GB913836A - Improvements in and relating to the synthesis of hydrogen cyanide - Google Patents

Abstract

Hydrogen cyanide is produced by vapour phase reaction, at between 350 DEG -600 DEG C., of methanol, ammonia and oxygen over a tin oxide/antimony oxide catalyst. The reaction may be effected over a fixed or fluidized bed of neat or supported catalyst. The catalyst may be prepared by mixing the oxides or compounds which decompose to the oxides and heating to 550 DEG -1100 DEG C. in an oxygen containing atmosphere to give a catalyst with a molar ratio of tin to antimony in the range of 0,1 to 20:1. The preferred method is to mix oxides obtained by the action of nitric acid of suitable concentration and calcining at 550 DEG -1100 DEG C. Other methods of preparation are referred to. When lower oxides are used as starting materials, the calcination is effected in two separate stages, the first stage being in the range of 300 DEG -650 DEG C. The gaseous reaction mixture is preferably diluted with steam or steam and nitrogen and contains ammonia and methanol in the mole ratio of 1:2 to 2:1 and 1 to 20% by volume of oxygen. Hydrogen cyanide recovery, after acid scrubbing to remove ammonia, may be by absorption in water or alkali metal hydroxides or carbonates.