SEPTEMBER, 1940
INDUSTRIAL AND ENGINEERING CHEMISTRY
HYDROGENATION OF COAL, PETF~OLEUM, OR TARS.I n future years this aspect of hydrogenation will be one of the most important industrial chemical reactions. Already in the petroleum field it has attracted wide attention. It results in upgrading of the raw materials. KO coke or tars are formed such as characterize cracking operations. Nine plants for the hydrogenation of petroleum have been constructed ‘and operated at various points in the United States, and are fully described in the literature (1). Their source of hydrogen is the reaction of waste refinery gases with steam to form hydrogen and carbon dioxide; the latter are removed by scrubbing with water under pressure or by triethanolamine. The hydrogenation of unsaturated products giving, for example, isooctane, has already been mentioned under the ethylenic linkage. When our petroleum riches begin to decrease, there is no question but that the hydrogenation of coal and tars will be pushed to the fore in order to furnish products now obtained from petroleum. Such plants in the petroleumpoor countries are now very important industrially for s u p plying motor spirits. This is true of both England and Germany. Fenske (3) gives flow sheets and general procedures for these operations. Our Government, or other forwardlooking research agencies, should study these procedures intensively from the American economic viewpoint, both from the chemical engineering and economic aspects. Then when the demand comes for a greater supply of motor spirits, solvents, and other such compounds than can be supplied by the petroleum industry, this can be met, in part at least, by the hydrogenation of coal. HYDROGENATION OF NITROGEN TO AMMONIA.No reaction that has been commercialized in recent years has had a more profound economic importance than the hydrogenation of nitrogen to ammonia, particularly by the catalytic processes such as the Haber-Bosch process. This has resulted in cutting the price of ammonia, not only for fertilizers but also for the manufacture of nitric acid for explosives and other purposes. It means that not only can we secure a t reasonable prices adequate supplies of nitrogenous fertilizers, but that the whole extensive nitrogen industry of the world is now based on a reasonably priced and practically inexhaustible raw material. This industry has shown the road to the most economical methods for carrying out hydrogenation and the cheapest
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means for manufacturing hydrogen. Such hydrogen is largely produced by a modified water-gas reaction in this country, or from the liquefaction of coke-oven gas in other countries. Full details of such procedures are given in articles already cited. HYDROQENOLYSIS. A recent and important feature of hydrogenation is the introduction of hydrogen accompanied by splitting of the molecule. This we call “hydrogenolysis”; excellent examples are given by Fenske (3). Sugars can be hydrogenated to give, in the first place, reduced products such as are now being commercialized by the Atlas Powder Company (4). Although the Atlas Powder procedure yields only hydrogenation products, other researches have carried the hydrogenation of these initial products, particularly of the sorbitol, to a further stage; the result is a carbon-to-carbon cleavage yielding glycerol and propylene glycol. Such a hydrogenolysis reaction has not been commercialized, but i t may well be that procedure to which industry can turn in case of a shortage in the normal supplies of glycerol or in case of an increased demand. Such hydrogenolysis reactions utilize catalysts a t elevated temperatures and pressures.
REQUIRED TABLE VI. HYDROGEN
Raw Material Phenol Naphthalene Olein Diisobutylene
TYPICAL PRODUCTS
FOR
Product Cyclohexanol Tetralin Stearin Isooctane
Cu. Ft. H1 Required ( a t 60’ F.) per Ton Product 23,000 12,000 2,600 6,700
Literature Cited Byrne, P. J., Jr., et al., IND.ENCI.CHEM.,24, 1129 (1932): Murphree, E. V., et al., Ibid., 32, 1203 (1940). Curtis, H. A., “Fixed Nitrogen”, A. C. 5. Monograph 59, New York, Reinhold P u b . Corp., 1936. Fenske, M. R., in Groggins’ “ U n i t Processes i n Organic Synthesis”, 2nd ed., C h a p . 8, p. 422, New York, McGraw-Hill Book Co., 1938. Taylor, R. L., Chem. & Met. Eng., 44, 588 (1937). U. S. Bur. Foreign & Domestic Commerce, private communicstion, 1940. U. S. Tariff Comm., Rept. 114, 41 et seq. (1937).
HYDROGENATION OF ANILINE CHARLES F. WINANS The Goodyear Tire & Rubber Company, A k r o n , Ohio
Technical cobalt oxide activated by powdered calcium oxide is recommended as a catalyst for the hydrogenation of aniline to cyclohexylamine. The presence of ammonia in the initial reaction mixture retards the conversion by dissolving the catalyst. The addition of dicyclohexylamine represses the loss of cyclohexylamine through autoalkylation and improves the yield of primary amines without interfering with the completeness of hydrogenation. I
Present address, Mellon Institute, Pittsburgh, Pennn
ATALYSTS and conditions of reaction for the hydrogenation of aniline to cyclohexylamine have been the subject of numerous investigations ( 3 ) . This paper describes the development of a process for improving the yield of cyclohexylamine (6) by the selection of catalysts and by the control of side reactions. The catalyzed chemical reactions are the hydrogenation of aniline to cyclohexylamine, CeHs.NHs 3Hz +CeHii.NHz (1)
C
+
the autoalkylation of cyclohexylamine,
+
2CeHii.NHt --f (CeHn)zNH NHI (2) and to a smaller extent the hydrogenolysis of cyclohexylamine to cyclohexane and ammonia,
INDUSTRIAL AND ENGINEERING CHEMISTRY
1216
TABLEI. COMPARISON OF CATALYSTS Catalyst
Time
Temp.
Hr.: m?n. Ni on kieselguhr
6 8 8 9 9
c. 200 200
Primary Amine
8ec. Amine
%
%
Ratio, Primary/ Sec.
57.5 63.8 60 31.2 32.5 51.5 48.8 33.6 58.5 53.1 50.5 63.3 62.5 70.2 66.5
22.5 2.56 21.2 3.05 200 27.6 2.16 250 66 0.47 250 66 0.49 27 1.91 Raney Ni S 200 3:50 225 17.7 2.76 8 250 60.4 0.55 0:37 280 28.6 2.04 0:30 275 37.6 1.42 12 4.2 Raney Co 0:49 290 COO5 0:48 285 28.9 2.19 COO' 0:30 285 22.1 2.83 Coo-CaO 0:lS 255 20.8 3.5 Coo-CaO 0:17 290 28.6 2.32 Tech. CoOb 0:50 . . . . N o reaction. . . . . 280 Tech. Coo-CaOC 0:20 280 68.9 9.2 7.5 Tech. Coo-CaO 0:30 285 60.6 7.1 8.5 0 Prepared by calcining precipitated cobalt oxalate a t 900' C. b Obtained from the Harshaw Chemical Co. c Lime was prepared by calcining powdered calcium hydroxide a t 900' C.
Expt. No. Aniline Grams 1 400 2 300 3 400 4 300 5 350 6 400 7 300 8 300 9 300 10 300 11 300 12 300 13 30 lb. 14 30 lb.
VOL. 32, NO. 9
The same products were obtained in a long reaction period a t 200" or in a short period a t 285" C., and the effect of prolonged heating a t elevated temperatures was evident in those cases where dicyclohexylamine was the principal product. There was little difference in behavior among nickel on kieselguhr, Raney nickel, and pure cobalt oxide catalysts. Radey cobalt and activated technical cobalt oxide gave superior results as judged by the increase in the ratio of primary to secondary amine, demonstrating that cobalt in these forms is inferior to nickel as a catalyst for alkylation.
Addition of Ammonia
The presence of ammonia in the reaction mixture should have the effect of repressing alkylation through mass action. . ... . .. However, when aniline was hydrogenated with Raney nickel in the presence of dry ammonia, the absorption amounted to only 55 per cent, and dissolved nickel was found in the filtered material. The products consisted of 45.3 per cent cyclohexylamine, 8.4 per cent- dicyclohexylamin-e, and '42.6 TABLE11. EFFECTOF DICYCLOHEXYLAMINE per cent recovered aniline. The ratio Primary Sec. Ratio, (CaHuhNH Catalyst Time Temp. Amine Amine Primary/Sec. Of primary to secondary amine Of 5.4 Grams Min. C. % % to 1 was an imnrovement over that ob... Raney Ni 37 280 58.5 28.6 2.04 tained withoucammonia, but the reac100 Raney Ni 20 280 59.1 11.8 5.0 64.5 30.2 2.1 tion was incomplete. Coo-CaO 17 280 10 280 78.8 19.1 1rjO. Coo-CaO 4 1 Ammonia inhibited the hydrogena28 270 63.2 10.6 6 .. 0 SO Coo-CaO ... Tech. Coo-CaO 30 280 60.6 10.3 5.9 tions using cobalt oxide so that a t the 100 Tech. Coo-CaO 20 280 93.8 3.9 24.0 end of one hour at 250-300" C. only 100 Tech. Coo-CaO 25 280 92 5 4.0 23.1 100 Recoveredfrom8 21 285 86.5 5.8 14.9 about 10 per cent absorption had been 27 285 100 Recoveredfrom9 90.5 5.7 15.9 obtained. The filtered product was pink 100 Recoveredfrom10 45 280 88.0 6.1 14.4 100 Recoveredfrom11 45 285 79.7 7.8 10.2 in color from dissolved cobalt. ~~
10 lb. 10 lb.
CtjHii.NHP
Tech. Coo-CaO Recoveredfrom13
25 50
+ Hz +CeHn + NHI
285 285
90.5 81.2
(3)
Hydrogenation reaction 1 occurs at temperatures of 2003OO0C.,depending upon the nature and activity of the catalyst. Autoalkylation reaction 2 is known to proceed a t 200" C. and above (7), but a t a slow rate so that hydrogenation may be completed before large quantities of dicyclohexylamine have been formed. Hydrogenolysis reaction 3 is noticeable at 275' but is not important below 325' C. Rapid hydrogenation also minimizes losses through this reaction. High-pressure hydrogenation equipment similar to that described by Adkins (1) was used here. The following description of an experiment illustrates the general procedure : A charge of 410 grams (4.4 moles) of aniline and 12.3 grams (3 per cent) of Raney nickel was placed in the autoclave and heated with shaking under an initial hydrogen pressure of 100 atmospheres. A t 200-225" C. absorption proceeded smoothly and more hydrogen was run into the autoclave t o maintain the pressure a t 75-100 atmospheres. In 3.5 hours the reaction had stopped at 70 per cent completion. Distillation of the filtered reaction product gave 213.5 grams (48.8 per cent) of cyclohexylamine, 70.6 grams (17.7 per cent) of dicyclohexylamine, 133 grams (32.5 per cent) of recovered aniline, and traces of cyclohexane with ammonia in the forerunnings. The ratio of primary to secondary amine was 2.76 to 1.
Comparison of Catalysts Table I shows the results of catalyst tests using nickel on kieselguhr (8), Raney nickel (6), Raney cobalt, pure cobalt oxide, and technical cobalt oxide (4) activated by lime. Freshly calcined powdered calcium oxide was the best activator for technical cobalt oxide; lump lime and commercial quicklime were poor.
4.8 6.4
18.8 12.7
Addition of Dicyclohexylamine
The Dresence of dicvclohexvlamine in the i e a c t i o n m i x t u r e a c t u a l l y repressed alkylation and improved the yield of primary amine without interfering with completeness of conversion. According to the data of Table I1 a definite increase in product ratio was shown with Raney nickel and cobalt oxide catalysts, and a large increase with activated technical cobalt oxide. As the catalyst was re-used, longer reaction times were required and the amount of secondary amine rose. The laboratory process has been translated into larger scale operation using a charge of 30 pounds aniline and 10 pounds dicyclohexylamine with results identical to those of the small scale. Cyclohexane (0.1 pound, 0.4 per cent) was recovered from the larger hydrogenations.
Acknowledgment The writer wishes to thank L. B. Sebrell and R. P. Dinsmore of The Goodyear Tire & Rubber Company for their interest in this work and for permission to publish the results.
Literature Cited (1) Adkins, Homer, IND. EXQ.CREM.,Anal. Ed., 4,342 (1932). (2) Adkins, Homer, and Cramer, H. I., J . Am. Chem. SOC.,52,4351 (1930). (3) Ellis, C.,"Hydrogenation of Organic Substances", New York, D.Van Nostrand Company, 1930. (4) Lommel, W., and Goost, T. (to General Aniline Works), U. S. Patent 1,927,129(Sept. 19,1933). (6) Raney, M., U. S. Patent 1,628,190(May 3,1927). (6) Winans, C. F. (to Wingfoot Corp.), Ibid., 2,129,631(Sept. 6, 1938). (7)Winans, C. F., and Adkins, H., J. Am. Chem. SOC.,54, 306 (1932).
