GB812780A - Process for preparing alkene nitriles - Google Patents

Abstract

Unsaturated aliphatic nitriles are obtained by the vapour phase reaction at 250-450 DEG , preferably about 350-400 DEG C., of a lactam with a molar excess of ammonia over a dehydration catalyst which is acidic in water. The ammonia may be present in amounts of 5 to 15 mols. per mol. of lactam. The dehydration catalyst, e.g. acid-treated clay, boron phosphate, or phosphoric acid on a carrier such as kieselguhr, fuller's earth or silica, is preferably used in the form of irregular lumps with a mean diameter of 5-6 mm. The vapour is passed through the catalyst mass. The pressure is about atmospheric, and may be from about 0.5 atm. to 1.5 atm., i.e. sufficient to draw or force the vapour through the catalyst. In an example caprolactam is 91.8 per cent converted to a mixture of 91 per cent 5-cyano pentene-1, 8 per cent aminocapronitrile and 1 per cent high-boiling residue. The nitrile reaction product is purified by distillation. Suitable lactams mentioned as starting materials are caprylolactam, 2-pyrrolidene, valerolactam and oenantholactam, giving respectively 7-cyanoheptene-1,3-cyano - propene - 1,4 - cyano - butene - 1 and 6-cyano-hexene-1.