Design, scale up and safe piloting of thymol hydrogenation and menthol racemisation

Abstract

The hydrogenation of thymol and the racemisation of a menthol mixture were investigated as part of the development of novel process for the production of l-menthol. The key innovation in this l-menthol process is the enzymatic resolution of l -menthol from 8 menthol isomers mixture. The productivity of the enzyme (mass of l-mentylacetate produced/mass enzyme) is a key performance measurement of this process. The demonstration of the required enzyme productivity was therefore a key objective of the process piloting. The effect of possible side products and impurities on the process also needed to be tested and therefore five cycles of piloting were performed using approximately 500 kg of feed into resolution in each cycle. The required quantities of the menthol mixture were obtained in pilot plant trickle bed reactor