GB870462A - Improvements in or relating to the production of acetonitrile - Google Patents

Abstract

Acetonitrile is prepared by reacting acetylene and ammonia at 500-650 DEG C. under atmospheric or super-atmospheric pressure in the presence of a catalyst comprising alumina and at least one alkali metal hydroxide, or at least one inorganic salt of an alkali or alkaline earth metal, or at least one organic salt which gives an alkali metal carbonate or thermal decomposition; the ammonia being present in excess of the stoichiometric quantity, and the steam partial pressure in the gases being maintained at 2-50 mm. Hg. The starting gases may also contain hydrogen and carbon monoxide. Suitable salts are NaCl, KCl, LiCl, CaCl2, BaCl2 and alkali metal carbonates. The process may be carried out in fixed or fluidised beds.ALSO:Catalysts suitable for the reaction of acetylene and ammonia to produce acetonitrile (see Group IV(b)) comprise alumina and at least one alkali-metal hydroxide, or at least one inorganic salt of an alkali or alkaline-earth metal, or at least one organic salt which gives an alkali-metal carbonate on thermal decomposition; preferred salts are the chlorides and alkali-metal carbonates. The catalysts may be prepared by adding the hydroxide(s) or salt(s) as an aqueous solution to aluminium hydroxide gel or alumina hydrate, drying the resulting pasty mixture, and roasting at 500-700 DEG C.; or by roasting the alumina and then adding the aqueous solution to the roasted alumina. Carbonaceous matter deposited on the catalyst during use may be removed by heating with an oxygen-containing gas at 500-650 DEG C. The catalyst may be used in fixed-bed or fluidised-bed operation; in the latter case, suitable apparatus comprises a synthesis tower and a smaller regeneration tower, the catalyst circulating continuously. The larger bed may have at the inlet a packed bed comprising a plurality of layers of small inert solid grains (e.g. of silica) with a grid having spaces of a few centimetres embedded in the uppermost layer; the grain size decreases from the bottom layer to the top layer. The uppermost layer may be covered by a fine mesh wire net. The fluidised bed may also contain one or more horizontal wire nets or porous plates.