Epimerisation of menthol stereoisomers: Kinetic studies of the heterogeneously catalysed menthol production

The heterogeneously catalysed epimerisation of neomenthol and isomenthol is a key step in the synthesis of menthol in the Symrise process (formerly know as Haarmann & Reimer process). A reaction model based on the experimentally determined kinetic and thermodynamic parameters was derived for industrial relevant conditions of 150-210 °C and 0.8-7.5 MPa hydrogen pressure. Results of experiments and modelling show a good agreement and thus the derived kinetic parameters can be used for the optimisation of batch slurry processes as well as of continuous fixed bed processes.