PROCESS FOR PREPARATION OF MENTHOL BY HYDROGENATION OF ISOPULEGOL

PROBLEM TO BE SOLVED: To provide a process which allows the preparation of substantially diastereoisomerically pure menthol by the hydrogenation of diastereoisomerically pure isopulegol.SOLUTION: The process for preparing racemic or optically active menthol comprises catalytically hydrogenating racemic or optically active isopulegol in the presence of hydrogen, and a catalyst which comprises nickel-, copper-, zirconium- and molybdenum-containing compounds. Concretely, the process prepares L-menthol by continuously catalytically hydrogenating L-isopulegol. In a synthetic method of menthol by the hydrogenation of isopulegol, hydrogenation is carried out under conditions that the hydrogen pressure is 5-200 bar and the temperature is 50-130°C, in the presence of a catalyst containing 30 to 70% by weight of oxygen compounds of nickel, calculated as NiO, 15 to 45% by weight of oxygen compounds of zirconium, calculated as ZrO, 5 to 30% by weight of oxygen compounds of copper, calculated as CuO, and 0.1 to 10% by weight of oxygen compounds of molybdenum, calculated as MoO.