I
WILLIAM R. THOMPSON1 and CHARLES H. PRIEN Denver Research Institute, University of Denver, Denver 10, Colo.
Thermal Extraction and Solution of Oil Shale Kerogen From each study we gain a little more knowledge of this important material -eventually correlation of results will show the mechanism by which kerogen was formed in oil shale D E S P I T E considerable research, much still remains to be known of the fundamental relationships between the oilproducing organic matter (kerogen) in oil shale and the inorganic matrix in which it is contained. T h e present study is an extension of work employing solvents as originally reported by Schnackenberg and Prien (70).
Mechanism of Solvent Action on Kerogen
Oil shale kerogen occurs both intimately mixed with inorganic material and in thin, organic-rich strata parallel to layers of high inorganic content. It has been postulated (70) as being chemically an amorphous, highly disordered, cross-linked macromolecular complex in which the main elements are inherently cyclic in nature, with numerous primarily paraffinic cross links bridged to both organic and inorganic molecules. The physical properties of such a high molecular weight space polymer depend upon four fundamental structural factors: Nature of the main chains and/or cyclic nuclei. Nature of the cross linkages, whether organic-inorganic bonds, organic-organic bonds, or both. Number of cross linkages. Ratio of organic to inorganic matter. Secondary forces bridging such macromolecules together in the aggregate are often equal to or greater than the primary valence forces within the molecules themselves. For example, Riley (9) has recently shown that the energy for merely separatidg the individual molecules (breaking secondary bridging valences) of the coal macromolecule is of the same order (58.5 kcal.) as that for rupturing of the C-C bond (pyrolysis) and thus thermally decomposing the molecule. This was true whenever the macromolecule exceeded 80 carbon atoms in size, an order not unexpected in kerogen. Included in the bonds to be ruptured Present address, Aerojet-General Corp.,
Azusa, Calif.
during pyrolysis are, of course, any primary or secondary valences involved in combinations between organic and inorganic matter. I n view of the geologic origin of kerogen these may include chelated rings in which, for example, a porphyrin-type organic structure is bonded, through chelation, to iron, copper, nickel, or other metallic atoms of the inorganic compounds present. Such chelates are extremely stable, even a t high temperature, and henc resist dissolution. The structures mentianed above could be expected to be only slightly susceptible to the action of solvents. They should thermally decompose before vaporizing. This is indeed the case for kerogen. The principal result of the dry pyrolysis of kerogen is partial fragmentation of the macromolecular complex resulting from rupturing an appreciable number of the cross linkages present, followed by further cracking to compounds of comparatively low molecular weight soluble in organic solvents. The decomposition of kerogen in a solvent medium under progessive heating is enhanced by the improved heat transfer characteristics of the solution process and modified by the ability of
e
the solvent to detach organic material from its original matrix. The solvent molecules must be capable of penetrating the solute and overcoming the forces of attraction between the solute molecules, separating them. Conversely, the solute molecules must be capable of diffusing into the solvent by overcoming the binding energies existing between the molecules of the solvent. I n the flow diagram illustrating this scheme for the diagram thermal solution of kerogen changes in the kerogen-inorganic complex are shown in the top horizontal line. Separation of the organic material from the shale mass, by whatever process, is shown by vertical lines. These in turn indicate alternative possibilities for the behavior of the organic material in the solvent. Probable types of enthalpy changes are shown in parentheses. Schnackenberg and Prien (70) studied the effect of solvent properties on the thermal solution of a 35-gallon-per-ton Colorado oil shale. It was decided to investigate the effect of the ratio of organic to inorganic matter on the thermal extraction of kerogen in solution to elucidate further the chemical structure of the organic matter. A lean and a
1 AHp AHd
(AH,,
- Entholpy of Pyrolysir - Enthalpy Dissolution
(AH, )
Of
+ T & q
AHso- Entholpy of Solvation AHs - Enthalpy ot Solution
COLLOIDAL DISPERSION
Enthalpy changes during thermal solution of oil shale kerogen >
VOL. 50, NO. 3
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359
Table
Shale
II.
Oil Content, Gal./ Total, Ton grams
Lean Rich Shale concentrate
Reactor Charge Components
Shale Charge Solvent Charge Inor- Organic/ Weight Ratio Crganic ganic inorSolSol- So!vent/ content, content, ganic Total vent/ vent/ inorgrams grams ratio ml. shale organic anic
20.3 45.7
1000.0 1000.0
124.8 273.6
875.2 726.4
0.14 0.38
1928.0 1928.0
1.87 1.87
14.99 6.84
2.14 2.58
75.3
589.5
272.8
316.7
0.86
1928.0
3.17
6.86
5.91
Table 111. Shale Oil Content, Gal./Ton 20.3
Extr. Temp.,
c.
200 300 400
Analysis of Product Extracts Hydrogen, 10.67 10.75 10.71
7.79
10.95 10.72 10.53
7.56 7.75 8.04
11.24 10.83 10.34
7.37 7.73 7.95
70
45.7
200 300 400
83.11 83.54 83.87 82.90 83.10 84.65
75.3
200 300 400
82.82 83.75 82.17
Table IV.
70
7.77 7.83
Product Extract Yields and Solution Equilibrium Constants Extr.
9% of
Temp.,
c.
&le charge
Yield % ,_ organic content
Lean
200 300 400
2.71 3.04 9.07
21.73 24.38 72.68
1.92 2.15 6.41
0.28 0.32 2.66
Rich
200 300 400
2.99 4.21 19.65
10.94 15.40 71.81
2.12 2.98 13.88
0.12 0.18 2.55
Shale concentrate
200 300 400
3.46 5.82 32.77
7.49 12.56 70.82
1.44 2.42 13.65
0.08 0.14 2.43
Shale
rich shale were selected; a low-ash kerogen concentrate was prepared to study the solution of a very rich organic complex. This was deemed preferable to using a naturally occurring very rich shale, as the organic component of very rich shales may differ from that occurring in the more common leaner shales. The effect of temperature upon the equilibrium extraction of kerogen was studied by thermal solutions at 200°, 300', and 400' C. Tetrahydronaphthalene (Tetralin) was selected as the solvent, on the basis of prior work. The pressure in the system was the autogenous pressure of the solvent at the temperature of each run. Experimental Procedures
An 8-kg. portion of each shale sample was ground to pass a 30-mesh screen. Another 23-kg. portion of the rich shale was ground to a - 100-mesh for use in preparing the concentrate. Each shale sample was assayed by the standard modified Fischer method. Standard U. S. Bureau of Mines analytical techniques for oil shale (12) were employed for moisture, ash, mineral carbonates, natural bitumen, total and organic
360
Carbon/ Hydrogen Ratio
Carbon,
INDUSTRIAL AND ENGINEERING CHEMISTRY
Grams mod. extr./mole solvent
Soh Equil. Constant
carbon and hydrogen, and total sulfur. Inorganic sulfur was measured by the Powell method (7). Nitrogen was determined by the standard macro-Kjeldahl method, using the 12'inkler modification and further changes as recommended by Mapstone ( 5 ) and by Pate1 and Sreenivasan (6). Because no simple method is known for the direct determination of oxygen, the organic oxygen content of each shale was approximated by assuming an average oxygen content of 9.57' for the organic phase. This value Mas found relatively constant by Stanfield and coworkers ( 7 1 ) for a number of Colorado oil shales ranging from 17.8 to 51.8 gallons per ton. This calculated value assumed constant for the shales investigated, was recomputed on a raw shale basis and added to the sum of the assay values for the other organic components, resulting in a value for the total organic content as determined by ultimate analysis. Data on these three shales are tabulated in Table I. Techniques for producing low-ash concentrates were studied to determine the best method for preparing comparatively large amounts of a lotv-ash material. The Trent amalgamation
OIL S H A L E KEROGEN
I'I w 35
1
& 30
P
-
1
15.3 G/T
I-
Y
E 25a
I
I
300
I
400
-
E
0 200
300
400
TEMPERATURE, V.
TEMPERATURE, "C
Figure 1. Effect of extraction temperature on extract yield Per cent of shale charged to reactor
method, as applied to shales by Quass (8), Himus ( Z ) , and Dancy (7), appeared to offer the most fruitful approach, although the ash content of the concentrate was not as low as that of concentrates prepared by the Hubbard method ( 3 ) . The amalgamation procedure consists of grinding pulverized oil shale in a mineral oil paste with water. A high proportion of the mineral matter is dispersed in the oil phase. The mineral oil is then extracted with a suitable solvent, leaving an enriched shale fraction. The oil content of the concentrate prepared in this manner was assayed as 75.3 gallons of oil per ton of concentrate (2650% oil by weight). Further analytical data are tabulated in Table I. An Aminco high-pressure shaking autoclave of the 43/a-inch series was used for the thermal solution process. The reactor vessel itself was a 5-liter, stainless steel bomb fitted with an internal, double hairpin water coil for use in controlling the reactor temperature. The rate of heat input to the heating jacket was controlled in the usual manner. A charge ratio of approximately, 1 volume of shale to 1.5 volumes of solvent was processed satisfactorily for the shale runs. The charge ratio for the concentrate solution runs was approximately 1 volume of concentrate to 2.4 volumes of solvent (Table 11). Preliminary runs showed that extraction equilibrium wab not attained until the charge was maintained a t the operating temperature for a t least one hour. Operational procedure for the thermal extraction runs was essentially the same as that employed in the previous thermal solution studies (70), except for minor
Figure 2. Effect of extraction temperature on product extract yield Per cent of shale organic content
modifications. Analysis of the resulting product extracts is shown in Table 111.
Results The yield of product extract as a function of the extraction temperature is shown in Table I V for each shale sample studied. Yield relationships are shown graphically in Figures 1 through 3. Figures 1 and 4 (a cross plot of the data) indicate that the amount of material extracted from the shale is a linear function of the organic content of the shale within the range of organic contents studied. Below 200' C. the fraction of material separated from the shale is essentially independent of the concentration of the organic content of the shale. With increasing extraction temperature the slope of the extraction isotherm approaches unity. Variation of product extract yield with extraction temperature is expressed as a function of shale organic content (Figure 2). A moderate increase in product extract yield is obtained for each shale between 200' and 300' C., with a much larger increase in yield between 300' and 400" C. In addition, the percentage of organic material extracted is an inverse function of shale organic cantent for thermal solutions at 200" and 300' C. At 400" C., however, the yield is essentially independent of the proportion of organic material in the shale. The net product extract yield calculated per mole of solvent charge as a function of extraction temperature (Figure 3) shows that a t 200" C. approximately the same weight of organic material is extracted per mole of solvent from the two shales, while the yield from the
I
200
I
I
I
300 TEMPERATURE, 'C
I
400
Figure 3. Effect of extraction temperature on product extract yield Grams of product extract per mole of solvent
concentrate was about one fourth lower. At 300' C., the yield obtained from the concentrate was between those of the two shales, with the 20.3-gallon-per-ton shale giving the lowest yield per mole of solvent. For the 400" C. extraction, the amount of organic material solubilized per mole of Tetralin was essentially the same for the 45.7-gallon-per-ton shale and the 75.3-gallon-per-ton concentrate and was over twice that obtained from the 20.3-gallon-per-ton shale. These data show that in the 200' to 300" C. range the yield of product extract is determined by the nature of the physical bonding forces in the macromolecular complex, the manner in which the bonds between the fragments are ruptured, and the ability of the solvent to transfer the organic particles from their matrix to bulk of the solvent. Several hypotheses explain the effect of variations in the organic-inorganic ratio upon the relative amount of kerogen extracted. If the kerogen macromolecules in each shale sample studied are similar in composition and size and under the influence of gentle pyrolysis these molecules have "depolymerized" to similar fragments, the energies involved in rupturing fragment-bridging forces control the yield, Because the proportion of organic-inorganic bonds per kerogen fragment must increase with decreasing organic content of the shale and greater percentage yields are obtained from shales of decreasing organic content, the energy content of these organic-inorganic bonds is thus of a lower order of magnitude than that of the organic-organic bonding valences. Enthalpy changes inVOL. 50, NO. 3
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MARCH 1958
361
w
I
I
45,
I
Figure 4. Product extract yield as a function of shale organic content
I
I
40
t
4
4 U
3
I
35 W J
!Ii-
a v r)
400 * C .
6.0
!Ax)
4
c
I
2
W z
25
-
Y
Q
7.8
-
4
-
7.6
-
c 20
w -
*
2
-
c
a
4
I5
+
i
W
+ 3
-
0
74
W
L
10
Figure 5. Effect of extraction temperature on C/H ratio of product extracts
0
a 5
I /
'''
3 0 0 'C.
0
200 ' C .
d
//**s =
/
0
-
0
IO
I
I
I
I
20
30
40
50
60
7.0 7.2
b
r
2 200
300 EXTRACTION TEMPERATURE,
400
'C.
SHALE ORGANIC C O N T E N T , PER CENT ( A S DETERMINED BY U L T I M A T E
ANALYSIS1
volved in the solution process show that such organic-inorganic bonds are probably adsorption attraction forces. An alternative hypothesis assumes that the composition of the kerogen in each shale sample is essentially the same, but the average size of the macromolecular complex increases with increasing shale organic content. Because gentle pyrolysis on the kerogen primarily destroys relatively easily broken cross linkages, the average size of the fragments produced at comparatively low extraction temperatures would be a direct function of the organic content of the shale. The solvent would then possess energy sufficient to rupture bonds holding comparatively smaller fragments in the matrix but insufficient to detach larger fragments as the latter would possess secondary bridging forces of a comparatively high energy level. Because the relative proportion of smaller fragments resulting from gentle pyrolysis would increase with decreasing organic content, greater percentage yields would be obtained from the leaner shales. At anextraction temperature0f400~C., the product extract yield was essentially independent of shale organic content. The kerogen macromolecular complex is highly cracked, forming fragments of comparatively the same size which are equally well solubilized by the solvent. The fact that pyrolysis of shale is a first-order reaction, and thus independent of reactant concentration, favors the hypothesis that pyrolysis of kerogen controls the extraction process at high temperature. A further hypothesis drawn from these higher temperature extraction studies is that either kerogen is present in two
362
distinct forms or that two different bonding mechanisms are involved. The first hypothesis was offered by Schnackenberg and Prien (70). In each of the three cases studied approximately 30% of the shale organic content was not extracted by the solvent a t 400' C. T h e composition of this fraction of the kerogen may possess internal valences such that the macromolecular complex is not appreciably cracked a t this temperature level, may have a composition making it relatively insoluble in the solvent used, or may possess bridging valences to the inorganic matrix of sufficient magnitude to resist rupture. Data recently published (4) show excellent agreement between the yields reported herein for the thermal solution at 400' C., with Tetralin as the solvent, and yields obtained by the U. S. Bureau of Mines at the same temperature and for the same extraction period with kerosine as the solvent. The carbon-hydrogen weight ratios of the various product extracts are plotted as functions of extraction temperature, original shale organic content, and yield of extract in Figures 5 , 6, and 7 , respectively. With one exception (the 200' C. extract from the 75.3-gallon-per-ton concentrate) all product extracts had carbon-hydrogen ratios greater than those of the original raw shale organic matter from which they were obtained. A similar increase in carbon-hydrogen ratio of product extracts obtained with Tetralin was reported previously (70). As that investigation also showed that paraffin-type hydrocarbon solvents, such as hexane, produced extracts of considerably lower carbon-hydrogen ratio, it can be postulated that Tetralin tends
INDUSTRIAL AND ENGINEERING CHEMISTRY
to solubilize preferentially high carbonto-hydrogen-ratio fragments of the original kerogen macromolecule-e.g., polycyclic naphthenic structures. Conversely, solvents of the hexane type tend to dissolve more paraffinic portions of the macromolecule. The extract from the 20.3-gallon-perton shale showed little change in carbon to hydrogen ratio with temperature (Figure 5). The 45.7-gallon-per-ton shale and the 75.3-gallon-per-ton concentrate exhibited nearly identical increases in carbon-hydrogen extract ratio as the temperature was raised. This. indicates a consistent uniformity in the type of fragmentation occurring in the lean shale as solution proceeds, a fact consistent with the hypothesis of bonding between organic and inorganic matter in these shales, as shown later on the basis of enthalpy data for the solution process. When a cross plot is made of carbonhydrogen ratio of extract oils us. originai organic content of the shale subject to thermal solution, three isotherms (Figure 6) are obtained. Progressively richer shales at 200' C. yield extracts of increasingly richer hydrogen content. At 300' and 400' C. this effect disappears suggesting that the initial macromolecular fragments from richer shales a t lower extraction temperatures are of lower carbon-hydrogen ratio than those obtained a t higher temperatures. Solubilization of these richer-shale fragments tends to overshadow the practically uniform carbon-hydrogen-ratio fragments obtained from the leaner shales. Additional evidence for this dual simultaneous soluti'm process is given later by analysis of enthalpy data.
OIL SHALE KEROGEN Figure 6. Effect of shale organic content on C/H ratio of product extracts
4 8.0
8.2
-
80
0
0
m4
4
X
2
7.8
U
-
4 8 7 G/T
75 3 G / T
.
I
-
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7.8
-
7.6
-
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I-
IX
:7.6 -
c a
I
a
0
7.4
8
-
0
i 0
10
20
30
40 ORIGINAL SHALE ORGAMIC CONTENT, PER CENT
Further support for the above postulate is found when the percentage of original organic matter solubilized is shown as a function of the carbon-hydrogen ratio of the extracts with original shale oil content as parameter (Figure 7). Enthalpy Relationships. Consideration of the enthalpy relationships determined for the solution processes leads to interesting conclusions. The flow diagram shows that these heat effects include changes in enthalpy due to pyrolysis of the kerogen, whether this reaction is a gentle “depolymerization” type of fragmentation or a drastic cracking of the macromolecular complex; removal of the organic fragments from the shale
7.4
7.2
Figure 7. Relationship between C/H ratio and yield of product extract
so
1 -
0 300 zoo *.CC 400 *C
7.0
0 20 40 60 $0 100 PaODUCT EXTRACT YIELD, PER CENT OF ORGANIC CONTENT
b
matrix; reaction, if any, with the solvent to form a complex; and a true heat of solution for the organic material in the solvent. No evidence was found to indicate any reaction of the fragments with the solvent to form a complex. The over-all enthalpy changes for each solution process were evaluated by plotting the logarithm of the solution equilibrium constant, K, as a function of the reciprocal of the absolute temperature. Assuming that in each case a saturated solution had been obtained, this constant K’, defined as the ratio of the quantity of shale organic material extracted to the fraction remaining in the shale, becomes the equilibrium constant
for the extraction and solution process. Values for the equilibrium constants calculated in this manner for each shale a t each extraction temperature are tabulated in Table IV, The effect of temperature on this equilibrium constant is best represented by the van’t Hoff equation (Figure 8). From the slope of the curve the value of AH, the over-all enthalpy change for the solution process Kerogen (in shale) +-kerogen (in solvent) can be determined, as given in Table V. By extrapolation (Figure 9) the enthalpy changes for the reaction Kerogen (pure) -+ kerogen (in solvent)
Figure 8. Determination of enthalpy change for kerogen (in shale) -+ kerogen (in solvent) Y
4
Figure 9. Determination of enthalpy change for kerogen (pure) 4 kerogen (in solvent)
b
$
1:
1
E 0.6 10
/
-
I I I I I I I 30 40 50 70 20 SHALE ORGANIC CONTENT, PER CENT (AS DETERMINED BY ULTIMATE ANALYSIS)
VOL.‘50, NO. 3
MARCH 1958
I
-
.
100
363
Table V. Temperature Effect on Enthalpy of Solution for the Reaction Kerogen (in shale) + kerogen (in solvent) Shale A_____ H , Kcal./Mole organic 200'300"Gal./ton content 300' C. 400' C. 20.3 45.7 75.3
0.81 2.11 3.09 4.70
12.48 27.36 46.27 100.00
16.27 20.40 21.80 23.00
-
Kerogena Enthalpy change for kerogen (pure) kerogen (in solvent) obtained by extrapolation in Figure 10. a
are obtained as +4.70 and +23.00 kcal. per mole, respectively, for the temperature ranges 200" to 300" and 300' to 400" C. These data indicate that enthalpy changes accompanying thermal extraction and solution of kerogen from oil shale are a function of both extraction temperature and organic content of the shale. The enthalpy value of 23 kcal. per mole obtained in the 300" to 400' C. range is greater than the energy required to disrupt secondary valence bridges (0.5 to 5 kcal. per mole for comparatively low molecular weight compounds) and hydrogen bonds (5 to 10 kcal. per mole), but is less than the energy required to rupture primary valence bonds (50 to 200 kcal. per mole). The evolution of hydrogen sulfide and carbon dioxide at higher extraction temperatures suggests that sulfur and carboxylic linkages are the most readily ruptured in the organicinorganic complex and thus possess bonding forces of a lower order of magnitude than those of other linkages. Between 200' and 300" C., however, the solution process is primarily a desorption of macromolecular fragments in which bond energies similar to van der Waals attraction forces are ruptured. The increase in heat requirement for extraction of shales with high organic contents, compared to that needed for leaner shales, suggests that the binding forces in the organic-inorganic complex are such that organic material is more easily removed from shales of lower organic content. One possible explanation, stated earIier, is that the size of the
kerogen macromolecule decreases with decreasing organic content. Such smaller macromolecules would possess weaker secondary bridging valences and thus would require less energy for extraction. An alternative hypothesis would assume that binding forces holding the organic material to its inorganic matrix are inherently weaker than the organic-organic bonds within the kerogen. In shales of low organic content, therefore, the net energy required to detach a fragment would be less as the proportion of organic-inorganic bonds is greater than in shales with a higher organic content. If the two reactions discussed above are summed algebraically, as suggested by Schnackenberg and Prien (70), the enthalpy change for the resultant expression is a measure of the heat effect involved in the formation of oil shale by combination of organic material with inorganic matrix. The order of magnitude of this heat effect can then be utilized to evaluate possible mechanisms by which oil shale may have been formed (Table VI). The enthalpy changes for the reaction given by Equation 3: Table VI, are positive and are a function of both organic content of the shale and extraction temperature. Extrapolation of these enthalpy data for each shale for the reaction Kerogen (pure) + kerogen (in shale) to a normal ambient temperature of 25' C. results in a AH for the 20.3gal.-per-ton shale of approximately 2 kcal. per mole, while AH for both the 45.7- and the 75.3-gallon-per-ton shales is about f 2 kcal. per mole. Mechanisms proposed for the formation of oil shale, such as adsorption or chemisorption of the organic materials on the inorganic matrix or a pseudopolyrnerization reaction between organic fragments, would be evidenced by a negative change in enthalpy. While the AH of -2 kcal. per mole obtained for the reaction Kerogen (pure)
---f
kerogen (in shale)
for the 20.3-gallon-per-ton shale is of the order of magnitude for an adsorption reaction, it is difficult to assign a mech-
Table VI. Enthalpy Changes for Reaction Kerogen (pure) 4 kerogen (in shale) Extr.
Temp.
---
Range,
Reaction
(1) Kerogen (in solvent) kerogen (in shale) kerogen (in solvent) (2) Kerogen (pure)
Kerogen (pure) + kerogen (in shale) (1) Kerogen (in solvent) + kerogen (in shale) (2) Kerogen (pure) kerogen (in solution) (3) Kerogen (pure) kerogen (in shale)
(3)
364
C. 200-300
20.3
A H , Kca1.lMole 45.7 75.3
gal./ton - 0.81 _ 4.70 3.89
300-400
INDUSTRIAL AND ENGINEERING CHEMISTRY
gal./%on gal./ton - 2.11 - 3.09 4.70 _ 2.59
4.70 _ 1.61
anism requiring an input of heat as seemingly required for the formation of richer shales. One must either assume the existence of geologic conditions favorable for the endothermic reactions required, such as condensation or rearrangement reactions, or assume the above extrapolation to a 25' C. temperature invalid because of a change in the mechanisms of extraction and solution at temperatures under 200' C. for shales of high organic content. These results suggest the need for similar work in which a polar solvent is employed as the solubilizing medium for kerogen. I n addition, solution studies using both types of solvents in the temperature range of 25' to 200' C. would be of value in extending the work reported here and thus aid in assigning a possible mechanism by which kerogen was formed in oil shale. Acknowledgment
T h e authors acknowledge the financial support afforded this investigation by the Research Corp., New York, in the form of a Frederick Cottrell grant and by the Denver Research Institute, University of Denver. The advice of Josef J. E. Schmidt, Denver Research Institute, in connection with certain physicochemical phenomena, and of Werner D. Schnackenberg, Denver Research Institute, with respect to analytical problems, has also been appreciated. Literature Cited
Dancy, T. E., Giedroyc, V.; J . Inst. Petroleum 36, 593 (1950). Himus, G. W., Basak, G. C.: Fuel 28, 57-65 (1949). Hubbard, A . B., Smith, H. N., Heady H. H., Robinson, W. E., U. S. Bur. Mines Rept. Invest. 4872 (1952). Jensen, H. B., Barnet, W. I., Murphy, W. I. K., U. S. Bur. Mines Bull. 533 (1953). Mapstone, G. E.: J . Proc. Roy. SOC. N . S. Wales 82, 129 (1948). Patel, S. M., Sreenivasan, A , , Anal. Chem. 20, 63 (1948). Powell, A. R., U. S. Bur. iMines Tech. Paper 254 (1921). Quass, F. W.,J . Inst. Petrsleum 25, 813 (1939). Riley,H. L., Gas IVorid138,?6 (1953). Schnackenberg, Mr. D., Prien, C. H., IND. EKG. CHEM. 45, 313-22 (19531: Stanfield, K. E., Frost, I. C.,McAuley, I V . S., Smith, H. N., L. S. Bur. Rept. Invest. 4825 (1951). -u_.Mines, S. Bur. h h e s , "Analytical Methods for Use on Oil Shale and Shale Oil," Petroleum and Oil Shale Expt. Sta., Laramie, Wyo. (1949). RECEIVED for review h4arch 15, 1957 ACCEPTEDJuly 1, 1957 ~
~
Division of Gas and Fuel Chemistry, 131st Meeting, ACS, Miami, Fla., April 1957. - 16.27 - 20.40 - 21.80 Abstracted from a thesis presented by 23.00 23.00 23.00 ~~William R. Thompson in partial fulfillment 6.73 2.60 1.20 of the requirements for the M.S. (Ch.E.) degree, University of Denver.
