HZSM-5 zeolite modification and catalytic reaction mechanism in the reaction of cyclohexene hydration

Abstract

This study investigated a three-phase (liquid–liquid–solid) reaction system of cyclohexene hydration where the catalyst was hydrophilic at the bottom of the water phase. Cyclohexene conversion was low since it was difficult for it to come into contact with the oil. The HCl-OTS-HZSM-5 catalyst was prepared by acid and alkylation modification, then subsequently characterized. Acid modification enabled HZSM-5 zeolite to remove some aluminum atoms, increasing specific surface area, pore volume, and acid sites. N-octyltrimethoxysilane (OTS) was grafted onto the HZSM-5 zeolite surface, i.e., alkylation modification, to improve the contact area between immiscible reactants. Consequently, cyclohexene conversion reached 24.07%. Cyclohexene hydration was calculated using the 34T cluster model, and bridging hydroxyl and water molecule adsorption sites were explored. Simulations confirmed that the reaction energy barrier for the HCl-OTS-HZSM-5 catalyzed hydration reaction = 46.67 kJ mol⁻¹, considerably less than that with HZSM-5 zeolite (73.78 kJ mol⁻¹). The theoretical results reasonably explain the experiments and provide guidance to prepare catalysts with high catalytic activity.