Effect of Catalysts on the Hydrogenolysis of Coal M. PELIPETZ, E. M. KUHN, S. FRIEDMAN, AND H. H. STOHCH C e n t r a l Experiment S t a t i o n , U . S . Bureau of Mines, P i t t s b u r g h 13, P a . T h e liquid product resulting from the primary liquefaction of coal has a complex structure and consists of materials t h a t are liquid a t atmospheric conditions. This liquid product contains dissolved and suspended semisolid and solid matter, the amount of which depends upon the degree of coal hydrogenation. The n-hexanesoluble fraction of the coal hydrogenation product is largely distillable and represents the most valuable product of coal hydrogenation. The fraction insoluble in n-hexane, but soluble in benzene, is undistillable and asphaltic in nature. Experimental data show that asphaltenes are produced in the first step of coal cleavage and, with the progreas of hydrogenolysis, can be quantitatively reduced to
form n-hexanesoluhle material. Elimination of asphaltenes from the primary product of coal liquefaction was considered the main object of this investigation. Fractions of the asphaltenes give rise to heat transfer difficulties in a continuous process. It was expected that selected catalysts would be active in promoting hydrogenolysis of asphaltenes, the sluggish step i n coal liquefaction. Investigation showed that zinc-antimony catalyst lowers the asphaltene content, especially a t low reaction temperature. Because tin proved to be one of the best catalysts in the primary cracking of coal, and zinc-antimony alloy showed activation in hydrogenolysis of asphaltenes, a combined tin and zinc antimony catalyst was tried.
I T H the depletion of natural oil reserves, finding a dependable source of liquid hydrocarbons becomes aproblem of national interest. The search for a suitable raw material for processing liquid hydrocarbons and related compounds invariably leads t o coal because immense reserves are available; published estimates indicate that the coal reserves of the United States are sufficient t o supply all of the nation’s fuel needs for almost 3000 years (1). Nevertheless, untreated coal lacks any substantial liquid fraction of its own. Extraction of bituminous coal with benzene yields only 1% semisolid matter. Direct pyrolysis of coal for 1hour a t 450’ C. under nitrogen pressure of 2500 pounds per square ihch in the presence of 1%tin and 0.5% ammonium chloride yields the following products: gaseous hydrocarbons, 5.9y0,;hydrogen sulfide, 0.11yo; ammonia, 0.79% ; benzene-soluble material, 1.20yo. However, when coal is subjected t o the same conditions and catalyst under 1000 pounds per square inch hydrogen pressure, 2.92% of hydrogen is consumed and the products of reaction, in per cent of ash moisture-free coal, are: gaseous hydrocarbons, 11.35%; hydrogen sulfide, 0.19%; ammonia, 0.06%;. benzenesoluble material, 69.70%; water of reaction, 6.20%; benzene-insoluble, 12.5%. It is apparent that hydrogenolysis causes drastic disruption of the coal structure. A comparison of the results upon preheating coal in the presence and absence of hydrogen clearly shows that the art of obtaining liquid products depends primarily on the reaction of coal and hydrogen. I n this connection, it is of interest to compare the ultimate analysis of bituminous coal and crude oil:
demonstrates that the essential difference in composition of bituminous coal and crude Texas oil is in the percentage of hydrogen. To obtain from bituminous coal a product similar in elementary composition t o Texas oil, i t is necessary t o add 6% hydrogen after elimination of oxygen.
Bruceton Coal, % b y Weight
Carbon Hydrogen Oxygen Sulfur Nitrogen
83.8 5.5 7.6 1.6 1.5
Texaa Oil,
% ’ by Weight 84.6 10.9 2.0
1.6
0.9
A comparison of the analyses after removal of oxygen as water Bruceton Coal, yo b y Weight Carbon Hydrogen
Sulfur
Nitrogen
91.8 4.9
1.7 1.6
Texas Oil,
% b y Weight 86.44 10.9 1.64 0.92
PRODUCTS OF COAL HYDROGENATION
When coal is subjected to the action of hydrogen at high temperature, gaseous, liquid, and solid products result. The liquid product of primary liquefaction is complex in structure, and consists of materials that are liquid at atmospheric conditions and distillable without decomposition within a reasonable range of temperature. The liquid product carries dissolved and suspended semisolid and solid matter. The amount of dissolved and suspended matter varies with the extent of hydrogenolysis from a completely solid or semisolid product of hydrogenation under mild conditions t o a completely distillable oil product under more drastic conditions. As has been mentioned, untreated coal contains only about 10% of benzene-soluble material. The solubility of hydrogenated coal increases with the extent of hydrogenation. Therefore, solubility in benzene was used to determine the extent of coal liquefaction. Because of the ease of measuring the amount of benzene-insoluble material, the percentage of liquefaction was determined on this basis, and includes not only liquid and solid material soluble in benzene but gaseous hydrocarbons as well. The material insoluble in benzene contains mineral material, unreacted coal, and partly hydrogenated coal, the molecular structure of which has not been sufficiently reduced in complexity * to be soluble in the benzene. The benzene-soluble material, after removal of the solvent, was extracted with technical n-hexane. Extraction with n-hexane serves as a qualitative evaluation of coal liquefaction product. The n-hexane soluble fraction is largely distillable at reasonable temperatures. It represents the most valuable product of coal hydrogenation. I n further discussion this fraction is designated “oil.” The insoluble fraction is undistillable and is soluble in selective solvents only. Hereafter, this fraction will be designated “asphalt.” The term “asphaltenes” would be perhaps more descriptive of this material and avoid confusion with other industrial uses of the word
IN D U S T R I A-L A N D E N G IN E E R IN G C H E M I S T R Y
1260
Vol. 40, No. 7
I00 90
80
70
6ot---t---ti----"----
60
t----+-----t
I
IW
HEAVY OIL VEHICLE INITIAL Hp PRESSURE
,050 W
I
\
40
\
I
I
NQ VEHICLE USED INITIAL Hp PRESSURE, 2,500
01a 5+
l
POUNDS PER SQ.IN.
I
I
I
\
20
IO
I
IO
Asphalt present
I
I
I
0
I '
30
I
60
90 TIME, MINUTES
120
1
I50
+ 0.5% ammonium chloride
60
30
180
Figure 1. Primary Liquefaction of Coal at 450" C. In presence of 1%stannous sulfide
I
Asphalt, present
Figure 2.
90 TIME, MINUTES
120
150
180
Primary Liquefaction of Coal a t 450' C.
In presence of 1%stannous sulfide
+ 0.05 % ammonium chloride
"asphalt." However, the latter is currently used in our laborsr tories as defined, and will be so employed in this paper. Table I gives ultimate analyses of two fractions of the coal hydrogenation product and those of Texas oil and of the original coal, calculated on sulfur- and nitrogen-free basis.
I n considering the origin of asphalt in the product of coal liquefaction, two possibilities were recognized: (1) that the asphalt is an intermediary product in oil formation through coal hydrogenation; (2) that asphalt results from condensation or polymerization of the oil. In the series of experiments designed t o test these possibilities, coal was hydrogenated under the same conditions but during different time intervals, and the amount TABLEI. ULTIMATE ANALYSISOF BITUMINOUS COAL, CRUDE of asphalt in the product of coal hydrogenation was determined. TEXAS OIL, AND Two FRACTIONS OF COALHYDROGENATIONTable I1 and Figure 1 present the results of these experiments. PRODUCT I N WEIGHT P E R CENT "Zero" reaction time in Tables I1 an& 111 and Figures 1 and 2 Asphalt from Oil from includes the preheating period to reaction tpmperature but Bruceton Coal HydroCoal HydroTexas zero time at that temperature, the autoclave being cooled imCoal genation genation Crude Oil mediately after reaction temperature is reached. The experiments of Table I1 were conducted in the presence of a vehicle free of asphalt. The possibility of vehicle influence on asphalt formation cannot be dismissed; therefore, study of asphalt formation in absence of vehicle was made. I n a series of
*
The analysis of the n-hexane-soluble fraction from coal hydrogenation is closer t o t h a t of Texas oil than t o that of the original coal, while that of the n-hexane-insoluble but benzene-soluble fraction (asphalt) is closer to that of the original coal. The 'analytical data presented in Table I show that there is a proglessive decrease in oxygen content from bituniinous coal through asphalt to oil. The oil from coal hydrogenation except for a lower hydrogen content resembles Texas crude. The decrease of oxygen content is more pronounced in the coal-toasphalt step than in the step from asphalt to oil. Simultaneously, the hydrogen content increases from coal t o oil but does not reach that of l e x a s crude oil. The rate of hydrogen increase is greater in the asphalt-to-oil step than in the coal-to-asphalt step. The presence of asphalt in the primary product of coal hydrogenation is undesirable because it reduces the quantity of oil and because only a limited amount of asphalt can be tolerated in the recycle oil. The asphalt, which is soluble in the light fraction of pasting oil, precipitates upon vaporization of this fraction in the preheating stage, and gives rise to heat transfer difficulties. Elimination of the asphalt from the primary product of coal hydrogenation way considered important in this investigation.
TABLE11. BATCHHYDROGENATION OF COALAT 450" C. PRESENCE OF HEAVY OIL AS VEHICLE
IN
+
(Initial hydrogen pressure 2000 lb./sq. in., catalyst 1%SnS 0.5% NHIC1) Liquefaction, Asphalt per Unit Test Duration of NO. Reaction, Hr. % of Liquefaction 0 85.9 0.708 173 174 177 178 179 180 181
TABLE111.
0.5 1 1.5 2 2.5 3
BBTCH
90.2 91.2 91.9 92.05 91.7 91.7
HYDROGEKATION O F COAL ABSEXCEOF VEHICLE
0.251 0.134 0.085 0.057 0.058 0.058
AT
460"
c. IN
+
(Initial hydrogen pressure 2300 lb./sq. in., catalyst 1%SnS 0.5% N H L I ) Liquefaction, Asphalt per Unit Test Duration of NO. Reaction, Hr. % of Liquefaction 223 207 209 217 210 206 208
89.1 90.7 91.0 92.0 92.3 93.4 93.4
0.325 0.215 0.071 0.024 0,024 0.021 0.021
INDUSTRIAL AND ENGINEERING CHEMISTRY
July 1948
1261
in the product of coal hydrogenation when vehicle was not used.
TABLEIV. ASPHALTFORMATION DURING HYDROGENATION OF The experiments of Table I1 were conducted a t a n initial hyCOALIN PRESENCE OF HEAVY OIL AND VEHICLEAT 450" C. drogen pressure of 2000 pounds per square inch gage as compared Test
Initial Hydrogen Pressure, Lb./Sq. I n . Gage 2000 2500 2000 2500
Duration of Reaction, Hr. 1 1 .2 2
NO.
177 137 179 259
TABLE V. r......*
Asphalt per U n i t of Liquefaction 0.134 0,150 0.057 0.054
BATCHHYDROGENATION OF ASPHALTIN GRAMS
.
'Asphalt Hydrogen Total output Gaseous hydrocarbons
Amount 49.80 1.76 51.56
-
Hydrogen 3.50 1.76 5.26
6,70 39.40 3.70 1.35 51.15
1.30 3.60 0.26 0.15 5.31
Oil
Asphalt Water Total
-
_ .
__
Oxygen 1.75
Carbon 44.00
1.75
44.00
.. -
~
0:?8 0.14 1.20 2.12
... 5.40 35.00 3.30
... 43.70
experiments (Table I11 and Figure 2) coal alone was hydrogenated a t 450" C. for various reaction periods, with the other conditions kept constant. The results of coal hydrogenation in the presence and absence of vehicle show similar trends-Le., a n increased reaction period decreases ksphalt formation. This excludes the assumption of asphalt origination through condensation or polymerization of the oil product. If it were the product of oil conversion, prolonging the reaction period would increase but not decrease the amount of asphalt in the'product of coal liquefaction. The difference between the curves representing liquefaction and asphalt formation indicates also that, in hydrogenation of coal, the production of asphalt precedes the production of oil. The formation of asphalt is a rapid reaction resulting in removal of about 56% of total oxygen content of the coal. The oxygen is eliminated mainly as water. Direct, comparison of the extent of liquefaction and asphalt formation between experiments in the presence of vehicle and those in the absence of vehicle indicates far lower asphalt content
with 2500 pounds for those of Table 111. T o find a means for direct comparison of the two series, some experiments in the presence of vehicle were repeated at 2500 pounds per square inch gage (Table IV). The results indicate t h a t an increase of initial hydrogen pressure from 2000 to 2500 pounds does not produce an appreciable effect on asphalt formation; therefore, direct comparison of the results of Tables I1 and I11 can be considered valid. HYDROGENATION REACTIONS
T o study the nature of coal hydrogenation reactions, the isolated asphalt was hydrogenated for one hour at 450" C. and an initial hydrogen pressure of 2500 pounds per square inch gage in the presence of 1% powdered tin and 0.5% ammonium chloride. The results are presented in Table V. Comparison (Table I) of the oxygen content of the original coal with that of the asphalt and oil produced during the initial step of coal liquefaction indicates t h a t cleavage of the coal structure proceeds chiefly through the elimination of oxygen while splitting of asphalt proceeds mainly through the rupture of carbonto-carbon bonds (Table V). If this assumption is correct, more drastic conditions should be necessary for hydrogenolysis of the asphalt than for t h a t of coal. To test this assumption, a series of experiments (Table VI and Figure 3) was conducted. Coal was hydrogenated for various periods at 400 O, 430 O , and 450' C., under an initial hydrogen pressure of 2500 pounds per square inch in the presence of 1% stannous sulfide and 0.57, ammonium chloride. The data show that, b y prolonging the reaction period t o 120 minutes at 400' C., practically the same degree of liquefaction is reached as at 450" and 430" C., b u t the product of coal liquefaction a t t h a t reaction temperature is primarily asphaltic in nature. Apparently hydrogenolysis of the asphalt requires a higher degree of activation than primary splitting of the coal. Table VI1 and Figure 4 give additional data on the temperature. coefficient of asphalt hydrogenolysis. Coal was hydrogenated for one hour at various temperatures in t h e presence of heavy oil as vehicle and 1% stannous sulfide and 0.5% ammonium chloride as catalyst under initial hydrogen pressure of 2000 pounds per square inch. These results show clearly the necessity of increased temperature for hydrogenolysis of the asphalt. POWDERED CATALYSTS
-?O
\I
60
Because the cleavage of coal into asphalt and the hydrogenolysis of the asphalt into oil occur a t different rates, it was expected t h a t selected catalysts would be active in promoting hydrogenolysis of asphalt, which is slower than the initial pyrol-
'
Liquefaction i t 430 C.
I
I
CatOlySt, I% SnS
+ 0.5% NH+CI
TABLE VI.
BATCHHYDROGENATION OF COALIN ABSENCEOF VEHICLEAT 450 O, 430 O , AND 400 O C.
Duration of Reaction, Min. 30 60 90 120 150 180
Liquefaction, % 450° C. 430" C. 400' C. 90.7 77.6 91 .o 86.0 92.0 88.7 92.3 91.2 93.4 90.7 93.4 90.6
Asphalt per U n i t of Liquefaction 430' C. 400'
450' C. 0.215 0,071 0.024 0.024 0.021 0.021
0,357 0,287 0.125 0,083 0.043 0.039
C.
0.815 0.826 0.810 0.756 0.750 0.750
TABLE VII. AT
0
Figure 3.
30
60
90 TIME, MINUTES
120
180
Liquefaction of Coal and Asphalt Formation
BATCHHYDROGENATION OF COALFOR ONE HOUR VARIOUSTEMPERATURES IN PRESENCE OF HEAVY OIL AS VEHICLE
T e s t No. 183 184 187 192
Reaction T e m p . , O C. 400 415 450 465
Liquefaction,
%
85.4 89.5 90.7 92.6
Asphalt per Unit of Liquefaction 1 .oo
INDUSTRIAL AND ENGINEERING CHEMISTRY
1262
Vol. 40, No. ?
100
90
80 70
60
c
W 2
050
5 n
40
30
20
400
Figure 4.
420
440 TEMPERATURE, 'C.
460
480
ysis of the coal. In the first st~rieboi experiments powdercd tin, zinc, arsenic, and antimony were tried (Table VIII). POWDERED TIN. The experimental results obtained R ith 1%; powdered tin and 0.50/G ammonium chloride are presented in Table VIII. For comparison, coal, in the absence of catalyst, was hydrogrnated for 1 hour a t 400" and 415" C. and an initial hydrogrii pressure of 1000 pounds with Tetralin as vehicle: Reaction Temp., O C.
55
400 415
So. 54
Duration of Reaction, Hr. 1 1
1
Zn
1
,
As
Sb
J
GOAL
C ATALYST
Effect of Temperature on Liquefaction and Asphalt Formation
Test
1
Sn
Liquefaction,
%
Asphalt per U n i t Liquefaction
55.7 58.4
0.420 0.326
These results shorn that 17, tin arid 0.5% ammonium chloride at 400" C. increase the degree of coal liquefaction 25.9% without decreasing the asphalt content. d t 415" C. the degrre of' liquefaction is increased 28.5y0 and the asphalt content decreased hv 9.570. POWDERED ZINC. The results oi coal hydrogenation in the presence of 1yo powdered zinc and 0.57, powdered ammonium chloride are also presented in Table VIII. A comparison of noncatalytic and catalytic liquefaction of coal reveals t h a t powderrd zinc increases liquefaction at 400 ' C. by 22.9% and at 415' b j 19.67,, and decreases the asphalt present in the product of liquefaction by 4.77?, a t 400" and slightly increases it at 415" C. The results show that powdered zinc in the presence of Tetralin is active in promoting the cleavage of coal but sluggish in the hrdrogenolysis of asphalt. POWDERED ARSENIC. Table VI11 gives results of coal hydrogenation in the presence of 1% powdered arsenic and 0.57, ammonium chloride. I n comparison with noncatalytic hydrogenation, powdered arsenic iricreases the degree of liquefaction 11.0% at 400" C. and 14.87, at 415", and decreases the percentage of asphalt in the product of coal hydrogenation by 14.870 at 400' and 5.5% at 415 C. POWDERED A N T m o w . The results of coal hydrogenation in the presence of 17, powdered antimony and 0.5yo ammonium chloride are shown in Table VIII. Compared with noncatalytic hydrogenation, the presence of powdered antimony decreases
Figure 5 . Effect of Catalyst, Temperature, and Duration of Reaction on Liquefaction of Coal and Asphalt Formation
liquefaction at 400' C . and increases it 7.6Yc at 415". Thrrt: i F aslight increase in asphalt, formation at 400' and a slight decrease at,415 ",C. The expt.rimenta1 results on the hydrogeiiatioii COXCLU~IONS. of coal in the presence of t,iri, zinc, arsenic, and antimony are summarized in Figure 5 . The follo\ving conclusions can be d r a w n The catalytic activity of tin is incwased considerably by t,empertiture increase, particularly x i t h respect t o asphalt split,ting. 111 the case of zinc the teniprraturr increase has far less effect' than increase in reaction t,ime. For arsenic the increase of reactiori temperature results in a 9ci;. increase in liquefaction; the rate oi asphalt hydrogenolysis remains practically unchanged. Anti-
TABLE VIII.
BATCHHYDROGENAT o s OF COALWITH 1% Pow-
DERED M E T A L AND 0.570 AMIdO?iIr;M CHLORIDE AS CbTALYS?, TETRALIN AS VEHICLE, AND IKITIAL HYDROGEN PRESSURE OF 1000 POUNDS Reaction Duration LiqueAsphdit pea Poirdtired Test T e m p , of Reaction, faction. % Liquefnotior Unit Of Metal No. O C. Hr. 0,478 1 72.4 Tin 385 87 0.672 80.0 0.5 400 96
Zinc
Arsenio
Antimony
89 92 100 98 102 67 82 69 71 84 75 73 107 114 116 111 105 109 118
120 123 125 130 133 136 138
400 400 415 415 415 385 400 400 400 415 415 415 385 400 400 400 415 415 415 385 400 400 400 415 415 415
1 3 0 ,6 1 3
1 0.5
1 3 0.5 1 3 1 0.5 1
3
0.5 1 3 1
0.5
1 3 0.5
1 3
81.6 89.2 83.4 86.9 89.6 55.7 59.7 78.1 84.6 75.0 75.3 87.8 62.7 34.1 66.7 82.4 58.3 73.2 87.8 49.6 35.4 48.5 50.6 58.6 66.0 81.0
0.447 0.350 0.493 0.230 0: 196 0.350 0.294 0.373 0.324 0,390 0,346 0.221 0.265 0.635 0.272 0.331 0.385 0.271 0.228 0,270 0.585 0.465 0.268 0.228 0.28V 0.202
INDUSTRIAL AND ENGINEERING CHEMISTRY
July 1948
1263
In presence of 1% Sn ( 1 ) (4) " " I' 1% Zn-Sb ( 2 ) ( 5 ) " " " I%Sn + I%Zn-Sb (3)( 6 )
Sn-Zn
Zn-As
Zn-Sb
COAL
30
0
CATALYST
60
90
I20
150
180
TIME, MINUTES
Figure 6. Primary Liquefaction of Coal in Presence of Tin-Zinc, Zinc-Arsenic, and Zinc-Antimony Alloy Catalysts
Figure 7.
Liquefaction of Coal and Asphalt Formation at 400' C.
30
80
I /
60
2
E50
K
ki!
40
30
,
,
. Asphalt ( 5 )
Asphalt ( 6 )
~~~~
0
30
60
90 TIME,MINUTES
Figure 8.
120
150
180
.
Liquefaction of Coal and Asphalt Formation at 4 1 5 O C.
mony displays unusual catalytic activity with temperature increase; a temperature rise from 400' to 415" C. results in 17.5% increase in liquefaction and 17.5% decrease in asphalt content. ALLOY CATALYSTS
In another series of experiments the alloys of tin-zinc, zincarsenic, and zinc-antimony were tried. The results of coal hydrogenation with the alloy catalysts are presented in Tables IX and X and summarized in Figure 6.
0
30
60
90
I20
I50
180
T I M E , MINUTES
Figure 9.
Liquefaction of Coal and Asphalt Formation at 400° C.
The following conclusions are drawn from an examination of the data: 1. The addition of zinc lowers the catalytic activity of tin in the primary cracking of coal. The high activity of pure tin can be reached only a t the expense of increased temperature and prolonged reaction periods. Both tin and zinc-tin alloy yield products containing about .the same amount of asphalt as when no catalyst is present. '2. Zinc-arsenic alloy is a less active catalyst than the metals taken separately. It is the only catalyst discussed in this paper
1264
INDUSTRIAL AND ENGINEERING CHEMISTRY
Vol. 40, No. '1
100
TABLE I X . BATCHH
os OF COALI N PRESENCE OF CHLORIDE WITH TETRALIN AS PRESSURE OF 1000 POUNDS
1% ALLOYAND 0.5qo VEHICLEAND INITIAL Alloy Sn-Xn
Test
KO. 42 40 39 45 44 43 52 50 51
%n-4-
.
49
48 47 59 60 61 62 63 64
Zn-Sb
Duration Reaction of Reaction, Temp., O C. Hr. 400 1/2 1 400 400 3 415 '/% 1 415 3 415 400 '/z 400 1 3 400 415 1/2 1 415 415 3 112 400 1 400 3 400 '/2 415 415 1 3 415'
Liquefaction,
Asphalt per Unit of Liquefaction 0.880 0.570 0,436 0,488 0.380 0.181 0,596 0.680 0,344 0.486 0.580 0.336 0,340 0,242 0,222 0,208 0.226 0.266
70
67.7 70.8 83.3 76.0 80.4 88.9 49.8 54.1 79.0 68.8 74.2 82.4 47.9 49.2 56.3
~
58.0
67.4 74.6
TABLEX. BATCH HYDROGENATIOS OF COAL IN PRESESCE O F TIP;, TIN-ANTIMONY ALLOY, AND L h N O N I U M C H L O R I D E WITH TETRALIN AS VEHICLEAND AN INITIAL HYDROGEN PRESSURE OF
Catalyst Compn.,
Test
70
1Zn-Sb ++ 0.5NHaCl
ISii
+ 0.5 ZnSb + 0.5 NHiCl
0.5 Hn
1000 P O U N D S
Reaction Temp.,
C.
30.
0
149 151 153 155 157 159 161 162 164 166 170 172
400 400 400 415 415 415 400 400 400 415 415 415
Duration of Reaction, Hr.
Liquefaction,
1/2
71.5 84.7 88.4 83.3 86.9 90.0 70.1 84.2 8 47 . 19 86.5 88.7
1 3
'12 1
3
'/2
1 3 1/2 1 3
yo
Asphalt per Unit of Liquefaction 0.253 0.210 0.163 0.204 0.190 0,088 0.365 0,252 0 . 21 73 40 0.171 0.092
9O 80
70
60 v-z
aw.
40
30
2o 10
0
4
The fact that use of zinc-arsenic a t 400" C. results in a product significantly higher in asphalt content than is obtained without a catalyst is difficult to explain on the basis of the assumption that asphalt is a necessary intermediate in the t,ransition from coal t,o oil. To retain this assumption, one must also assume that the zinc-arsenic is a negative catalyst, for the hydrogenolysig of asphalt. I t appears simpler to assume that the transition from coal t,o oil can occur without passage through the asphalt stage, and, as a consequence, that asphalt formation is a n alternative reaction of the primary dissociation products of coal. This latter assumpt,ion is in accord with the fact that, in highly dissociating solvents, such as phenolic compounds, t,he molecular weight of coal is comparatively l o x (260 t o 4qO). Stabilization of such units by hydrogenolgsis of carbon-to-oxygen bonds would yield an oil vithout passage through an asphalt stage. There are not sufficient experiment,al data to determine which of the two hypotheses is correct. THREE-COMPONENT CATALYST
The results of catalyst testipg suggest the use of a three-component catalyst which may simultaneously promote primarv cracking of coal and asphalt hydrogenolgsis. As tin proved t o he one of the best catalysts for primary cracking of coal and zincantimony alloy was active in asphalt hydrogenolgsis, it was ,lecided to investigate the action of tin and zinc-antimony conibinations. Table XI presents the results.
60
30
:50
120
90
180
T I M E , MINUTES
Figure 10.
Liquefaction of Coal a n d Asphalt Formation a t 415" C.
Table XI and Figures 9 to 10 summarize the data from coal hydrogenation with tin alone and with tin and zinc-antimony catalysts.
TABLE XI. whose use at, 400" C. results in a product significantly higher in asphalt content than is obtained without a catalyst. At 416' C. the differences in asphalt contcint, using different catalysts and no catalyst, are small and probably not significant. 3. At 400" C. the zinc-antimony alloy cat,algst results in a product of significantly lower asphalt content than when no catalyst is used.
1% Zn-Sb ( 2 ) ( 5 )
"
W
p 50
HYDROGENATION O F COAL I S PRESESCE O F WITH TETRALIN AS YEHICLC AND I N I T I A L HYDROGER' PRESSURE OF 1000 POUXDS %.4TCH
VARIOUS CATALYSTS
-Temp., O C. 400 400 400 415 415 415
Time,
Hr.
0.5 1 3 0.5 1
3
1% Sn
Asphalt per Liquefaction, unit of R liquefaction 80.0 0.672 81.6 0.447 89.2 0,390 83.4 0.493 86.9 0.230 89.6 0.196 0
+
400 400 400 415 415 4 15
0.5 1 3 0.5 1 3
1%, " Sn . 1 % ," 71.5 84.7 88.4 83.3 85.9 90.0
Zn-Sb 0,253 0,210 0.163 0.204 0.190 0.088
141, Zn-Sb -.________ Asphalt per Liqucfaction,
5%
47.9 49.2 66.3 58.0 67.4 74.6 0.5% S n io.1 84.2 87.9 84.1 86.5 88.7 I
I
unit of liquefaction 0.340 0.242 0.222 0,208 0.226 0,200
+ 0.5'% ,
Zn-Sb 0.356 0,262 0,rao 0.274 0.171 0,092
,"
CONCLUSIONS
The experimental results in the presence of Tetralin as vehicle show: (a)a combination tin and zinc-antimony catalyst enhances the hydrogenolgsis of asphaltenes to a greater degree than zincantimony and a t the same time activates the primary cracking of coal to the same extent as tin alone. ( b ) Increasing the amount of the combined tin and zinc-antimony catalyst t o 27, fails to improve materially the degree of coal liquefaction. (c) The presence of a vehicle or solvent in coal hydrogenation is undesirable in that larger amounts of asphaltenes appear in the product than when no vehicle is used. LITER4TURE CITED
(1) Yellot, J. I., Coal Technologg, 1, 3 (1946). RECEIVEDM a y 6, 1947. Presented before t h e Divkion of Gas a n d Fuel Chemistry a t t h e 111th Meeting of the AirEmcaN C H E U I C A LS O C I ~ T Y , Atlantic City, N J. Published b y permission of t h e Director, U. S.Bureau of Mines.
