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ANALYTICAL CHEMISTRY, VOL. 50, NO. 7, JUNE 1978
release of large volumes of oxygen from the decomposing peroxydisulfate; this is minimized by carrying out the reaction a t 30 -Dsia Dressure.
(6) D. A. House, Chem. Rev., 62, 185 (1962). (7) I. M. Kolthoff and I. K. Miller, J . Am. Chem. SOC.,73, 3055 (1951). (8) C. F. D'Eiia, P. A. Steudler, and N. Corwin, Limnol. Oceanogr.,22 760 (19771. (9) G.-W.'Fuhs, Int. J . Environ. Anal. Chem., 1, 123 (1971). (10) ASTM Method D2912-70, Part 26, ASTM Standards, American Society for Testing and Materials, Philadelphia, Pa., 1976.
I .
LITERATURE CITED (1) K . J. Collins and P. J. Le B. Williams, Mar. Chem., 5 , 123 (1977). (2) P. D. Goulden and P. Brooksbank, Anal. Chem., 47, 1943 (1975). (3) J. M. Baldwin and R. E. McAtee, Microchem. J . , 19, 179 (1974). (4) P. W. Menzell and R. F. Vaccaro, Limnol. Oceanogr., 9, 138 (1964). (5) P. J. Le B. Williams. Limnol. Oceanogr., 14, 292 (1969).
for review December
' 9
Accepted February
21, 1978.
Correlation of Shale Oil I-Alkeneln-Alkane Ratios with Process Yield 1. T. Coburn,' R. E. Bozak, J. E. Clarkson, and J. H. Campbell* Lawrence Livermore Laboratory, University of California, Livermore, California 94550
When shale oil, obtained by pyrolyzing oil shale in an autogenous or inert gas environment, is analyzed by gas chromatography, the ratio of the 1-alkene to the n-alkane of the same carbon number can be correlated linearly with the percent oil yield. No pretreatment of the crude oil to remove tar bases or other components of the mixture is necessary. The method provides an analytical technique that may be useful in evaluatlng in-situ retorting conditions.
Oil pyrolytically driven from oil shale is modestly rich in certain unsaturated aliphatic hydrocarbons. This is one of the principal differences between petroleum crude oil and shale oil. In particular, petroleum crude oils normally contain no 1-alkenes (I),while shale oil contains these and other olefins (2, 3 ) . A variety of gas chromatographic (GC) techniques have been used t o evaluate oil shale retorting methods (4-11). However, t h e correlation of percent yield with the l-alkene/n-alkane ratio has not been previously exploited. I n earlier work in this area, there is an indication that the ratio of total olefins to total saturates (or n-paraffins) decreases when retorting is carried out under less than optimum conditions (12). For example, retorting runs with constant heating rates produce less oil (12-14) and a lower total olefin/total saturate ratio (15) at low heating rates. The gas chromatographic method proposed here, which focuses on the relationship of specific 1-alkeneln-alkane ratios for compounds of the same carbon number, is superior to previous gravimetric methods and to methods based on total olefin/saturate ratios. The ethylene/ethane ratio in off-gas from the retort has also been recommended as a retorting index (16),but the present method has greater applicability in the absence of extensive cracking. With a nonpolar column (10% SP2100 on 100/120 Supelcoport, 8'/min programmed run with N2 flow a t 25 cm3/min), gas chromatographic traces of crude shale oil show a characteristic doublet feature for hydrocarbons in the C7 through C12regions. The first band of the doublet pair is the 1-alkene and the second, t h e n-alkane of the same carbon number (8,17). The larger this ratio of 1-alkene to n-alkane, the greater t h e yield of shale oil from the retort run during Chemistry Department, Boston University, Boston, Massachusetts.
~~~
Table I. Gas Chromatograph Operating Conditions for Determination of Shale Oil 1-Alkeneln-Alkane Ratios (C, to C,, Hydrocarbons) Carrier Nitrogen, flow rate 25 cm3/mln Detector temperature 375 ' C Injector temperature 250 'C 60 to 350 "C a t 8 'Cimin Column oven temp (programmed heating rate) 10% SP2100a on 1001120 mesh Column Supelcoport support; 3 m X 3.2 mm stainless steel tubing Sample size 1 PL a SP2100 is a methyl silicone oil similar to OV-1 or SE30; SP2100 was supplied by Supelco Inc., Bellefonte, Pa. which the sample was produced. This correlation can be used to evaluate retorting in terms of the percent oil yield (based on Fischer Assay) for given process conditions. It is equally useful for both small (100 g) lab pyrolysis experiments and certain pilot retort runs (125 kg).
EXPERIMENTAL Gas Chromatography Procedure. Two gas chromatographs were used: the Hewlett-Packard model 5849 and the Varian model 2700. The instruments had dual-flame ionization detectors and were operated using the standard conditions outlined in Table I. There was no change in the results when helium was substituted for nitrogen as carrier gas. The oil samples from various experiments were found to vary widely in viscosity. Carbon disulfide was used as a diluent to reduce the viscosity and ensure injection of a standard sample into the chromatograph. The CS2does not give a significant peak with a flame ionization detector and therefore does not appear to interfere with the determination. Standardization and calibration by co-injection of a synthetic mixture (CS2 as solvent) were accomplished in the usual way. Careful control of conditions and the use of calibration curves are essential for consistent and accurate analyses when different chromatographs are employed. Figure 1 shows a typical trace obtained from a crude shale oil under these conditions. The 1-alkeneln-alkane ratios were determined directly from the ratios of peak areas calculated either with a Hewlett-Packard model HP5840 or a model HP3380A recording integrator connected to the chromatograph. The integration parameter of major interest is the slope sensitivity, which was set at 0.1 mV/min. Shale. Oil shale was obtained from the Anvil Points Mine in Colorado. The powdered samples were prepared by crushing and
0003-2700/78/0350-0958$01.00/0 Q 1978 American Chemical Society
ANALYTICAL CHEMISTRY, VOL. 50, NO. 7, JUNE 1978 Table 11. Oil Yield vs. 1-Alkene/n-Alkane Ratio for C, to C Sample No.
a
TC-12 11-139 TC-14 11-141 11-149 TC-42 TC-48 TC- 20 11-143 11-145 TC-18 TC-22 TC-28 TC-34 TC-56 11-147 TC-40 TC-26 TC-30 TC-50 A zero flow
Heating rate, “ C / h
External gas flow rate,a cm’imin
Oil yield, % FA 98.4 98.1 96.1 96.8 96.6 89.9
’
A p p r m mate column temperature I - C I
100
and C, Hydrocarbons 1-Alkenein-alkane
C8 180 0 0.73 120 0 0.70 64 0 0.60 60 0 0.63 30 0 0.36 20 0 0.50 0.50 19 0 91.0 0.50 0.50 19 0 90.8 0.51 0.51 18 0 92.8 0.51 0.52 6 0 88.3 0.45 0.35 5 0 85.7 0.35 0.37 5 0 86.1 0.40 0.39 5 86.7 2.0 0.45 0.47 5 7.0 91.9 0.55 0.54 5 15.0 92.9 0.56 0.58 2 0 84.9 0.31 0.32 18 2.3 93.7 0.55 0.55 18.5 2.0 90.4 0.49 0.53 19 6.3’ 92.5 0.57 0.58 19 98 98.6 0.56 0.64 indicates autogenous conditions. Sweep gas contained 2% oxygen.
’
120
140
160
180
200
220
C a r b o r number
Figure 1. Typical chromatogram of product shale oil for carbon numbers C, through C,2. This chromatogram was obtained using the conditions listed in Table I
sieving several 4- to 12-kg pieces. The material passing a 20-mesh screen (800 pm) was retained, and coarser material (about 40% of the total) was discarded. The density of the retained material was 2.25 g/cm3, corresponding to a yield of 93.0 L/103 kg (22.3 gal/ton) (18). This master batch was divided into several small samples by a spin riffling technique. Four accurately weighed samples of about 95 g each were sent to a commercial laboratory for Fischer Assay. The results gave a yield of 91.5 f 1.3 L/103 kg (21.9 f 0.3 gal/ton) and a mean oil density of 0.910 g/cm3. During the course of this work, in-house assays were also run periodically in the Fischer heating mode with the apparatus previously described (19). The oil yield from 10 assays was 8.407 f 0.071 wt %. The mean density of the assay oil was 0.917 g/cm3, giving a yield in volume units of 91.7 f 0.8 L/103 kg (22.0 f 0.2 gal/ton). Analyses were conducted on several portions of the powdered raw shale to characterize the material and ensure that the spin riffling procedure gave uniform samples. The results of these analyses were: total carbon, 15.97 f 0.05 wt %; acid-evolved COz, 22.19 f 0.05 wt 70.The acid-evolved C02is assumed to be derived from inorganic carbon. The organic carbon content is then 9.91 f 0.06 wt % of the raw shale. The material used in the pilot retort was also obtained from the Anvil Points Mine; it was crushed and sieved using a procedure similar to that for the powdered material. The size range was between 1.2 and 2.5 cm, and the grade approximately 24 gal/ton.
959
C, 0.75 0.72 0.57 0.65 0.58
-.
c,
c,
c,,
0.82 0.77 0.70 0.72 0.63 0.58 0.57 0.59 0.58 0.42 0.44 0.46 0.53 0.63 0.66 0.33 0.63 0.63 0.67 0.78
0.80 0.74 0.68 0.75
0.68 0.73 0.55 0.69 0.59 0.50 0.50 0.43 0.46 0.34 0.33 0.43 0.51 0.44 0.59 ... 0.54 0.53 0.63 ...
0
0.61
0.67 0.57
0.59 0.58 0.45 0.43 0.48 0.51 0.63
0.68 0.40
0.64 0.61 0.66 0.79
Oil Generation. Retorting of the powdered oil shale was carried out in a modified Fischer Assay type apparatus. Details of the equipment are described elsewhere (19). The retort furnace is completely programmable, allowing use of any heating schedule. All retorting experiments were carried out at linear heating rates (Le., d T / d t = constant). Bulk oil samples were analyzed. Conditions and results are compiled in Table 11. An overall mass balance was calculated by comparing the weight loss during heating to total products collected. The mass balance typically ranged from 99.0 to 101.0%. Oil was also obtained from shale samples processed in the Lawrence Livermore Laboratory (LLL) 1.5-m (125-kg)pilot retort. Details of this retorting apparatus have been given elsewhere (20). The retorting front velocity was approximately 1.5 m/day for the experiments reported here. Oil samples were collected throughout the run by means of an off-spout at the base of the retort. At the time of sampling, the thermal profile through the retort was also recorded. All oil samples were kept refrigerated until they were analyzed so as to minimize possible side reactions of the alkenes. Bulk oil samples were analyzed. Oxidation of Crude Shale Oil. A suspension of 0.9 cm3shale oil (a bulk oil sample), 20 cni3 distilled water, and 50 cm3 reagent-grade acetone was mixed with 3.0 g of reagent-grade potassium permanganate. The resultant mixture was stirred at room temperature in a round-bottom jlask surmounted with a water-cooled reflux condenser. After 5 h, the characteristic permanganate color had begun to fade, and by 30 h, the solution had become brown. The suspension was then filtered by means of Celite Filter-Aid and washed several times with aqueous acetone giving an opalescent filtrate. The modified oil was extracted into benzene, and the concentrated benzene solution injected directly into the gas chromatograph; the chromatogram was run under standard conditions. The leading peak of‘each of the characteristic hydrocarbon doublets was eliminated by this oxidation process.
RESULTS AND DISCUSSION Table I1 and Figure 2 show the 1-alkeneln-alkane ratios for Ci through Clo and C12hydrocarbons determined from gas chromatograms of shale oils. T h e oils were obtained by retorting powdered shale samples of the same grade a t different heating rates and/or different external sweep gas environments. Both of these retorting variables have been found to affect process oil yield (as percent of Fischer Assay) (14). The ratios were calculated from integrated chromatogram peak areas of the corresponding 1-alkene and n-alkane peaks (see for example Figure 1). Chromatographic samples were spiked with pure 1-alkenes (1-octene, 1-nonene, and 1-decene) and with even-carbon-numbered n-alkanes (C6 through C16) to
960
ANALYTICAL CHEMISTRY, VOL. 50, NO. 7. JUNE 1978
100
95 90 85
1
100
95 90 85 0.2
0.4
0.6
0.8
1-al kene/ii-al kane
100 95
I (e) C,, -
1
I
-
85
0 0.2
0.4
0.6
0.8
1-al keneln-al kane (YOFA) vs. shale oil 1-alkeneln-alkane ratio for C, through C,,and C,2 hydrocarbons. The oils were
Figure 2. Yield as percent Fischer Assay
produced in the following gas environments: autogenous (@), inert external sweep gas (0),and slightly oxidizing (A). The solid lines are based on a linear regression analysis of all the data. The dashed lines are from a linear regression analysis of the autogenous data minimize the chance of misassignment of peaks. Oxidative removal of the 1-alkenes also confirmed this assignment. Since the peaks partially overlap, the integration does not represent true peak areas. but rather the area between minima in the chromatogram. This. of course. does not affect our developing or using the correlation in Figure 2 as long as the chromatograph operating conditions given here are used for all analyses. Different analysis conditions may be used, but one must re-establish the correlation parameters for the new conditions. T h e present analysis was carried out only for carbon numbers C7 through CI2. Overlapping peaks from other compounds make lower carbon number ratios difficult to obtain accurately. At high carbon numbers (>12), the 1-alkene peak fails to separate well from the n-alkane peak of the same carbon number. Again, ratios cannot be obtained by means of t h e present method. Presumably, the use of a capillary column would extend the technique to longer chain compounds, b u t this would require a sacrifice in the simplicity of the present method. The Cll 1-alkene has a significant shoulder due t o some other compound or compounds with rather similar retention time on this column (see Figure 1). Therefore with chromatographic conditions as defined. only the 1-alkene to n-alkane ratios for C7 through C,,, and CI2 compounds can be used as yield indicators. A baseline correction inherent in the integration method eliminates complications from compounds that resolve poorly on this column (tar bases for example) and from compounds
present in minute amounts. This is so even when retention times are sufficiently close that problems might be anticipated. The correlation fails to hold only when there are overlapping peaks due to Compounds present in rather large quantity (>lo% of the alkene or alkane peak). There are, in fact, some compounds of this sort, quite likely internal alkenes (17), which interfere with some of the ratios. However, only when the integrator fails to uniformly include or exclude the overlapping peak does the ratio become meaningless. A visual scan of the chromatogram allows one to discard or rerun those analyses where a significant overlapping peak has been erroneously included. We thus obtain ratios t h a t permit a reasonable correlation. Difficulties due to overlapping peaks diminish as the oil yields approach 10070 Fischer Assay (FA). The method is most successful between 8070 and 100% Fischer Assay. This is a range of process yields for which an accurate method of determination is important. An improved correlation is anticipated as chromatography conditions are defined that provide a better resolution of the 1-alkene from the n-alkane peak (perhaps by use of capillary column techniques). However, the satisfactory correlation with less than optimum peak resolution is noteworthy. T h e various heating rates and external sweep gas environments studied (see Table 11) were designed to simulate in-situ retorting conditions. The autogenous conditions, of course, simulate the environment inside a block or particle, where the oil is produced in the gases generated during
ANALYTICAL CHEMISTRY, VOL. 50, NO. 7, JUNE 1978
961
Table 111. Linear Regression Analysis of Data for Oil Yield vs. 1-Alkeneln-AlkaneRatioa
c, Conditions
m 35.4 36.2
b 73.4 72.8
c* 1.41 1.37
m 35.6 35.9
b 73.7 73.1
m 1.43 31.9 1 . 6 4 31.8
b 73.3 72.8
u m 1.54 36.2 1.70 35.8
b 70.6 70.4
o 1.56
Cl, m b 31.5 76.2 1.61 30.3 76.3
1.90 2.24
1.81
36.8
72.6
1.64
72.7
1.67 35.4
70.5
1.56
2.21
U
Autogenous only Autogenous and inert gas flow Autogeneous,inert 36.8 72.7 gas, and oxidizing ’ The results are given in terms of sents the standard deviation.
32.0
the coefficients m and b [of the linear equation, oil yield = b
Table IV. Results from Multiple Regression Analysis of Oil Yield with 1-Alkeneln-Alkane Ratios for C, through C,, and C , , Hydrocarbons (autogenous conditions only) I. Correlation matrix Oil yield C, C8 c, Cl, 0.971 0.968 0.993 C, 0.970 0.987 0.987 C,, 0.933 0.942 0.922 0.941 C,, 0.957 0.956 0.949 0.949 0.917 11. Correlation coefficients for the expression: C, C,
C, = 73.63 c, = 18.99 C, = 19.56
ClO
c 9
U
c, = -1.21
C,, = -3.71 C,, = 2.44
pyrolysis. The N2 and C 0 2 sweep gases simulate the product-gas composition for an air-driven combustion retort. The slightly oxidizing conditions (see Table 11) are meant to imitate cases in which traces of O2 have by-passed the combustion zone. As is apparent in Figure 2, the few oils produced under nonautogenous conditions correlate less well. However, scatter in the data and relatively few data points from nonautogenous experiments make it difficult to assess the significance of this trend. A linear regression analysis of the data points in Figure 2 provides a set of simple expressions (Table 111) for calculating oil yield from measured 1-alkene/n-alkane ratios of C7 through Clo and CI2 hydrocarbons. The scatter is as much or more due to imprecision in gravimetric oil yield determinations (19) as it is to imperfections in the predictive power of the ratio method. A multiple regression analysis of the data was also carried out to obtain an expression for the oil yield in terms of the five variables (Le., C7 through Clo and C121-alkeneln-alkane ratios). Such a n analysis may be of little value since the correlation between the 1-alkeneln-alkane ratios themselves is quite good. This is illustrated in Table IV where the results of a multiple regression analysis to the autogenous data are shown. The values of the various elements in the correlation matrix are all greater than 0.9, indicating a strong correlation between the independent variables (Le., 1-alkene/n-alkane ratios). In fact, the correlation between the C7 and C8 1alkeneln-alkane ratios is better than the correlation of those two quantities with oil yield. The results of this data analysis suggest that it may be just as accurate to analyze only the 1-alkeneln-alkane ratio of either the C7 or C, carbon number or to average the results. This ratio can be related to oil yield via the corresponding coefficients given in Table 111. A good correlation between the various 1-alkeneln-alkane ratios is not unexpected. The reactivity of the 1-alkene functionality (or of its radical precursor) on which the yield correlation relies should be little influenced by hydrocarbon chain length; the similar slopes obtained from the linear
-
29.8 76.6
0
m x (ratio)]; o repre-
i
regression analyses imply t h a t this is the case. Although a significant correlation of the 1-alkeneln-alkane ratio with yield does not necessarily imply a causal relationship between the two variables, it would be surprising if the chemistry involved in the retorting process were inconsistent with the results. Under the conditions of the experiments, a decrease in oil yield leads to additional coke formation (14). During coking, oil is converted to a carbonaceous residue with a high C / H ratio (13,14). Both 1-alkenes and the radical precursors that generate 1-alkenes would be ideal acceptors for the excess hydrogen produced during coking. An increase in n-alkane production should result. Therefore, formation of alkenes and alkanes under conditions that favor coking should decrease the 1-alkeneln-alkane ratio as observed. Evidence t h a t oil degradation occurs mainly in the condensed or adsorbed phase rather than in the vapor phase has previously been presented (14). Extent of destruction of initially formed 1-alkenes or their precursors by hydrogenation, isomerization to internal olefins, or conversion to coke should be directly related to the amount of time in the condensed or adsorbed phase. The simplest explanation for this correlation-that 1-alkenes are the principal source of coke-is one possibility. Due to their greater reactivity, 1-alkenes should be more susceptible to coking than internal olefins and aromatics and much more susceptible than saturates. However this simple picture is not consistent with the report that the yield of saturates increases as total yield decreases (15). This would require that 1-alkenes convert to coke plus saturates [Le., Cn(l.aenel Cx(coke) + Cn.x(saturatel] if the “simple” explanation is to be viable. During a normal retorting operation, one collects oil in bulk samples. I t is these bulk samples that have been subjected to analysis. They are viscous, dark brown mixtures, which contain tar bases and acids and which have a significant residue on distillation. Analysis of these crude bulk samples by gas chromatography and the calculation of selected 1alkeneln-alkane ratios provide a convenient, direct determination of yield and of the effectiveness of a particular retorting method. Usual pretreatments (4, 15, 17) (e.g., chromatographic separation of a hydrocarbon concentrate, extraction of tar bases and acids, or distillation) or use of a capillary column (21) is not required. The method can be used as a complement to other yield determination methods (19). Furthermore, it may provide a possible on-line method of monitoring process-yield from a commercial-scale in-situ retort and of evaluating changes in retorting variables (e.g., temperature of thermal wave maximum, rate of advance of the thermal wave, effect of various amount of added gases) during in-situ oil production. In those field experiments where collection of a total bulk sample of oil is difficult because of incomplete trapping of all volatiles, the ratios should still provide a n indication of process yield since the 1-alkene and n-alkane of the same carbon number have similar volatility. The method predicts oil loss that results from coking but not from combustion during the in-situ process. This is both a limitation and an advantage. However, for field applications,
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ANALYTICAL CHEMISTRY, VOL. 50, NO. 7, JUNE 1978
Table V. Oil Yield for Retort Run S-10 Predicted on the Basis of 1-Alkeneln-Alkane Ratio for C, through C, Hydrocarbons Time Predictsince ignition ed Sample vield. Sample source h min % F A h No. 510-1 Retort base 15 35 95 17 s10-2 Retort base 04 96 S10-3 Retort base 20 15 95 S10-4 Retort base 22 53 96 . . . . . . 95 510-5 Retort base 29 S10-6 Retort base 08 94 95 av 510-7 Heat exchanger N o . 1 E n d o f e x p t 98 S10-8 Heat exchanger No. 2 End of expt 99 s 1 0 - 9 Heat exchanger No. 3 Endof expt 98 98 av a Yield from mass balance = 96.0%. the correlation must be extended to shale other than that of the homogeneous master batch used for its derivation. T o assess the potential applicability of the 1-alkenelnalkane correlation derived here to field retorting experiments on other batches of shale, oil from an experiment on the Lawrence Livermore Laboratory (LLL) in-situ simulation retort was analyzed. Several oil samples were taken a t different times during the experiment from an off-spout a t the base of the retort (20). Samples of oil were also taken a t the completion of the experiment. The yield predicted from the 1-alkeneln-alkane ratio correlation and that determined by mass balance are compared in Table V. The agreement is quite good. Routine application of this method to retorting studies presently underway at LLL will more accurately define its potential. Applying this correlation to 1-alkeneln-alkane ratios taken from earlier work reported in the literature allows a number of interesting conclusions. For example, the low olefin-tosaturate ratio from early in-situ experiments suggests low oil yields such as have recently been reported (12, 22). Furthermore, this correlation along with previously published chromatograms (7)suggest that a bitumen-free shale prepared from oil shale by an extraction method (23) is rather similar to a kerogen concentrate heated isothermally a t 360 "C ( 7 ) . That is, the 1-alkeneln-alkane ratios are qualitatively the same for the two kerogen samples. We are presently looking closely a t this and similar analytical methods that may contribute to our understanding of retorting processes.
ACKNOWLEDGMENT T h e authors gratefully acknowledge the technical support
of G. Koskinas, J. Taylor, and P. Rossler in carrying out certain phases of this work. The support of the LLL General Chemistry Division, and in particular the GC work of J. Cupps, was also very valuable. We express appreciation to J. Ackermann and W. Sandholtz, who permitted us to sample the LLL 125-kg pilot retort.
LITERATURE CITED "Encyclopedia of Chemical Technology", Kirk-Othmer, Ed., Interscience Publishers, New York, N.Y., 1964, p 849. T. Iida. E. Yoskii, and E. Kitatsuji, Anal. Cbem.. 38, 1224 (1964). G. H. Dinnen, R. A. Van Meter, J. F. Smith, C. W. Bailey, G. L. Cook, C. S. Allbright, and J. S.Bail, 'Composition of Shale-oil Naphtha", U . S . Bur. Mines Bull., No. 593 (1961). D. E. Ander and W. E. Robinson, J . Org. Cbem., 35, 661 (1971). J. J. Cummins and W. E. Robinson, J . Cbem. Eng. Data, 9, 304 ('1964). E. J. Gallegos, Anal. Cbern., 43, 1511 (1971). D. A. Scrima, T. F. Yen, and P. L. Wamen, "Developments in Future Energy Sources", T. F. Yen and G. J. Chilinger, Ed., Vol. 1, Elsevier, Amsterdam, 1974, pp 321-336. J. S. Leventhal, Cbem. Geol.. 18, 5 (1976). W. E. Robinson, in "Organic Geochemistry",G. Eglintonand M. I. J. Murphy, Ed., Springer-Verlag, New York, N.Y., 1969, p 619. A. G. Douglas, in "Organic Chemistry". G. Eglinton and M. 1. J. Murphy, Ed., Springer-Verlag. New York, N.Y., 1969, p 161. R. E. Poulson, H. B. Jensen, J. J. Duvall, F. L. Harris, and J. R. Morandi, Anal. Instrum., 10, 193 (1972). G. Salomonsson, "Oil Shale and Cannel Coal", G. Sell, Ed., Vol. 2, The Institute of Petroleum, London, 1951, p 260. N. D. Stout, G. H. Koskinas, J. H. Raley, S. D. Santor, R. J. Opila, and A. J. Rothman, Colo. Sch. Mines Q . , 71, 153 (1976). J. H. Campbell, G. H. Koskinas, T. T. Coburn, and N. D. Stout, in "Tenth Oil Shale Symposium Proceedings", Colorado School of Mines Press, Golden, Colo., 1977, p 148. L. P. Jackson, C. S. Allbright, and R. E. Poulson, Am. Cbem. Soc., Div. Pet. Cbem.. Preor. 23. 771 (1977). I . A. Jacobson, A. W. Decora,'and G . L. Cook, Am. Cbem. Soc., Div. Fuel Cbem., Prepr., 19, 183 (1974). A . G. Douglas, G. Eglinton, and W. Henderson, in "Advances in Organic Geochemistry, Proceedings of the 7th International Meeting on Organic Geochemistry", G. D. Hobson and G. C. Speers, Ed., Pergamon Press, New York, N.Y.. 1968, p 369. J. Ward Smith, "Theoretical Relationship between Density and Oil Yield for Oil Shales", U . S . Bur. Mines Rep. Invest., 7248 (1969). N. Stout, G. Koskinas, and S. Santor, "A Laboratory Apparatus for Conbolled Time/Temperature Retorting of Oil Shale", Lawrence Livermore Laboratory Report UCRL-52158 (1976). W. A. Sandholtz and F. J. Ackerman, "Operating Laboratory Oil Shale Retorts in an In-Situ Mode", Lawrence Livermore Laboratory . Report . UCRL-79035 (1977). P. C. Uden, S.Sggla, D.E. Henderson, A. Carpenter, Jr., and H. F. Hackett, Am. Cbem. Soc.. Div. Pet. Cbem.. Preor.. 23. 767 (1977). H. B. Jensen, R. E.'Poulson, and G. L. Cook: A b . Cbem.'Soc.,'Div. Fuel Cbem., Prepr.. 15, 113 (1971);, J. W. Smith, "Ultimate Composition of Organic Material in Green River Oil Shale", U . S . Bur. Mines Rep. Invest., 5725 (1961).
RECEIVED for review December 2, 1977. Accepted March 13, 1978. This work was performed under the auspices of the U S . Department of Energy by the Lawrence Livermore Laboratory under contract No. W-7405-Eng-48. Reference to a company or product name does not imply approval or recommendation of the product by the University of California or the U S . Department of Energy to the exclusion of others that may be suitable.
