INDUSTRIAL AND ENGINEERING CHEMISTRY
806
Vol. 45, No. 4
only 0.01% of the feed. It appears that most of the carbon is deposited during the first few hours on-stream, after which further deposition is relatively slight. Carbon deposition has been observed to be more serious for heavier paraffins than for n-pentane: also, it is more pronounced for paraffins containing cycloparaffins than for pure paraffins. A related observation is t h a t some impurities, not,ably oxides of carbon, are catalyst poisons.
ever, have been made. In one run, molybdena-silica-alumina catalyst 64, after having been previously revivified 35 times, was used for 188 hours for isomerization of n-pentane without revivification. During the first 152 hours the temperature was constant a t 830' F. (433" C.); during the last 35 hours, it was constant a t 860" F. (460" (3.). During the first 60 hours the total coonversion declind slon~lyfrom about 44 to 28%; during the remainder of the time at 830" F. it declined further almost negligibly to 27%; during the time a t 860" F. it was approximately 37 to 38%. During the entire run the ultimate yield of isopentane, uncorrected for the minor proportion of other liquid conversion products, was 92 to 95%. In another run, in which the temperature was 830' F. a t the start and was increased 5' F. every 4 hours until 860' F. was reached, the total conversion was approximately 4S% for 52 hours: the ultimate yield of isopentane m a s approximately 90%.
LITERATURE CITED
(1) Egloff, G., Hulla, G., a n d Komarewski, V. I., "Isomerization of Pure Hydrocarbons," h-ew York, Reinhold Publishing Corg., 1942. (2) Fowle, M. J., Bent, R. D . , C i a p e t t a , F. G . , P i t t s , P. M., a n d Leum, L. N . , Advances in Chem. Ser., S o . 5, 76-82 (1951). (3) Greensfelder, B. S.,Archibald, R. C., and Fuller, D. I>.,Chem. Eng. Progr., 43, 561-8 (1947). (4) Haensel, V., and Donaldson, G. R., IXD.ENG.CHEM.,43, 2102-4
(1951). ( 5 ) RicCabe, C . L., a n d Halsey, G. D., J . Am. Chem. Soc., 74, 2732-4
CARBON DEPOSITION
(1952).
Deposition of carbon on the catalyst does not seem excessive. I n the 188-hour run a t 830" and 860" F., the carbon amounted to
RECEIVED for review March 22, 1932.
ACCEPTED December 19,1952.
Catalyst-Pressure Relationshi
Hydrogenolysis of Coal M. G. PELIPETZ, J. R. SALMQN, JARIES BAYER, AND E. L. CLARK Synthetic Fuels Research Branch, Bureau of Mines, Bruceton, P a .
T
HE coal-hydrogenation process for producing liquid fuels
secrit'ive firsborder react~ions( 2 , 5 ) . In the first of these, coal is converted t o an asphaltenic material, in t,he second, the asphaltenic substance is converted to oil. Conditions were selected under which the conversion of coal was restricted t o asphaltenes with only minor amounts of gaseous hydrocarbons and oil. Operation under these conditions has been reported by t'he Coal Research Laboratory of Carnegie Institute of Technology (1). As a result, it was possible to consider the conversion as a firstorder reaction during B-hich b en zene-insolu b le material, coal, was changed t o a benBene soluble material, asphaltene.
or chemicals might be considerably more attractive economically if it Fvere operable at, lower pressures. Hydrogen pressures of 5000 to 10,000 pounds per square inch gage areat pres2.0 ent required to obtain reaction rates suitable for industrial ap1.8 plication. Because the reaction of coal with hydrogen is c catalytic, use of a more active 8 1.6 catalyst is one possible way of ti reducing the hydrogen pressure 0 needed for t h e liquefaction. s 1.4 Considerable work has been L done on catalysts for coal hy$ drogenation, but the greater g 1.2 part of this work has consisted m w i of empirical testing of various m catalytic materials. I n this & 1.0 m study two catalysts were com3 w pared by determining specific reaction rates for each catalyst g0.e 2 a t several pressures. Thus, a w numerical measure of catalyt'ic
EXPERIMENTAL WORK
Coal from the Rock Springs bed (bituminous C), D. 0. Clarke Mines, Superior, W'po., ivas used for the experiments. A typical ultimate compositioii of this coal is as follows:
50.6 0
activity was obtained, and the effect of pressure on the rate of coal hydrogenation could be evaluated. T o simplify interpretation of the data, use was made of information, obtained pre-
P
viously, which indicated that t,he hydrogenation of coal appears to proceed via trvo con-
F i g u r e 1. Organic Benzene-Insolubles R e m a i n i n g d u r i n g Hydrogenation of Rock Springs Coal
Q
0'4~o O.Z0
IO
20
40 TIME, MINUTES (INCLUDING 5MINUTES FOR REACTION DURING HEATING TO 4OO'C.l x)
A t 400° C., tin sulfide plus ammonium chloride catalyst
Hydrogen
75 4.9
Carbon
71.1
a&
0.7 13 3 6 3 2 2
Nitrogen Sulfur Ox gen
Moisture
1 5
April 1953
INDUSTRIAL AND ENGINEERING CHEMISTRY
-
807 RESULTS AND DISCUSSION
~~
TABLE I. PRODUCT DISTRIBUTION IN HYDROGENOLYSIS OF ROCK SPRINGSCOALAT 400" C. IN PRESENCE OF TINAND MOLYBDENUM CATALYST
Product-distribution and hydrogen-consumption data are Initial summarized in Table I. ExHydrogen ReHvdroGaseous Pressure, action Benzenegen tensive experience with this insoluAsphalBenzene- hydroCarbon Lb./Sq. Time, Expt. concoal has shown t h a t it conbles carbons dioxide Inch Gage Min. tene Oil solubles sumed No. Water tains 37* of organic matter Catalyst, Tin which is resistant t o hydro4.15 1.76 5.91 0 88,96 1.44 2.59 2.05 1607 1000 0.49 23.92 4.92 28.84 60.12 2.77 2.91 6.57 1630 1000 1.39 30 genation and may be regarded 34.01 5.30 46.20 4.95 51.15 3.17 8.45 1754 2.45 1000 60 as an impurity. The data 90.59 3.06 1.19 4.25 0 1.40 1601 2000 2.59 2.07 0.32 in Table I, therefore, in34.04 48.78 3.12 51.90 5.64 3.30 1633 2000 7.62 30 3.07 14.63 63.57 5.24 68.81 6.42 1745 2000 2.79 3.74 10.59 60 clude a corresponding correction. The reaction times given 82.12 5.04 2.84 7.88 0 3.07 2.92 5.02 1.17 1622 3000 58.14 7.53 65.67 19.44 2.38 9.32 30 6.06 1664 3000 3.20 in Table I represent the time 4.84 72.77 7.32 80.09 1.57 7.59 1755 3000 10.47 4.21 60 during which the autoclave Catalyst, Molybdenum contents were a t reaction tem38.57 1.49 40.06 18 49.80 2.47 2.61 6.18 500 1.56 perature. For the "zero-time" 51.56 3.20 54.76 31.54 4.99 1.98 9.03 32 500 2.62 tests the autoclave was heated 3.46 47.88 1.60 49.48 36.59 2.06 21 1000 10.50 2.60 58.22 3.76 61.98 22.33 6.86 32 1.66 9.80 1000 3.35 t o reaction temperature and immediately cooled. The pres56.71 2.75 59.46 26.41 3.44 1.97 23 11.11 2000 2.97 13.20 4.24 68.98 4.56 73.54 1.48 36 11.40 2000 3.67 sure values listed are the ini4.13 64.80 3.89 68.69 15.65 1.32 24 13.26 3000 3.76 tial pressures of hydrogen in 71.58 8 . 0 8 6 . 0 4 77.62 0.51 5.26 34 3000 4.22 12.53 the autoclave before heating. 11.94 5.18 67.29 5.62 73.91 21 0.80 4000 11.88 4.08 The pressures at reaction tem4.07 72.78 7.19 79.97 5.77 34 0.39 14,02 4000 4.97 perature were approximately 2.5 times as great. Plots of the logarithm of The experimental procedure and method of calculation were the percentage of benzene-insolubles remaining as a function similar t o those described previously (3, 6). Two of the best of contact time are presented in Figure 1 for the series with coal-hydrogenation catalysts-tin and molybdenum-were chosen tin and in Figure 2 for the series with molybdenum. The for comparison. I n one series of tests, tin ( l % , based on coal) contact time used in the construction of these curves was the as stannous sulfide and ammonium chloride (0.5y0 of coal) were time during which the charge was actually kept a t 400" C. added in finely powdered form t o the coal in the autoclave. I n plus a 5-minute correction factor for the preheating and coolthe second series, the coal was neutralized with sulfuric acid and ing periods. Figures 1 and 2 indicate t h a t the conversion of impregnated with ammonium molybdate in a n amount equivabenzene-insoluble matter t o benzene-solubles, water, and gaseous lent t o 1% of molybdenum based on coal. A detailed descripproduct was a first-order reaction with respect t o insolubles tion of this method of impregnationis given inaprevious paper ( 4 ) remaining. The specific reaction rates, calculated from the slopes of -the lines, -are listed in Table 11: Moisture- and Ash-Free Coal, Weight %
.
'
TABLE 11. SPECINCREACTION RATES,K , FOR HYDROGENOLYSIS OF ROCK SPRINGSCOALAT 400" C. IN PRESENCE OF TIN A N D
MOLYBDENUM
Catalyst
Initial Hydrogen Pressure Lb./Sq. Inch'Gage
PI0
Sn
1000 2000 3000
I n Figure 3, these rates, plotted as a function of initial hydrogen pressure, fall on two parallel straight lines, one for tin and one for molybdenum. The relationship between the specific reaction rate, K (min.+), and the initial hydrogen pressure, P (pounds per square inch gage), is K = 1.5 X 10-6P for tin and K = 1.5 X 10-62' 0.0225 for molybdenum. The constant 0.0225 in the second equation represents the difference in activity between the two catalysts; in terms of initial hydrogen pressure, this constant equals 1500 pounds per square inch gage. Thus, t o obtain the same conversion of Rock Springs coal at 400" C., the initial pressure must be 1500 pounds per square inch gage higher with tin than with molybdenum. Figure 4 represents a plot of benzene-solubles formed as a function of benzene-insolubles remaining. Benzene-soluble material is composed of asphaltene and oil; but, as can be seen
+
TIME, MINUTES (INCLUDING 5 MINUTES FOR REACTION DURING HEATING TO 4 0 O O C . )
Figure 2. Organic Benzene-Insolubles Remaining during Hydrogenation of Rock Springs Coal At 400° C., molybdenum catalyst
K,
Minute-' 0.03040 0.03960 0.05134 0.06618 0.08453 0.01575 0.03081 0.04560
INDUSTRIAL AND ENGINEERING CHEMISTRY
808 9.0
I 0 - T i n catalvst
I .o
0
1000
2000
3000
4(
I N I T I A L HYDROGEN PRESSURE, p.s.i g.
Figure 3.
Effect of Pressure o n Specific Rate Constant
0
Vol. 45, No. 4
1.2% of water was formed. This quantity of water appears to have been produced instantaneously or in a very short time. Subsequent formation of water was directly proportional t o the disappearance of benzene-insolubles, no matter which catalyst was used. At longer contact times and higher hydrogen pressures more water was formed n i t h molybdenum than with tin. Because an increase in water formation coincided with a decrease in carbon dioxide formation, the higher yield of water is probably due t o the hydrogenation of carbon dioxide. The rate of formation of gaseous hydrocarbons was similar to t h a t of the formation of viater. rlbout 1% of gaseous hydrocarbons v a s formed either instantaneously or in a short time, again n-hen 95% of the benzene-insoluble matter was present. The rest of this gas was formed in direct proportion to the disappearance of benzene-insolubles. About 3 % of carbon dioxide n-as obtained with the first amount of water and gaseous hydrocarbons With increasing hydrogen pressure and contact time, less carbon dioxide was found in the product. -4s mentioned above, hydrogenation of carbon dioxide probably caused its disappearance. B s the reaction may be represented as a first-order reaction and the ratio of the products (gas, water, and benzene-soluble oils) remained fairly constant for different pressures and catalysts, it appears that a quasi-homogeneous substance was converted by the same mechanism under all of the experimental conditions of this study. One may postulate t h a t during the liberation of water, hydrocarbon gas, and carbon dioxide from the first 5% of coal the coal was convertpd t o a homogeneous substance which v-as capable of direct reaction x-ith hydrogen. This supposition is strengthened by the fact t h a t hydrogenation of lower-rank coals results in the production of large amounts of water and carbon dioxide during the first few minutes of reaction, as mould be required to approach the composition of the homogeneous material t h a t has been postulated for Rock Springs coal in this case. The benzene-insolubles obtained a t different stages of coal hydrogenolysis varied in hydrogen content. According t o Table 111,higher hydrogen pressure resulted in higher atom ratios of hydrogen to carbon, indicating that there
from Table I, asphaltene constituted the bulk of the benzenesolubles. The linear relationship between these two fractions of t h e product indicates that Rock Springs coal is a quasi-homogeneous substance. Figure 4 indicates t h a t approximately 5% of the coal disappeared before any soluble mat e r i a l was formed. This part of the coal was converted into carbon dioxide, water, and gaseous hydrocarbons. Complete conversion of the organic benzene-insoluble matter (100 parts) of the coal would have resulted in over 80 parts of b e n z e n e - s o l u b l e matter consisting mainly of asphaltene, the balance being gaseous h y d r o c a r b o n s, carbon dioxide, and water. I n Figure 5 the formation of water and gaseous hydrocarbons and the hydrogen consumption are plotted as B E N Z E N E - I N S O L U B L E S REMAINING, WEIGHTfunctions of benaeneP E R C E N T M.A.F. C O A L insolubles remaining. Figure 4. Relationship of Remaining When 95% of the benBenzene-Insolubles to Benzene- Solubles Produced zene-insolubles were still p r e s e n t , a b o u t Oil plus asphaltene
10 0 0
?-< ..
0
Figure 5. Relationship of Water and Hydrocarbon Gas Production and Hydrogen Absorption to Conversion of Benzene-Insolubles
April 1953
INDUSTRIAL AND ENGINEERING CHEMISTRY
lecular weight due t o splitting of the less stable compounds. I n t h e light of the present data this mechanism appears more probable than one of thermal cracking of the benzene-insoluble materials followed by a saturation of t h e fragments.
TABLE 111. ULTIMATECOMPOSITION OF BENZENE-INSOLUBLES REMAINING Expt. No.
.
Initial Hydrogen Pressure, Reaction Lb./Sq. Time, Inch Gage Min.
1607 1630 1754
1000 1000 1000
30 60
1601 1633 1745
2000 2000 2000
1622 1664 1755
3000 3000 3000
Hydrogen
0
5.4 5.20 5.32
30 60
0
5.3 5.85 5.76
0 30 60
5.73 5.79 5.60
Benzene-Insolubles Carbon Nitrogen Sulfur Catalyst, Tin 79.35 82.33 84.25
Oxygen
H/C Atom Ratio
1.9 2.07 2.14
0.85 0.98 1.44
12.5 9 42 6.84
0.817 0.758 0.758
79.9 81.80 84.91
1.90 1.94 2.03
0.95 1.30 2.77
11.95 9.12 4.51
0.796 0.858 0.814
81.83 82.50 79.80
1.97 1.87 2.02
0.82 2.14 3.90
9.60 7.65 8.66
0.840 0.842 0.842
Catalyst, Molybdenum 77.70 2.02 80.57 2.09
1976 1734
500 500
18 32
5.19 5.51
2.17 3.38
12,92 8.44
0.801 0.821
1982 1733
1000 1000
32
21
5.64 5.52
78.84 78.63
1.95 2.02
2.56 3.54
11.01 10.30
0.858 0.842
1970 1761
2000 2000
23 36
5.59 5.19
78.43 73.55
1.87 1.86
3.15 6.75
10.96 12.65
0.855 0.847
1969 1759
3000 3000
24 34
5.72 5.15
75.96 70.84
1.77 1.69
5.54 5.73
11.01 16.59
0.904 0.872
1977 1758
4000 4000
21 34
5.64 5.18
74.72 70.44
1,63 1,82
5.07 6.39
12.94 16.17
0.906 0.882
might be a direct addition of hydrogen t o the benzene-insoluble fraction, with concomitant removal of carbon dioxide, water, and gaseous'hydrocarbons. This implies that the formation o f benxene-solubles probably proceeds by means of saturation of the benzene-insolubles, with a possible subsequent decrease of the mo-
(6) Weller, S., Pelipets, M. 42, 330-4 (1950).
809
LITERATURE CITED
(1) Falkum, Einar, and R. A., Fuel, 29, (1950). (2) Pelipets, M.,Kuhn, Friedman, S., and
Glenn, 178-84
E. M., Storch, H. H., IND.ENG.CHEM.,
40,1259-64 (1948). (3) Pelipetr, M. G., Weller, S., and Clark, E. L., Fuel, 29, 208-11 (1950). (4) Weller, S., and Pelipetz, M. G., IND.ENG.CHEM.,43, 1243-6 (1951). (5) Weller, S., Pelipetz, M. G., and Friedman, S., Ibid., 43, 1572-9 (1951). G., Friedman, S., and Storch, H. H., Ibid.,
RECEIVED for review May 15, 1952. ACCEPTED December 10, 1952. Presented before the Division of Gas and Fuel Chemistry, AMERICAN CHEMICAL SOCIETY, State College, Pa., May 5, 1952.
Action of Light on Tar Fractions U
C. R. KINNEY AND M. B. DELL T h e Pennsylvania State College, State College, Pa.
T
HE deposition of insoluble matter frequently observed when
..
I
3
.
solutions of various bituminous products, particularly coal tars, are allowed to stand is familiar to everyone who has worked with these materials, b u t the cause is obscure. Hubbard and Reeve, working with carbon disulfide solutions of tars, suspected t h a t a reaction with the solvent occurred (IO), b u t later considered the possibility of oxidation (9). Weiss e(16, 1 7 ) compared aniline and toluene solutions and found t h a t while the aniline solutions remained clear a precipitate appeared in the toluene solutions. H e also found t h a t the longer tars were allowed to stand in contact with solvents, such as benzene, toluene, carbon disulfide, and chloroform, partly in solution, the greater was the amount of insoluble matter obtained on filtration. Joestes and Siebert (11) observed t h a t cresol-Tetralin extracts of a Hessian brown coal deposited a precipitate when exposed t o sunlight. And in 1948, Green and Thakur (8) reported analyses of precipitates obtained from benzene solutions of tar on standing. The analyses suggested, although Green and Thakur did not so state, t h a t oxidation was involved in the precipitation. These authors also investigated the effect of ultraviolet light on the deposition of free carbon and found a definite increase. Oxidation, accelerated b y the action of light, has been shown by Thurston and Knowles (16)t o increase the rate of weathering of bituminous binders and coatings. I n view of these results, i t was of interest t o determine whether precipitation from tar extracts was related to this weathering prop.erty of tars. For this investigation, pentane extracts of several
tars and bituminous materials containing the so-called tar oils were exposed to light under various conditions. SAMPLES USED
The properties of the four bituminous materials investigated in detail are given in Table I.
TABLE I. PROPERTIES OF TARS Property Sp gr. 2O0/2Oo ASTM' dist.. D 2030, O C.. wt. 70 RT-170 170-235 235-270 270-300 300-350 350-400 Pentane-soluble, wt. %
Coke Oven 1.18
Dehydrated Water Gas 1.16
Horizontal Retort 1.25
2.3 7.2 10.0 6.1
0.7 15.0 13.0 8.1
...
... ...
0.6 4.9 7.4 4.9 11.3
...
(
