GB793020A - Improvements in preparation of nitriles - Google Patents

Abstract

Nitriles are prepared from aliphatic acids and ammonia by a method comprising a first step of reacting one or more (C8-C20) aliphatic acids and ammonia in liquid phase at a temperature above the melting-point of said acids to form water and a mixture of amides, nitriles, unreacted acids and ammonium salts and removing the water of reaction substantially as rapidly as it is formed, and completing the conversion of said mixture to nitriles in a second step under vapour phase conditions in the presence of ammonia and a dehydration catalyst; said ammonia being introduced into the vapour phase step of the process in an amount greater than that required to saturate the water-of-reaction. The ratio of ammonia entering the liquid phase is preferably between 1.2 and 2.0 mols. per mol. of acid, and the ammonia from the vapour phase step may be cycled through the liquid phase step. The liquid phase step is preferably carried out in the presence of a dehydration catalyst and at a temperature of between 200 DEG and 300 DEG C., and the vapour phase step is preferably carried out at between 300 DEG and 400 DEG C. The dehydration catalyst is preferably insoluble in the aliphatic acids, e.g. activated alumina, silica gel, titania gel and acid clays. Other catalysts specified are phosphoric acid butyl stannoic acid, and zinc and copper salts of coconut oil fatty acids, soya bean fatty acids, stearic acid, palmitic acid, oleic acid and tallow acids. Aliphatic acid reactants may be saturated or unsaturated and include caprylic, pelargonic, capric, undecylenic, lauric, tridecylic, myristic, pentadecylic, palmitic, margaric, stearic, nonadecylic, arachidic, behenic, linoleic, linolenic, oleic, therapinic, arachidonic, elaidic and fatty acids derived by hydrolysis from palm, coconut and soya bean oils. The examples describe the preparation of coconut oil fatty acid nitriles using an apparatus adapted for continuous working.