Hydration of cyclohexene over zeolite ZSM-5: improved catalyst performance by alkali treatment

Hierarchical ZSM-5 has been synthesized and treated with alkali (Na 2 CO 3 ) solutions. The catalysts are characterized with many techniques and studied in the hydration of cyclohexene. The characterization results show that with increasing the concentrations of alkaline solutions, the crystallinities increase and then decrease; the sever treatment leads to the destroy of the zeolite crystals; the external surfaces and mesopore volumes increase; the amounts of weak and strong acid sites, as well as the Brønsted acid sites increase and then decrease, while the amounts of Lewis acid sites increase. In the hydration of cyclohexene, both the conversions of cyclohexene and the selectivity of cyclohexanol first increase and then decrease. The best performance is obtained over ZSM-5 treated with 0.5 M Na 2 CO 3 solution with 13.0 % cyclohexene conversion and 99.3 % selectivity of cyclohexanol.