Patent ID: 6429344
Filing Date: 2002-08-06
Classification: C07B,C07C

Abstract:
A process for the preparation of d,l-menthol by catalytic hydrogenation of a starter selected from the group consisting of thymol, isomenthol, d-menthol, d- and l-neomenthol, d- and l-isomenthol, d,l-neomenthol, d,l-isomenthol, d,l-neoisomenthol, and mixtures thereof, using hydrogen and by catalytic rearrangement of menthol stereoisomers in the presence of hydrogen, wherein hydrogenation is carried out with hydrogen at hydrogen partial pressures between 2 and 50 bar and at temperatures of 100 to 200Â° C. and the catalytic rearrangement is carried out at a hydrogen partial pressure between 0.1 and 20 bar and at temperatures of 0 to 140Â° C. and the catalysts used are noble-metal catalysts containing metals of subgroup VIII, wherein the d,l-menthol content of the catalytic rearrangement reaction mixture is over 60%.