GB738986A - Improvements relating to the production of diphenylamines - Google Patents

Abstract

Diphenylamines are prepared by heating anilines or a nuclear alkylated derivative thereof in the liquid phase with a catalyst (see Group III) comprising a mixture of a copper salt, a finely-divided metal and a chloride capable of liberating hydrochloric acid. In the preparation of diphenylamine from aniline, temperatures of 300-400 DEG C. and pressures of 300-400 pounds per square inch with a heating period of 3-6 hours, are suitable. In examples aniline is converted to diphenylamine using various catalyst mixtures.ALSO:Catalysts used in the production of diphenylamines from aniline, or a nuclear alkylated derivative thereof, by heating in the liquid phase, comprise a mixture of a copper salt, a finely divided metal, and a chloride capable of liberating hydrochloric acid. Suitable copper salts are cupric chloride, cupric sulphate and cuprous chloride in anhydrous or hydrated form. The chloride capable of liberating hydrochloric acid is ammonium chloride or an amine hydrochloride, e.g. aniline hydrochloride. The finely divided metal is copper or a metal which is higher in the electromotive series than copper and lower than calcium. Iron is preferred, and copper bronze may be used. The hydrochloric acid liberating substituent of the catalyst mixture may be omitted if cupric chloride and for example iron or zinc, are used. Generally the catalyst contains approximately equal parts by weight of each constituent, and about 10 per cent of the catalyst is used relative to the amine. The catalyst composition may change, mainly by deposition of metallic copper during the process, but catalytic activity is maintained by the addition of a hydrochloric acid liberating chloride, e.g. aniline hydrochloride, to the catalyst residue. In examples catalyst mixtures containing hydrated cupric chloride or anhydrous cuprous chloride, iron, zinc or copper bronze powders and ammonium chloride or aniline hydrochloride are used in the preparation of diphenylamine from aniline.