Organic compounds -- part of the class 532-570 series – Organic compounds – Amino nitrogen containing
Patent
1994-05-17
1995-07-04
Raymond, Richard L.
Organic compounds -- part of the class 532-570 series
Organic compounds
Amino nitrogen containing
C07C20924
Patent
active
054301874
DESCRIPTION:
BRIEF SUMMARY
FIELD OF THE INVENTION
This application is a 371 of PCT/EP92/02918 filed Dec. 16, 1992.
The present invention relates to a method of manufacturing dibenzylamine from benzaldehyde and ammonia with catalytic hydrogenation.
BACKGROUND
Dibenzylamine does not form any carcinogenic nitrosamines and can be used as a starting compound for manufacturing the vulcanization accelerator tetrabenzylthiuram disulfide, which also forms only nitrosamines of low volatility that remain in the rubber. The manufacture and use of this vulcanization accelerator is therefore largely harmless to health.
Dibenzylamine is specifically manufactured by hydrogenation of benzonitrile with Pt catalysts (U.S. Pat. No. 3,923,891). Other suggested syntheses for dibenzylamine start with benzylamine (Synthesis (1), 70 (1979); J. Organomet. Chem. 208 (2), 249 (1981); Chem. Lett. (6), 889 (1984); Ind. J. Technol. 23 (7), 266 (1985)). In addition, dibenzylamine occurs as a byproduct in the industrial synthesis of benzylamine from benzaldehyde by reaction with ammonia and catalytic hydrogenation with Raney nickel (Ullmanns Encyclopadie der technischen Chemie, 4th edition, Volume 8, 440): NH.sub.2 +H.sub.2 O H.sub.5 --CH.sub.2 N.dbd.CH--C.sub.6 H.sub.5 +H.sub.2 O .revreaction.C.sub.6 H.sub.5 --CH.sub.2 NHCH.sub.2 --C.sub.6 H.sub.5
Dibenzylamine is therefore formed via the stages of monobenzylamine and N-benzylbenzylidenimine and can be separated from the intermediate reaction mixture by fractionation. The reaction mixture can also contain tribenzylamine as a secondary product, and benzyl alcohol and toluene as reduction products of benzaldehyde. According to Ullmanns Encyclopadie, Volume 8, Page 440, in the reaction a mixture of 470 kg monobenzylamine, 2 kg benzylbenzylidenimine, 1 kg dibenzylamine, and 1 kg benzyl alcohol is obtained, for example, from 500 kg of benzaldehyde (4.72 mol) and 110 kg ammonia (6.47 mol)--in other words, with a stoichiometric excess of ammonia at 100.degree. C.
In addition, J. Amer. Chem. Soc. 61 (1939), Page 3566 describes the manufacture of monobenzylamine with dibenzylamine as a byproduct, by reacting benzaldehyde with a mere stoichiometric excess of ammonia under conditions of catalytic hydrogenation with Raney nickel as the catalysts. According to the example cited therein, a mixture of 287 g monobenzylamine and 21.7 g dibenzylamine is obtained from 3 mol benzaldehyde and 3 mol ammonia--in other words, using stoichiometric amounts relative to monobenzylamine formation, but using a stoichiometric excess of ammonia relative to dibenzylamine formation, at 70.degree. C. On the other hand, according to Table 1 of this citation, the amount of dibenzylamine can predominate (80.8% versus 11.8% monobenzylamine) when using stoichiometric amounts of benzaldehyde and ammonia (1/2 equivalent) relative to dibenzylamine formation.
SUMMARY OF THE INVENTION
Hence, there is a need for an economic method of manufacturing dibenzylamine from benzaldehyde and ammonia by catalytic hydrogenation. The goal of the present invention is to provide such a method in which, in particular, a higher selectivity for dibenzylamine is achieved and a catalyst that is easier to handle can be used, and yet smaller amounts of catalyst metal are required.
This goal is achieved by the invention, which comprises a method of manufacturing dibenzylamine by reacting an amount of benzaldehyde and an amount of ammonia in the presence of hydrogen and a hydrogenation catalyst in an inert organic solvent, wherein the reaction is performed with an ammonia concentration of >0.5 mol ammonia per mol benzaldehyde and with a hydrogenation catalyst comprising at least one platinum metal, and/or a ferrous metal on a carrier.
The advantageous result according to the invention--especially the high selectivity for dibenzylamine, over 90%, with practically complete benzaldehyde conversion--is very surprising given the prior art cited at the outset. With regard to the molar ratio of reactants benzaldehyde and ammonia, the prior art discourages the excess ammonia to b
REFERENCES:
patent: 2217630 (1940-10-01), Winans
patent: 3293891 (1975-12-01), Greenfield et al.
Synthesis (1). 70-74 (Jan. 1979).
J. Organomet. Chem. 208(2) 249-251 (1981).
Chemistry Letters (6), 889-890 (1984).
Indian J. Technol. 23(7), 266-268 (Jul. 1985).
Ullmanns Encyclopadie der technischen Chemie, 4th Edition, vol. 8, 440-441 (1974).
Introduction to Organic Chemistry, 4th Edition, A. Streitwieser and C. H. Heathcook, 1990, pp. 782-784 (corresponding to German text, attached, pp. 927-928).
J. American Chem. Soc 61, 3566-67 (Jul.-Dec. 1939).
Bergfeld Manfred
Weuste Burkhard
Akzo N.V.
Raymond Richard L.
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