254
Energy & Fuels 1990,4, 254-263
The OP method can be utilized for the assessment of thermal evolution of organic matter in the Tertiary Niger delta. It can also be applied in differentiating marine from nonmarine organofacies, especially for the maturity range equivalent to Ro% 0.4-0.6. OP is therefore a useful index for palaeoreconstruction studies including source-rock/oil and oil/oil correlations in oleanane-occurring sedimentary basins.
Acknowledgment. We gratefully acknowledge the assistance of Professor D. H. Welte, Professor D. Leythaeuser, Dr. J. Rullkotter, Dr. R. G. Schaefer, Mr. M.
Disko, and several others of the Institute for Petroleum and Organic Geochemistry, KFA, Julich (West Germany), where part of the analytical aspects of this work was carried out by O.T.U. We are also very grateful to the Shell Petroleum Development Co. (Nigeria) for providing a grant, samples, and some background geological data. Dr. Simon Brassell and the anonymous reviewers are gratefully acknowledged for their critique of the manuscript. Registry No. 18a(H)-Oleanane,30759-92-3;18@(H)-oleanane, 471-67-0; olean-l3(18)-ene,3399-27-7; hopane, 471-62-5.
Comparison of Maceral Group Chemistries for a New Albany and an Ohio Oil Shale Kerogen D. N. Taulbee,* E. D. Seibert, L. S. Barron, and T. L. Robl Center for Applied Energy Research, University of Kentucky, 3572 Iron Works Pike, Lexington, Kentucky 4051 1-8433 Received October 6, 1989. Revised Manuscript Received February 2, 1990
A sample of the Clegg Creek Member of the New Albany oil shale of northwestern Kentucky has been demineralized and separated into maceral group coacentrates by density gradient centrifugation (DGC). Results from this separation are compared t o previously reported results from a sample of the Cleveland Member of the Ohio Shale of northeastern Kentucky. Both kerogens originated from similar source materials but were deposited in what is believed to have been a euxinic basin versus upwelling environment, respectively. Petrographically, the New Albany kerogen was composed of bituminite, 84.7 vol 90;other liptinites, 7.5 vol %; vitrinite, 6.7 vol %; and trace inertinites. DGC processing of this kerogen yielded three maceral group concentrates containing 84.4 vol % liptinites (excluding bituminite), 95.7 vol % bituminite, and 38.5 vol % vitrinite, respectively. Chemical parameters corrected to a 100% maceral group basis including H/C, N/C, O/C, pyrolysis yields, and density exhibited similar trends in both kerogens. However, these calculated parameters for vitrinite and liptinites from the New Albany were, without exception, closer to the corresponding values for bituminite than were analogous Cleveland values. These findings along with microscopic observations of more frequent, partially decayed alginite and vitrinite macerals and a significantly higher bituminite concentration indicate that the New Albany kerogen was more extensively reworked during deposition than the Cleveland Member sample. Further, these data infer that bituminite macerals are the end product of bacterial decay not only of alginite precursors but of vitrinite precursors as well.
Introduction The Devonian black shales that outcrop in a semicircular pattern around central Kentucky (Figure 1)are low ranked and correlate with major oil and gas source rocks in both the Illinois and Appalachian Basins. Certain stratigraphic intervals have sufficient organic carbon to be considered as oil shales. In western Kentucky the black shale is mapped as the New Albany Formation, which is divided from top to bottom into the Clegg Creek, Camp Run, Morgan Trail, and Blocher Members.’ In eastern Kentucky, the Devonian shales are present as the Ohio Formation, which is subdivided into the Cleveland Member (top), the Three Lick Bed, and the Huron Member.2 Organic carbon concentration is the highest in the upper portions of both formations, Le., the Clegg Creek Member (1) Lineback, J. A. AAPG Bull. 1968,53, 1291-1303. (2) Provo, L. J.; Kepferle, R. C.; Potter, P. E. AAPG Bull. 1977, 62, 1703-1713.
of the New Albany and the Cleveland Member of the Ohio. Both kerogens plot in the type I1 field on a van Krevelen diagram and may be classified as a “mixed type” kerogen, that is, containing more than one maceral type a t greater than 5 % concentration. Although both the bulk chemistry and lithology of the Clegg Creek and Cleveland Member Shales are similar, they are not stratigraphically equivalent. Recent detailed correlations based on paleontologic, lithologic, and geochemical markers indicate that all but approximately the upper meter of the New Albany correlates with the lower portion of the Huron Member of the Ohio Shale.3-4 In addition, carbon-sulfur and trace element relationships (3) Kepferle, R. C. Geological Society of America ‘81 Field Trip Guidebooks; Roberts, T. G., Ed.; AGI: Falls Church, VA, 1981; Vol. 2, pp 334-335. (4) Robl, T. L.; Barron, L. S. Devonian of the World, Vol. ZZ: Sedimentation; McMillan, N. J., Ambry, A. F., Glass, D. J., Eds.; Canadian Society of Petroleum Geologists: 1987; Mem. 14, pp 377-392.
0887-0624/90/2504-Q254$Q2.50/0 0 1990 American Chemical Society
E n e r g y & Fuels,
Maceral G r o u p C h e m i s t r i e s of K e r o g e n s
Vol. 4 , No. 3, 1990 255
Illinois
,J
-
-
-.--I
Figure 1. Map of Kentucky showing Devonian outcrop area (Black) and sampling sites for the New Albany (NA) and Cleveland
Member samples.
along with phosphate distribution suggest the shales were deposited under different environments, with the New Albany being deposited under euxinic basin conditions, such as present in the Modern Black Sea, and the Cleveland Member being deposited under an upwelling regime similar perhaps to the Modern Namibian Shelf.5q6 Our investigation of these kerogens is based on the separation and concentration of maceral groups using density gradient centrifugation (DGC) as originally described by Dyrkacz and c o - ~ o r k e r s . ' ~With ~ this technique, macerals are dispersed across a CsCl density gradient during high-speed centrifugation according to their density. DGC has been gaining wider application in the study of coal macerals as recently reviewed by Gellingg with more limited application to the study of kerogens.'@l3 This latter application of DGC may prove to be of significant value in simplifying the added complexities of oil shales that arise from such factors as the greater abundance and variety of mineral components, more frequent contributions by more than one maceral type (at least for many type I1 kerogens), and a generally broader diversity in depositional environments relative to most coals. DGC, coupled with acid demineralization, allows one to address each of these added complexities by removal of the bulk of the mineral matrix, separation of the various maceral groups, and comparison of similarly sourced kerogens to better discern the effects of deposition. The purpose of this work is to characterize the maceral components of the kerogen for the major oil shale types in Kentucky with the objective of developing fundamental information for processing and geochemical research. Because we have previously reported on the separation and (5) Leventhal, J. S. Am. J. Sci. 1987, 287, 33-49. (6) Robl, T. L.; Taulbee, D. T.; Barron, L. S. Prep.-Am. Chem. Soc., Diu. Pet. Geochem. 1989,34 (l), 81-86. (7) Dyrkacz, G. R.; Bloomquist, C. A. A.; Horwitz, E. P. Sep. Sci. Technol. 1981,16, 1571-1588. (8) Dyrkacz, G . R.; Horwitz, E. P. Fuel 1982, 61, 3-12. (9) Crelling, J. C. Prepr. Chem. Soc., Diu. Fuel Chem. 1989, - Pap.-Am. . 34 (1). 249-255. (10) Sentfle, J. t.; Yordy, K. L.; Barron, L. S.; Crelling, J. C.; Proceedings of the 1987 Eastern Oil Shale Symposium, KECL87-175, Kentucky Energy Cabinet Laboratory, Lexington, KY, March 1988; pp 155-168. (11) Robl, T. L.; Taulbee, D. N.: Barron. L. S. Energy __ Fuels 1987, I , 507-513. (12) Taulbee, D. N.; Hagan, M.; Robl, T. L.; Barron, L. S. Proceedings of the 1985 Eastern Oil Shale Symposium, KEC185-147, Kentucky Energy Cabinet Laboratory, Lexington, KY, April 1986; pp 291-300. (13) Taulbee, D. N. Chemical and Pyrolytic Properties of the Kerogen and Maceral Concentrates of a Devonian Oil Shale. MS Thesis, Chemistry Department, University of Kentucky, August 1986.
Table I. Oil Shale Properties (As Determined Basis) New Albany Cleveland 14.1 14.0 %C 1.66 1.78 %H 0.46 0.44 % N % s, 5.3 1.96 % moisture 0.8 1.9 77.7 76.2 % ash (HTA) % mineral C 0.3 0.1 Fischer assay, g/ton 13.7 14.6 NA o i l Shale
(-100 M e s h 1
-HF X 2 -Boric acid Kerogen
- 2 4 DGC
I I "
A DGC
DGC
Runs
lntial S e p a r a t i o n Fractions
DGC
Figure 2. Separation scheme for New Albany kerogen. The Cleveland separation was conducted on 16 x 60 mesh and was concluded with the recovery of the initial fractions. characterization of macerals from the Cleveland Member of the Ohio Shale,11-13this paper will emphasize data from a similar treatment of the Clegg Creek Member of the New Albany Formation and make comparisons between the two.
Experimental Section Oil Shale Samples and Kerogen Preparation. The oil shales used in this study were CAER master samples NAS-001 and CLE-002, referenced for the remainder of this report as NA and CLE. They originate from the Clegg Creek Member of the New Albany Shale from Bullitt County in northwestern Kentucy and the Cleveland Member of the Ohio Shale from Lewis County in northeastern Kentucky, respectively (Figure 1). Both samples were sequentially passed through a jaw crusher, a roller mill, screened, and stored under Ar. The CLE study sample was screened to 16 X 60 mesh whereas the NA study was conducted on a -100-mesh sample. Selected properties for these shales are given in Table I. Demineralization was based on commonly used HF digestion procedures with certain modification^."-'^ The major modifications include omission of HC1, normally used for carbonate dissolution, and substitution of H3B03 for HN03 to remove
256 Energy & Fuels, Vol. 4 , No. 3, 1990
neoformed mineral fluorides. LiAlH4and/or HN03, which may be used to remove iron sulfides, were omitted to minimize organic alterations since these latter reagents are relatively harsh with respect to the organic matrix.14 Density Gradient Centrifugation. A Beckman Model 52-21 centrifuge fitted with a 1900-mL-capacity,titanium JCF-Z zonal core rotor was used for all DGC separations. The technique was adapted from that of Dyrkacz and co-worker~’~~ with procedural The NA kerogen details as applied to the CLE given was processed in a like manner with the exceptions that sample loading was increased from 6 to 8 g/run and a stepped versus linear gradient was used. NA Separation Scheme. A total of 188.1 g of kerogen was processed in a series of 24 DGC runs in an ”initial”NA separation (Figure 2). The rotor effluent from each run was divided into 23 density fractions plus the sink material (termed pellet) recovered from the outer wall of the rotor. Equivalent fractions from the 24 repeat runs were composited. Sample recovery averaged 75% with the bulk of the loss attributed to pyrite-enriched particles that passed through and exited the rotor during loading or were not quantitatively recovered from the sink material on the rotor wall. DGC processing of the CLE kerogen was essentially the same as for the “initial” NA separation. Selected density fractions from the initial NA separation, as denoted in Table 11, were reprocessed in an effort to enhance maceral purity. Density fractions that were enriched in a given maceral group were composited (e.g.,the 1.00-1.17 g/mL fractions for liptinites, 1.20-1.23 g/mL for bituminites,and 1.25-1.30 g/mL for vitrinites), yielding three composites enriched in liptinite, bituminite,and vitrinite, respectively. These enriched composites were gently reground in a mortar and pestle and reprocessed in separate DGC runs. The gradients for the reprocess runs were tailored to maximize volume in the respective density ranges of the three maceral groups. The rotor effluent from each of the reprocess runs was divided into 10 density cuts. No effort was made to recover the pellet for these runs. On the basis of petrographic analyses of the 30 density fractions thus recovered, three final concentrates, enriched in liptinites, bituminite, and vitrinites,respectively, were composited. These final concentrates were Soxhlet extracted with benzene/methanol (80/20 v/v) for 24 h to remove residual surfactant prior to analysis. Analyses. The analytical and petrographic procedures used for the NA samples were essentially the same as described12J3for the CLE. Briefly, petrographic analyses were conducted on minipellets prepared from a low-fluorescence resin and hardener. Alginite (-98%) and sporinite (-2%) were grouped under the liptinite heading. The bituminite maceral is normally classified as a liptinite but was treated separately in both studies due to both high abundance and substantial differences in chemistry and pyrolytic behavior relative to the other liptinites. The vitrinite group included vitrinite and degrado-vitrinite. The inertinite group included fusinite, semifusinite,and granular micrinite. Since no density fraction from the NA separation contained more than about 1% total inertinites, counts for these macerals were summed with vitrinites to which they were most similar in density. A minimum of 250 counts was taken on each fraction from the initial NA separation and a minimum of 1000 counts on the final concentrates. Volatile matter, fixed carbon, and high-temperature ash (HTA) were determined on 5-10-mg samples by thermogravimetric analysis (TGA) with a Perkin-Elmer Model TGS-2. Carbon, hydrogen, and nitrogen values were determined on a Leco Model 600 combustion analyzer. Total sulfur was determined on a Leco Model SC32 combustion-IR analyzer, pyritic sulfur was determined as the stoichiometric equivalent of acid-extractable iron (raw shale excluded), and organic sulfur was calculated as the difference between the two. Oxygen was determined as C 0 2 by use of a pyrolysis train and Coulometrics Corp. C 0 2coulometer. Pyrolysis. A CDS Model 820-GS analytical pyrolysis unit was used to pyrolyze small 1-2-mg samples. This unit utilized a flame ionization detector to monitor hydrocarbon evolution and could be configured to monitor total hydrocarbon yield and relative (14) Durand, B.; Nicaise, G. In Kerogen: Insoluble Organic Matter from Sedimentary Rocks; Durand, B., Ed.; Editions Technip: Paris, 1980; pp 35-53.
Taulbee et al. partitioning of the hydrocarbon components between oil and gas or interfaced with a capillary GC to determine the relative production of individual oil c o m p o n e n t ~ . ~ ~ J ~
Results and Discussion Petrographic Analyses. Both the New Albany (NA) and Cleveland Member (CLE) kerogens are composed of varying proportions of terrestrially and marine derived organic matter. Woody plants, charcoal, and spores comprised the terrestrial components preserved as vitrinites, inertinites, and sporinites, respectively. Algal and bacterial decay products were preserved in the form of alginite and bituminite which comprised the bulk of the kerogen. For both kerogens over 98% of the liptinites (excluding bituminite) consisted of alginite. Both lamalginite and telalgin@ were present, the telalginite primarily consisting of Tasminites which exhibited a wide range of decay. The NA kerogen contained only trace amounts of inertinite. This may have been due to settling out of these denser units prior to reaching the NA depositional site which was thought to be farther from the Catskill delta, the proposed source of terrigenous material for both dep~sites.~’J* Though the usage of the term bituminite to describe a kerogen maceral type is not universally recognized, the nomenclature used in this and previous studies is based on that of Hutton,l6 who has offered perhaps the most comprehensive and detailed description of kerogen macerals currently available. Thus, the usage of the term bituminite in this report is the same as that of HuttonlG and analogous to the “sapropelic kerogen” described by Barrows.lg Under Hutton’s system, bituminite would be classified as a liptinite but was treated separately here due to both high abundance and substantial differences in chemistry and pyrolytic behavior. Bituminite was the most abundant maceral for both kerogens, accounting for about 41 vol % of the CLE and 84% of the NA. It is a n amorphous material that tends to be intimately associated with pyrite and other maceral types causing it to disperse across the density gradient during centrifugation. This dispersion resulted in decreased separation efficiency, particularly in the higher density ranges where bituminite/pyrite composites partitioned to the same densities as did discrete vitrinite and inertinite particles. One of the more interesting reflected-light observations for the NA was an occasional sighting of what appeared to be a single maceral particle in which both reflectance and morphology ranged from that of an altered or poorly preserved alginite on one side of the particle to that of bituminite on the other side with a continuum between the two. Less frequent but analogous observations were made for bituminite/vitrinite composites. Under blue light, a shift in fluorescence was noted from bright yellow-green for distinctly figured alginites, to orange-red for partially degraded, to dull red-brown for highly degraded alginites. Bituminites either were nonfluorescent or fluoresced a dull red-brown. As with reflected light, an occasional particle was observed that exhibited a fluorescence continuum ranging from dull orange on one (15) Taulbee, D. N.; Seibert, E. D. Energy Fuels 1987, 1 , 514-519. (16) Hutton, A. C. Int. J . Coal Geol. 1987, 8, 203-231. of Pet. Geol. Bull. 1951, 35, 2017-2040. (17) Rich, J. L. Am. SOC. (18) Potter, P. E.; Maynard, J. B.; Pryor, W. A. Final Report of Special Geological Geochemical and Petrologic Studies of Deuonian-Mississippian Shales of the Central Appalachian Basin; H. N. Fish Laboratory of Sedimentology, University of Cincinnati: Cincinnati, OH, 1980. (19) Barrows, M. H.; Cluff, R. M.; Harvey, R. D. Proceedings: Third Eastern Gas Shales Symposium; METC/SP-79/6; Morgantown Energy Technology Center: Morgantown, WV, 1979; pp 85-114.
Energy & Fuels, Vol. 4, No. 3, 1990 257
Maceral Group Chemistries of Kerogens
Figure 3. New Albany vitrinites (V) exhibiting a continuum in morphology and reflectance that appears to correlate with the extent of depositional alteration. I, inertinite; B, bituminite; 325X, oil immersion.
side, in what appeared to be an alginite, to low fluorescing or nonfluorescing on the other side, in what would be more accurately described as bituminite. These observations were interpreted as partial, sometimes localized degradation of the maceral precursors. On average, the CLE alginites were more well-defined and fluoresced a bright yellow whereas the NA alginites showed a broader fluorescence range from bright yellow to a dull orangebrown. This difference in the fluorescence spectrum was interpreted as more extensive depositional reworking of the New Albany alginite precursors, not maturity differences. If burial history accounted for the additional fluorescence red-shifting for the New Albany alginites, then this shift would have been more uniform with few if any bright yellow fluorescing alginites. This was not the case since a broad range of alginite fluorescence values were observed with a clear correlation between the magnitude of red-shifting and the extent of depositional decay. What was more unexpected was the apparent continuum in both reflectance and morphology observed between vitrinite and bituminite macerals. Figure 3 shows a series of vitrinites preserved at what appears to be varying stages of bacterial decay as evidenced by the lower reflectance and increasingly amorphous appearance. These observations provided the first indication that not only alginite precursors, but perhaps vitrinite precursors as well, were converted to bituminite precursors during or just prior to burial. Chemical evidence in support of this conjecture is presented later. Initial DGC Separations. Petrographic analyses for both the NA and CLE separations are shown in Figure 4 on a volume percent basis. Bituminite recovery maximized at approximately 1.21 g/mL and skewed toward higher densities for both separations. The dispersion of bituminite toward the higher densities resulted in low purities
New Albony S e p o r o t i o n
$
60
-
40
-
20
-
5 2
-I
o >
-
1.00
110
I20
I30
I 40
I50
1.40
1.50
GRADIENT DENSITY ( g / m I ) Clevelo n d
1.00
1.10
I. 2 0
S e p o r o 1Io n
1.30
GRADIENT D E N S I T Y
Figure 4. Maceral Group recoveries from DGC separation of New
Albany (top) and Cleveland (bottom) kerogens.
of the denser macerals from both kerogens, particularly for the NA. Under the microscope, bituminite recovered at a gradient density of about 1.21 g/mL was relatively clean of foreign materials, whereas that recovered in higher density fractions was more often associated with denser
258 Energy & Fuels, Vol. 4, No. 3, 1990
Taulbee et al.
Table 11. Initial DGC Separation of New Albany Kerogen" density range, gimL 1.00-1.08 1.08-1.12 1.12-1.15 1.15-1.17 1.17-1.18 1.18-1.19 1.19-1.20 1.20-1.2 1 1.21-1.22 1.22-1.23 1.23-1.24 1.24-1.25 1.25-1.26 1.26-1.27 1.27-1.28 1.28-1.29 1.29-1.30 1.30-1.31 1.31-1.32 1.32-1.34 1.34-1.36 1.36-1.40 1.40-1.50 pellet
sample 1 2 3 4 5 6 7 8 9
io 11
12 13 14 15 16 17 18 19 20 21 22 23 24 kerogen whole rock
% S total (dry)
sample 1 2 3 4 5 6
3.21 3.38 3.51 3.95 4.12 4.46 4.73 5.08 5.42 5.72 6.05 6.46 6.72 7.24 7.46 9.04 10.02 13.54 29.15 20.23 5.30
7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 kerogen whole rock
sample
90 FeS,
1 2 3 4
5 6 7 8 9 10 11 12 13 14 15 16 17 18 19
2.64 2.68 2.64 3.11 3.27 3.82 4.25 4.79 5.26 6.14 6.85 6.87 7.39 8.33 9.09
av density,* g/mL 1.050 1.110 1.140
org density
1.1347 1.1511 1.1609 1.1572 1.1612 1.1629 1.1620 1.1651 1.1671 1.1654 1.1673 1.1695 1.1673 1.1668 1.1637 1.1638 1.1633 1.1592 1.1564
1.178 1.188 1.197 1.205 1.215 1.225 1.235 1.245 1.255 1.264 1.275 1.285 1.295 1.305 1.314 1.330 1.350 1.380 1.450
wt % 0.32 0.28 0.31 0.33 0.50 1.22 1.95 2.71 2.62 2.49 2.54 2.42 2.26 1.97 1.81 1.79 1.77 1.55 1.43 2.56 2.79 5.33 15.93 41.72
% C (dry)
5% H (dry)
% N (dry)
66.7
7.91
1.04
76.9 75.4 77.2 77.7 77.6 76.5 75.5 74.4 73.4 73.7 73.1 72.1 71.2 70.5 69.2 68.9 67.2 66.6 66.1 63.3 59.3 33.7 50.7 14.2
8.21 7.86 7.63 7.55 7.38 7.21 7.23 7.08 6.96 7.00 6.86 6.67 6.69 6.71 6.53 6.47 6.28 6.27 6.25 5.93 5.47 3.21 4.91 1.59
1.71 1.78 2.10 2.25 2.30 2.35 2.30 2.34 2.27 2.31 2.27 2.24 2.25 2.25 2.21 2.18 2.07 2.13 2.08 1.95 1.87 1.04 1.71 0.46
% 0 org (dry)
90 VM
90 FC
90 ash (HTA)
6.76 6.82 6.91 7.17 7.08 6.28 6.11 6.16 6.21 6.16 6.29 6.07 6.52 6.08 5.98 5.80 5.81 5.63 3.88 4.83 5.34
73.6 78.5 74.0 69.9 64.9 63.9 62.9 62.4 62.4 61.3 61.0 60.1 59.4 58.5 58.8 57.9 57.0 56.9 56.9 54.3 53.6 53.8 52.1 39.1 46.3 16.2
9.4 14.9 18.8 23.0 29.9 31.3 32.3 31.9 31.5 31.8 31.0 31.3 31.5 31.8 30.8 30.8 31.0 30.1 29.9 31.1 30.7 28.4 26.8 18.3 25.2 5.5
5.4 6.1 6.1 4.0 3.4 3.1 4.3 4.8 5.5 6.5 7.0 7.6 8.4 9.0 9.8 10.8 11.4 12.3 13.3 14.5 16.1 19.8 41.8 26.5 77.7
0.019
liptinite, vol % 97.4 92.5 76.8
bituminite, vol % 2.6 6.9 22.4
0.020
65.6
33.6
0.023 0.025 0.025 0.026 0.026 0.027 0.027 0.027 0.027 0.027 0.027 0.027 0.027 0.027 0.026
36.8 16.4 8.4 4.0 4.8 3.2 5.6 4.8 4.0 5.6 5.9 8.0 8.5 8.0 6.9
63.4 80.4 88.4 89.2 88.8 88.0 82.7 81.0 77.1 79.5 77.9 76.8 74.7 78.9 79.7
H/C (dry)
N/C
1.41
0.013
1.27 1.24 1.18 1.16 1.13 1.12 1.14 1.13 1.13 1.13 1.12 1.10 1.12 1.13 1.13 1.12 1.11
O/C (dry)
0.065 0.066 0.068 0.071 0.071 0.064 0.062 0.063 0.065 0.065 C.067 0.066
0.071 0.068
% mineral water
4.9 4.1 4.0 5.3 5.9 6.8 7.9 8.6 9.4 10.4 11.3 12.0 13.2 14.2 15.3 16.7 18.4 21.2 26.7 58.4 38.1
vitrinite, vol 90 0.0 0.5 0.8 0.8 0.8 2.8 3.2 6.0 6.4 8.4 11.5 13.9 18.4 14.9 16.3 14.9 16.5 12.3 12.8
inertinite, vol % 0.0 0.0 0.0 0.0
0.0 0.4 0.0 0.8 0.0 0.4 0.3 0.3 0.5 0.0 0.0 0.3 0.3 0.8 0.5
Maceral Group Chemistries of Kerogens
Energy & Fuels, Vol. 4, No. 3, 1990 259 Table I1 (Continued)
70 FeSz 10.27 11.75 15.21 20.88 49.77 34.90
sample 20 21 22 23 24 kerogen whole rock a
H / C (dry)
N/C
O/C (dry)
1.12 1.13 1.12 1.10 1.14 1.16 1.34
0.027 0.027 0.027 0.027 0.027 0.029 0.028
0.068 0.066 0.069 0.071 0.087 0.072 0.284
liptinite, vol %
bituminite,
vitrinite, vol %
inertinite,
7.6 12.4 14.0 9.3
82.9 77.6 79.6 87.6
8.4 9.2 5.2 2.2
1.2 0.8 1.2 0.9
12.6
78.4
7.6
1.4
vol
70
vol %
Fractions 1-7 were reprocessed for final liptinite concentrate, 8-10 are bituminites, and 13-17 for vitrinites. *Interpolated data.
3 50 300 2 50 2 00 I 50 I O 0 0 50 -
eoch 0 0 I glmL
W l recovery l t r o m r per
4 00
** *** * * *
g r a d l e n t increment)
P
%saolso@+Ww* oooooo
*** 08
I
I
t
0 00
I*
*I*
I
I10
IO0
I
I20
I
I
I
I30
I
I
I
I
I20
I10
I
I30
*
NA CLE 0 1
I
I
I50
I40
r
Oo40
*
I
I
I O 0
*
* * "
m
I I50
I40
GRADIENT DENSITY lg/mLI 40
-
30
-
20
-
Mineral
Wt%
Y
Moiler I M M I
z
NA CLE
0 010
l < t
IO0
0
0 000
IO0
*
*
I20
I 10
I30
I
I
I 10
I
I
120 GRADIENT
I
I
130
0 12 r
*
O
I
I50
I40
***** * *** ******* 01
*
I
I40
n
I I50
DENSITY
0 00
1
IO0
I
I10
I
I
I20
I
I
I
I30
I
I 4 0
1
J
150
Figure 5. Weight recovery (top) and mineral matter content (bottom) of density fractions from New Albany separation in units of g per 0.01 g/mL gradient increment.
Figure 6. Organic molar ratios for New Albany and Cleveland density fractions. *, New Albany; 0,Cleveland.
macerals and particularly with finely disseminated iron sulfides. The NA separation attempted here represents possibly a worst case for maceral concentration by DGC due to a substantial pyrite and bituminte content, the latter being highly prone to incorporate foreign materials, particularly pyrite. Similar difficulties were encountered for the CLE separation where the pyrite and bituminite content were relatively lower though still significant. Earlier work with the CLE kerogen indicated that maceral associations could be lessened slightly by grinding the raw shale to a smaller mesh size but at the expense of reduced reliability of the petrographic analyses. Vitrinite recovery maximized around 1.25-1.30 g/mL for the NA separation and 1.28-1.34 g/mL for the CLE. The highest vitrinite concentrations from the CLE separation were about twice that from the corresponding NA fractions in spite of the fact that the NA sample was processed as -100-mesh material compared to 16 X 60 mesh for the CLE. There was also a significant enrichment of inertinites at higher density for the CLE separation ranging to just over 50 w t % for the last fraction. The proportion of both iron sulfides and total ash in the NA DGC fractions increased steadily with increasing density (Table 11). The magnitude of this increase was about twice that previously reported for the CLE separa-
tion12J3and likely accounts for the more pronounced tailing of the NA bituminite recovery curve (Figure 4). X-ray diffraction indicated that residual mineral matter in both kerogens was composed of iron sulfides, both pyrite and marcasite, and titanium dioxides, primarily rutile with trace anatase detected in the NA. For the NA separation, the material that pelleted against the outer wall of the centrifuge rotor contained 50 w t % iron sulfide and accounted for approximately 80% of the total iron sulfide loaded to the centrifuge. Organic H / C and N/C molar ratios for the NA density fractions changed rapidly up to a gradient density of about 1.20 g/mL but remained relatively constant a t higher density (Figure 6). The corresponding CLE plots exhibited a continuous decrease in the H / C ratio across the gradient. The CLE O / C and N/C ratios increased up to about 1.2-1.3 g/mL, corresponding to the maximum frequency of bituminite and vitrinite, and remained relatively constant or declined slightly a t higher gradient densities. The differences in analogous NA and CLE plots a t higher density are thought to reflect both improved separation efficiency and a significant contribution from inertinite macerals for the CLE kerogen. The NA fractions exhibited little change in volatile matter (VM) or fixed carbon (FC) values beyond about 1.2
GRADIENT D E N S I T Y
Taulbee et al.
260 Energy & Fuels, Vol. 4 , No. 3, 1990
lo
100
-
90
-
c 3
eo
-
$
70
-
I
0 I 0
- 2 0
24
I w
0 >
*'
(E
0
+-+. r
-
,--> 50
2o
t
,1!0
I
1
,
1 I7
1
I9
1
,
1
1
21
1
1
, 23
8
0 0
I25
DEVStTY G R A D I E N T i p / mL1
Figure 8. Recentrifugation of bituminite-enriched fractions (NA).
DENSITY G R A D I E N T ( g / m L )
Figure 7. Recentrifugation of liptinite-enriched fractions.
and weights (- - - * - - -) of the initial Liptinite concentration (4-) New Albany fractions selected for reprocessing. The solid horizontal line (-) depicts the purity and density range of the "final" liptinite composite from DGC reprocessing, and the x denotes the average density of this composite. g/mL (Table 11) as contrasted with an invere variation for these parameters for the CLE separation. Table I1 also shows the densities for the NA fractions calculated to a mineral-matter-free (MMF) basis. Values for the lighter fractions could not be calculated due to lack of pyrite data, but it appears that the organic density increases up to about 1.2 g/mL, maximizes at a density near that of maximum vitrinite, and then declines slightly in the denser fractions. This small decline in the higher density fractions correspond to an increase in liptinite content. Further, the relatively constant values for organic molar ratios, % FC, 5% VM, and organic density for the higher NA density fractions indicate that the liptinites and bituminites which partitioned to these fractions were not necessarily chemically different than the equivalent macerals in lighter fractions. Rather, partitioning of these macerals to higher density was controlled by more frequent association with mineral matter. Liquid Nitrogen Treatment. In an effort to disrupt a portion of the kerogen-mineral associations using presumed differences in rates of cooling/contraction, an aliquot of NA kerogen was dropped into liquid N2. Comparison of the DGC weight recovery curves for the liquid N2 treated versus nontreated samples indicated no significant improvement in separation efficiency. This avenue was not pursued. Recentrifugation of New Albany Density Fractions. Selected density fractions from the NA separation as denoted in Table I1 were combined and recentrifuged in an effort to improve the purity and quantity of the maceral groups (Figure 2). Results for reprocessing of the liptinite-, bituminite-, and vitrinite-enriched composites are shown in Figures 7, 8, and 9, respectively. Initial separation fractions 1-7 were combined and reprocessed by DGC to obtain the final liptinite sample. The region of the gradient from which the final liptinite concentrate was recovered during reprocessing (1.0-1.17 g/ mL) corresponded to fractions 1-4 of the initial separation. The weighted average liptinite purity for initial separation fractions 1-4 was 82.6 vol % as compared to a final purity of 84.4 % following recentrifugation. Similarly, the final bituminite concentrate was recovered from 1.20-1.21 g/ mL, corresponding to fraction 8 of the initial separation.
Bituminite concentration (-O-.) and weights (- - - * - - -) of initial fractions; vertical lines bracket initial fractions composited for reprocessing;the horizontal line and X depict purity, density range, and average density of the final composite; weights of the density fractions from reprocessing (-.. + --).
50
t
124
125
126
121
128
129
130
131
132
DENSITY GRADIENT l a / m L 1
Figure 9. Recentrifugation of vitrinite-enriched fractions (NA). Vitrinite concentration (.-o-.)and weights (- - - * - - -) of the initial and weights (---+---) fractions; vitrinite content of density fractions from reprocessing; vertical lines bracket the initial fractions composited for reprocessing; the horizontal line and x represent purity, density range, and average density of the final composite. (-e-#-.-)
The improvement in bituminite purity was from about 89% initially to 95.7% in the final concentrate (Figure 8). The final vitrinite concentrate was recovered from 1.27-1.31 g/mL with a vitrinite content of 38.5 vol ?6 (Figure 9). The weighted vitrinite content for the corresponding density range in the initial fractions (15-18) was 15.1 vol %. The highest purity vitrinite fractions were recovered between 1.27 and 1.31 g/mL during reprocessing (Figure 9) even though the feed sample used for this step was initially recovered between 1.25 and 1.30 g/mL (initial fractions 13-17). Dyrkacz reported an increase in the averge density for coal vitrinites immediately following demineralization.20 However, the vitrinite density shift shown in Figure 9 is believed to result from a different mechanism than he observed since there was a 2-month delay between demineralization and the initial NA separation. Microscopically, it was noted that a substantial portion of the bituminites in initial separation fractions 13-17 were associated with iron sulfides or vitrinites. When this sample was recrushed prior to recentrifugation a portion of these associations were disrupted allowing both maceral types to partition to a different density, Le., bi(20) Dyrkacz, G. R.; Bloomquist, C. A. A.; Ruscic, L.; Horwitz, E. P. Prepr. Pap.-Am. Chem. SOC.,Diu. Fuel Chem. 1983, 28 ( l ) ,96-96.
Energy & Fuels, Vol. 4 , No. 3, 1990 261
Maceral Group Chemistries of Kerogens
Table 111. Final Composites from DGC Reprocessing of New Albany Density Fractions av org density, density, liptinite, bituminite, vitrinite, liptinite, bituminite, vitrinite, g/cm3 g/cm3 vol % vol 7 0 vol % wt% wt% wt% liptinites bituminite vitrinites kerogen liptinites bituminite vitrinites kerogen liptinites bituminite vitrinites kerogen
1.132 1.213 1.282
1.106 1.170 1.181
% VM
% FC
73.1 59.8 56.8 46.3
23.1 35.2 33.5 25.2
84.40 2.10 5.40 7.52 %
ash
3.00 5.15 8.75 26.45
1.0 2.2 38.5 7.7
14.60 95.70 56.10 84.76 %C
(dry)
80.53 76.89 72.09 50.74
70 H (dry) 8.77 7.54 7.06 4.91
83.4 2.0 5.0 7.0 % N
(dry)
15.5 95.7 55.6 85.0
70 org S
1.91 2.66 2.42 1.70
1.15 1.60 1.52
normdmmf
% org 0, normdmmf
H/C
N/C
O/C
8.96 7.87 7.81 7.73
1.95 2.78 2.68 2.68
5.63 7.47 8.08 7.60
1.298 1.167 1.167 1.154
0.020 0.030 0.029 0.029
0.051 0.070 0.076 0.071
tuminites to lower density and vitrinites to higher. This resulted in a C1.25 g/mL fraction that was approximately 99 vol 70bituminite and a 1.3-1.31 g/mL fraction that was 51.5 vol 70 vitrinite. Unfortunately, there was only about 0.1 g of material recovered in this latter fraction requiring that lower purity fractions be composited to obtain adequate material for subsequent analyses. Even so, the final composite exhibited more than a 2-fold improvement in vitrinite purity as a result of recentrifugation. Calculated Maceral Group Properties. Data presented in this section were derived from the three final composites for the NA (Table 111) and from the four density fractions representing the highest concentrations of liptinites, bituminite, vitrinites, and inertinites, respectively, for the CLE. The empirical density values for each of these concentrates were corrected for mineral contentz1to obtain organic density values. These corrected values along with petrographic data were then used in the calculation of average maceral group densities. The calculated maceral group densities were in turn utilized to convert the volume percent petrographic data to a weight percent basis. This lengthy approach permitted the calculation of average maceral group chemical parameters as shown in Table IV. Results of these calculations show that the density of the NA liptinites was a significantly higher 1.09 g/mL compared to a 1.02 g/mL for the CLE liptinites. Conversely, the calculated vitrinite density for the NA, 1.21 g/mL, was lower than for the CLE, 1.26 g/mL. Organic molar ratios exhibited similar trends in both samples; that is, the H / C ratio declined for the denser macerals, the N / C ratio maximized in the bituminite macerals, and the O/C ratio increased from liptinite to vitrinite. Just as for the calculated densities, the extremes for these ratios were consistently found in the CLE groups. To emphasize this point, the H / C molar ratios for both separations are plotted in Figure 10 as a function of macera1 group density. The data generally plot along a straight line as expected, but the tendency of both the NA density and H / C values to cluster relative to the CLE is evident. Total hydrocarbon (HC) pyrolysis yields15are presented on a unit organic carbon basis in Table IV. Pyrolysis yield for each kerogen was slightly greater than measured for the corresponding oil shale, perhaps due to a reduction in (21) Smith, J. W. Report of Investigations, L E R C / R I - 7 6 / 6 Laramie Energy Research Center: Laramie, WY, 1976; 10 pp.
% org C, norm dmmf
5.51 7.16 7.30 4.83
% org H, norm dmmf
% N,
org 0 (dry)
%
(dry)
90 HZO 0.80 0.85 1.02 1.03
1.10 2.30 39.45 8.00
%
82.29 80.22 79.75 79.81
70 mineral
FeS,
material
2.6 3.1 8.1 34.9
3.9 5.2 11.4 38.1
16-
14
-
x
*
05
or
13
1 1
09
15
HIC MOLAR R A T I O
Figure 10. H/C molar ratios and maceral group densities for New Albany (*) and Cleveland ( X ) maceral group concentrates. Both density and H/C ratios are calculated to a 100% maceral group basis. 2 00
X
I50
* X
0
Y J
*
*
New A l b o n y
x Clrrclond
;I O 0
*
v I
X
x
050 -
0 90
IO0
I IO
I
20
DENSITY
I30
I 40
I 50
q l m i
Figure 11. Hydrocarbon pyrolysis yield and maceral group densities calculated to a 100% maceral group basis. HC yields are expressed on a unit carbon basis relative to the NA oil shale which was arbitrarily assigned a value of 1.0 (*, NA; X, CLE). secondary coking and/or cracking reactions upon removal of the mineral matrix. Calculated maceral group values for total HC yield for the liptinite and vitrinite groups of
262 Energy & Fuels, Vol. 4 , No. 3, 1990
Taulbee et al.
Table IV. Comparison of New Albany and Cleveland Maceral Group Properties (Calculated to 100% Maceral Group and dmmf Basis) density, g/cm3 % org C % org H '70 org N % org S liptinites bituminite vitrinites inertinites kerogen
NA
CLE
NA
CLE
NA
CLE
NA
CLE
NA
CLE
1.09 1.17 1.21 1
1.02 1.16 1.26 1.40
82.72 80.19 78.77
81.68 78.69 75.67 83.14
9.19 7.84 7.59
10.14 7.40 6.54 4.53
1.78 2.80 2.63
1.43 3.12 2.47 2.13
1.07 1.68 1.76
1.74 1.89 2.22 1.78
79.71
NA liptinites bituminite vitrinites inertinites kerogen
5.24 7.47 9.29
7' 0 org 0 CLE 5.00 8.91 13.10 8.42
NA 1.324 1.165 1.148
NA 0.0048 0.0078 0.0084
CLE 0.0081 0.0094 0.0110
2.68
FC/org NA 0.250 0.460 0.482 0.460
o/c
N/C CLE 1.48 1.12 1.03 0.65 1.07
7.60 SIC
liptinites bituminite vitrinites inertinites kerogen
7.73 H/C
C CLE 0.10 0.46 0.69 0.90 0.48
NA 0.019 0.030 0.029
CLE 0.015 0.034 0.028 0.022 0.029 0.030 HC pyrolysis yieldn NA CLE 1.35 1.67 1.10 1.18 0.86 0.65 0.58 1.05 1.13
NA 0.048 0.070 0.089 0.072 HC NA 1.10 1.29 1.06 1.14
CLE 0.046 0.085 0.133 0.076 0.080 gas yieldb CLE 0.78 1.26 1.20 0.98 1.06
OThe HC pyrolysis yield data are on a unit carbon basis relative t o the New Albany shale assigned a value of 1.0. b T h e pyrolysis gas yield data are relative to the gas yield from the New Albany shale arbitrarily assigned a value of 1.0.
the NA again clustered near bituminite relative to analoalginite in a set of Cleveland and New Albany core samgous CLE values. ples,ll consistent with a parent-daughter relationship The pyrolysis data are plotted in Figure 11 as a function between alginite and bituminite precursors. of maceral group density where, as expected, the less dense The NA alginites showed a lower hydrogen content and macerals exhibit the highest HC yield. Once again, these higher density relative to the CLE. Attempts to recenpoints plot along a relatively straight line with the outtrifuge concentrates of this maceral to obtain higher purity ermost values exhibited by the CLE groups. The data in indicated that the lower hydrogen content and higher Table IV without exception indicate that the average aldensity was inherent and not due to maceral or mineral ginite and vitrinite properties in the NA maceral groups impurities. Microscopically, the NA alginites generally appear to converge on those of bituminite relative to appeared to be more degraded and on average, exhibited analogous CLE maceral groups. longer wavelength fluorescence (red-shifted) under blue Discussion of Results. The New Albany kerogen, the light than their CLE counterparts. Further, there was a focus of this work, is in many respects similar to the continuum in both morphology and wavelength of maxiCleveland Member kerogen. Both are comprised of the mum fluorescence from highly figured bright yellow same maceral types and have similar bulk chemical comfluorescing alginites to nonfluorescing, amorphous bitupositions. The hydrogen content of both the NA and CLE minites. Visually, the red-shift in fluorescence correlated vitrinites is high compared to typical coal vitrinites of with disfiguration, i.e., extent of degradation. If in fact comparable rank. However, the NA kerogen contains a bituminites are derived via alginite precursor degradation much higher proportion of bituminite as well as notable as it appears, it is reasonable to expect a continuum in differences in the chemical composition of the other machemical properties which would correlate with the extent cera1 types. of precursor degradation. Thus, the convergence of The differences in chemistry of analogous maceral types chemical parameters between the NA alginites and bituin these kerogens may be due to one of three factors, i.e., minites relative to the same maceral types in the CLE may a difference in rank, differences in the precursor or source be explained by the fact that, on average, the NA alginite chemistry, or differences in the environments of deposition. precursors appear to have been more extensively decayed Since both shales show similar vitrinite reflectance ( R , during deposition. In other words, the NA alginites were 0.55) similar pyrolysis response, and both are of Upper more bituminite-like. Devonian age (major changes in terrigenous plant fauna The NA vitrinites were also, in general, more degraded did not occur till much later), we believe that most of the appearing than the CLE vitrinites (Figure 3). Unexpectdifferences in chemistry can be attributed to differences edly, the NA vitrinites were higher in hydrogen, were lower in the extent of decomposition of the maceral precursors in density, and produced more HC product during pyroa t the depositional site. This reasoning is supported by lysis than did the CLE vitrinites. Similar to the alginthe presence of bituminite at substantially higher levels itelbituminite continuum, a continuum in morphology and in the NA kerogen relative to the CLE since bituminite reflectance between vitrinite and bituminite was observed is thought to originate from the decomposition products in the NA. This observation along with the convergence or residue from algae, faunal plankton, and b a ~ t e r i a . " Q ~ ~ ~in~ chemical parameters suggests that vitrinite precursors This maceral was observed to inversely correlate with may also be converted to bituminite precursors during deposition. Since the bituminite properties measured for both kerogens generally fell between those of the liptinites (22) Teichmuller, M. Fortschr. Geol. Rheinl. Westfalen 1974, 24, and vitrinites, then in order for the chemical properties 65-112. of these latter two groups to converge on those of bitu(23) Stack, E.; Mackowsky, M.-Th.; Techmuller, M.; Taylor, G. H.; minite during depositional alteration, the same chemical Chandra, D.; Teichmuller, R. Stach's Textbook of Coal Petrology,3rd ed.; Gebruder Borntraeger: Berlin, Stuttgart, 1982. moieties would have to remain undigested for both, similar
-
Energy & Fuels 1990, 4 , 263-270
263
On the basis of visual and chemical evidence, it was concluded that the bituminite maceral as defined in this study is the end product of bacterial degradation not only of alginite but of vitrinite precursors as well. The chemical evidence was based on the convergence of numerous chemical parameters including density, pyrolysis yield, and organic elemental ratios for the more extensively decayed liptinites and vitrinites of the New Albany kerogen. For both oil shales, the liptinite macerals as defined in this study were found to exhibit the highest H/C ratio and pyrolysis yield and lowest aromaticity, density, and N/C ratios.
byproducts would have to form in situ, or perhaps some combination thereof. At the least, the relatively high hydrogen content of the vitrinites and the chemical differences between like macerals in the two kerogens stress the importance of the environment of deposition in setting the ultimate chemistry of the sediment.
Summary The efficiency of DGC maceral concentration for both kerogens was diminished by the presence of high levels of bituminite which tends to be intimately associated with iron sulfides and other maceral types. Improvements in maceral purity were obtained from DGC reprocessing of selected density fractions. However, this improvement was minimal for the New Albany liptinites due to a relatively high average density of these partially decayed macerals and the resulting increased density overlap with bituminite.
Acknowledgment. We acknowledge the assistance of Dr. J. Hower, G. Wild, G. Thomas, and M. Moore. The work reported here was conducted at the Kentucky Center for Applied Energy Research administered by the University of Kentucky with funding provided by the Commonwealth of Kentucky.
Oxygen Compounds in Athabasca Asphaltene Z. Frakman, T. M. Ignasiak, E. M. Lown, and 0. P. Strausz* Department of Chemistry, University of Alberta, Edmonton, Alberta, Canada, T6G 2G2 Received August 10, 1989. Revised Manuscript Received February 19, 1990 Specific classes of oxygen-containing compounds in the low molecular weight, acetone-extractable portion of Athabasca asphaltene have been isolated and identified. They include fluorenones, benzofluorenones, and dibenzofluorenones; tri- and pentacyclic terpenoid carboxylic acids; carboxylic acids of dibenzothiophene, n-alkanes, anthracene, and dibenzofuran; and bi-, tri-, tetra-, and hexacyclic terpenoid sulfoxides. The most abundant classes were the terpenoid sulfoxides and carboxylic acids. The total amount of identified material comprises 1.3% of the asphaltene and, with the exception of some aromatic acids, has also been detected in the resin fraction of the bitumen. These materials effect the solubilization of the asphaltene micelles in the maltene fraction of the bitumen.
-
Introduction The variety of polar compounds present in bitumen and defined in general as materials containing oxygen, sulfur, and nitrogen is considered to have a major influence on the behavior of oil during the course of production from the reservoir, through the various steps in refining, to the quality of the finished product. Polar compounds may greatly influence recovery techniques by either acting as surfactants which affect the interfacial tension between oil and water or modifying the wettability of the reservoir rocks due to chemisorption on the mineral surfaces. The presence of polar material is also related to problems in the upgrading of crude oil and the stability of refined products. Also, through their ability to participate in intermolecular acceptor-donor systems, the polar compounds may facilitate the dispersion of asphaltene in bitumen and increase the viscosity of oil. The polar compounds are distributed in both the maltene and asphaltene fractions of bitumen, with the asphaltene having the highest heteroatom concentration. In the maltene fraction of the Athabasca bitumen, using a combination of chromatographic methods, distillation, and mass spectrometry, it was possible to isolate and *To whom correspondence is to be directed. 0887-0624/90/2504-0263$02.50/0
identify several homologous series of such heteroatomcontaining compounds as carbazoles; quinolines; porphyrins; alkanoic carboxylic acids; mono- and diunsaturated carboxylic acids; terpenoid carboxylic acids; fluorenols, including 9-n-alkylfluoren-9-01s;substituted fluorenones such as 1,4- and 3,4-dimethylfluorenones; and di-, tri-, tetra-, and hexacyclic terpenoid sulfides and sulfoxides.'-'* (1)Payzant, J. D.;Hogg, A. M.; Montgomery, D. S.; Strausz, 0. P. AOSTRA J . Res. 1985. I . 203-210. (2)Mojelsky, T.W.f Montgomery, D. S.; Strausz, 0. P. AOSTRA J. Res. 1986,3, 25-33. ( 3 ) Hoffman, C. F.; Strausz, 0. P. Am. Assoc. Pet. Geol. Bull. 1986, 70,1113-1128. (4)Cyr, T.D.;Strausz, 0. P. J . Chem. SOC.,Chem. Commun. 1983, 1028-1030. (5)Cyr, T.D.;Strausz, 0. P. Org. Geochem. 1984, 7, 127-140. (6)Payzant, J. D.;Mojelsky, T. W.; Cyr, T. D.; Montgomery, D. S.; Strausz, 0. P. Org. Geochem. 1985,8, 177-180. (7)Mojelsky, T.W.;Strausz, 0. P. Org. Geochem. 1986, 9, 31-37. (8)Mojelsky, T.W.;Strausz, 0. P. Org. Geochem. 1986, 9, 39-45. (9)Payzant, J. D.;Montgomery, D. S.; Strausz, 0. P. Tetrahedron Lett. 1983,24,651-654. (10)Payzant, J. D.;Cyr, T. D.; Montgomery, D. S.; Strausz, 0. P. Tetrahedron Lett. 1985,26,4175-4178. (11)Cyr, T.D.;Payzant, J. D.; Montgomery, D. S.; Strausz, 0. P. Org. Geochem. 1986,9,139-143. (12)Payzant, J. D.;Montgomery, D. S.; Strausz, 0. P. Org. Geochem. 1986,9, 357-369. Strausz, 0.P.; Lown, E. M.; Payzant, J. D. In Geochemistry of Sulfur in Fossil Fuels; Orr, W., White, C., Eds.;ACS Symposium Series, in press.
0 1990 American Chemical Society
