514
Energy & Fuels 1987,1, 514-519
Comparison of the Hydrocarbon Pyrolysis Products from a Devonian Type I1 Kerogen to Those from Kerogen/Mineral Blends Darrell N. Taulbee* and Edward D. Seibert Kentucky Energy Cabinet Laboratory, Lexington, Kentucky 40512 Received June 12, 1987. Revised Manuscript Receiued September 8, 1987 Kerogen isolated from the Cleveland member of the Ohio shale of northeastern Kentucky was pyrolyzed in the presence of several inorganic matrices to study the effect of organic/inorganic interactions during pyrolysis. These matrices included quartz; Fischer-assayed, combusted, and fluid-bed-retorted oil shale; a carbon-deficient illitic shale; Fithian illite; and chlorite. Each of the inorganic matrices was blended with the kerogen isolate to provide nominal kerogen concentrations of 50%, 25%) lo%, and 2%. All samples were pyrolyzed in a stream of He as both total hydrocarbon evolution and gas production were monitored. The production of selected hydrocarbon components from neat kerogen pyrolysis were compared to those from 1 0 1 and 50:l kerogen/mineral blends. In addition, two illites were either acid or base washed prior to blending with kerogen in order to study the effect of clay acidity during pyrolysis. All of the minerals studied, except quartz, induced product changes in the form of yield loss and greater aromatic component production. There was a general correlation between the extent of aromatic formation and coking loss, and the more acid clays were found to be the most catalytically active. There is also evidence of carbonium ion intermediates as indicated by changes in the 1-alkene:n-alkane and l-alkene:2-alkene ratios for the acidlbase-washed clays.
Introduction Oil shale kerogen research a t the Kentucky Energy Cabinet Laboratory (KECL) has focused on the chemical and pyrolytic characterization of a Cleveland oil shale kerogen from northeastern Kentucky. That work, previously reported,’ included chemical isolation of the kerogen from the rock and separation and concentration of the major maceral groups, followed by chemical and pyrolytic studies of those groups. The work reported here is a continuation of that study and focuses on the interaction of the pyrolysis products with components of the rock matrix during pyrolysis. The processes by which solid kerogen is transformed by thermal retorting to liquid hydrocarbons and gas may be conceptually divided into four stages: (1)thermal breakdown of the kerogen to form liquid, gaseous, and solid char products; (2) the migration and interaction of liquid and gaseous products within the rock matrix; (3) the expulsion of the products from the rock and further reactions with the surfaces of the rock and reactor walls; (4) coalescence and condensation of the products, which are somewhat unstable and thus subject to further reaction. The first two stages occur intraparticlely and, with the exception of the shale particle size, are not largely affected by processing variables. The second two stages involve reactions that occur outside of the particle involving organic/organic interactions as well as interactions with the reactor walls, particle exteriors, and condensation train. These latter reactions are subject to limited control by variation of the retorting process parameters. Due to the complexity of pyrolysis chemistry, it is practically impossible to characterize kerogen/rock matrix interactions directly. However, to an extent, the nature of these interactions may be deduced by comparison of the pyrolysis products from isolated kerogens with those from kerogen/rock blends. It has been observed that the py(1)Taulbee, D. N.;Barron, L. S.; Robl, T. L.; Hagan, M. Proceedings, 1985 Eastern Oil Shale Symposium: Kentucky Energy Cabinet: Lexington, KY, 1986; pp 291-300.
0887-0624/87/2501-0514$01,50/0
rolysis products from whole rock are generally enriched in lighter hydrocarbons, particularly in the C1to Clo range, compared to those from isolated kerogen^.^^^ Also, total hydrocarbon production, on a unit carbon basis, is found to be less for the whole rock than from the kerogen isolate.’ Espitalie et ala4found up to 80% of the hydrocarbon product retained for a type I1 kerogen when a 5 0 1 illite/ kerogen blend was pyrolyzed. The level of hydrocarbon yield reduction has also been shown to be affected by kerogen type, with the more hydrogen rich type I kerogens showing a lesser decrease in pyrolysis yield than type I1 and I11 kerogen^.^ The mineral constitution of the rock matrix has been shown to have a strong effect on hydrocarbon yield, with quartz and calcite showing little or no effect and the acid clay minerals inducing the greatest yield reductions.24 The available literature does not allow for more than simple qualitative statements as large variations have been found for given mineral types. It does appear that the more acidic clays are generally more active catalytically. Accordingly, this latter factor was a subject of investigation in this work. The mechanisms for mineral matrix interactions during pyrolysis are not completely under~tood.~There are two major mechanisms to consider. The first is the cleavage of the organic matrix via a free-radical mechanism that favors the evolution of straight-chain aliphatics and Cz hydrocarbons. The second mechanism is the cracking of the hydrocarbon products via a carbonium ion mechanism that favors isoparaffins, internal olefins, and C3 gases.6-8 (2)Dembicki, H.; Horsfield, B.; Ho, T. T. Y. AAPG Bull. 1983,67, 1094-1103. (3) Horsfield, B.; Douglas, A. G. Geochim. Cosmochim. Acta 1980.44, 1119-1131. (4)Espitalie, J.; Madec, M.; Tissot, B. AAPG Bull. 1980,64,59-66. (5)Larter, S. R.; Douglas, A. G. J.Anal. Appl. Pyrolysis 1982,4,1-19. (6) Greenfelder, B.S.;Voae, H. H.; Good, G. M. Ind. En#. Chem. 1949, 41,2573-2582. (7) Alexander, R.; Kani, - R. I.; Woodhouse, G. W. J. Anal. ADDL .. PYrolysis 1981,3,59-70. (8)Hershkowitz, F.; Olmstead, W. N.; Rhodes, R. P.; Rose, K. D. Geochemistry and Chemistry of Oil Shales; Miknis, F. P., McKay, J. F., Eds.; ACS Symposium Series 230;American Chemical Society: Washington, DC, 1983;pp 301-316.
0 1987 American Chemical Society
Kerogen and KerogenlMineral Blend Pyrolysis
Energy &Fuels, Vol. I , No. 6,1987 515
Row Shole (Clevelond Member-16 x 60 mesh)
Table I
t c
( 1 ) HF (Silicate Dissolution)
(2) Boric Acid (Miner01 F1uor;de Removol)
Kerogen
+ Bitumin +
inorganic matrix chlorite
FeS,
quartz
Bitumin Extroction (Benzene/Methonol 4: 1 ) Kerogen 8 FeS2
Bitumin
surface area, carbon m2/g
% total
KP7 illitic shale
Figure 1. Kerogen isolation procedure.
Clays have been used as a substrate to s t u d y both types of mechanism: although under geologic conditions freeradical mechanisms are thought to predominate.' There are of course other reaction pathways of significance such as cyclization, dehydrogenation, and addition. However, these latter mechanisms are not believed by the authors to be as important in terms of controlling the final product make and are, to a large degree, dependent on the two mechanisms listed above. The objective of this effort was to s t u d y the effect of the rock matrix on secondary reactions d u r i n g pyrolysis, particularly hydrocarbon yield loss. Samples of the whole rock as well as "pure" minerals were selected. Whole rock materials included spent shales from Fischer assay, fluidized bed retorting, and combustion. A sample of the Three Lick bed from northeastern Kentucky was also included. The Three Lick bed is an illitic green shale, devoid of organic carbon with an inorganic composition similar to that of the Cleveland member of the Ohio shale. A Fischer-assayed Green River shale was included for comparison.
The work reported here is b y no means an exhaustive s t u d y but only scoping i n nature, intended to determine the most promising direction for future efforts. Experimental Section Inorganic Matrices. The inorganic matrices employed in this study are shown in Table I along with comments on origin. All of these materials were crushed and screened to -325 mesh prior to blending with the kerogen. BET surface area measurements were made by nitrogen absorption. Kerogen Isolation. The kerogen used in this study was isolated from the Cleveland member of the Ohio shale of Lewis County, KY. Figure 1 outlines the isolation procedure used a t
u
20%
N
00%
Fithian illite fluid-beda spent shale
combusted" shale
Fischer assay (Cleveland shale) Fischer assay ' (Green River shale)
source/comment Yancey County, NC, via Ward's Natural Science var. novaculite, Hot Springs, AR, via Ward's Natural Science from Three Lick member of the KP7 core of Fleming County, KY illite no. 35, Fithian, IL, via Ward's Natural Science from Cle-002 master sample processed at 554 "C by steam fluidization (20 X 30 mesh) from fluid-bed spent shale maintained at 900 "C for 1h in room air from split of Cle-002 master shale samole from Anvil Points, e0
0.1
0.4
0.5
23.5
0.7
62.7
5.1
5.2
0.1
9.1
6.2
3.0
10.7
3.2
the KECL. The use of HC1, HN03, and LiA1H4 was avoided in this procedure in order to suppress kerogen alteration reactions a t the expense of a greater residual inorganic content. The high-temperature ash content of this material was 11%,consisting primarily of FeSz with lesser amounts of TiOz. Following demineralization, bitumin was removed from the kerogen by overnight extraction with benzene/methanol (4:l). The kerogen was stored in a vacuum desiccator until used for mineral/kerogen blend preparation. The kerogen chemistry and isolation procedure are described in more detail elsewhere.' Total Hydrocarbon Yield and Gas Production Study. For this phase of the study, all minerals were added to the kerogen at nominal mineral/kerogen ratios of 1:1,3:1,101, and 501. These mixtures were then blended for three minutes in a ball mill prior to pyrolysis. The kerogen/mineral samples were weighed into quartz reactor boats such that 1.0 f 0.01 mg of kerogen was loaded into the boat regardless of the mineral content. This kept total hydrocarbon
I
#2
1
I
I
Heating Coils Ip Thermocouple 1 I I
1
Capillary GC
In CCW position, carrier gases follow solid lines and dashed lines in CW position.
Figure 2. Simplified schematic of CDS analytical pyrolysis unit.
1.6
"The Cle-002 master sample was taken from the Cleveland member of the Ohio shale of Lewis County, KY.
He
FID
0.2
Taulbee and Seibert
516 Energy &Fuels, Vol. 1, No. 6,1987 production approximately the same from run to run, thereby avoiding nonlinear detector response. The boats were then placed into the furnace of the analytical pyrolysis unit, Figure 2, swept with He a t 50 cm3/min, heated rapidly to 300 OC and then at 10 OC/min to 600 OC for 3 min. Approximately 20% of the product exiting the reactor tube was routed directly to a flame-ionization detector (FID),which was used to monitor the total hydrocarbon evolution. After the appropriate weight corrections were made, the total response from the kerogen/mineral blends expressed on a unit kerogen basis was ratioed to the total FID response from 1mg of "neat" kerogen pyrolyzed on the same day. This provided a measure of the relative change in total hydrocarbon yield, which was attributed to interaction with the mineral matrix. The remainder of the product stream was routed through an 18 in. X 1/8 in Tenax trap maintained at ambient temperature. This trap scrubbed the hydrocarbon components that contained approximately five or more carbon atoms while allowing lighter components to pass to a second FID. The FID response was integrated for those components that passed through the trap and was assigned to gaseous hydrocarbons. At the conclusion of the run, the Tenax trap was heated to desorb the liquid components, which were then routed to the same FID. This provided a gas:total hydrocarbon ratio for the kerogen/mineral blends which was divided by the equivalent ratio obtained from 1 mg of neat kerogen, which served as a calibration standard. This latter value was then multiplied by the corresponding total hydrocarbon evolution ratio, i.e., kerogen mineralmeat kerogen ratio, to determine the gas yield relative to that from an equivalent amount of neat kerogen. This cumbersome scheme was necessitated by instrumental variations, which required standard calibration daily. At least two aliquots from two kerogen/mineral blends along with a t least two kerogen standard samples were pyrolyzed per day. This procedure was repeated on a t least three different days for each blend. The data presented in this report represent an overall average for all runs. Capillary Gas Chromatography Studies. The procedure used for this phase of the study was essentially the same as for the hydrocarbon yield study just described. The differences were that only 1O:l and 5 0 1 mineral/kerogen blends were pyrolyzed and a t the conclusion of the run, the Tenax trap was switched in line with a 25 m x 0.25 mm methyl-phenyl-bonded phase fused silica capillary GC column. This column, which was routed to a FID, was cooled to 0 "C immediately prior to desorption of the Tenax trap. Following desorption, the capillary column was temperature programmed at a rate of 10 OC/min to 270 "C and maintained for 3 min. Twenty five of the major liquid components were tentatively identified based on retention time and previous work.' The integrated detector response for these components was normalized to 100% for subsequent calculations. Clay Acidity Study. Splits of the Fithian illite and KP7 illitic shale were stirred with solutions of either 1N HCl or 1N NaOH for 1h at a liquidclay ratio of approximately 251. The clays were rinsed thoroughly with deionized water and dried prior to preparation of 501 clay/kerogen blends. These blends were pyrolyzed in the same manner as described above.
" 1 2
0.8
2
0.6
'i u2
OTotal Production
0
40
60
80
100
80
100
80
100
% FITHIAN ILLITE
2
0.8
0
20
40
60
% KP7 ILLITE
0
2
0.8
a
0.61
0
40
20
60
% CHLORITE
Figure 3. Total hydrocarbon and hydrocarbon gas evolution from pyrolysis of kerogen/inorganic blends (on a unit carbon basis relative to yield from "neat" kerogen).
2 3 w
0.8
i
0.61
l A Gas Production OTotal Production
1.2
0
-
2
z 1.0 - b4 0 0.8
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-
Y
-
E
3
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Y
-
-
0.4
Results and Discussion Total Hydrocarbon Yield and Off-Gas Production Study. For this study, all of the inorganic matrices were crushed to -325 mesh and blended in a ball mill with kerogen a t varying ratios. These mixtures were then weighed into quartz reactor boats and pyrolyzed as described in the experimental section. The curves of Figures 3 and 4 show the total hydrocarbon and off-gas yields for the kerogen/mineral blends relative to the corresponding yields from "neat" kerogen. The most radical reductions in yield were noted for pyrolysis of the Fithian illite blends. For the 50:l Fithian illitelkerogen blend, total hydrocarbon production decreased to about 60% of that from neat kerogen while off-gas production decreased to about 40%, indicative of product coking. The trends shown in the other two plots of Figure 3, representing pyrolysis of the KP7 illitic shale and chlorite
20
I
0
20
I
I
40
I
I
60
I
80
I
~
100
% FISCHER ASSAYED SHALE (CLEVELAND1
Figure 4. Total hydrocarbon and hydrocarbon gas evolution from pyrolysis of kerogen/inorganic blends (on a unit carbon basis relative to yield from "neat" kerogen).
blends, show a decrease of about 13% and 18% in total production and about 9% and 5%, respectively, in gas production for the 50:l blends. This is again indicative
Energy & Fuels, Vol. 1, No. 6, 1987 517
Kerogen and KerogenlMineral Blend Pyrolysis 1.ooo
I 79-
‘Neat’ Kerogen
&H3
Acid Washed Untreated
0.800
E3 Base E3
Washed
Gas
0.600 0.400
0.200 0.000 FITHIAN ILLITE
KP7 ILLITE
Figure 5. Total hydrocarbon and hydrocarbon gas production from 50: 1 mineral/ kerogen blends.
of product coking, though of a lesser magnitude than that measured for Fithian illite. The curves in Figure 4 show the results from pyrolysis of the three kerogen/processed shales blends. Results for the combusted and Fischer-assayed Cleveland shale blends showed similar reductions in both total and gas production for the 50:l blends, again indicative of coking reactions. This similarity is noteworthy considering that the Fischer-assayed shale contains potentially reactive coke deposits whereas the combusted shale has an oxidized surface and contains little or no carbon. There are also differences in the pore size distribution and surface area. However, regardless of these differences, these two matrices showed similarities in both this phase of the study as well as the next. The fluid bed spent shale blends in Figure 4 exhibited less activity than the other processed shales. Though not presented, results from pyrolysis of the Fischer-assayed Green River shale blends were similar to those for the fluid-bed-processed shale. Results from pyrolysis of quartz/ kerogen blends were indistinguishable from pyrolysis of neat kerogen. The bar graph in Figure 5 shows both total hydrocarbon and hydrocarbon gas production for the 50:l acid-washed, base-washed, and untreated Fithian and KP7 illite blends. Total yield reduction was greater for all three Fithian illite blends than for the KP7 illitic shale. For both clays, the total hydrocarbon yield was lowest for the acid-washed and greatest for the base-washed materials. This observation is consistent with previously demonstrated correlations between catalytic activity and clay acidity? It also suggests a major role for acid catalysis during product coking. Capillary GC Studies. The objective of the final phase of this study was to gain insight into the pathways of secondary reaction by monitoring the relative change in production of selected liquid components. The pyrolysis configuration and procedures were the same as in the previous phase, except that, at the end of the temperature program, the Tenax trap was switched in line with a capillary GC prior to desorption. Shown in Figure 6 are capillary tracings for “neat” kerogen, and kerogen/mineral blends that contained 98% chlorite, Fischer-assayed Cleveland shale, and Fithian illite, respectively. The most obvious difference between the neat kerogen and kerogen/mineral pyrograms is the increase in production of aromatic components, particularly BTX, as compared to the straight-chain 1-alkeneln-alkane pairs. To express these changes in more quantitative terms, the integrated areas for eight of the major aromatic components were summed and divided by the sum of the integrated areas of 15 straight-chain aliphatic and olefinic hydrocarbons. As shown in Figure 7, all of the minerals studied induced a general shift to greater product aro-
1.i
:
98% Fithian Illite
Figure 6. Capillary GC tracings of “neat” kerogen and mixtures of kerogen plus chlorite, Fischer-assayed Cleveland shale, and Fithian illite. 1.250-
1
.ooo-
0Kerogen
0.750-
LSS! KP7 Illite EZZi Chlorite 0 Combusted Shole
0
LL 0
0.500-
=
Fluid Bed Fircher Array Fithion Illite
0.250.
O.Oo0.
IO‘.
Kerogen 90% Mineral
2 % Kerogen 98% Minerd
Figure 7. Aromatic:aliphatic liquid component ratios.
maticity as compared to the products liberated from pyrolysis of neat kerogen. By far the most active mineral in this respect was Fithian illite. This is somewhat puzzling ,since the last phase of this study indicated that Fithian illite was the most active mineral in terms of catalyzing coking reactions, and it is generally known that aromatics are more prone to undergo coking reactions than are aliphatics. However, this tendency to coke a portion of the aromatic liquid product is believed to be more than offset by a tendency to enhance secondary addition, cyclization, and dehydrogenation reactions, resulting in a net gain in liquid product aromaticity. It is speculated that this tendency to form aromatics is directly responsible for the high rate of coking observed for Fithian illite. This is because a more rapid rate of aromatic formation would subsequently result in a higher concentration of these components within the pyrolysis furnace to undergo coking reactions. This is supported by the observation that the
Taulbee and Seibert
518 Energy & Fuels, Vol. 1, No. 6, 1987
0Kerogen KP7 Illite Chlorite H Combusted Shale EZZi Fluid Bed Fischer Assay D Fithian Illite
10% Kerogen 90% Mineral
ACID WASHED FI
2 % Kerogen 98% Mineral
UNTREATED FI
Figure 8. Sum of normalized area % values for benzene, toluene, and m- and p-xylenes.
o'6I01n 0.50
BASE WASHED FI
n
0Kerogen Chlorite
0 c D? 0
0 Combusted IdFischer Assay
=
10% Kerogen 90% Mineral
Fluid Bed Fithian Illite
2% Kerogen 98% Mineral
Figure 9. Cyc1ohexane:benzene ratios.
extent of coking loss shown in Figures 3-5 roughly correlates with the higher aromatic:aliphatic ratios in Figure 7. Figure 8 shows the sum of the normalized area% values for benzene, toluene, and m-and p-xylenes. The trend is similar to that of Figure 7, showing the activity of the three processed shales to be exceeded only by that of Fithian illite. Considering both the total production and gas yields shown in Figures 3 and 4, the magnitude of this change is generally too great to be explained solely by the dealkylation of aromatic structures. Instead, these small one-ring aromatic structures must result from formation by either cyclization and dehydrogenation of aliphatic liquids or by addition and subsequent dehydrogenation of gaseous ~ o m p o n e n t s . ~This * ~ ~latter ~ * ~ reaction pathway, that is addition and dehydrogenation involving gaseous hydrocarbons, would help explain why both gas yield and total hydrocarbon production, as plotted in Figures 3 and 4, decreased. This was in spite of the fact that, on the average, gas production was only about 20% of the total product. Thus, the release of even relatiavely small quantities of gaseous hydrocarbons during coking, in addition to those from cracking of liquid components, should have resulted in a measurable increase in off-gas production. As an indicator of dehydrogenation reactions, a bar graph of the cyc1ohexane:benzene ratios was constructed as shown in Figure 9. A substantial change in this ratio was observed for all the matrices studied. Though this gives no indication of the source for these cyclic components, i.e., primary production, cyclization of liquids, or
Figure 10. Capillary chromatograms from pyrolysis of 50:l Fithian illite/ kerogen blends.
addition of gases, the magnitude of change in this ratio is such that it does suggest a significant role for dehydrogenation. The chromatograms of Figure 10 show the liquid hydrocarbon products recovered from pyrolysis of acidwashed, base-washed, and untreated Fithian illite blended with kerogen at 50:l. The more obvious differences in these chromatograms are a reduction in the l-a1kene:nalkane ratios and a slightly greater relative production of aromatic components for the acid versus base-washed blends. The integrated detector response from these chromatograms was used to construct the bar graphs shown in Figure 11. The first bar graph represents the average l-a1kene:n-alkane ratio calculated from eight alkene/alkane pairs. There is an increase in this ratio from the acidto the base-washed illite. This observation is consistent with a carbonium ion mechanism since alkenes are more prone to H+attack6. This mechanism is supported by the second plot of Figure 11, which shows the average l-alkene:2-alkene ratio for a series of straight-chain hydrocarbons. It is generally known that free-radical mechanisms tend to favor cx-olefin formation, whereas carbonium ion intermediates favor the formation of internal olefins. Thus, the change in the l-alkene:2-alkene ratios suggests a more important role for carbonium ion intermediates for the acid-washed clay blends. Though not presented here, results from larger scale pyrolysis studies did show an increase in the C3to C2product make as well as an increase in the isobutane to n-butane ratio. Both of these latter observations are also consistent with a carbonium ion intermediak6 This is not to imply that free radicals are not the predominant mechanism but rather that they are not the sole mechanism. The third bar graph of Figure 11, which shows the change in the cyc1ohexane:benzene ratio, can be interpreted as an increase in dehydrogenation reactions in the presence of acid clays.l0 The fourth plot shows the greater relative (10) Fogelberg, L. G.; Gore, R.; Ranby, B. Acta Chem. Scund. 1967,
(9)Billaud, F.; Freund, E. J. Anal. Appl. Pyrolysis 1984,6,341-361.
21, 2041-2049.
Energy & Fuels, Vol. 1, No. 6,1987 519 1 -Alkene/n-Alkane I-
1 -Alkene/S-Alkene
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'
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-
Summary Cyclohexane/ Benzene Ratios
-
0.4
0.0
I
Aromatic/ n-Hydrocarbon Ratios
0 6 0 4
0 2
00
forming reactions, selective destruction of straight-chain aliphatics, or a combination of the two. The final plot is the ratio of hydrocarbons containing between six and nine carbon atoms compared to those containing between 10 and 15 carbon atoms. This last plot is simply an indication of the greater volatility of the liquids from the acid-washed clay blends, i.e., an indicator of more extensive secondary reaction induced by the acid clays. Finally, it should be noted that close scrutiny of all the chromatograms showed that the liquid components that were favored during pyrolysis in the presence of these inorganics were generally the same, differing only in the extent of production.
1
c6-c9/c10-c!5
With the exception of quartz, pyrolysis in the presence of all the minerals studied induced measurable changes in product yield and composition. Thus, yield losses during pyrolysis due to organic/inorganic interactions cannot be attributed to any single component of the rock matrix. The product changes that were noted generally took the form of hydrocarbon yield losses and consistently greater oil aromaticity. These changes were greatest for Fithian illite blends and least for chlorite and the KP7 illitic shale with the processed shales falling between these extremes. There was a general correlation between the extent of aromatic formation and coking loss. Finally, the decrease in product yield, lower 1-alkene:n-alkane ratios, and lower l-alkene:2-alkene ratios for the acid- versus base-treated illite blends suggest a role for carbonium ion intermediates in addition to free-radical mechanisms during pyrolysis.
"i
All
Production Ratios
0 10
ACID UNTREATED BASE WASHED WASHED
Figure 11. Selected liquid component ratios from pyrolysis of 5 0 1 Fithian illite/kerogen blends.
aromatic content of the liquids from the acid-washed blends. Since the absolute yield from the acid blends was less than that from the base-washed blends, it is unclear if this change results from an enhancement of aromatic
Acknowledgment. The authors gratefully acknowledge the support provided during this project by Cathy Poole, T. Robl, C. Jones, D. Perkins, M. B. Harris, and D. Milburn for their assistance and numerous analyses. Also, we acknowledge the KECL publication staff for the many hours contributed to the preparation of this manuscript. The work reported here was conducted a t the Kentucky Energy Cabinet Laboratory operated by the University of Louisville with funds provided by the Kentucky Energy Cabinet. Registry No. Illite, 12173-60-3;chlorite, 14998-27-7.
