SHALE OIL
Composition of Crude Shale C. U. DINNEEN, JOHN S. BALL,
AND
H. M. THORNE
Petroleum and Oil-Shale Experiment Station, Bureau of Mines, Laramie, Wyo. INCE there is no comA t present there is n o commercial oil-shale industry in duced in the Royster-T.V.A. mercial oil-shale industhe United States. Therefore, laboratory analysis and retort were obtained from comparison of the composition of shale oils furnish infortry in the United States Colorado oil shale. mation on their characteristics and on processing probtoday, it is desirable to obRetorts have been classified lems. Nineteen shale oils from seven different countries tain as much information as ( 1 ) as (1) those in which heat were analyzed. The shale oils not only differ as a class possible f r o m l a b o r a t o r y is transferred t o the shale from petroleum but also show substantial differences in analyses concerning the charthrough a wall, as represented composition among themselves. The composition is ina c t e r i s t i c s of s h a l e oils. by the Pumpherston, Parry, fluenced by both shale source and retorting conditions. Therefore, 19 crude shale oils Rockesholm, blarecaux, Petit The sulfur and nitrogen contents of the oil are primarily were analyzed by the same (also known as Cantieny), dependent on shale source. Also, when ordinary retorting procedure to obtain directly and Salermo retorts; (2) those methods are used, the shale source is a factor in the hydrocomparable results. Eight in which heat is tranferred carbon composition of the oil. The use of high temperaof the oils were produced to the shale from combustion ture retorting produces oils of greater aromaticity. Comfrom Colorado oil shale in exgases generated in the retort, perimental retorting operaparison of the results obtained permits characterization of as represented by the KTU the crude shale oils, evaluation of the factors affecting tions. One of the oils was and gas combustion retorts; their composition, and determination of the relationship obtained f r o m T e n n e s s e e and (3) those in which heat shale. The other 10 oils between American and foreign shale oils. is transferred to the shale bv were from foreign commerpassing previously heate& cial operations and so are repgases through the shale bed, resentative of shale oils actually being utilized a t present. as represented by the gas flow, Itoyster, and Lantz retorts. In Comparison of the results obtained permits characterization of addition, the high temperature process is carried out in what is the crude shale oils, evaluation of the factors affecting their essentially a class 1 retort in which rapid conversion is obtained composition, and determination of the relationship between a t high temperatures. Oils produced by this process a t two temAmerican and foreign shale oils. peratures, 1200" and 1500" F., were included in the present investigation. The Ljungstrom process is unique in that it uses EXPERIMENTAL tubular electric heaters to heat the oil shale in place and thus recovers only volatile product. The suggested classifications Kineteen samples of crude shale oil produced in seven different are not rigid, as modifications are often practiced such as the countries were analyzed by a laboratory procedure which was a introduction of steam or air into the spent shale bed in the modification of the Bureau of Mines routine method for crude Pumpherston retort. petroleum (8). The modification of the method was necessary The gravities of the oils range from 2" to 43" .4PI, with nearly because of the differences in composition between shale oil and all in the 15" to 30" range. The relatively heavy gravity indipetroleum. cates in general a small quantity of low-boiling material. However, due to differences in composition of the oils there is no Briefly, the method used to obtain the results reported in this definite correlation between gravity and distillation range. The paper is as follows: A 300-ml. sample is distilled a t a pressure of about 760 mm. of mercury until a vapor temperature of 200" C. 1500°F. high temperature oil has the heaviest gravity but one is reached. Starting at a vapor temperature of 50" C., a fracof the highest naphtha contents. tion is obtained at each multiple of 25' C. The distillation resiThe results in Table I1 show that sulfur and nitrogen contents due is further distilled a t a pressure of 40 mm. of mercury until a vary from about 0.6 t o over 3%. The significance of these variavapor temperature of 300' C. is reached. Seven fractions are taken in 25" C. multiples starting a t 150" C. Properties are determined on the crude shale oil, on each of the fractions and residue, and on composites of fractions 1 to 7 (naphtha), 8 to 10 Table I. List of Determinations Made in Bureau of Mines (light distillate), and 11 to 14 (heavy distillate) respectively. Crude Shale Oil Analysis The particular determinations that are made are hsted in Table Crude Shale Oii I.
S
COMPARISON OF CRUDE SHALE OILS
The shale oils analyzed in this work generally have compositions intermediate between petroleum and coal-tar distillates. However, among themselves the shale oils have a rather wide range of composition. Consequently, accurate characterization of each individual crude shale oil requires a detailed study. Properties of Crude Shale Oils. Some of the major differences among crude shale oils are evident from the inspection tests in Table 11. In this table the oils are designated by country and type of retort used. All of the American oils except that pro-
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Specific gravity Sulfur
kitroien
Pour point Viscosity
Composite Fractions T a r acids T a r bases Hydrocarbon analysis of neutral oil Sulfur Nitrogen
INDUSTRIAL AND ENGINEERING CHEMISTRY
Vol. 44, No. 11
PETROLEUM-SHALE OIL Table 11.
SulCountry U.S.A.
Spain South Africa Australia Sweden Scotland France
previously, the retorting process also differs from the more usual eduction methods. For the other oils, the distillate up to 400" F. ranges from 1.5 to 39%, while the residuum ranges from 12.5 t o 60%. These large differences are illustrated in Figure 1, which shows the distillation curves for some of the oils.
Inspection Tests on Crude Shale Oils
Retort NTU Pumpherston Gas flow Royster Parrv Gas F m b u s t i o n 1200 F. high temperature 1600° F. high temperature Royster-T.V.A. Pumpherston Salermo Pumpherston Rockesholm Ljungstrom Pumpherston Pumpherston Marecaux Petit Lantz
Viscosity 6. u.,' Seo.'
fur, Wt.
Nitrogen, Wt.
0.74 0.77 0.61 0.67 0.87 0.69
1.78 1.57 2.10 1.97 1.81 2.13
16.5
0.82
2.46
60
47
1.6 9.3 27.9 24.7 27.0 13.3 43.4 30.4
.0.76 3.38 0.40 0.64 0.56 1.65 0.71
Below 5 Below 5 70 55 60 Below 5 Below 5 75
62 220
0.35
3.08 0.88 0.68 0.85 0.52 0.68 0.11 0.77
20.5 21.5 25.0 24.3
0.51 3.00 3.40 0.61
0.90 0.53 0.65 0.54
65
Gravity, API 19.8 25.7 16.0 19.7 20 3 is.6
%
%
Pour Point,
F.
90 60 70 90 70 85
30
Below 5 60
atlO0' F. 280 50 660 230 155 310
D
FRANCE, PETIT
50 63 54 77 29 48 87
46
45
50
tions is perhaps more evident if considered in terms of the quantities of sulfur and nitrogen compounds in the oils. An approximation of these quantities can be made, using an average molecular weight estimated from boiling range and density and assuming that only 1 atom of sulfur or nitrogen is present in the molecule. Most of the oils contain about 5% sulfur compounds, but three of them contain about 20%. The foreign oils and the oil (Royster-T.V.A.) from Tennessee shale contain less than 15% nitrogen compounds compared with 30 to 50% in the Colorado oils. As one of the main objects of shale-oil refining research is the production of gasoline that is low in both sulfur and nitrogen, it is evident that there are differences in the magnitude of this phase of the refining problem, depending on the oil being processed. Most of the oils have high pour points that are probably due to the presence of paraffinic material, although in some instances condensed ring compounds may also be a contributing factor. The variations shown by both pour-point and viscosity values emphasize the necessity of characterizing each individual shale oil. Laboratory Distillation. Distillation data for the oils are shown in Table_III. The oil from the Ljungstrom process is quite different from any of the others in that it consists almost entirely of distillate boiling below 600" F. However, as stated
Table 111.
U.S.A.
Retort
NTU
Pumpherston Gas flow Royster P a r r combustion Gas y 1200" F. high temperature 1500° F. high
Scotland France
Pumpherston Salermo Pumpherston Rockesholm Ljungstrom Pumpherston Pumpherston Marecaux P etit Lantz
November 1952
:f$z
,:Jot$,
$.
Figure 1.
.
34,
17.6 1.5 4.9 144.. 9 4
29.4 12.8 13.2 16 4.6
40.0 25.3 31.6 3 27 1 . 63
45 12.7 60.0 50.2 4 39 .9 7
39.2
13.5
19.7
27.2
$5:
:
2
4 6 8 1 0 1 2 1 4 FRACTION NUMBER Distillation Curves for S o m e Crude Shale Oils
Hydrocarbon Composition. The oils have a wide range of hydrocarbon compositions. Furthermore, the change in composition with respect to boiling range is not uniform among the oils. Consequently, the chemical composition of an oil cannot be judged from an analysis of any one fraction. Table IV gives the hydrocarbon composition as determined by silica gel adsorption analysis (2,s)of the naphtha and light distillate fractions. The napthas range from the saturated Droduct from the Ljungstrom oil to the aromatic material from high temperature retorting. Excluding the oils from these two rather unusual processes, the other distillates show very substantial differences. For example, the aromatic contents of the naphthas vary from 10 to over 50% and those for the light distillate from 20 to 80%. The light distillates for all but two of the oils have a higher aromatic content than do the corresponding naphthas. This is due, in part, t o the fact that in the analytical method used aromatics include all molecules containing an aromatic ring. Hence, for the same actual weight per cent of carbon atoms in benzene rings, the light distillate would have about a 50% higher aromatic content than the naphtha. Actually, the results in Table I V do not show any such regular increase, as the aromatic contents of the light distillates are 10 t o 200y0 greater than those of the naphthas. In general, the increase in aromatics is accompanied by a decrease in both olefins and saturates. However, two of the samples, the American NTU and Spanish Pumpherston oils, have more saturates in the light distillate than in the naphtha.
: : : -
15,
2,
R2;;z;:+:yA. 3g:$ Spain South Africa Australia Sweden
%
Distillation of Crude S h a l e o i l s Distillate, Volume %
Country
U.S.A.,GAS FLOW
13,
25,
42,
18,
19.1 14,6 71 66 .. 85
16.9 20'4 24'7 20.8
32.1 37.1 35 1 .. 13
31.8 27.2
19.5 2 ,3
19.4 24,9
34.4 43.6
202..38 25.1 28,
23 2 7 .. 59 19.7
2 25 5 .. 70 22.0
3 21 6 .. 0 7 35.4
1 19 9 .. 2 4 21.5
INDUSTRIAL AND ENGINEERING CHEMISTRY
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data in Table V show that the heavy distillate for the gas flow oil is more aromatic. Similarly, the heavy distillate from the French Pumpherston oil Naphtha Light Distillate is more aromatic than the Scot,ch Pumpherston oil, SatuAroSatuAroalthough the light distillates from the two oils are rates, Olefins, matics, rates, Olefins, matics, Country Retort % % % % % % quite similar. U.S.A. NTU 33 48 19 37 34 29 Sulfur and Nitrogen Distribution. Shale oils Pumpherston 32 43 25 28 35 37 27 42 31 27 43 30 generally have rather high sulfur and nitrogen conGas flow Royster .. .. 27 41 32 tents (Table 11). However, in preparing useful Parry 27 48 25 26 45 29 Gas ;ombustion 27 51 22 27 42 31 products, the content of these elements in distil1200 F. high temperature 10 39 51 10 29 61 late fractions is of primary importance. Sulfur 1500' F. high m d nitrogen \yere determined on each of the comtemperature 0 0 100 2 3 95 Royster-T.V.A. 25 21 54 5 17 78 posite fractions and on the residuum, with the reSpain Pumpherston 42 42 16 56 18 26 sults given in Table VI. The sulfur contents of South Africa Salermo 37 48 15 32 40 28 Australia Pumpherston 45 43 12 40 37 23 the fractions from any given oil are all of about the Sweden Rockesholm 24 35 41 3 16 81 same magnitude. For the oils from Colorado shale Ljungstrom 63 11 26 5 30 65 there is a tendency for the sulfur ,content to be Scotland Pumpherston 47 43 10 36 36 28 lower in the higher boiling fractions. For the rest France Pumpherston .. .. 33 36 31 of the oils the sulfur content increases slightly with 58 28 24 48 hlarecaux 31 41 Petit 25 22 53 24 18 58 boiling range. These trends, however, are not very Lantz 37 47 16 25 41 34 pronounced. Consequently, simple distillation processes will not yield any reasonably wideboiling range fraction materially lower in sulfur Table V. Specific Gravities and Aniline Points of Fractions than the charge oil. The nitrogen content of the fractions, on the i n the Heavy Distillates from Some Crude Shale Oils Fraction Scotch French other hand, increases with boiling range, as illustrated by the KO, Gas Flow Royster Puinpherston Pumpherston fact that the residuums have 2 to 10 times the nitrogen content SPECIPIC GRAVITY of the naphthas. Table IV.
11 12 13 14
Hydrocarbon Group Distribution i n Lower Boiling Fractions from Crude Shale Oils
0.903 0.921 0.936 0.946
0.889 0.904 0.917 0.927 . ~ N I L I S EP O I N T ,
11 12 13
14
36.4 40.4 43.8 47.8
11 12 13 14
7.7 13.3 25.3 53.3
47.8 48.8 57.8 65.3 VISCOSITY AT
7.0 11.5 19.2 37.8
0.873 0.889 0.893 0,902
0,890 0.908 0,922 0.939
c. 60.2 66.8 73.6 77.6
49.8 53.2 55.4 58.6
100' F.,CS. 5.8 12.5 12.8 25.6
6.2 11.7 24.4 63.2
The erratic change in composition n-ith boiling point is also evident in the heavy distillates from the oils. As the adsorption method is not easily applicable in this higher boiling range, the chemical composition is estimated from physical properties, even though these are affected by the presence of nonhydrocarbon materials. The gravities, aniline points, and viscosities of fractions in the heavy distillate from some of the oils are shown in Table V. Although the compositions of the light distillates are very similar for the gas flow and Royster oils, the
EFFECTS OF SHALE SOURCE AND RETORTING METHOD
The preceding discussion has pointed out the wide range of composition covered by shale oils as they are currently produced throughout the world. The most important factors affecting their composition are shale source and retorting method. Although these variables are undoubtedly interrelated, it would be advantageous to have some information as to their principal effects. The Colorado oils vere produced from essentially the same shale, so properties of these oils that show a marked similarity should be a function primarily of shale source. Also, externally fired retorts of the Pumpherston type have been used extensively throughout the world, so that differences in oils produced in such retorts should be a t least in part a function of shale source. Consideration of the crude shale-oil properties shown in Table I1 indicates that both the sulfur and nitrogen content of the oils depends on shale source. The sulfur contents of the Colorado oils cover a range of only 0.26%, while the total range covered by all the oils exceeds 3%. Similarly, the nitrogen values for the Colorado oils sholy only half the variation shown by all of the
Table VI. Distribution of Sulfur and Nitrogen i n Distillates from Crude Shale Oils Sitrogen Content of Fraction, Wt. % Sulfur Content of Fraction, Wt. 7' Country and Retort U S A NTU U:S:A:' Pumpherston U S A ' Gas flow U:S:.4:: Royster U S 4 Parry U:S'h:' Gas combustion U S'A ' 1200° F high temp U:S:A" 1500' F' high temp: U.S,A::Royster1T.V.A. Spain Pumpherston South' Africa Salermo Australia, Pdmpherston Sweden, Rockesholm Sweden, Ljungstrom Scotland, Pumpherston France Pumpherston France' Marecaux France' Petit France,' Lantz
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Light disNaphtha tillate 0.77 0.84 0.71 0.81 0.89 1.03 0.79 0.75 2.34 0.27 0.43 0.41 1.42 0.70 0.27 0.42 3.17 2.94 0.50
Heavy distillate 0.79 0.56 0.66 0.67 0.89 0.70 0.81 0.74 2.98 0.36 0.60 0.54 1.47
Residuum 0.70 0.61 0.58 0.60 0,87 0.65 0.79 0.74 3.35 0.40 0.55 0.57 1.69
0:29 0.40 2.82 3.26 0.62
0:41 0.58 2.83 3.24 0.69
Light disNaphtha tillate 1.24 1.17 1.18 0.51 1.21 1.30 1.27 0.99 0.98 0.51 1,37 1.17 0.97 2.37 3.20 1.30 0.22 0.31 0.18 0.38 0.14 0 50 0.24 0.10 0.30 0.17 0.07 0.13 0.43 0.13 0.58 0.40 0.35 0.15 0.16 0.37 0.27 0 11
Heavy distillate 1.60 1.94 1.79 1.79 1.70 2.03 3.26 4.11 0.75 0.76 0.85 0.50 0.62
INDUSTRIAL AND ENGINEERING CHEMISTRY
0:Bz 0.85 0.65 0.81 0.53
Residuum 2.04 3.00 2.48 2.28 2.50 2.47 3.71 4.02 1.44 1.15 1.30 0.81 0.97
1:is 1.36 1.04 1.14 1.20
Vol. 44, No. 11
PETROLEUM-SHALE OIL oils. Furthermore, the average nitrogen content of the Colorado oils is more than twice that of the highest of the foreign oils and over three times as high as their average. This high nitrogen content would seem to be a unique feature of oils produced from Colorado oil shale. The Pumpherston-type retort, with minor modifications, was used to obtain six of the oils analyzed. The hydrocarbon composition of the distillate boiling up to 600’ F. from each of these oils is shown in Table VII. These distillates have an extremely wide variation in composition, which must be at least partly due to the shale from which they were produced. The two oils produced in the Royster retort from Colorado and Tennessee shales, respectively, also have widely different compositions (see Table IV). The importance of shale source on hydrocarbon composition is also shown by the results given in Table VI11 for distillates from Colorado shale oils produced in various retorts. These distillates (excluding those from the high temperature process) show much less variation in hydrocarbon composition than do those produced from different shales by the same type of retort, either Pumpherston or Royster. It appears, therefore, that all oils produced from a given shale by similar retorting methods will have similar hydrocarbon compositions.
retorting after a minimum residence time, thus limiting secondary reactions in the retort. This may account for the differences in boiling-range distribution of the Colorado oils. SUMMARY
Shale oils produced in the United States and in several foreign .countries were analyzed by a standardized laboratory method. The results indicate that the oils differed greatly in such properties as sulfur and nitrogen content, pour point, distillation range, and hydrocarbon composition. The lower boiling distillates from the oils range from materials containing over 50% saturates and/or nearly 50% olefins t o those consisting essentially of aromatics. Furthermore, the hydrocarbon composition of the oils does not vary in a systematic manner with boiling range. The sulfur is evenly distributed throughout the boiling range, whereas the nitrogen content of the higher boiling fractions is several times that of the lower boiling fractions. Both source of shale and retorting conditions must be considered in predicting the composition of a crude shale oil. The source of the shale may foretell the sulfur and nitrogen content of the oil and under ordinary circumstances has an important effect on the hydrocarbon composition. An increase in retorting temperature increases the aromaticity of the oil produced, until a t about 1500” F. the oil consists essentially of aromatic compounds. Residence time among other retorting variables apparently affects primarily the boiling-range distribution of the
Table VII. Hydrocarbon Composition of Distillate Boiling up to 600” F..fromOils Produced in Externally Fired Retorts of the Pumpherston Type .inalysis of Dim. Boiling up to
-.
nnn’ __- F
Saturates, Country a n d Retort U S A P u m herston Spain,*kump%erston Australia, Pumpherston Sweden Rockesholm Scotlanh Pumpherston France, Pumpherston
%
0;’.
Olefins, Aromatics,
30 51 42 12 42 33
%
%
38 27 39 24 39 36
32 22 19 64 19 31
ACKNOWLEDGMENT This project was part of the Synthetic Fuels Program of the Bureau of Mines and was performed a t the Petroleum and OilShale Experiment Station, Laramie, Wyo., under the general direction of H. P. Rue. The authors wish to thank P. P. Veneziano, and G. S. Terrana, who made many of the analytical determinations. The work was done under a cooperative agreement between the University of Wyoming and the Bureau of Mines, United States Department of the Interior. The sample from the Tennessee Valley Authority was furnished through the courtesy of T. P. Hignett, Development Section, Division of Chemical Engineering. Procurement of the samples from foreign countries was arranged by Bureau of Mines’ personnel during visits to these countries and acknowledgments are given in the reports (4-7) of those visits.
Table VIII. Hydrocarbon Composition of Distillate Boiling up to 600’ F. from Some Oils Produced from Colorado Oil Shale Analysis of Dist. Boiling u p t o
finw F.. ..- _
Retort
NTU
Pumpherston Gas Bow Royster Parry Gas combustion 1200O F. high temperature 1500O F. high temperature
Saturates,
Olefins,
Aromatics,
36 30 27 27 26 27 10 1
36 38 43 41 46 44 36 1
28 32 30 32 28 29 54
%
%
%
LITERATURE CITED Cattell, R. A . , Guthrie, Boyd, and Schramm, L. W., “Retorting Colorado Oil Shale-A Review of the Work of the Bureau of Mines, U. S. Department of the Interior,” Second Oil Shale and Cannel Coal Conference. Glaseow. 1950. (2) Dinneen, G. U., Bailey, C. W., Smith,’J. R., and Ball, J. S.,
98
(1)
If retorting temperatures differ by several hundred degrees Fahrenheit, products having very different chemical compositions can be obtained. As shown in Table VIII, the oil produced a t 1200’ F. has nearly twice the aromatic content of the oils produced at ordinary retorting temperatures. Retorting at the still higher temperature of 1500’ F. produces an oil composed essentially of aromatic compounds. Temperature is, of course, not the only retorting variable, but the available data do not permit accurate evaluation of the others. I n practice, residence time, for example, is undoubtedly very important because the more common retorting processes probablv ouerate rather near the lowest oractical temoerature. aa evidenced by the similarities in composition shown in Table ViII. Those retortsemploying an internal flow of hot gas as a retorting medium might be expected to sweep out the products of I
Anal. Chem., 19, 992 (1947). (3) Dinneen, G. U., Thompson, C. J., Smith, J. R., and Ball, J. S., Ibid., 22, 871 (1950). ( 4 ) Guthrie. Boyd. and Kloskv. Simon. U. S. Bur. Mines. R e d Invest. 4776 (1951). ( 5 ) Kraemer, A. J., and Thorne, H. M., Ibid., 4796 (1951). (6) Thorne, H.M., and Kraemer, A. J., Ibid., 4736 (1950). (7) Thorne, H.M.,and Kraemer, A. J., “Oil-Shale Operation in the Union of South Africa,” U. S. Bur. Mines, Rept. Invest. (in I
(8)
preparation). Wenger, W. J., and Ball, J. S., U. S. Bureau of
_
M i n e s , Rept.
Invest. 4517 (1949).
_
+ November 1952
+
*
RECEIVED for review December 11, 1961. ACCEPTED May 5, 1952. Presented before the Division pf Gas, Fuel, a n d Petroleum Chemistry a t X I I t h International Congress lof Pure and Applied Chemistry, New York, 1951.
+
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