e i t h e r c o p r e c i p i t a t e d w i t h the a s p h a l t e n e s d u r i n g p r e c i p i t a t i o n o r d i s t r i b u t e d between t h e s o l i d a s p h a l t e n e phase and t h e s o l u t i o n a f t e r p r e c i p i t a t i o n was c o n s i d e r e d . A s e r i e s o f r e a c t i o n s o f NiOEP w i t h a s p h a l t e n e s i n c h l o r o f o r m were performed i n w h i c h t h e p r e c i p i t a t i n g s o l v e n t was changed from methanol-acetone t o n-pentane. F i g u r e 4 shows t h e r e l a t i o n s h i p o f log [ N i 0 E P ] v s l o g [ N i O E P ] i f o r b o t h m e t h a n o l - a c e t o n e and n-pentane d e a s p h a l t i n g s o l v e n t s . Changing t h e d e a s p h a l t i n g s o l v e n t has o n l y a s m a l l e f f e c t on t h e NiOEP u p t a k e by t h e a s p h a l t e n e s . Thus i t appears t h a t t h e r e a c t i o n between NiOEP and a s p h a l t e n e s o c c u r s i n t h e c h l o r o f o r m s o l u t i o n and i s n o t dependent on t h e a s p h a l K

a s p

s o

25.

NGUYEN AND FILBY

Table V.

395


Ni Contents of Asphaltenes a f t e r Reaction with NiOEP and NiDME i n Chloroform 3


[NiOEP]

a

b g o l

6 3

[ NiOEP]

a s p

[NiDME]

b gol

[NiDME]^

moles/mL

mole/g

mole/mL

mole/g

0.00563

0.0043 + 0.0028

0.00473

0.22 + 0.02

0.0112

0.0124 + 0.0021

0.00943

0.48 + 0.03

0.0224

0.0639 + 0.0082

0.0189

0.90 + 0.03

0.0449

0.0686 + 0.011

0.0380

i.81 + 0.02

0.0562

0.0712 + 0.012

0.0473

2.24

0.0845

0.118 + 0.0087

0.0707

3.56 + 0.02

0.112

0.140 + 0.014

0.0950

4.38 + 0.02

0.225

0.267 + 0.0092

0.190

8.73 + 0.01

0.393

0.425 + 0.0065

0.329

16.5 + 0.01

0.562

0.759 + 0.007

0.471

23.7 + 0.01

0.844

1.530 + 0.0051

0.712

33.0 + 0.01

0.956

40.5 + 0.02

±

0.02

Mass of asphaltenes used i n each reaction = 50 mg, volume of the reaction medium = 30 mL, reaction time = 4 hr, deasphalting/wash solvent = methanol-acetone (1:1 v/v).

^Solution concentrations at equilibrium (yM). C

E r r o r terms are + one standard deviation from counting s t a t i s t i c s .



F i g u r e 4. E f f e c t o f p r e c i p i t a t i n g s o l v e n t on NiOEP uptake by a s p h a l t e n e s : a) methanol-acetone ( o ) ; b) n-pentane (Δ).

25.

NGUYEN AND FILBY


397

tene p r e c i p i t a t i o n conditions. The mechanism of association of the porphyrins with the asphaltenes may be π-π bonding between asphal tene polycondensed-sheet structures and the porphyrin macrocycle, similar to that between planar aromatic structures i n an asphaltene micelle. However, a x i a l bonding of nitrogen-containing asphaltene constituents to the N i ion i s also possible. The stronger asso c i a t i o n exhibited by NiDME with asphaltenes compared to that of NiOEP undoubtedly r e s u l t s from hydrogen-bonding from asphaltene components to the oxygen f u n c t i o n a l i t y of the ester groups on the DME ligand. The d i s t r i b u t i o n of n i c k e l i n the asphaltenes as a function of molecular weight before and a f t e r reaction with Ni(acac)2 and NiDME, respectively, was measured by size exclusion chromatography (SEC). The n i c k e l (as 6 % i ) contents i n the four nominal molecular-weight ranges, >9000, 9000-3600, 3600-2350, and 9000

9000 - 3600 3600 - 2350

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