PETROLEUM-SHALE OIL
_ I
CONCLUSIONS
The observation that the iso-olefin plus cyclo-olefin and the isoparaffin plus cycloparaffin contents of the five 10% fractions of shale oil decrease as the nitrogen contents increase leads to the conclusion that in the degradation of kerogen during the retorting of oil shale, the yield of is0 plus cyclic compounds depends primarily upon the denitrogenation of nitrogen compounds, and that this is less complete for compounds of hi her molecular weight. However, in the higher boiling half of sfale oil, an unexpected increase in the isoparaffins plus naphthenes and the decreases in iso-olefins plus cyclo-olefins and in polycyclic aromatics suggest that the sequence of steps in the degradation of the nitrogen compounds originally formed from kerogen during retorting is a8 follows: nitrogen compounds to isoparaffins $us naphthenes, t o iso-olefins plus cyclo-olefins, to aromatics. hese results also suggest that the polycyclic naphthenes of higher molecular weight do not dehydrogenate as readily as those of lower molecular weight.
Nonhydrocarbons i n Shale Oil
Table X.
Elemental Type Distribution, Wt. % S 0
Fraction
N
0- 10 10- 20 20- 30 30- 40
41 40
17 11
49
9 10 9 12 9
40- 50 0- 50 50-100
0-100
54 61
50 64 59
10
42 49
42 36
30 38 27 31
Molecular Type Distribution, Wt. ’% Mono-NSO Di-NS0
97 94
79 81 87 87 0 30
3 6
21 19 13 13 100 70
The constancy of the hydrocarbon composition of the lower boiling half of shale oil leads to the conclusion that kero en consists predominantly of homologs of a complex structure tfat upon degradation yield hydrocarbons having the same distribution of structural types. The trends in molecular weight distribution of the hydrocarbons, the NSO compounds, and the total shale oil fractions suggest that there are no hydrocarbons in the higher boiling portion of the 50 t o lOOyo fraction of shale oil. If the hydrocarbon molecular weight curve in Figure 3 is extrapolated to 490, which is the avera e molecular weight of the hydrocarbons found in the 50 to lOO# fraction, this molecular weight corresponds to a distillation point of 60% and all these hydrocarbons would be contained in a 50 to 70% fraction. Therefore, approximately
the highest boiling 30% of shale oil must contain essentially no hydrocarbons. ACKNOWLEDGMENT
The sample of shale oil studied was obtained through a cooperative agreement between Standard Oil Co. (Indiana) and the U. S. Bureau of Mines. The authors are grateful for discussions with A. P. Lien and for the infrared analyses and interpretation by P. J. Launer. LITERATURE CITED
Ball, Dineen, Smith, Bailey, and Van Meter, IND. ENG.CHEW, 41, 581 (1949). Belser, U. S. Bur. Mines, Rept. Invest. 4769 (1951). Botkin, Chem. & Met. Eng., 24, 876 (1921). Ibid., 26, 398 (1922). Clark, “Semimicro Quantitative Organic Analysis,” p. 37, New York, Academic Press, Inc., 1943. Dineen, Bailey, Smith, and Ball, Anal. Chem., 19, 992 (1947). Dineen, Thompson, Smith, and Ball, Ibid., 22, 871 (1950). Dinerstein and Klipp, Ibid., 21, 545 (1949). Dundas and Howe, U. S. Patent 1,469,028 (1923). Garrett and Smythe, J. Chsm. SOC.,81, 449 (1902). Ibid., 83, 763 (1903). Gavin, U. S. Bur. Mines, Bull. 210 (1922). Gray, J . SOC.Chem. Ind. (London), 21, 845 (1902). Guthrie, U. S. Bur. Mines, Bull. 415 (1938). Horne and Bauer, U. S. Bur. Mines, Rept. Invest. 2832 (1927). Kilpatrick, Prosen, Pitser, and Rossini, J . Research Natl. Bur. Standards, 36, 559 (1946). Lepper, “Official Methods of Analysis of the Association of Official Agricultural Chemists,” p. 742, Washington, D. C., Assoc. of Official Agricultural Chemists, 1950. McKee, “Shale Oil,” New York, The Chemical Catalog Co., Ino., 1925. Matteson, Anal. Chem., 22, 172 (1950). Mensies and Wright, J . Am. Chsm. SOC., 43, 2314 (1921). Nottes and Mapstone, J . Inst. Petroleum, 37, 259 (1951). Robinson, J . Chem. Soc., 127, 768 (1925). Robinson, Trans. Roy. SOC.Edinburgh, 28, 561 (1879). Ibid.. 29. 265 (18801. Schlenk,’Ann.,’ 565; 204 (1949). Smith, Smith, and Dineen, Anal. Chem., 22, 867 (1950). U. S. Bur. Mines, Rept. Invest. 4457 (1949). Ibid., 4471 (1951). Zimmerschied, Dinerstein, Weitkamp, and Marschner, IND. ENQ.CHEM.,42, 1300 (1950). REC~IVE for D review January 18, 1952.
High Temperature Shale
A C C E P T ~September D 10, 1952.
Oil
PRODUCTION AND UTILIZATlON F. E. BRANTLEY, R. J. COX, H. W. SOHNS, W. I. BARNET, AND W. I. R. MURPHY Petroleum and Oil-Shale Experiment Station, Bureau of Mines, Laramie, Wyo.
M
ANY retorts have been developed for producing a shale oil from which gasoline and other liquid fuels can be derived. These are operated in such a way that the oil is not subjected to a high temperature after it has been formed and released from the shale, thereby avoiding excessive cracking with consequent low liquid yields. I n the best of these retorts quantities of oil and gas almost equivalent to the yields obtained from the same shale by the Fischer assay method of analysis ( 7 , 8) are produced. For example, when Green River shale is processed, about 66 weight % of the organic matter is converted. to oil, 12% to gas, and 22% to a carbonaceous residue which re-
November 1952
mains on the spent shale. Quality of oil varies with retorting conditions, but generally high specific gravity, high pour point, and high sulfur and nitrogen contest are characteristic. The naphtha fraction may contain 50% or more olefinic and approximately 20% aromatic hydrocarbons, although little if any benzene or toluene, the most valuable aromatics in motor fuel and chemical manufacture, are found. Aromatic content, including nitrogen, oxygen, and sulfur compounds, increases with boiling point of the fraction, reaching 65% in the heavy gas oil, whereas percentages of paraffinic, cycloparaffinic, and olefinic hydrocarbons decrease. The major constituents of the gas produced
INDUSTRIAL AND ENGINEERING
CHEMISTRY
2641
B e n c h scale experiments are described i n which pulverized oil shale is h e a t e d a t a t m o s p h e r i c pressure a n d t e m peratures i n t h e range 1200" t o 1800' F. Under these conditions, t h e oil produced contains a m u c h higher percentage of low-boiling a r o m a t i c s t h a n does t h e oil produced i n conventional retorts a t lower t e m p e r a t u r e s . Oil yields for t h e series ranged f r o m 47 t o 59 weight % of Fischer assay, t h e m a x i m u m oil yield occurring a t a b o u t 1500" F. C a s production increased rapidly w i t h increase i n t e m p e r a t u r e . T h e m a i n constituents of t h e gases produced a t t e m p e r a t u r e s u p t o 1700' F. were m e t h a n e , hydrogen, ethylene, a n d carbon dioxide, whereas t h e gas produced a t 1800" F. consisted a l m o s t entirely of a n equimolar mixt u r e of carbon monoxide a n d hydrogen. Aromatic cont e n t of t h e n e u t r a l n a p h t h a fraction of t h e oil increased w i t h increase i n t e m p e r a t u r e a n d was a l m o s t 1 0 0 ~ ofor
t h e 1700' oil. T h e highest benzene yields were o b t a i n e d i n t h e t e m p e r a t u r e range 1500" t o 1700' F. a n d a m o u n t e d t o a s m u c h a s 5 kallons f r o m each t o n of 50-gallon-per-ton shale. Shale oils produced by high t e m p e r a t u r e retorting at 1200°, 1500", a n d 1700' F. were analyzed. These oils differ greatly i n composition f r o m those produced at ordinary retorting t e m p e r a t u r e s . Increasing t h e t e m p e r a t u r e of retorting increases t h e aromaticity of t h e oil. T h e produ c t a t a b o u t 1500" F. consists a l m o s t entirely of a r o m a t i c hydrocarbons a n d sulfur a n d nitrogen compounds. F u r t h e r m o r e , a s higher retorting t e m p e r a t u r e s a r e used, t h e c o n t e n t of benzene a n d n a p h t h a l e n e increases until, i n oil produced a t a b o u t 1700' F., t h e y are virtually t h e only compounds presen t i n t h e n a p h t h a a n d light-gas oil ranges, respectively. 4
+
+
carried out in the retort rather than in two separate systems. from Green River shale in low temperature retorts are methane, To accomplish the same degree of cracking of low temperature ethane, carbon dioxide, carbon monoxide, and hydrogen, with shale oil, a high-boiling, unstable oil must be reheated to high small percentages of other paraffinic and olefinic hydrocarbons temperatures with all the usual difficulties of such an operation. and hydrogen sulfide. Also, in retorting, an inert carrier is present on which a t least However, experimental x-ork as reported in this paper has part of the coke can be deposited and carried out of the system, shown that when retorting is carried out a t high temperatures, thus simplifying one problem attendant to high temperature 1200' to 1800° F., considerably different liquid and gaseous prodcracking. ucts are obtained. -4lthough a t these temperatures the yield The rate of conversion of the organic matter in Green River of oil is only about 50 to 60% of Fischer assay, the gas yield is shale to oil and gas has been determined for temperatures up to much higher, and the percentage of organic matter removed is 977" F. (6). Extrapolation of these data to the range 1500" about 5 to 10% greater than is removed during the Fischer assay to 1800" F. indicates that, a t these temperatures, the convereion or in the better types of conventional retorts. An oil of higher is accomplished in a fraction of a second. To attain such a short specific gravity containing a larger percentage of material boiling reaction time, small shale particles must be used to improve heat in the naphtha range is produced. At retort temperatures above transfer rates as oil shale is a poor heat conductor. Although 1500" F. this naphtha consists predominantly of benzene and tolordinarily the grinding cost would be an extra burden on the procuene. The gas contains appreciable quantities of olefins, paress, this retorting method can utilize fines that usually are disticularly ethylene, At temperatures near 1800' F. only a small carded in low temperature retorting operations, and in this way quantity of oil but a large volume of a gas, consisting essentially can improve the over-all of an equimolar mixture of economy of conventional recarbon monoxide and hyt o r t i n g operations. The drogen, is produced. value of the products obAlthough the more valutained is such that special able aromatic hydrocarbons shale preparation for this are missing from shale oils process may also prove to produced a t low retorting be profitable. temperatures, these can be The procedure followed produced by thermal crackin the initial phases of the ing a t high temperatures present investigation was ( 8 ) . However, as conversimilar t o that suggested by sion of the ehale organic Lewes (6) and Yeadon (9) matter to oil in a retort for the carbonization of coal probably is essentially a and other solid fuels-that cracking reaction, several is, the pulverized oil shale advantages ensue from rewas fed to the top of a torting a t a temperature heated, vertical tube and level sufficiently high for the allowed to fall down through direct production of lowthe tube into a spent shale boiling a r o m a t i c s w h e n receiver, from the top of these are desired. Shale oil which the oil vapors and apparently is released from the gases were removed. Reshale as a vapor or mist, torting of the shale took Tvhich lends itself to further place during its free fall in cracking in the retort. This the tube. The present avoids a subsequent high study consisted primarily of temperature cracking determining the effects of operation. Less equipment temperature on the quantity is n e e d e d a n d m o r e and quality of liquid and economical use of heat is gaseous products that a-ere possible when the high Figure 1. Photograph of Vertical T u b e High obtained. t e m p e r a t u r e cracking is Temperature Retort 2642
INDUSTRIAL AND ENGINEERING CHEMISTRY
Vol. 44, No. 11
PETROLEUM-SHALE OIL The experimental unit (Figure 1) used in this investigation is shown diagrammatically in Figure 2. The retort was constructed of a 10-foot length of steel tubing, having an inside diameter of 1.5 inches and a wall thickness of 0.375 inch. The tube was suspended vertically in a heating chamber made from a 10-inch
steel pipe lined with fire clay. Three natural-gas burners, spaced a t equal intervals vertically in the furnace and controlled manually to give the desired tube temperature, supplied the necessary heat. Shale was fed from a feed hopper by a variable-speed screw feeder and allowed t o fall freely through the tube to the spent shale receiver and vapor separator. The vapors from this receiver-separator passed successively through a water-cooled RAW SHALE HOPPER condenser, a condenser operated a t 15' F., a SIGHT PORT condenser cooled by dry ice, and two acetonedry ice traps. The noncondensable gases from this train were filtered through glass VARIABLE SPEED SCREW FEEDER wool to remove oil fog, then metered and compressed into storage cylinders from which samples were taken for mass spectrometer analysis. Operation of the gas compressor PRESSURE EQUALIZER LINE was controlled by a manometric switch set to maintain a pressure within the retort of 1to 2 inches of mercury below atmospheric pressure. Retort temperatures were measured a t three points on the outside wall of the tube by chromel-alumel thermocouples connected to an indicating pyrometer.
WATER JACKE
EXPERIMENTAL WORK MILD STEEL TUBE 10"O.D., LENGTHsB FT.
Retorting experiments were made a t temperatures in the range 1200' to 1800' F. a t 100' F. intervals and in some instances a t 50" F. intervals. Data given in this paper are from experiments in which oil was produced a t temperatures of 1200', 1500', and 1700' F. for detailed analysis (4). The 1800'F. run was of short duration, as the product of chief interest a t this temperature was the gas. A 50-gallon-per-ton shale from the Bureau of Mines Anvil Points mine near Rifle, CO~O., crushed and screened to the desired particle size, was used. An analysis of the shale is given in Table I. Feed rates for the different runs were varied from 6 to 200 grams per minute. The shale particle sizes investigated ranged from 16 to minus 100 mesh. Shale of minus 20 to plus 65 mesh was used in the runs reported in this paper. Operations normally were carried out a t a pressure of minus 1 to minus 2 inches of mercury to prevent the oil vapors from entering and condensing in the feeder system. Average vapor retention time in the retort tube for a typical 1500" F. run was calculated to be approximately 2 seconds, as compared to less than a second for the shale.
GAS COLLECTION SPENT SHALE
WATER CONDENSER
Figure 2.
November 1952
CONDENSERS
TRAPS
FILTER
Diagram of Vertical Tube High Temperature Retort
INDUSTRIAL AND ENGINEERING CHEMISTRY
2643
DISCUSSION OF RESULTS The best feed rate for maximum yield of oil and gas under good operating conditions was about 60 grams per minute. This is equivalent to a mass shale rate of 650 pounds per hour per square foot of retort cross-sectional area.
is a factor that should receive attention in designing a retort to operate in this temperature range. At 1200" F. no carbonate decomposition occurred, whereas at 1500' F. about 6y0 and a t 1800' F. 80% of these minerals decomposed. Material balances on the three high temperature runs arc given in Table 11. The oil yields ranged from 47 to 59 weight yo of Fischer assay, the maximum occurring a t about 1500' F. Conversion of the organic matter to oil, gas, and coke was 38, 42, and 20 weight %, respectively, for the 1500° F. run, as contrasted with 66, 12, and 22 weight %, repectively, for the low temgerature Fischer assay (8).
Table 111.
g601 /
Oil Gas Water Spent shale Loss
-AROMATICS INCLUDING N AND S COMPOUNDS
4
Material Balances o n High Temperature Retorting Runs Recovery, W t . Yo of Raw Shale Charged 1500' F. 1700' F. 1200' F.
z
PARAFFINS AND NAPHTHENES
9.7 5.8 0.9 82.0 1.6
Raw shale charged
0
Effect of Retorting Temperature Naphtha Composition
66.0
__
4.3 __
4.9 __
100.0
100.0
100.0
on
Shale of minus 20 to plus 40 mesh gave the best results, although minus 20 mesh was satisfactory. Particles larger than 16 mesh were not thoroughly retorted, whereas minus 65 mesh presented a dust problem in the condenser system. This problem would not be so important, however, in a larger unit with a more efficient dust removal system. A comparison of the spent shales, after retorting at various temperatures, and the raw shales, as shown in Table I , indicates that removal of organic matter increased with retorting temperature, ranging from 70y0a t 1200" F. to 90% a t 1800" F. The comparatively low amount of organic removal a t 1200' F. was due to a retention time too short t o effect more complete removal. Organic matter removal a t 1500" F. was 79% for the run cited and has been as high as 84% for other runs a t this temperature. This is 1 to 5% higher than removal accomplished during Fischer assay of the shale. Ash analyses of raw and spent shales indicate that a considerable amount of decomposition of the carbonates in the shale took place under the retorting conditions used in this work. As this is an endothermic reaction, it
806,-
roo -
-_--
----_.
Table I .
Organic matter Water Mineral Cor .Ish
Raw Shalea 29.5
1200' F. 11.2
1.5
i6.i
12.2 56.8 ~
72 7 ~
...
15.3
__
. .
io
HIGH-TEMP.RETORT HIGH-TEMP. RETORT
Spent Shales 1500' F. 1700' F. 1800O F. 8.5 2.3 4.7 76.2
HAYES R E T O R T
(12000)
Analyses of Raw a n d S p e n t Shales
(1500O)
...
4.2 91.1 -~ ~4
I
84.3
Total 100.0 100.0 100.0 100.0 Fischer assay of raw shale: 50 gai./ron, 18.9 wt. 7% oil,
2644
8.9 18.6 1.6
Crude shale oils produced from several different retorts are compared with high temperature retort crudes in Table 111. In general, the high temperature oils had a higher specific gravity, lower viscosity, lower pour points, and contained higher percentages of naphtha than do oils from conventional retorts. Only the high temperature oils contained appreciable percentages of naphtha boiling below 250" F. The tar acid- and tar base-free naphtha fractions of the high temperature crudes, although about equal in percentage, varied in composition with the temperature of retorting. This difference is illustrated graphically by Figure 3. The aromatic content increased from approximately 50% a t 1200' F. t o almost 100% at 1500" F. and above, producing naph-
Figure 3.
Q
11.2 13.1 0.6 70.8
3 VOLUME OF C U T ,
100 0
Figure 4.
S U M P E R C E N T OF CRUDE
Distillation Curves of Shale Oils Produced by Various Methods of Retorting
INDUSTRIAL A N D ENGINEERING CHEMISTRY
Vol. 44, No. 11
PETROLEUM-SHALE OIL Table 111.
that more than 80% of the available carbon dioxide in the mineral carbonates was evolved, yet only a small percentage of carbon dioxide appeared as such in the gas, most of it having been reduced to the monoxide.
Cornparision of High Temperature Retort oil w i t h Other Crude Shale Oils High Temperature 1 ~ 5 0 0F.~
1200'' F.
Crude oil analysis Specific gravity, 6Oo/0O0 F. 'API a t 60' F. Sulfur, wt. % Nitrogen, wt. Yo Pour point, F. Viscosity, SUS a t 100' F. Distillation summary, vol. %" Naphtha Light distillate Heavy distillate Residuum LOSS Total Naphtha,analysis, vol. % Tar acids T a r bases Hydrocarbon group analysis of neutral naphtha, vol. % Paraffins and naphthenes Olefins Aromaticsb
0.956 16.5 0.84 2.46
60 47 39.2 13.5 19.7 27.2 0.4
._
1.063 1.6 0.76 3.08 -5 62 38.4 15.4 18.3 25.9 2.0
_
_
KTU
Gas Flow
Union Oil
Hayes
0.931: 19.8 0.74 1.78 90 280
0.959 16.0 0.51 2.10 70 660
0.945 18.2 0.71 1.89 75 280
0.925 21.5 0.80 2.5 55 48
2.7 15.7 34.4 45.8 1.4
1.5 12.8 25.3 60.0 0.4
2.7 14.3 34.7 48.0 0.3
_
100.0
100.0
100 0
1.2 9.2
0.3 6.9
3.0 7.8
10 39 51
2 2 98
I
33 48 19
Bureau of Mines crude shale oil analysis method (8).
b Including sulfur and nitrogen compounds.
thas a t the higher temperatures having Motor Method octane numbers near 100. Treating to remove sulfur and nitrogen should produce an excellent blending stock for aviation-grade fuel. Figure 4, giving distillation analyses of various crudes, shows that the lighter fractions are not present in quantity in oils retorted by the common types of retorts, particularly the NTU, Union, and gas flow, in which the oil vapors are rapidly swept out of the retort by combustion or recycle gases. The yields of various aromatic and nonaromatic groups of hydrocarbons contained in oils produced a t 1200", 1500', and. 1700" F., as shown in Table IV, were calculated from the quantities of oil and the detailed analyses of these oils which are described in (4). Benzene and naphthalene yields both increased consistently with increase in retort temperature from 1200' to 1700" F., whereas the Ce to C16 alkylbenzenes decreased. Toluene, styrene, ethylbenzene plus xylenes, and CQto CISpolycyclic aromatics increased from 1200' to 1500' F. then decreased as the temperature was raised to 1700' F. On the other hand, the nonaromatic hydrocarbons decreased from 1200" to 1500" F. and were practically absent in the 1700" F. oil. The yield of material boiling above about 530' F. at 760 mm. of mercury increased only about 10% over the entire temperature range. The net effect of increasing retorting temperature appears to be to increase aromatization of nonaromatic and dealkylation of monocyclic and polycyclic aromatic hydrocarbons. I n the oil made a t 1700' F., many of the compounds that might prove difficult to separate in preparing a high-grade benzene from oils produced a t lower retorting temperatures are absent. Manufacture of styrene-grade benzene from this oil should require only simple refining. Gases produced a t 12OOo,1500°, 1700",and 1800" F.are compared in Table V in volume and composition with those produced by Fischer assay retorting. The latter are considered to be typical of gases produced by conventional, low temperature, indirectly heated retorts. The volume of gas produced increased rapidly, and the composition changed considerably with increase in retorting temperature, as seen in Figure 5. This was due t o more complete conversion of the organic matter in the shale at increasing temperatures, to cracking of oil vapors and decomposition of mineral carbonates, and, in the higher temperature range, to reactions between hydrocarbons and carbon dioxide. Formation of hydrogen and carbon monoxide by the latter reaction at 1800' F. produced an almost equimolar mixture of hydrogen and carbon monoxide, comparable to synthesis gas produced by the water gas method. The spent shale analysis for this run shows
November 1952
26.2 20.3 30.2 20.6 2.7
COMMERCIAL POSSIBILITIES
The liquid products from ~ temperature oil-shale rehigh 100.0 100.0 100.0 torting that have the best commercial value are the lower 2.6 4.8 1.2 8.2 15.9 8.8 boiling aromatic hydrocarbons, benzene, toluene, the xylenes , and naphthalene. At present, 27 21 18 42 55 53 benzene is in great demand, 31 24 29 owing largely to ita use in the production of synthetic rubber but also because of its expanding use as a raw material for many organic chemicals. For example, in 1950, whereas about 35% of the total U. S. production of benzene went to the manufacture of styrene, 22 and 11%)respectively, were used for production of synthetic phenol and nylon (2). Coal tar benzene production has failed to keep up with the rapidly increasing U. S. requirements for this important chemical, As a result, various petroleum companies are engaging in its production from petroleum fractions. A supplementary source entirely separate from coal or petroleum is now evident in shale oils produced at high temperatures. Toluene and the xylenes normally are used largely 8 s solvents and gasoline blending stocks, so their demand is not accelerating as rapidly as is the demand for benzene. However, naphthalene is at present in rather short supply, because it is the raw material for one method of making phthalic anhydride. Use of this anhydride in resin and plasticizer manufacture is increasing rapidly. The major gas constituent with economic value other than as fuel is ethylene. This hydrocarbon is produced in a fairly high concentration and in considerable quantity as the result of re-
~
_
Table IV.
_
-
Yield of Liquid Products f r o m H i g h Temperature Retorting Yield, Gal./Ton of Shale& 1200° 1500° 1700°
Aromatic hydrocarbons Benzeneb Tolueneb Ethylbenzene Xylene Styrene C, t o Cia akylbenaenes Cs t o CISaromatic olefins Naphthalene Other Cs to Clr polycyclic aromatics Total Cs to Cx aromatic hydrocarbons Nonaromatic h drocarbons Ca, Cs,and
c7 CB cs to
db
C1r
Total Ca to CISnonaromatic hydrocarbons Thiophenes 0 Other sulfur compoundsC Nitrogen compounds other than tar bases6 T a r acids0 T a r basesC Unidentified and higher boiling material
}
F.
F.
F.
1.1
3.9
1.7
4.9 0.7
0.2
0.0 0.0
::: }
0.9 0.4
0.1 0.9 0.0 0.1
0.6 0.1 0.8
0.0
0.0 1.6
0.5
-
1.3
-
0.1 -
4.0
9.2
7.3
6.1 0.6
3.4
0.0
0.0
0.0
0.6 1.8
_
_
0.0 0.1
-
-
9.1
3.5
0.1
0.1
0.2 0.3 0.2 9
0.2 0.6 01 .. 24
10.8 -
11.2 -
0.0 0.0 0.0 0.03 0.03 0.1 0 . 00 11.8 -
Total oil yield 25.6 26.4 19.3 a Fischer assay of raw shale was 5 0 gal./ton. b Includerr material recovered i n the retort gas. C With boiling points below about 530" F. a t 760 mm. of mercury.
INDUSTRIAL AND ENGINEERING CHEMISTRY
2645
Table V.
Composition and Q u a n t i t y of G a s Produced by High Temperature a n d Fischer Assay Retorts High Temperature Retortingo 1500' F. 1700' F. c u . ft./ c u . it./ Mole % tond Mole 7 tond ." 13.1586 34.3 2744 39.5 1769 30.6 2449 4.1 184 0.4 34 0.4 19 0.0 0 23.4 1060 10.0 804 5.3 239 0.2 14 0.3 12 1.3 106 0.1 0.2 14 6 4.6 20 8 9.3 748 9.1 409 13.5 1084 0.1 3 0.2 17
1200' F. Gas Constituent 0 Hydrogen Methane Ethane Propane Ethylene Propylene Acetylene Methylacetylene Carbon monoxide Carbon dioxide Hydrogen sulfide
Mole % 16.4 29.4 6.5
c u . ft./ tond 302 542 119 16 358 161 0 3 99 234 8
0.9
19.4 8.7 0.0
0.2 5.4 12.7 0.4
__
--
__
__
__
1800' F. c u . ft./ Mole c7, tond
Fischer Assay Retortingb a tc930' u . ft./F.
"-1
I
I
1
I
1
,,L
b 0 1200
-_
-_
I 1300
I 1400
1 1500
I 1600
I 1700
966
-
PROCESS DEVELOPMENT
The eff'ects of various methods of heat transfer to the shale are being investigated in a number of bench scale retorts now in operation. I n one of these the shale is allowed to flow down a hot inclined surface, receiving heat both by radiation and conduction. I n two other retorts the shale is carried through the high temperature zone by an inert gas, being entrained in one case and fluidized in the other. Each of the above-mentioned retorts is heated externally, but experiments on "autothermic" heating are being conducted in the fluidized bed retort. I n these experiments a portion of the heat required for retorting is supplied by combustion of a portion of the organic material remaining on the hot spent shale. hnother method of transferring heat to the shale to be investigated a t a later date is by intimate contact of the raw shale with hot solids.
1800 T-
OF.
Composition of High Temperature Retort Gas at Various Temperatures
The demand for these ethylene derivatives is high and is constantly increasing, so the use of ethylene from retort gases would likely be of economic interest. Other valuable products obtainable fromhightemperatureretortingof oil shaleincludebutane for use as liquefied petroleum gas or in gasoline blends, propylene and butenes for production of polymer gasoline, and crude tar acids. The quantityof some products that could be produced from one 20,000ton-per-day shale plant are compared in Table VI with the total U. S. production of these products from all sources in 1949. The plant is assumed to operate 310 days per year and to use 30-gallonper-ton shale. Shale of this quality was used for calculations instead of the 50-gallon-per-ton shale on which the work in this report was carried out, as it more nearly represents the average Green River shale which can be mined economically in large tonnage. For this purpose the yields reported herein for 50gallon-per-ton shale were calculated to yields for 30-gallon-perton shale for Table VI. A preliminary cost estimate for high temperature shale retorting and processing of the crude products was made with the cooperation of personnel a t the Bureau of Mines Oil-Shale Demonstration Plant at Rifle, Colo. This estimate showed a reasonably short pay-out time for the entire shale mining and processing installation. Therefore, further experimental investigation of the process on bench scale and semipilot plant scale is being carried out.
2646
100.0
-
Table VI. Annual Production of Chemicals Available f r o m High Temperature Retorting
CARBON MONOXIDE
TEMPERATURE,
Figure 5.
n
/ 4
4.9 23.7 8.4
tond 249 207 79 32 23 19 0 0 47 229 81
0.0 0.0
Total 100.0 1,842 100.0 4,485 100,o 8,014 100.0 16,370 a Fischer assay of raw shale was 50 gal./ton. Fischer assay of raw shale was 57 gal./ton. Based on mass spectrometer analysis, C4 and heavier hydrocarbons were calculated out and quantities added t o the oil. d Gas volumes a t 60' F. and 760 mm. bf mercury.
torting a t about 1500" F. Some separation process, such as hypersorption, would yield a gas containing ethylene in concentration satisfactory for use in chemical production. The major uses of ethylene as a chemical raw material in 1950 were ethyl alcohol, 33%; ethylene oxide, 33%; and ethyl benzene, 8% ( 1 ) .
Mole % 25.7 21.4 8.2 3.3 2.4 2.0
Chemical Benzene Toluene Xylene Solvent naphtha Crude tar acids Naphthalene Ethylene a
b
P
Provdlotion (1000 Gal.) 157,200 82,200 57,100 5,000 12,400 235 0006 1,280:OOOb
Estimated Annual Production from a 20,000-Ton/Dav Shale ' Plant5 1000 of u.,s. gal. production 14,600 9.3 8,200 7.5 1,800 3.2 2,400 48.0 680 5 5 29 l O O b 12.4 29l',OOOb 22.7
Based o n 310 operating days per year, using 3O-gal./ton shale. Thousand pounds.
SUMMARY
High temperature retorting of Green River oil shale was investigated a t various temperatures bet\%-een1200" and 180OO F. Organic matter removal ranged from 70% at 1200' F. to 90% a t 1800' F. This compares favorably with the usual amount of organic matter removed during Fischer assay, which amounts to approximately 75 to 80%. Oil yields for the series ranged from 47 to 59 weight of Fischer assay, the maximum oil yield occurring a t about 1500" F. Gas production increased rapidly with increase in temperature, ranging from approximately 1800 cubic feet per ton of shale for the 1200" F. run to 16,400 cubic feet for the 1800' F. run, as compared to 970 cubic feet of gas liberated during Fischer assay. At temperatures up t o 1700' F. the main constituents of the gas are methane, hydrogen, ethylene, and carbon dioxide. At 1800° F. the main constituents are carbon monoxide and hydrogen. Apparently, most of the organic constituents react with the
INDUSTRIAL AND ENGINEERING CHEMISTRY
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PETROLEUM-SHALE OIL mineral carbon dioxide at this temperature to form hydrogen and carbon monoxide. Aromatic content of the neutral naphtha fraction of the oil increased with increase in temperature, reaching a maximum of almost 1 0 0 ~ for o the 1700' F. oil. The highest benzene yields were obtained in the temperature range 1500" to 1700" F. and amounted to as much as 5 gallons from each ton of 50-gallonper-ton shale. ACKNOWLEDGMENT
This project was part of the Synthetic Liquid Fuels Program of the Bureau of Mines and was performed a t the Petroleum and Oil-Shale Experiment Station under the general direction of H. P. Rue and H. M. Thorne. Special thanks are due various members of the personnel of the station for their valuable assistance in carrying out this project. The work was done under a cooperative agreement between the University of Wyoming and the U. S. Department of the Interior, Bureau of Mines.
LITERATURE CITED (1) Aries, R. S., and Copulsky, W., Oil Gas J., 49, NO. 9, 54-6 (July 6, 1950). (2) Chem. Eng. News, 28,3866-70 (1950). (3) Dinneen, G. U., Ball, J. S., and Thorne, H. M., IND.ENG.CHEM., 44, 2632 (1952). (4) Dinneen, G. U., Smith, J. R., and Bailey, C. W., Ibid., 44, 2647 f1952). (5) Hibbard, A. B., and Robinson, W. E., U. S. Bur. Mines, R e p t . Invest. 4744 (1950). ( 6 ) Lewes, V. B., Brit. Patent 9988 (Nov. 20, 1913). (7) . . Stanfield, K. E., and Frost, I. C., U. S. Bur. Mines, Rept. I n u e s t . 4477 (1949). (8) Thorne, H. M., Murphy, W. I. R., Stanfield, K. E., Ball, J. S., and Horne, J. W., paper presented a t Second Oil Shale and Cannel Coal Conference, Glasgow, Scotland, July 1950. (9) Yeadon, J. R., Brit. Patent 114,971 (Jan. 25, 1918), RECEIVED for review January 22, 1952. ACCEPTED May 19, 1952. Presented a t the XIIth International Congress of Pure and Applied Chemistry, New York, September 1951.
(High Temperature Shale Oil)
PRODUCT COMPOSITION G . U. DINNEEN, J. R. SMITH, AND C. W. BAILEY Petroleum and Oil-Shale Experiment Station, Bureau of Mines, Laramie, Wyo.
C
RUDE shale oil is obtained by retorting the solid organic material occurring in oil shale. The purpose of the present investigation was to determine the composition of oils produced by retorting a t temperatures substantially higher than those normally employed ( 3 ) . Detailed analysis of the products presented a complex problem, as shale oils usually contain saturated, olefinic, and aromatic hydrocarbons, plus significant amounts of nitrogen- , sulfur- , and oxygen-containing compounds. Therefore, simple physical property correlations do not give satisfactory results. T o obtain an adequate picture of the composition of shale-oil distillates, a number of techniques including fractional distillation, adsorption, and spectrometry are used. PRELIMINARY TREATMENT OF SAMPLES
The three samples studied in the present investigation were produced as described in (.2) at temperatures of 1200', 1500°, and 1700' F., and the oils are designated by these temperatures. The quantities available for analysis amounted t o about 2.5 liters for the 1200' F. oil, 2 liters for the 1500' F. oil, and 0.8 liter for the 1700' F. oil. Because of the differences in sample size, the scheme of analysis used on the 1700' F. oil differed somewhat from that used for the other two. A schematic presentation of the work done on the 1200" and 1500' F. oils is shown in Figure 1. The 1700' F. oil was fractionated directly in a manner similar to that used for the neutral oils from the 1200' and 1500' F. oils, The separation into four wide-boiling cuts (see Figure 1) was made to permit more efficient extraction of the tar acids and tar bases. Also, by making a number of analytical fractionations, the time during which a given sample was maintained at elevated temperature was minimized. The four wide-boiling cuts were prepared using a 5-liter flask equipped with a Claissen head packed to a depth of several inches with glass beads. T o minimize cracking, fractions 2 and 3 were distilled a t pressures of 40 and 1 mm. of mercury, respectively. As shown-in Table I, the oils have roughly the same boiling-range distribution, but their chemical compositions are quite different, as indicated by the densities and viscosities. The sulfur contents of the two oils and of the fractions
November 1952
from them show only minor differences. The nitrogen may be separated into two classes. Basic nitrogen is present in compounds, principally pyridines and quinolines, that may be titrated by perchloric acid in a glacial acetic acid solution ('7); nonbasic nitrogen is present in compounds, principally pyrroles, not titratable by the above reagent. As shodn in Table I, the distribution of the two classes of nitrogen with respect to boiling range is very different. The sediment values shown in the table represent the mineral and carbonaceous matter that was insoluble in benzene. All results reported in this paper are on the basis of the crude shale oils as analyzed without correction for this sediment. Each of the first two fractions was extracted with 10% aqueous sodium hydroxide to remove acidic materials and then with 10% aqueous sulfuric acid to remove basic constituents. The raffinate oil was neutralized with dilute caustic and washed with distilled water. The tar acids and tar bases were liberated from the aqueous extracts, recovered, and reserved for analysis. The yields of tar acids and tar bases and some properties of the neutral oils are shown in Table 11. The fractions from the 1500' F. oil are more aromatic than those from the 1200' F. oil. The sulfur contents of the neutral oils from the second fractions are higher than those of the raw fractions because of the removal of large quantities of tar bases that are low in sulfur. The nitrogen results in Table I1 show that the dilute acid extraction was effective in removing the basic nitrogen from the first fractions but not from the second fractions. It has been found previously that effectiveness of extraction decreases in higher boiling materials. The nitrogen results in Tables I and I1 are not directly comparable as the former are on the raw fractions, whereas the latter are on the neutral distillates. However, the generally lower nonbasic nitrogen values in Table I1 show that some of this type of nitrogen compounds was removed by acid extraction. COMPOSITION OF NEUTRAL DISTILLATES
Distillation. The neutral oils from the wide-boiling fractions were subjected to an analytical fractionation, as indicated in Figure 1, to improve the results obtainable by adsorption and spectrometry. The distillation of the material boiling up to
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