Reaction kinetics and mechanism for hydration of cyclohexene over ion-exchange resin and H-ZSM-5

The kinetics of liquid-phase cyclohexene hydration over ion-exchange resin and H-ZSM-5 were, respectively, investigated in a batch autoclave reactor. In order to identify the reaction mechanism involved in the heterogeneous cyclohexene hydration, a pseudo-homogeneous (PH) model and three heterogeneous models based on the Langmuir–Hinshelwood–Hougen–Watson (LHHW) mechanism and Eley–Rideal (ER) mechanism were established to correlate the kinetic data. The results indicated that the heterogeneous models exhibited a more satisfactory agreement with the experimental data than the PH model. According to the kinetic studies and spectroscopic analysis, it is proposed that cyclohexene hydration catalyzed by H-ZSM-5 belongs to the ER mechanism, which accounts that the reaction is between adsorbed water and bulk cyclohexene, while it belongs to the LHHW mechanism over the ion-exchange resin. Nevertheless, the activation energies are similar for the two catalysts, which implies similar controlling steps are encountered in the reaction.

► Kinetic study of cyclohexene hydration with H-ZSM-5 and resin catalysts.
► Four models based on different mechanisms are used to correlate the kinetic data.
► Cyclohexene hydration over resin catalyst follows LHHW mechanism.
► Cyclohexene hydration over H-ZSM-5 catalyst follows ER mechanism.