Patent ID: 6274771
Filing Date: 2001-08-14
Classification: C07C

Abstract:
A continuous process for the manufacture of 3,5,5-trimethylcyclohexa-3-en-1-one (.beta.-isophorone) by isomerization under homogeneous catalysis of 3,5,5-trimethylcyclohexa-2-en-1-one (.alpha.-isophorone), obtained by trimerization of acetone in alkaline medium, the said process being characterized in that the following stages are carried out:a) .alpha.-isophorone and a solution of an alkaline hydroxide are continuously introduced into a reaction region,b) the reaction mixture is brought to reflux at a temperature at least equal to 150.degree. C. and under a pressure P1 of less than or equal to atmospheric pressure,c) the following are continuously and simultaneously removed from the reaction mixture:1) the .beta.-isophorone of the vapour phase, by distillation under a pressure P2 which is less than P1 and at a temperature at most equal to 150.degree. C.,2) heavy products, by drawing off, so that their content by weight is at most equal to 7% in the reaction mixture, andd) the distillation condensates are continuously returned to the reaction region.