GB590768A - Method of preparation of acetonitrile - Google Patents

Abstract

A catalyst for the preparation of acetonitrile from acetylene and ammonia (see Group IV) is prepared by precipitating sodium aluminate with a solution of zinc and chromium nitrates, washing the gelatinous precipitate of hydrated alumina and zinc and chromium hydroxides so as to remove a part, but not all of the sodium nitrate present, and calcining this precipitate. The catalyst may then be heated in a current of ammonia at 500 DEG C. It may be revivified by passing air or steam over it at 450-500 DEG C.ALSO:Acetonitrile is prepared by passing a mixture of ammonia and acetylene, in the moist state, at atmospheric pressure and at temperatures between 300 DEG C. and 500 DEG C., over a catalyst containing an acetylene hydration catalyst (comprising zinc oxide), a dehydration catalyst (comprising alumina) and a dehydrogenation catalyst (comprising chromium oxide) (see Group III). Preferably the catalyst is slightly alkaline and the ammonia is employed in slight excess, e.g. 10 per cent excess, together with a little steam. The acetylene may be bubbled through water at 60 DEG C. before the reaction, and the reaction may be started at 300-350 DEG C., being raised to 450-500 DEG C. as the catalytic activity diminishes. The catalyst may be given longer life by purifying the acetylene before use by washing with a mixture of sulphuric and chromic acids, followed by passage over activated carbon, and is preferably divided amongst two or more reactors in series, with condensation of acetonitrile between reactors. Suitable materials for the walls of the reactors are non-oxidizing steel, quartz, aluminium, and ceramic materials. The hydrogen leaving the apparatus is washed with water, which dissolves the ammonia and acetonitrile present. The ammonia in the solution is utilized by passing through it the acetylene entering the reactors, and the acetonitrile is separated by distillation in the form of its azeotrope with water, which is worked up according to the method of Specification 590,767, [Group III], with ammonium carbonate to give pure acetonitrile.