Studies on production of cyclohexanol by hydration of cyclohexene I. Effects of zeolite structure and crystal size

The effects of the structure of zeolites (ZSM-5, MCM-22, and β) and the crystal size of ZSM-5 on their activity and selectivity for the hydration of cyclohexene were studied. β, which has channels formed by 12-membered rings, had the highest conversion of cyclohexene and the lowest selectivity for cyclohexanol because of the high yields of dimeric of cyclohexene and dicyclohexyl ether. MCM-22 had the lowest activity of 0.8% and ZSM-5 with 12-membered ring channels gave a good activity of 7.5% and a good selectivity for cyclohexanol more than 99%. ZSM-5 was the better catalyst for the hydration of cyclohexene. The crystal size of ZSM-5 significantly affected the hydration of cyclohexene. The smaller the crystal size of ZSM-5 was, the higher the zeolite activity. This was because when the crystal size decreased, the number of the adsorption sites located near the pore mouth on the external surface of zeolite increased.