GB361004A - Improvements in the manufacture and production of hydrocyanic acid and its salts - Google Patents

Abstract

Hydrocyanic acid and its salts are obtained by passing a gaseous mixture containing ammonia, oxygen and at least one hydrocarbon over an oxidation catalyst at from 500-1300 DEG C., preferably from 700-1200 DEG C. Aliphatic, cycloaliphatic and aromatic hydrocarbons are suitable, but preferably one or more lower members of the aliphatic series, such as methane, ethane, ethylene, &c., are used. The proportion of oxygen used varies from 0,2 molecular proportion for a mixture of 1 molecular proportion each of hydrocarbon and ammonia to 1 molecular proportion of oxygen for each carbon atom of the hydrocarbon plus 0,25 molecular proportion of oxygen for any atomic proportion of hydrogen present in the hydrocarbon and ammonia. Excess of either hydrocarbon or ammonia serves as a diluent, or other inert gases may be added for that purpose. The effluent gases may be used again after replacing the substances consumed, or they may be used for heating purposes. The reaction is exothermic, and may be carried out at atmospheric, increased or reduced pressure. Suitable catalysts include the noble metals, such as platinum, iridium, rhodium, palladium, osmium, gold or silver, as such or alloyed with each other or with other metals and the rare earths, cerium, lanthanum, thorium, aluminium, iron, tin, zinc, cadmium, bismuth or uranium in the form of difficultly fusible compounds, such as oxides, phosphates, or mixed phosphates. The noble metal catalysts are usually employed in the form of nets or like structures, while the above base metal compounds are preferably deposited on a heat-resisting carrier, such as silica or alumina gel. The products may be cooled to obtain hydrocyanic acid, or allowed to act at temperatures from 500-900 DEG C., after removal of water vapour if required, on alkali or alkaline-earth metal oxides or hydroxides or salts which are readily convertible thereto to obtain cyanides and cyanamides, and preferably gas mixtures richer in oxygen are used for this purpose to increase the yield. Details of various gas mixtures and different catalysts which may be used are given in examples.