Hydrogenation of High-Temperature Tar from Bv-Product Coke Ovens J
H. H. STORCH, L. L. HIRST, AND C. H. FISHER Central Experiment Station, U. S. Bureau of Mines, Pittsburgh, Penna.
H. K. WORK AND F. W. WAGNER Jones & Laughlin Steel Corporation, Pittsburgh, Penna.
WO economic factors make catalysts, a t 200 atmospheres Aromatic solvents can be produced from the hydrogenation of coal pressure and 450" C. These high-temperature coke-oven tar by hydrotar a subject of immediate results show that stannous chlogenation. As judged by their composition, importance in the United States: ride is a much better catalyst these solvents appear to be of possible the competition presented to the than molybdenum trioxide for industrial importance. tar industry by the production the hydrogenation of high-temof aromatic compounds from perature tar. The data obtained show that two phases petroleum, and the necessity for The British Fuel Research or stages of hydrogenation are essential: disposal without loss, and preferLaboratory (7) reports the reLiquid phase, in which the tar is mixed with ably a t a profit, of large quantisults of experiments on liquida small amount of catalyst and pumped ties of coke-oven gas. A conphase hydrogenation of highinto the converter along with hydrogen siderable amount of experimental temperature vertical-retort tar work on the hydrogenation of in an experimental plant. under pressure, and the vapor phase, in low-temperature tar has been The throughput was 200 cc. which the 210-300' C. fraction of the liquiddescribed in publications issued per hour of tar made by the phase product is vaporized in a stream of in Great Britain (6, 17) and carbonization of a Yorkshire hydrogen and passed through a bed of Japan ( 1 , 3, 1 2 ) ; but little ingas coal. This tar hydrocatalyst particles about l/g inch in diameformation has been published on genated almost as readily as the hydrogenation of high-temlow-temperature tar. Tests ter. The temperature and contact time in using 0.1 to 0.5 per cent of perature tar. the liquid phase are about 450' C. and 2 King (18) states that horivarious catalysts (molybdehours, and in the vapor phase, 510' C. and num trioxide, hydrogen chlozontal-oven tar is more difficult 0.5 minute, respectively. ride, stannous chloride, hyto hydrogenate than the proddrogen iodide) showed that uct from vertical ovens. He also presents some results obtained by Chemical Reactions, the most satisfactory one was'& mixture'of 0.1 per cent Ltd., on the liquid-phase hydrogenation of high-temperature molybdenum trioxide plus an equal quantity of hydrogen tars. These results were obtained using 0.5 per cent of a iodide. Recycle experiments showed that this high-temcatalyst (composition not disclosed) finely dispersed in the perature vertical-retort tar yielded about 86 per cent of a tar, a t a pressure of 200 atmospheres of hydrogen and 450" C. middle oil which was a satisfactory raw material for vaporA typical experiment showed that a topped coke-oven tar phase hydrogenation. which gave only 38 per cent of distillate (to 360" C.) yielded The objective of the work described in the present paper upon hydrogenation 98 per cent of a product, 54 per cent of was to determine the optimum conditions, yields, and character of the products obtainable in the destructive hydrogenawhich distilled to 360 O C. During this liquid-phase operation a considerable portion of the "free carbonJJwas converted t o a tion of high-temperature, by-product-coke-oven coal tar. The experiments were carried out in the coal-hydrogenation liquid product. The term "liquid phase" is somewhat inexperimental plant (15, 27) a t the Central Experiment Stacorrect, for a considerable quantity of the product vaporizes tion of the U. S. Bureau of Mines in cooperation with the in the stream of hydrogen. It is employed to differentiate Jones & Laughlin Steel Corporation. the procedure from that in which a fixed catalyst is used and Some constituents of the tar-hydrogenation oils of possible where practically all of the raw material is vaporized in a commercial importance are listed in Table I. The yield stream of hydrogen passing through the catalyst bed. While low-temperature tar can be hydrogenated in vapor phase with data of this table mere estimated from the work described in later sections of this paper. About one third of the oil only a relatively slow rate of catalyst deterioration ( 6 ) , highproduct consists of chemicals that are of industrial importemperature tars require treatment in the liquid phase betance. I n estimating the benzene, toluene, and xylene yields, fore a fixed catalyst is used in the vapor phase. it was assumed that the aromatic contents indicated by sulCawley (9) presents some results on liquid-phase hydrofonation are substantially correct. The aromatics in fracgenation of both low- and high-temperature tars, using 0.5 tions 6 and 7 of Table XV were taken as xylenes. The cycloper cent molybdic acid and 0.5 per cent stannous chloride as
T
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February, 1941 TABLE I.
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INDUSTRIAL A N D ENGINEERING CHEMISTRY
PRODUCTS FROM HYDROGENATION OF TOPPED HIGH-TEMPERATURE TAR(IN VOLUME PERCENT) From Liquid-Phase Hydrogenation Concn. in Yield based overhead on topped oil0 tar
From Vapor-Phase Hydrogenation Conen, in Overhead Oils YieldC based Total Recycle on topped Yield Based on Substance Actual Correctedb tar Topped Tar 0.26 0.27 0.0 0.0 0.0 0.27 Phenol 0.74 0.76 0.0 0.0 0.0 0.76 Cresol 0.50 0.51 0.64 0.38 1.19 1.70 Benzene 1.64 1.69 2.17 1.27 3.98 5.67 Toluene 1.83 1.87 2.19 1.28 4.00 5.87 Xylene 1.40 5.23 Tetrahydronaphthalene 1.36 3.07 9.60 11.00 0.57 0.59 0.85 0.50 1.56 2.17 Cyclohexane 1.28 Methylcyclohexane 1.14 1.18 0.75 2.35 3.51 0.59 0.50 Dimethylcyclohexane 0.57 0.29 0.91 l.$O 8.86 12.86 Total chemicals listed 8.61 7.54 23.59 32.45 18.64 25.84 15.16 High-flash naphtha 18.09 47.41 66.05 27.50 38.70b 22.70 Total oil distilling to 207' C. 26.70 71.00 98.50 a The oil distillin in the stream of hydrogen passing throuqh the liquid-phase converter: it is the steady-state raw roduct from wkch the final products are separated by distillation. b $he feed stock to the vapor-phase converter contained about 16% distilling to 207O C if this had been completely removed, the concentrations of the various chemicals in the vapor-phase overhe;d oil would have been about as listed in the "Corrected" column. c Calculated by assuming a steady state, concentration of 22.7% of overhead oil distilling to 207O C. The overall volume yield in the vapor phase of oil distilling below this temperature is (103 27.50) X 0.94 = 71.0%, where 27.50 is the percentage yield of oil distilling to 207' C. in the liq,uid-phase prqduct, 103 is total liquid-phase oil yield in volume % of the topped tar, and 0.94 is the vapor-phase yield of oil distilling t o 207' C. as volume %/100 of the liquid-phase product boiling above 207' C.
.
-
hexane and methylcyclohexane yields were estimated by assuming that methylcyclopentane and other cyclopentane derivatives were absent. It was assumed that the naphthenes in the fraction boiling a t 120-130" C. were dimethylcyclohexanes and that the liquid- and vapor-phase fractions boiling a t 200-206" C. contained 30 and 60 per cent, respectively, of tetrahydronaphthalene. Two thirds of the oil product consists of materials boiling in the high-flash naphtha range. This fraction contains large amounts of polymethylbenzenes and polymethylcyclohexanes. These compounds have not yet been separated on a commercial scale from coal tar and for this reason do not have immediate commercial interest. Such separations from hydrogenated tar can, however, be readily made. The benzene, toluene, and xylene yields can be raised if desired to about 4, 9.0, and 7.5 per cent, respectively, by dehydrogenation of some of the products listed in Table I. The 9.0 per cent toluene yield is close to the maximum yield of toluene reported by Hall and Cawley (14) for tar hydrogenation.
Small Autoclave Tests on Catalysts and Contact Time The tar hydrogenated was obtained from the Jones & Laughlin Steel Corporation. It had been distilled to 230" C. to remove water and valuable tar acids and solvents. The analyses for both the raw tar and the topped tar boiling above 230" C. are given in Table 11. A somewhat higher yield-viz., 6 per cent by weight-of oil boiling up to 230" C. as compared with 2.8 per cent shown in Table I1 was obtained by distilling 249 grams of the topped tar through a 6-inch (15.2-cm.) indented column. The distillate to 300" C. was 18 per cent by weight. This discrepancy may have been caused by sampling errors or by differences between the Engler distillation flask used for the distillations presented in Table I1 and the column used for the distillation up to 300" C. The hydrogenation experiments were carried out in 1.2-liter bombs. About 190 grams of residual tar were placed in the bomb, the air was flushed out, and hydrogen was added until the pressure at 20" C. was 1500, 1700, or 1800 pounds per square inch (105, 120, or 126 kg. per sq. cm.), usually the last. Nearly 2 hours were required to bring the temperature to 440' C., where it was maintained for 3 hours. In two experiments the hydro-
genation gases were released (after cooling), fresh hydrogen was added, and the experiment repeated. The liquid and solid products, excluding several grams adhering to the walls, were transferred to a 250-cc. bottle and centrifuged. The centrifuged oil was poured from the bottle, the material (about 8 grams) remaining in the bomb was washed into the centrifuge bottle with acetone, and the combined residues were washed six times with acetone. The first three acetone washings and the centrifuged oil were distilled through a 6-inch indented column; fractions were collected at 70-200", 200-230°, and 230-300 C. O
The experimental conditions are given in Table 111: the temperature of all ex: perimenis was 440" C. The maximum pressure attained during the experiments, the pressure drop, and the volume of the hydrogenating gases are also given in Table 111. The effect of time may be determined by comparing experiment 2 with 1 and 4. These experiments were made with 3, 6, and 9 hours of contact time, respectively, and the bomb was cooled and refilled with hydrogen a t the end of every 3hour period. The material distilling to 300" C. increased from 21.0 per cent in the 3-hour test to 24.3 per cent for 6 hours and 31.8 per cent for 9 hours (Table IV). Moreover, the acetone-insoluble residue decreased from 4.6 a t 3 hours to 3.8 a t 6 hours, and 3.2 a t 9 hours (Table IV). These data indicate that the tar hydrogenated uniformly without the accumulation of refractory residue. In this connection the decrease in specific gravity and tar acid and base contents of the distillates (Table V) with increased time of hydrogenation is noteworthy. Increased gas yields were also observed (Table IV). Comparison of experiment 20, in which no catalyst was employed, with any of the other 3-hour experiments shows the importance of catalyst. When catalyst was omitted (experiment 20) the hydrogen consumption was least, the insoluble residue was greatest, and the liquid products had the highest specific gravity (Tables I11 and IV). The highest yield of insoluble residues, the highest specific gravities (centrifuged oil), and the lowest distillate yields
TABLE11. ANALYSESOF RAWAND TOPPEDTARS Ultimate analysis Hydrogen % Carbon, % Nitrogen, Yo Oxygen, % Sulfur, Yo
$3 Ztio
g%:
(?5.80 C.) Free carbon, yo Float test at 32' C., sec. Flash point. C. Fire point C. Distillation '% At ZOOo 6. At 230° C. At 235' C; Total tar acids at 235' C., % Phenol yo Cresylib acids % Light oil (200b C.), % Naphthalene, Yo
Raw Tar
Topped Tar
5,63 91.09 1.02 1.42 0.76 0.06 16.2 3.0 1.165 4.0
5.46 92.37 1.15 0.54 0.45 0.03 16.9 0.04 1.207 8.58 348 139 158
..
79 95
..
..
4:98 1.39 3.59 4.71 6.51
0.5 2.8 3.4 0.58
..
o:i3 1.89
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TABLE111. EXPERIMENTAL CONDITIONS FOR SMALL AUTOCLAVE TESTSAT 440' C . Expt. No.
Total Time
2
Hours 3 6 9
1
4
Catalyst
% of tar
O.5MoOs Same Same
+ O.5SnS
Initial Pressure L b . / s q . in.
Tar Used
Hydrogen Consumed
( k g . / s q . cm.) 1500 (105)
Crams 218 245.2 185.8
G./1008 . tar 2.44 3.93 6.51
la71 6
2: 61 3.52 3.48 2.07 1.94 3.68 2.69 3.33 3.67 3.5s 3.61 4.14 4.02
1500 (105) 18000 (126)
3 3 5 3 7 3 3 21 3 20 22 3 23 3 25 3 24 3 27 3 55 3 54 3 59 3 a SnCL.ZH20. b Chlorine equivalent t o 0.5 per cent SnClt .2Hz0. First 3 hours. d Second 3 hours. e Third 3 hours. f Approximate total Consumption for 9 hours,
...
lSOOd (126) 17006 (120)
1800 (126) 1800 (126) 1800 (126) 1800 (126) 1800 (126) 1800 (126) 1800 (126) 1800 (126) 1800 (126) 1800 (126) 1800 (126) 1800 (126) 1800 (126)
Maximum Pressure
..
187.8 191.6 199.3 185.1 196.4 194.4 204.6 195.9 191.1 192.8 192.5 193.8
Pressure Drov
L b . / s q . in. ( k g . / s q , cm.) 3200 710 3210 690 3820 690 4340 380 4320 220 3620 920 3610 870 3490 980 3910 810 4130 380 3500 1080 3820 820 3640 980 3650 1030 3630 1020 3670 980 3590 1090 3600
Vol. of Hydrogenating Gases a t 0' C.
Cu. ft. (liters) 1.65 (47) 1 . 8 1 (51) 2.34 (66) 3.22 (91) 3 . 0 5 (87) 1 . 7 5 (50) 1 , s 4 (52) 1.81 (51) 3 . 0 8 (87) 3.08 (87) 1 . 6 5 (47) 2 . 4 1 (68) 1.81 (51) 1 . 7 3 (49) 1.82 (52) 1 . 8 0 (51) 1 37 (39 1:50 (421
TABLEIV. SMALL AUTOCLAVETESTS, LIQUEFACTION YIELD,AND DISTILLATION DATA -Products, yoExpt. Liquids Mechanical Acetone Amount, Temp., NO. solids~ Gases" Loss, % Insol., %b %e Sp. gr. ' C. 2 94.1 3.7 2.2 4.6 76 .. 86.4 5.8 7.8 1 3.8 81 12.1 4 80.6 7.3 3.2 72 26 1:041 92 3.2 4.8 3.2 26 3 1.078 83 93.6 3.5 5 2.9 3.7 83 26 1.081 90.7 3.1 6.2 26 7 3.8 85 1,080 93.6 6.9 21 4.2 82 27 1.126 4.4 93.3 6.5 20 2.3 78 25 1.175 4.1 22 5.0 90.9 3.6 85 26 1.081 3.6 4.2 26 23 93.3 3.1 81 1.116 3.9 25 92.8 3.3 3.5 25.5 85 1.086 4.7 3.4 25.5 24 89.8 85 5.5 1.087 5.0 3.7 27 96.5 ... 88 4.5 3.7 3.4 55 91.8 85 1:072 23 4.8 54 6.4 88.8 3.8 87 23 1.070 5.6 83 90.6 3.8 3.3 59 23 1.062 Percentage of tar and hydrogen used. b Percentage of tar and hydrogen used: not corrected for catalyst. c Percentage of material centrifuged. d Percentage = cc. distillate X 100/grams tar f grams hydrogen. e 100 per cent, less per cent gas, per cent distillate, and per cent insoluble residue; includes losses
+
...
..
...
..
were observed in experiments 21, 23, and 20, in which cobalt sulfide, a mixture of cobalt and stannous sulfides, and no catalyst, respectively, were used. The halogen-containing compounds were more effective than the other catalysts tested. Both organic and inorganic halogen compounds were effective (stannous chloride in experiments 3, 5, 7, and 22; ammonium chloride in experiments 24, 25, and 27; pentachlorophenol in experiments 54 and 55; and iodoform in experiment 59). These catalysts were very effective in increasing the hydrogen consumption, in decreasing the amount of insoluble residue, and in lowering the specific gravity of the products (Tables I11 and IV). The halogen-containing catalysts also raised the content of saturated hydrocarbons and low-boiling material (Tables IV and V). Since saturated hydrocarbons are cracked more easily than aromatics, it is possible that the increased yields of saturated hydrocarbons and low-boiling distillates are related. Iodoform was the most effective catalyst, as judged by the data obtained in experiment 59 (Tables IV and V). Iodine compounds are preferable to chlorine derivatives for an additional reason; viz., in the experimental plant it was found that use of the latter catalyst resulted in clogging of high-pressure lines with ammonium chloride and caused considerably more corrosion than iodine compounds. Only traces of carbon monoxide and unsaturated hydrocarbons were found in the hydrogenation gases. The main
Centrifuged Oil Distillate, % d To T~ To 200" C. 230° C. 3OOOC. 9.0 21.0 10.2 4.3 24.3 15.2 7.6 31.8 10.4 27.0 5.2 11.3 5.1 25.7 26.7 6.1 11.1 9.3 23.1 3.9 17.5 3.2 6.9 6.4 11.8 26.5 3.5 8.0 21.5 23.6 4.3 9.0 26.1 5.4 11.8 30.8 6.6 14.2 12.5 6.5 28.5 12.5 8.5 26.9 30.8 13.4 6.5
...
Distn. residue, %" Found Calcd.' 64.5 69.3 65.2 54.6 51 40.9 56.0 65.8 58.6 66.6 57.5 65.8 65.3 64.4 61.5 71.4 65.0 59 70.2 65.1 68.3 61.5 65.1 52.6 59.7 56.6 63.4 56.6 64.1 52.6 51.6 60.0
constituents were paraffinic hydrocarbons. The highest carbon dioxide yield was found in experiment 20, in which no catalyst was used; possibly increased amounts of carbon dioxide were hydrogenated in the presence of catalysts. The yields of hydrogen sulfide and ammonia were small and variable.
Liquid-Phase Continuous Tests in Experimental Plant HYDROGENATIOK O F TOPPEDTARWITHOUT REFLUXOR RECYCLE.I n the early plant tests an attempt was made to convert all of the tar, in one pass through the converter, to material boiling below 330" C. The raw material was topped tar from the Jones & Laughlin Steel Corporation; an analysis of this material is given in Table 11. The catalyst employed consisted of 0.5 per cent ammonium chloride plus the same amount of stannous sulfide. The converters used in the liquid-phase tar work were identical with those employed in coal-hydrogenation assays (16,W7). Two converters were connected in series; the temperature in the first 'was 400" C. and in the second 450-460" C., and the pressure was 4500 pounds per square inch (316 kg. per sq. cm.) in both. As shown in Table VI, during the first 49 hours of operation the ratio of overhead t o heavy oil was between 2.41 and 3.54. The "overhead" is the oil which vaporized in the stream of hydrogen that bubbled up through
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INDUSTRIAL AND ENGINEERING CHEMISTRY
February, 1941
TABLEV. COMPOSITION OF DISTILLATE BOILING BELOW 300” c. IN SMALL AUTOCLAVE TESTS ~ p gr. .
Expt. No. 2 1
4 3 5 7 21 20 22 23 25 24 27 55 54 59
(15.6O C.) 0:990 0,969 0.981 0.986 0.987 0.991 1.012 0.975 0.997 0.979 0.989 0.979 0.980 0.971 0.973
,
Distillate % by Volume
Tar
bases 5.9 6.0 5.0 4.5 4.5 4.0 8.0 8.6 3.5 7.3 6.0 6.5 4 3 4 3.2
SP. gr4 (15.6
Phenols 10.4 9.0 8.5 7.5 8.5
O:Q85 0.961 0.978 0.982
8.0 11.0 10.0 7.5 9.8 8.5 8.0 10 7.2 7.2 7
0:99l 1.018 0.969 0.994 0.975 0.985 0.977 0.975 0.967 0.970
C.)
Neutral Oil % by Volume OleAro- Satufins matics rates 3.5 96.0 0.5 6.0 91.0 3.0 4.5 92.5 3.0 5.5 86.2 8.3 6.0 86.2 7.8 3.5 95.3 1.2 5.0 94.3 0.7 7.0 92.7 0.3 6.0 84.5 9.5 7.0 92.1 0.9 6.0 92.5 1.5 6.0 93.5 0.5 5.5 93.0 1.5 4.5 91.5 4 4.0 91.5 4.5 5.5 91.5 3
267
With topped tar, operations were not continued long enough to attain a steady state; hence further liquid-phase experiments are desirable. However, Table VI1 indicates that it is possible to hydrogenate topped tar with a combined recycle (centrifuged heavy oil plus bottoms from distillation of overhead oil) of 40-60 per cent of the total feed. The operation in run 42, which was continued for about 100 hours, proceeded smoothly. The ratio of overhead to heavy oil increased with each generation up to the ninth, where it was 3.8, and in the tenth generation the contact time was decreased from its value of about 2.5 hours during previous generations to about 2.1 hours; the ratio of overhead to heavy oil was thus reduced to 1.8. Just how far one can push this ratio without causing excessive coking (as in run 23-C of Table VI) remains to be determined. The data thus far obtained indicate that the limit is somewhere between 4 and 9; extensive and rapid coke formation occurs when this limit is exceeded. In the experiments of Table VI1 the insolubles present in the feed were hydrogenated slowly, an approximately steady state being reached in the fifth and sixth generations with both raw and topped tar. There appears to be no reason for expecting any difficulty in converting either raw or topped tar to an overhead oil boiling below 300” C. by re-
the tar. This oil was subsequently condensed and separated in a cold trap. The heavy oil was that which overflowed into a standpipe inside the converter and was discharged through special valves (15). Fairly smooth operation was obtained, with no evidence of coking. When, however, the ratio of overhead to heavy oil was increased to more than 9 in run 23-C, coke began t o form, and a t the end of about 20 hours there was extensive TABLEVI. HYDROGENATION OF RESIDUAL TARWITHOUT REFLUXOR stoppage of the second converter. This beRECYCLE” havior indicated definitely that recycling an Rnn Nn 23-A 23-B appreciable fraction of (he charge would be 400 407 Temp. No. 1 converter C. Temp. No. 2 converter: C. 452 456 essential. Tar feed, lb. (kg.)/hr. 11.4 (5.2) 11.9 (5.4) Data on the overhead and heavy oils are also H?absorbed, % of tar feed 6.2 5.5 ?Z .” of tar + H? given in Table VI. Some distillation results Overhead oil 65.1 58.5 65.2 18.4 24.2 Heavy oil 7.1 and solvent tests on the low-boiling fractions of Gas 17.3 27.7 16.5 the overhead oil (Table XXII) indicate that Ratio, pverhead/heavy oil 2.41 3.54 9.32 Total time of run, hr. 31 18 28 these fractions are good solvent materials. It is interesting to no‘ie that while the tar feed Data on Overhead Oil % distilling at contained 8.7 per cent of materials insoluble in 20-200 c. 18.7b 20.50 20.4d acetone, the heavy oils of runs 23-A and 23-B 200-230O C. 14.1 15.1 14.0 230-270’C. 17.9 15.9 15.9 had only 5.88 and 6.47 per cent, respectively. 270-300° C. 16.4 11.5 12.5 9.8 14.8 13.0 300-330° C. Hence, taking account of the ratios of overhead Over 330’ C. 23.1 22.2 24.2 to heavy oil, it appears that about 80 per cent sp. gr. of combined dist. to 330’ c. 0.967 0.961 0.959 7.4 7.4 6.1 of this insoluble material is hydrogenated in a i”,~ ~ ~ ~ 3.5 ~ ~ 3.5 ~ , 2.9 * , Neutral oil single pass, and therefore it was to be expected Sp. gr. 0.961 0.954 0.956 that with proper recycle this “insoluble” matter Olefins, yo 5.0 5.5 7.0 Aromatics, % 88.0 81.6 88.0 should be completely hydrogenated. Saturates, % 7.0 13.0 5.0 HYDROGENATION OF RAW AND TOPPED TAR Data on Heavy Oil WITH REFLUXAND RECYCLE.In further plant gravity 1,133 I. 145 ... tests some information concerning the effect of Acetone insol % 5.88 6.47 ... Vacuum distn: at 4 mm., % to 200’ C. 38.1 40.0 ... recycling and of varying reflux temperature was Tar acids in dist., % 9 .o 10.5 ... obtained. These experiments were carried out dist.9 7% 0.5 0.0 ... S gr 1.014 1.025 ... in a single converter with a water-cooled coil in O%fiIl;,,% 4.5 8.0 ... the top section of the converter. The temperaAromatics % 95.0 91.5 ... ture of this reflux coil was controlled by varySaturates.’% 0.5 0.5 ... # Converter pressure 4500 lb./sq. in. (316 kg./sq. om.). hydrogen pumping rate 2513300 ing the amount of water fed to it. The most cu. ft. (7.1-8.5 cu. m.) ’er hr.; catalyst, 0.5% stannous &fide + 0.5% ammonium’ohloride. pertinent data for these tests are presented in b Sp. gr., 0.874. k. gr., 0,864. d Sp. gr., 0.865. Table VII. “Generation” means those periods of 25-30 hours each during which heavy oil was accumulated and a t the end of which a cycling the fraction boiling over this temperature. After new batch of tar plus recycle stock was prepared. Generations 1 to 4 with raw tar and 1 to 6 with topped tar are not the tests shown in Table VI1 were completed, the converter included in Table VII. was drained and examined to determine the amount of “coke” accumulated. About 1 pound of soft, carbonaceous Fairly steady operation was obtained with raw, untopped solid was found after about 370 hours of operation. Since tar during the generations 3 to 6, with a recycle of 25-30 about 5 pounds must be accumulated before stoppage occurs per cent. The results indicate a net increase per pass of in our 3-inch (7.6-cm.) i. d. converter, i t is apparent that about 11 per cent in the 20-200” C. fraction and about 25 per cent in the 20-300” C. fraction of the overhead oil, with continuous operation for more than 3 months should be posgas losses of about 12 per cent of the tar feed plus hydrogen sible in a unit of industrial size before a shutdown for cleaning absorbed. is necessary. O
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INDUSTRIAL AND ENGINEERING CHEMISTRY
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perienced. The data on hydrogen consumption show that 34 34 42 42 42 42 there was an increase from R u n No. 5 6 7 8 9 10 Generation No. 2.8 to 5.7 per cent from run Raw Raw Topd. Topd. Topd. Topd. Make-up t a r Reaction temp;, C. 440 443 447 447 448 452 43-1 to 44-1. At the same 322 310 307 307 307 307 Reflux temp. C time the temperature and 5.4(2.45) 5.6 (2.55) 6.1 (2.8) 6.3 (2.9) 5.9 (2.7) 7.2(3.3) Feed lb. (kg.')/hr: 24 23 43.4 28.8 24.2 19.8 % hLavy oil recycle in feed ratio of hydrogen t o oil vapors 0.0 0.0 21.1 20.5 21.1 21.1 yo overhead oil bottoms in feed Hz absorbed % of feed 6.0 5.2 were increased. The sharp 5.2 5.1 5.2 5.4 26 26 16.5 16.0 17.0 15.0 T o t a l time df generation, hr. drop in hydrogen consumption Yields as Per Cent of T a r Feed plus Hydrogen in run 4 4 2 probably is due Overhead oil Total 59.1 56.7 54.4 57.6 61.5 52.1 to the lower ratio of hydro11.4 10.9 11.1 11.8 11.9 10.3 N e t t o ZOOoC. 30.7 28.7 41.1 40.4 42.3 33.9 gen to oil vapor, but catalyst N e t t o 300° C. 29.0 31.8 24.4 19.7 15.5 28.5 Heavy oil deterioration is probably in11.9 11.5 17.6 18.8 18.6 15.4 Gas Overhead/heavy oil ratio 1.8 volved also. A corresponding 2.3 2.0 2.2 2.8 3.8 2.4 2.2 3.0 6.0 4.4 4.7 insol. in feed 4.2 2.9 4.1 3.4 4.0 5.2 drop in the percentage of Insol. in heavy oil D a t a on Overhead Oil saturates in the product of 0.947 0.939 0.941 0.943 0.942 0.943 run 4 4 2 should be noted (Table 21.9 27.5 28.3 22.8 22.9 22.0 distilling 20-200' C . IX). The net increases in the 0.870 0.859 0.839 0.839 0.834 0.853 17.7 22.1 15.6 15.1 16.5 15.6 low-boiling (20-210" C.) frac230-270' C. 23.4 24.6 27.8 26.6 25.5 26.9 tions are from 5.0 per cent in 16.7 16.2 21.6 21.6 21.0 20.5 270-300' C. runs 43-2 and 43-3 to 22 per 10.8 10.0 9.0 300-330O C. 8.8 3.0 5.0 6.1 Over 330' C. cent in run 44-4. Using the 0.934 0.942 0.942 0.942 0.946 gr. of. combined 20-330' C. 0.944 S3.t a r acids in 20-330° C. 6.4 6.5 3.0 3.0 3.1 3.3 results of run 44-4, the over-all 1.5 1.9 1.6 1.6 2.4 1.9 yo t a r bases in 20-330' C. yield in the vapor phase would Neutral oil 0.941 0.945 0,940 0,940 0.924 0,940 Sp. gr. be about 85 per cent by 2.0 2.0 2.0 3.5 2.6 Olefins % 4.5 Aromalios, % 85.0 83.0 79.0 78.0 73.2 75.0 weight of the oil feed for 24.8 23.0 18.4 20.0 Saturates, 9% 11.0 13.5 materials boiling up t o 210" C. a Converter pressure 4000 lb./sq. in. (282 kg./sq. cm ) . hydrogen pumpin r a t e 350-400 cu f t . (9.95-114 cu Since the Specific gravity Of m.)/hr . catalyst, 0.1% stannous sulfide in all generatibis plus o 86% (C1H481)20 In generation 1 0 9% Haiowax' in gene;.'ations 2 and 3,0.1% CHIa in generations 4 and 5,and 0:05% CHI2 in generations 5 t o i0 of runs 32-35, the oil feed was 0.94 and of inclusive, and all of run 4 2 . the product (to 210" C.) 0.85, the volume yield was 94 per cent. In connection with Table IX, the work of the British Fuel The over-all yield of oil boiling up to 300" C. may be estiResearch Laboratory on the hydrogenation of tars, using mated by using the results of the ninth generation of run 42. pelleted molybdenum sulfide catalysts (6, 7 ) , showed that From these data the yield is calculated as about 75 per cent by the character of the product (that is, ratio of aromatics to weight of oil and 25 per cent of gas based upon the total feed saturates) can be readily controlled by proper choice of (tar plus hydrogen), or 80 per cent of oil based upon the catalyst and operating conditions. topped tar alone. Since the specific gravity of the topped tar is 1.207 and of the liquid-phase product (boiling range, Composition of Tar-Hydrogenation Products UD to 300' C.) about 0.94, the volume vield is about 103 Der Since the principal purpose of hydrogenating tar usually cent. has been to produce motor fuels, little effort has been devoted Vapor-Phase Operation to examination of the products and isolation of pure compounds. Low-temperature tar, which is converted into motor A vapor-phase converter 48 inches (122 cm.) long and of 1.5 fuel more readily, is usually preferred to high-temperature inches (3.8 em.) inside diameter, containing a catalyst basket tar as a raw material for hydrogenation. Consequently less 12 inches (30.5 em.) long, was set up for hydrogenation of the attention has been given to the hydrogenation of high-temliquid-phase product from the hydrogenation of Jones & perature tar and the nature of the products thus obtained. Laughlin high-temperature tar. The catalyst used was However, adequate analytical data are available t o indicate alumina gel impregnated with ammonium molybdate t o the that aromatic and naphthenic hydrocarbons predominate in extent of 25 per cent of its weight. A fraction of the liquidthe neutral fractions, and that under certain conditions phase product boiling below 300" C. was used as raw material phenols of high molecular weight are converted into phenol, for the vapor-phase converter, This charging stock concresols, xylenols, and hydrocarbons. Oils produced by liquidtained 9.0 per cent boiling to 200" C., 16.4 per cent to 210" C., phase hydrogenation contained appreciable amounts of ole37.4 per cent t o 230" C., 78.6 per cent to 270" C., and fins, phenols, and nitrogen bases, but only traces of these sub98.5 per cent to 300" C.; 4.5 per cent of tar acids and 2.9 per cent of tar bases. The tar acids and bases were almost completely reduced in the OF VAPOR-PHASE TARHYDROGENATION TABLE VIII. SUMMARY vapor phase; only a trace of Av . Net Production of Low-Boiling Oils Temp. Ratio Hz these constituents appeared in in Cata- t o Oil Contact HZ Gases 20135175210Run the products. No. Oil Feed R a t e lyst Vaporsa Time0 Used Produced 135O C. 175' C. 210' C. 235' C . Per cent of oil f e e d The various runs listed in Lb. (kg.)/hr. a C. M i n . .-43-1 3.95(1.8) 455 14.4 0.52 2.8 4.5 2.4 0.2 8.6 -5.lb Table VI11 were 12 to 20 hours 3.3 0.9 1.2 -0.8 4.0 5.0 0.33 474 20.0 4.40(2.0) 43-2 4.0 1.5 0.4 -0.8 4.1 5.5 0.37 long. Contact times of 0.3 43-3 481 24.8 3.24 (1.47) 3.9 2.4 1.5 -1.2 5.7 7.5 0.38 481 37.2 2.09 (0.96) 44-1 to Oe5 minute, temperatures 44-2 6.4 2.3 6.5 -0.7 2.9 4.3 3.13(1.42) 0.35 495 26.0 5.8 2.0 6.9 -4.3 0.35 3.0 6.1 495 19.8 4.08 (1.86) 44-3 of 490-515° C., and ratios of 8.9 3.8 9.2 -4.2 2.8 5.0 0.43 510 15.3 4.09 (1.86) 44-4 hydrogen to Oil vapor Of l5 Moleoular weight of oil assumed to be 150 for calculating these values. to 37 were investigated. No b N e t losses. unusual difficulties were exTABLE VII.
HYDROGEKATION O F JONES 82
L.4UQHLIN
TARWITH REFLUXAND RECYCLE^
F
1;:;
El
2::;-
0
INDUSTRIAL AND ENGINEERING CHEMISTRY
February, 1941
TABLE IX. COMPOSITION OF 20-235" C. FRACTIONS OF VAPORPHASEPRODUCT Run No. 43-1 43-2 43-3 44-1 44-2 44-3 44-4 Composition, vol. yo Olefins 0.6 0.6 1.3 1.6 0.8 0.8 1.6 25.2 34.3 28.6 31.0 31.4 Saturates 27.0 28.2 Aromatics 72.4 74.0 71.0 65.1 70.1 67.4 67.0 Sp. gr. 0.904 0.903 0.901 0.895 0.902 0.898 0.891
TABLEX. ULTIMATE ANALYSESOF PRODUCTS Sp. gr. Per Cent by Weight (15.6' SampleC . ) H C N O S Liquid phase. runs 42-8 and -9 1 0.946 9 . 5 3 89.00 0.13 1.10 0.24 1A 0.948 9.47 89.04 0.04 1 . 4 3 0.02 Vapor phase, runs 44-3 and -4 2 0.919 10.17 88.84 0 . 0 1 0 . 9 5 0.03 2A 0.921 10.15 89.04 0.00 0.75 0.06 Samples 1 and 2 are the original oils after drying over Drierite. Samples 1A and 2A are t h e same oils a f t e r extraction with sodium hydroxide and sulfurio acid solutions.
TABLEXI. DISTILLATION OF OVERHEAD OILSO Boiling Range, O C.: 30023527020188207300 330 235 270 188 207 Per Cent b v Volume of Overhebd Oil 10.4 22.0 20.3 7.6 16.5 Liquid phase 20.1 10.5 .6 23.3 13.3 29.0 Vapor phase 23.3 18.6 17.8 5.7 11.8 17.6 Coal, liquid phaseb 18.1 Specific Gravity of Fraction (15.6' CJC 0.961 0.991 >1 0.924 0.945 Liquid phase 0.823 0.952 0.987 Vapor phase 0.834 0.905 0.932 0.967 0.981 61994 0.956 0.808 0.942 Coal, liquid phase Tar Bases, Volume Per Cent of Fraction Liquid phase 3.5 3.7 1.5 0.5 0.5 1.0 Vapor phase 0 0 0 0 0 ... Coal, liquid phase 4.8 9.0 7.5 5.0 3.0 3.0 Tar Acids, Volume Per Cent of Fraotion Liquid phase 3.5 7.4 3.0 2.5 2.0 1.5 Vapor phase 1.0 1.0 0 0 0 Coal, liquid phase 7.6 38.0 37.5 25.4 15.2 10.0 a Oils distilled a t atmospherio preasure through well-insulated 6-inch indented columns. b Overhead oil produced b y hydrogenating coal from the hlcKay bed, Washin ton (16). c Hyfrometer. c
269
The destructive hydrogenation of Russian tars gave gasolines that contained aromatic hydrocarbons, such as benzene, toluene, 0-, m-, and p-xylenes, and apparently ethylbenzene (24). Among the unsaturated compounds, those with seven t o eleven carbon atoms containing a double bond at the second carbon atom were reported. The presence of five- and six-carbon naphthenes and of hydrocarbons with a tertiary carbon atom was mentioned (24). Hall and Cawley (14) made an extended analysis of the products obtained by hydrogenating a low-temperature tar. Aromatic and naphthenic hydrocarbons comprised 82 to 99 per cent of the product boiling up t o 300' C. The gasoline fraction was distilled into twenty-six fractions, and each fraction was examined further. Toluene and naphthalene were identified. The presence of benzene, ethylbenzene, the three xylenes, and many cyclo entane and c clohexane derivatives was indicated by their anarytical data (143: Morgan and Veryard (2i) detected benzene, toluene, na hthalene, and phenols among the products obtained by hycf)rogenating low-temperature tar. Characterization of Products Overhead oils from the eighth and ninth generations of run 42 (Table VII) and the third and fourth generations of run 44 (Table VIII) were selected for an examination that was more extensive than the routine analyses previously described. Specific gravities and ultimate analyses of these oils are given in Table X. The vapor-phase oil is less dense and of higher hydrogen content than the liquid-phase product. The carbon contents of the two oils are almost identical, but the vaporphase oil contains less nitrogen, oxygen, and sulfur than the liquid-phase product. Possibly the loss of low-boiling constituents during the treatment with sodium hydroxide and sulfuric acid is rEsponsible for the fact that the neutral oils (1A and 2A of Table X) have slightly higher specific gravities than the original oils.
...
stances were found in the products of vapor-phase hydrogenation; and the latter consist almost entirely of aromatic and saturated hydrocarbons (3). It is likely that in the early stages, a t least, tar hydrogenation on a commercial scale in the United States will make products other than motor fuel. The products of the present work may be considered potential sources of bulk chemicals (phenol, cresol, xylenol, benzene, toluene, xylene, cyclohexane, methylcyclohexane, tetrahydronaphthalene, and naphthalene) and solvents. The presence of most of the compounds listed above was either established or indicated. For purposes of comparison, a brief account is given of the analytical data reported by previous investigators of tar hydrogenation: Hydrogenation at 470-490" C. and 200 atmospheres pressure by And8 (1, 8 ) of creosote oil gave a product that consisted mainly of aromatic and naphthenic hydrocarbons. The products from the creosote oil contained more aromatics and naphthenes than the products obtained in a similar manner from low-temperature tar, shale oil, and mineral oil. The products boiling below 170" C., obtained by Cawley, Hall, and King (10) from a creosote oil (specific gravity 1.065 at 15" C., 12.6 per cent tar acids) contained about 70 per cent saturated and 25-30 per cent aromatic hydrocarbons. Whether the saturated hydrocarbons were paraffinic or naphthenic was not determined. Rheinfelder (26) identified benzene, toluene, and xylene in a neutral oil produced by hydrogenating coal tar. The neutral oils boiling below 70" C. appeared to be a mixture of naphthenes and paraffins; small quantities of unsaturated and aromatic hydrocarbons were present. Hydrogenation caused the production of low-boiling phenols and bases at the expense of the higher homologs.
TABLEXII. NEUTRAL-OIL FRACTIONS Boiling Range, C.: 20188207235270235 270 300 188 207 Per Cent by Volume of Overhead Oil Liquid phase 18.7 6.8 15.8 21.3 19.8 Vapor phase 23.1 13.2 29.0 23.2 10.5 Coal, liquid phase 15.9 3.0 6.5 12.3 15.2 Specific Gravity (15.6' C.)5 Liquid phase 0.816 . . 0.941 .. . . 0.989 Vapor phase 0.834 0.905 0.932 0.952 0.987 Coal, liquid phase 0.777 0.869 0.906 0.941 0.969 Olefinsb. Volume Per Cent of Neutral Oil Fraction Liquid phase 4.2 1.2 0.8 0.6 0.4 0 0 0 0.4 Vapor phase 1.0 Coal, liquid phase 10.4 7.8 7.6 7.6 16.0 Aromatics, Volume Per Cent of Neutral Oil Fraotion Liquid phase 45.8 86.4 91.2 93.0 93.6 Vapor phase 52.0 73.0 83.0 83.0 84.6 Coal, liquid phase 19.2 45.6 58.0 66.0 64.0 Saturateso. Volume Per Cent of Neutral Oil Fraction 8.0 6.4 6.0 Liquid phase 50.0 12.4 Vapor phase 47.0 27.0 17.0 17.0 15.0 Coal, liquid phase 70.4 46.6 34.4 26.4 20.0 0 H drometer b Sofuble in 3 volumes of 86% sulfuric acid. 0 Insoluble i n 86 and 98.5% sulfuric acid. c
..
300330 10.1
....
15.5
. . .. 0 :9?9
1.4
....
12.8 95.6
.. . .
59.4
3.0
....
27.8
Distillation in Small Still For preliminary characterization of tar-hydrogenation products and to obtain data that could be compared with those obtained for liquid-phase coal-hydrogenation oils (If?), the liquid- and vapor-phase oils (samples 1and 2 in Table XI) were distilled into several fractions, and each fraction was analyzed for carboxylic acids, phenols, olefins, aromatics, and saturated hydrocarbons. Olefins, aromatics, and saturates were determined by extracting 5-cc. samples of neutral oil successively with 86 and 98.5 per cent sulfuric acid ( 1 1 ) . The results bf these analyses and the data obtained are given in Tables X I and XII.
The vapor-phase oil contained more low-boiling constituents than the two liquid-phase products (Table XI). The coalhydrogenation oil contained considerably less low-boiling hydrocarbons than the tar-hydrogenation oils (Table XII) . The low aromatic content of the first fraction of the coal oil (sample 3) is probably responsible for its low specific gravity. Only negligible amounts of carboxylic acids, polyhydric phenols, and substances soluble in potassium carbonate were found in all the fractions. The coal-hydrogenation fractions contained more phenols and nitrogen bases than the tarhydrogenation oils; the vapor-phase products were virtually neutral. Most of the phenols in the liquid-phase tar products consisted of phenol, cresols, and xylenols. Since the original tar had been topped to 230" C., these compounds were produced during the liquid-phase hydrogenation. Table XI shows that nitrogen bases boiling below 230" C. also were produced by hydrogenation. The specific gravities of the neutral-oil fractions varied according to the composition, the fractions with the highest aromatic contents having the highest specific gravities (Table XII). The liquid-phase tar oil had more olefins than the vapor-phase product, which was virtually free of olefins. W t h the exception of the first fraction, all the fractions of the liquid-phase tar oil contained more aromatics than the corresponding fractions of the vapor-phase products (Table
DISTILLATE PERCENT BY VOLUME
XII). All fractions of the coal-hydrogenation oil contained more saturates than the tar-hydrogenation fractions. Table XI11 gives the refractive indices of the saturated hydrocarbons obtained from the fractions in Table XI1 and shows that the saturates from tar-hydrogenation oils are more naphthenic than those produced by hydrogenating coal. Since the coal-hydrogenation fractions also contained more total saturates than the tar oils (Table XII), the oil derived from coal contains considerably more paraffins than those prepared by hydrogenating tar. ~~
0
Boiling Range, 5-188
188-207
207-235
Liquid Phase Av. boiling point, C.b Refractive index (20' C . ) Rings per av. mo1.0 Carbon atoms in rings, $&d Naphthenes, 70e
110 1 4225 0.9 73 91
Av. boiling point, C.6 Refractive index (20' C.) Rings per av. mo1.C Carbon atoms in rings, 7 0 d Naphthenes, % e
145 1.4332 1.0 67 100
.... ... ... ... ...
O
C.:
235-270
....
.... ....
....
.... .... ....
.... .... ....
220 1.4632 1.7 86
255 1.4711 1.8 83
....
270-300
300-330'
285 1.4812 2.0 80
.... .... ....
....
....
285 1,4780 1.8 72
.... ., ., .. .. .. ..
Vapor Phase 197 1.4570 1.6 89
>loo
....
....
....
....
....
McKay Bed Coal, Liquid Phase Av. boiling point, C. 150 200 220 255 285 310 1.4545 Rcfraetive index (20" C.) 1.4178 1.4392 1.4449 1.4510 1.4590 Rines oer av. mo1.c 0.4 0.8 0.8 0.8 0.9 0.8 Car606 atoms in rings, %d 26 44 41 37 32 33 32 67 .... Naphthenes, 70e 5 Fractions described in Table XI1 were washed with S6r/, sulfuric acid and then with 3 portions of 98.5% acid. b Estimated. 0 Estimated by comparing boiling points and refractive indices with those given in Figure 3. d Calculated from carbon atoms in rings (assumed t o be 6-membered) and total carbon atoms in molecule, which was estimated from boiling point. e Determined from figure given by McArdle a n d co-workers ($1).
....
..
....
Distillation in Fifty-Plate Still The neutral oils (samples 1A and 2A, Table X) were distilled through a more efficient still into about sixteen narrow-boiling fractions; these fractions were studied further to determine the compounds or types of compounds present. The packed section (0.79 inch or 2.0 cm. in diameter, 60 inches or 152 em. long) of the still was filled with stainless steel rings 3/az inch (2.4 mm.) inside diameter (28). According to previously reported tests (28) the height equivalent t o a theoretical plate for this packing is about 1.1 inch (2.8 cm.). Two liters of oil were distilled from the 3-liter still reservoir with a reflux ratio of about 10 to 1. The distillation curves obtained with this still for the two neutral oils (samples 1A and 28, Table X) are given in Figure 1. Both curves have plateaus with approximately the same levels, but the plateaus for the vapor-phase product are more pronounced than those in the curve obtained with the liquid-phase oil.
COMPOSITIOX OF NEUTRAL-OIL FRACTIONS PRODUCED BY TABLE XIV. APPROXIMATE LIQUID-PHASE HYDROGEXATION' Fraction No.
Distillin& Range.
$4 by Volume
7 by W&ht
2
FIGURE1. DISTILLATION CURVES OF OVERHEAD OILS PRODUCED BY TARHYDROGENATION
TABLEXIII. REFRACTIVE INDICES AND APPROXIMATE COMPOSITION OF SATURATED HYDROCARBONS"
Refractive S p Gr Index Refractivity % by Volume of Fraction (15.6' C : ) b (20' '2.) Intercept0 Olefins Aromatics Saturates
1.4173 1.045 68-75 1.10 0.91 0.748 1.4315 1.042 75-85 1.85 1.53 0.784 1.4164 85-95 0.65 1.4292 1:0k4 95-105 2.12 1:74 0:+74 1.4627 1.054 105-120 2.15 1.87 0.821 1.4435 1.047 120-130 0.85 0.71 0.796 1.4755 1.057 130-140 2.24 2.00 0.841 1.4737 1.056 140-1 55 1.35 1.20 0.840 1.4824 1.054 155-175 2.84 2.59 0.860 1.4954 1.053 175-185 2.25 2.11 0.888 1.4997 1.053 186-200 4.09 3.89 0.897 11 1.5204 1.057 200-206.5 4.99 4.92 0.931 12 1.5322 1.061 2.05 2.05 0.947 13 206.5-210 1.6369 1.066 5.04 0.945 14 210-2 19 5.04 1.5279 1.061 2.30 2.28 0.937 15 219-226 a Sample l A , Table X, was distilled through a 60-inch (152-.om.) column packed with stainless-steel rings: atmospheric pressure was 740 mm. b Hydrometer; temperature corrections made by tables in citation 83. C Refractive index less one half t h e densitv _ (89). . . 1 2 3 4 5 6 7 S 9 10
Vol. 33, No.
INDUSTRIAL AND ENGINEERING CHEMISTRY
270
Liquid-Phase Fractions Analvtical data obtained with tge fifteen fractions of the liauid-phase Droduct - (sample lA, Table X ) are given in Table XIV. Although considerable amounts of the oil distilled in the benzene, methylcyclohexane, toluene, and xylene range, the largest fractions were obtained above 175"C. It is of interest that most of the dicyclic hydrocarbons boil above this temperature. As will be noted later from the physical constants, it is prob-
INDUSTRIAL A N D ENGINEERING CHEMISTRY
February, 1941
able that dicyclic hydrocarbons (such as tetrahydronaphthalene) comprised a high percentage of the high-boiling oil. The approximate contents of olefins, aromatics, and saturates were determined by extracting 5-cc. samples of each fraction with 86 and 98.5 per cent sulfuric acid. The results (Table XIV) show that, although the lower fractions contain preponderant amounts of saturates, the higher fractions are principally aromatic. As was to be expected, the fractions in the benzene, toluene, and xylene range were relatively rich in aromatics and the intermediate fractions were rich in saturates. The lower fractions have the highest olefin values. Table XIV shows that much of the benzene and toluene distilled in the 68-75" and 95-105" c. temperature intervals, which agrees with the reports of previous workers (8). Refractive indices, specific gravities, and refractivity intercepts, which also show that the higher fractions are principally aromatic (Table XIV),are in general agreement with the composition indicated by the sulfonation data. AND AROMATIC CONTENTS OF FRACTABLE XV. DISPERSION TIONS PRODUCED BY LIQUID-PHASE HYDROGENATION
Fraotion
Boiling Range,
1 2
68-75 75-85
No.
4 5 0
7 8
9 10 11 12 13 14 15
c.
95-105 105-120 120-130 130-140 140-155 155- 175 175-185 185-200 200-206.5 206.5-210 210-219 219-225
Dispersion X 104 83.2 80.4 83.4 117.4 92.6 127.0 123.7 128.4 132.3 130.4 136.1 149.9 174.8 159.8
Ratio, ~ i Aromatics, ~ ~% by Weight ~ ~ From From sulfodis: nation0 Density persion 111.8 16.1 24.8 16.4 103.1 6.0
c";o":,
108.3 143.7 116.9 151.7 148.0 150.0 149.7 146.0 164.6 159.0 185.8 171.3
12.1 53.5 22.8 66.2 61.7 66.9 66.7 65.2 91.1 83.4
.. ..
20.5 61.7 32.5 72.5 65.5 66.7 70.2 73.3 96.9 87.6
....
a Calculated from the sulfonation data in Table XIV by using densities of the aromatios believed to be present.
An attempt was made to estimate both the proportion and nature of the aromatics present from the dispersion and calculated refractive indices of the hydrocarbons removed by sulfonation. To estimate the aromatic contents of the fractions from the dispersion, the tables of Grosse and Wackher (IS)were used, and the presence of olefins and nonhydrocarbons was ignored. Although the values thus obtained for the higher fractions agree moderately well with the aromatic contents indicated by sulfonation, the values for the lower fractions were much lower than the sulfonation values (Table XV). Moreover, the calculated indices for the benzene and toluene removed by sulfonation are low. Accordingly, the aromatic contents estimated for the lower fractions by sulfonation probably are high. A reasonable explanation for this .discrepancy is that the olefins which survived the treatment with 86 per cent sulfuric acid were extracted with 98.5 per cent acid, thus giving low-olefin and high-aromatic results. That these results are, however, moderately accurate is shown by the following tests: A second extraction of liquid-phase fractions 1, 2, 4, and 6 (Table XIV) and vapor-phase fractions 1, 4,and 5 (Table XVII) with 15 cc. of 86 per cent sulfuric acid removed only small amounts of oil (about 1 per cent). Since 98.5 per cent sulfuric acid can remove small but appreciable amounts of some saturates, the "olefin-free'' oils were washed with 97 per cent acid. The resulting data for saturates were almost identical with those obtained by the standard method.
Using the refractive indices of the fractions determined before and after treatment with sulfuric acid and the percent-
r
i
I
I
I
1
1
27 1 1
1
I
I
I
I
I
I
I
156
g1.54 N
s
5
0 1.52 W
1.48
8 BOILING WINT, 'C.
FIGURE 2. REFRACTIVE INDICES AND BOILING POINTS OF DIFFERENT TYPESOF AROMATIC HYDROCARBONS
ages of aromatics and saturates indicated by the sulfonation data, the refractive indices of the aromatics removed by sulfonation were calculated. The values thus calculated for the - aromatics boiling above xylene are given in Figure 2. Comparison of the calculated refractive indices with those of pure hydrocarbons (Figure 2) indicates that the aromatics removed were principally polymethylbenaenes and tetrahydronaphthalene. Apparently naphthalene was not present in large quantities. Although certain assumptions were made in calculating the refractive indices of the aromatics removed, i t is believed that, owing to the large differences in the refractive indices of known hydrocarbons boiling above 160" C., these results are significant. Moreover, the conclusions drawn from the calculated refractive indices agree with the fact that polymethylbenzenes and polynuclear aromatics predominate in related pyrolytic products, such as coal tar and light oil (by-products from coke ovens). The refractive indices and approximate composition of the saturates produced by liquid-phase hydrogenation are given in Table XVI. The number of cyclohexane rings per average molecule was estimated by comparing the boiling points and refractive indices of the saturated oils with those shown in Figure 3. The percentages of the carbon atoms present in rings were estimated from the number of rings (assumed to be cyclohexane and decahydronaphthalene derivatives) and carbon atoms in the average molecule; the number of carbon
BOILING POINT, 'C
FIGURE 3. REFRACTIVE INDICES OF PARAFFINS AND NAPHTHENES BOILING BELOW 330' c.
I N D U S T R I A L A N D E N G I N E E R I N G CHEMISTRY
272
atoms per molecule was estimated from the boiling point. In spite of possible errors and the assumption that the cyclic hydrocarbons consist mainly of cyclohexane derivatives, the conclusion that the saturated hydrocarbons are predominantly naphthenic seems inescapable.
Vol. 33, No. 2
TABLE XVIII. DISPERSION AND AROMATIC COXTENTS O F FRACTIONS PRODUCED BY VAPOR-PHASE HYDROGENATION
Ratio ~ i Aromatics, ~ ~% by ~ Weight ~ Di,spersion From From Fraction sion (104) dis; sulfoNo. ' C. X 104 Density persion nationn 1 76- 8 5 100.1 124.3 42.1 30.2 2 85- 95 77.1 TABLEXITI. REFRACTIVE I N D I C E S AND APPROXIMATEC O M 95-105 3 iii:~ 86.4 1i:9 l7:7 POSITION OF SATURATED HYDROCARBONS FROM LIQKID-PIIAS~ 4 105-120 129.2 156.4 78.9 68.1 120-130 5 89.3 28.5 17.0 112.3 HYDROGENATION" 6 130-140 130.9 71.6 156.0 75.1 C 7 140-155 114.7 52.6 50.8 139.2 Rings Atpms 156-1 75 8 117.0 54.9 50.7 137.3 Distilling Refractive per in Naph175-184 9 123.4 141.5 62.2 59.0 Fraction Rpge. Index Av. Rings, thenes, 184-184.5 126.5 63.2 62.4 143.9 10 126.7 62.5 144.0 11 184.5-185 65.0 No. C. (20' C.) hIo1.b '%c Yod 125.1 185-200 12 54.7 59.4 141.8 1.4026 1 68-75 0.7 70 63 200-204 140.7 75.6 153.4 13 78.0 75-85 0.9 1.4223 2 86 > 100 14 204-206 151 84.3 8 6 . 4 161.3 .O 1.4123 0.8 76 85-95 73 3 206-210 15 174.1 164.2 1.4161 95-105 68 4 0.8 79 210-215 178.4 16 190.0 .. .. 1.4189 0.8 105-120 5 77 63 215-225 17 168.5 155.9 .. 0.8 120-130 6 1 4238 59 85 a Calculated from t h e volume per cent d a t a in Table XVII by using the 0.9 130-140 1.4289 7 94 63 densities of appropriate aromatic hydrocarbons, such as benzene, toluene, 1 , 4 3 3 1 1.0 94 140-155 8 67 eto., believed t o be present. 1 AA-1 .75 1.2 1.4432 .__ . 9 70 >loo 1.4534 78 175-185 1.5 10 >loo 1.4589 1.7 85 11 185-200 >loo 1.4587 200-206.5 1.6 76 12 >loo 1.4542 63 13 206.5-210 1.3 ... 1.4585 14 210-219 1.5 68 156 1.4612 219-225 15 1.6 70 ... 11 T h e fractions of Table X I V (5-cc. samples) were washed with 3 volumes 0 TETRAHYDRONAPHTHALENE of 86% sulfuric acid and then with 3 portions of 98.5% acid. X POLYMETHYLBENZENES b Estimated b y comparing t h e boiling points and refractive indices with .> 1 5 4 those of known hydrocarbons (Figure 3). c Calculated from t h e number of rings (assumed t o be 6-membered) per average molecule and t h e total number of carbon atoms. d Estimated b y t h e method of MoAidle and co-workers (reference 21). a Boiling Range,
..
..
...
:: z
2152
s Vapor-Phase Fractions The vapor-phase oil was similar to the liquid-phase product in that the largest fractions boiled above 155" C. (Table XVII and Figure 1). From the plateaus (1, 2, 3, and 4 in Figure 1) in the distillation curve and the physical constants of the fractions, it appears that the first four fractions consist largely of cyclohexane, benzene, methylcyclohexane, and toluene.
2
81 50
148 80
100
120
140 160 EOILING POINT, "C.
180
200
220
FIGURE 4. REFRACTIVE INDICES AND BOILINGPOINTS OF DIFFERENT TYPESOF AROMATICHYDROCARBONS
T h e a r o m a t i c content8 estimated from the dispersion and density by the Refractive Fraction Distilling % by %,by Sp. Gr. Index Refractivity % by Of Fraction m e t h o d of G r o s s e a n d No. Range, C. Volume Weight (15.6' C . ) b (20' C.) Interceptc Olefinsd Aromatics Saturates' Wackher (IS) are given in 1 76-85 1.66 1.45 0.809 1.4490 1.047 1.8 38.6 59.6 Table XVIII. With the exXF,-RF, 1.4210 0.10 0.08 2 __ _ _ 1,4295 2.01 1.71 3 95-105 O.'iiS 1:043 0'. 6 16:6 8i:S ceptions of fractions 1, 4, 2.47 2.23 105-120 1.2 1.4756 23.6 0.830 75.2 1.063 4 1.01 120-130 1.4429 1.16 and 5, the aromatic contents 73.0 0.799 26.4 1.045 0.6 130-140 2.36 73.2 1.4766 6 2.57 0.4 26.4 0.843 1.057 estimated from the disper7 1.36 50.0 140-155 0.828 49.8 1.052 1.4645 1.51 0.2 4.27 155-175 40.0 0.856 54.0 1.051 1.4768 4.68 8 0 sion agree well with those 4.70 175-184 0.876 63.0 1.4884 4.93 9 0 37.0 1.052 indicated by sulfonation data 2.18 184-184.5 2.26 36.8 0.883 63.2 1.050 1.4896 10 0 1.36 0.884 65.0 1.4907 1.41 11 184.5-185 1.050 0 35.0 (Table XVII). 3.97 185-200 0 12 3.84 0.886 56.0 1,4894 1.048 44.0 0.921 82.2 1,5140 5.03 200-204 1.055 13 5.05 0 17.8 The calculated refractive 204-206 14 0.940 90.4 1.5246 6.08 1.056 9.6 0 5.20 indices of the aromatics re0.947 89.6 1.5322 4.43 206-210 10.4 15 4.57 0 1.060 0.943 88.6 1.5366 5.03 210-215 11.4 16 5.17 1.067 0 moved from the vapor-phase 0.929 84.6 1.5230 5.13 215-225 15.4 17 5.19 1.060 0 fractions by sulfonation indicate that the aromatics boiling from 160" to 207" C. c o n s i s t e d p r i n c i -p a l l-y of polymethylb&zenes and tetrahydronaphthalene (FigAs determined by extraction with three volumes of 86 per ure 4). The presence of tetrahydronaphthalene in the cent sulfuric acid (11) the lower fractions contained traces of fraction boiling a t 204-206" C. was confirmed by the isolation olefins, but the higher fractions consisted entirely of aromatics of a solid derivative, o-tetrahydronaphthoylbensoic acid. and saturated hydrocarbons (Table XVII). The second, From the calculated refractive indices and the fact that cooling of the distillate did not cause solidification, the third, and fifth fractions were largely saturated, whereas the naphthalene contents of fractions 16 and 17 appear t o be other fractions were highly aromatic. The physical constants in Table XVII agree with the comlow. position of the fractions indicated by successive extractions Refractive indices of the oils that survived the treatment with sulfuric acid. with 86 per cent sulfuric acid and three portions of 98.5 per TABLE XVII. APPROXIMATECOMPOSITION O F NEUTRAL OIL FRACTIONS PRODUCED PHASEHYDROGENATION^ O
BY VAPOR-
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RECENT PROGRESS IN CHLORINATION, 1937-1940 E. T. MCBEE AND H.B. HASS Purdue University and Purdue R-h Foundation,hfayetta, Ind. The literature of the past few y e e r a discloses mueh active interest in the chlorination of organic compounds. Some of the meent discoveries in t h i s field are reviewed and discussed. A m o n g them are the substitutive peroxide-catalyzed chlorination of ol&, c h l ~ r i ~ t with i ~ nsulfuryl ~ chloride, chlor i ~ t i in ~ u intimate eontact with a liquid mess of metallic chlorides, preparation of
polychloropropanes, chlorination of natural gas, chlorination of aromatic compounds, chlorinolysis of para5n hydroearbons, high-pressurechlorination of paraffin h y d r o c a r b o n s , hexachloroethane as a d o rinating agent, the use of a capillary for introducing chlorine into material to be dorineted, chlorination of esters, and chlorination of rubber.
HE mechanism of the substitutive chlorination of eaturated hydrocarbons has been a subject of repeated discussions ever since Pease and Wals (&5) pointed out that the methanechlorine reaction is strongly inhibited by oxygen. Them authors did not attempt to decide between the two mhst obvious chain mechanisms, 2 and 2A:
chlorine molecules. If this latter conclusion is correct, one should fmd in a repetition of Brown,Kbarasch, and Chao's experiment a t elevated temperature that a reaction which produoes racemization at 0" C. will yield an optically active product a t 30(t400° C. Vaughan and Rust (6'8) found that the rate of reaction of ethane with chlorine in the gas phase a t moderate temperatwe is directly proportional to the concentration of the C1,+2cl* paraffin and the chlorine. This is in agreement with the CI' C E +CHaCl+ €I H* *;CIS HC1+ C1* (2) reanlta reported by P e w and Wals (&5) for the thermal C1* CE-HCI +CHI*; CHI' ck-+CHGl Cl* (24 chlorination of methane. Apparently the &ai0 mechmim predominatm at these conditions (vapor phase and moderate temperature), and the thermal bimolecular processes become Brown, Kharaech, and Chao (3) brought forward strong important only a t higher temperatures. The latter in the evidence in favor of mechsnism 2A. They prepared active case of ethane is above 270" C. amyl chloride (I-chlom-2-methylbube) and showed that l,zdichlorc&methyIbutane, which is one of the products . The so-called induced subtitution into parefsns and saturated chlorides wbich o c c w simultaneously with the formed in ita chlorination, is optically inactive. This result addition of chlorine to a copresent ole611is apparently a chain is to be expected if the intemediate is the free radical CHI mechanism initiated by the addition reaction. This conclnsion is based on the fact that such induced substitution is I C&€,-C-CH,Cl, since such entities do not retain a stable greatly diminished by the presence of oxygen. The addition reaction which may occur to some extent by wociation in steric conliguration. aolution is little aiTected by oxygen. Chain reactions m y be promoted in a number of other ways. It has been pointed While these d t a seem unequivocal for the conditions employed (0" 0.with free chlorine, 80' C. with sulfuryl out many times that light and heat cause the chlorine m o l e d e to become d i d t e d into chlorine atoms, a component ohloride and peroxides), it would be premature to conclude in the established mecbanism. Also, carhon surfaces tend that this mechanism holds for all conditions. Vaughan and to promote reaction (@, hut this may be interpreted 88 tbe Rust (62) presented evidende which indicates that a t rather high temperatures, substitutive chlorination may occur by effect of more surface area (68) acting to prcduce more a thermal bimolecular metathesis between hydrocarbon and chlorine atoms. presumably, the increased surface area
+
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+
I
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138
INDUSTRIAL A N D ENGINEERING CHEMISTRY
acts also to terminate chains. The termination of a chain m y occur in several ways: the collision of a radical or atom with a mlid surface such as the wall, collision of a radical or atom with oxygen, and the combination of radicals and atom. Recently (6t) it wag shown that very smsll amounts of tetraethyllead, which presumably yields ethyl radicala when heated, accelerate g a s and liquid-phase chlorinations enormously. Also, hexsphenylethane, which yields tripheuyhethyl readily, catalyzes liquid-phase chlorination, and momethane acta as a catalyst in the vapor phase. These d t a constitute additional evidence in support of the chain
mechunism. The formation of olefins and chloro-olehs during the
chlorination of many saturated compounda a t elevated temperatures is a fact well establiabed. Such side reactions cannot be explained as simple pyrolysis of chlorinated produ& because with comparable experiments much higher temperatum are usudly required to obtain the m e degree of ole& formation in the absence of free chlorine. It seema likely that at least some of this secondary reaction occnra, as by ‘‘iiduced” decomposition (63). A newly formed energyrich alkyl chloride may lose energy by losing hydrogen chloride or by collision with another alkyl chloride which, by mamu of ita acquired energy, undergoes disruption.
a t Bath chl&tiea.
One of the intewting recent developments in the field of ohlorination is the technique of using a molten salt bath in direct contact with the reagents. Low-melting m i x t u h 6f substancea such as scdium, calcium, and aluminum chlorides
Vol. 33, No. 2
are maintained a t a suitable temperature, and the chlorine and the material to he chlorinated are bubbled through. The agitation thus produced in the bath fseilitates good control of the temperature which, in these extremely exothermic reactions, is higbly desirable. Since metallic halides frequently serve as catalysts for the pyrolysis of organic chlw rides, salt bath cblorinatiom may be controlled to yield olefins or chlorwle6na as well as saturated substitution products. The fission of carbon-carbon bonds to yield products of fewer carbon atoms than the starting material has also been r e p o h d to occur under these conditions. Grebe,M y , and Miley (16)patented a prows for preparing carbon chlorides which consists essentially in passing a mixture of chlorine and a saturated aliphatic hydmosrbon or its p&y chlorinated derivative into molten metal chlorides maintained a t a temperature above 250‘ C. The following equations were given to illustratS the reaction: ca‘cl, CaCL C,“I
+ 3cI*-C*CL + 4HCl + BCIS-GCL + CCL + 6HC1 + 8CL C.CL + CCL + 8HCI
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(a) (4) (6)
More recently, this work was extended to chlorinations in which the rewtion products contsin hydrogen in addition to carbon and chloriqe. Reilly disclosed the preparation of l,l,%ttichloroethane (61) and the chlorination of acetylene (SS), ethylene chloride (60), ethane (@), and ben5ene (68). In the preparation of l,l,%trichlomethane, ethylene chloride is chlorinafed in a molten salt bath at 300‘ to 426O C. If a higher bath temperature is employed, the principal prcduota are di- and trichloroethylene. Acetylene is mixed with a nonflammable chlbrinated hydrocarbon such 88 emhn
