Selective hydration of dihydromyrcene to dihydromyrcenol over H-beta zeolite. Influence of the microstructural properties and process variables

Ii-beta zeolite has been tested for the hydration of dihydromyrcene (DHM) to produce dihydromyrcenol (DHM-OH). By using a non-protic co-solvent like acetone, in order to work under a single phase system, reasonable conversion with excellent selectivity to DHM-OH is obtained, although some double bond isomerization of the terpene is also taking place. The reaction is not controlled by intrapore diffusion, and samples with different crystal sizes gave similar activities and selectivities. However, defect free beta samples with high hydrophobic character are preferred for the reaction due to their improved adsorption properties for non-polar molecules. Working with those materials more than 50% yield of DHM-OH was obtained with a selectivity close to 100%. The influence of zeolite hydrophobicity was further proved in a two-phase liquid reaction system. In such conditions,best results were achieved with the most hydrophobic catalysts. (C) 2000 Elsevier Science B.V. All rights reserved.