GB761166A - The method of manufacturing hydrogen cyanide - Google Patents

Abstract

<PICT:0761166/III/1> Hydrocyanic is manufactured by passing a mixture of ammonia and methane or other gaseous hydrocarbon, at 800-980C DEG ., through a bed of fluidized iron-free granular alumina catalyst, which may also contain 0.5-2 mol per cent of an oxide of thorium, titanium, zinc, zirconium, hafnium, silicon, cerium, or calcium. The gas mixture passes, through tube 3, into silica or porcelain tube 1 at a velocity sufficient to maintain the granular catalyst in a fluidized condition, and product gases are withdrawn at 8. Tube 1 is surrounded by furnace 9. The catalyst is prepared by dissolving crystalline aluminium hydroxide in aqueous sodium hydroxide solution and, after diluting, passing steam through. After cooling, the solution is filtered to ensure absence of iron and iron compounds, which have been precipitated as hydroxide. Dilute mineral, e.g. hydrochloric, acid is added dropwise to the pure sodium aluminate solution to pH 6. Ammonia is then added to pH 8, and the resulting solution filtered. If a mixed catalyst is required, hydrochloric acid containing a metal salt, e.g. thorium nitrate, is used. The aluminium hydroxide, or mixed hydroxide gel, is steamed while kneading, dried, and roasted at 300 DEG C. Iron-free water is sprinkled on the roasted cake, which cracks into uniform granules, and the granules are washed with water containing ammonium sulphate until chloride ion-free, and dried at 500 DEG C.