GB836364A - Improvements in and relating to the manufacture of secondary amines - Google Patents

Abstract

Aliphatic or cycloaliphatic secondary amines containing from 8 to 22 carbon atoms are prepared by conducting in a closed circuit the steps of contacting in the liquid phase in a reaction zone in the presence of a hydrogenation catalyst a nitrile and/or primary amine containing from 8 to 22 carbon atoms with gaseous hydrogen at 150 DEG to 250 DEG C. and at a pressure of from atmospheric to 250 p.s.i.g.; continuously venting from the reaction zone a gaseous mixture of hydrogen and ammonia, the latter being formed during the reaction, at a rate of from 1 to 4 mols. of mixture per mol. of reactants per hour; passing the vented gas mixture to a separating zone and separating therefrom the ammonia; and passing the hydrogen back to the reaction zone. The preferred starting materials are straight-chain aliphatic nitriles containing from 8 to 18 carbon atoms, such as the alkyl and alkylene nitriles derived from the fatty acids of fats and oils, e.g. tallow, coconut oil, soybean oil and cottonseed oil. The cycloaliphatic nitriles derived from tall oil and rosin acids may be used. The primary amines corresponding to and derived from the nitriles by hydrogenation may also be used. Specified catalysts are Raney nickel and copper-chromium oxide. The amount of catalyst is generally about 0.4 to 3% by weight based on the weight of catalytic metal. The presence of water should be avoided and the reactants and catalyst dried. In an apparatus described the vented gas mixture is cooled to about 25-65 DEG C. and then scrubbed in countercurrent with water to dissolve the ammonia. The presence of hydroxides and metallic soaps should be avoided. The secondary amine may be bleached in situ during the reaction by incorporating an inert bleaching agent in the reaction mixture, e.g. 1 to 3% of fuller's earth, bentonite, kieselguhr or activated carbon.