Kinetic Equations for Liquid-Phase Selective Hydrogenation of Benzene to Cyclohexene

The Ru-M-B/ZrO_2 catalyst with high selectivity for cyclohexene from benzene hydrogenation was prepared. Under the conditions of no inside and outside diffusion, the curves of the concentration of benzene, cyclohexene and cyclohexane versus time over the Ru-M-B/ZrO_2 catalyst were measured. Some kinetic parameters of the selective hydrogenation of benzene to cyclohexene such as reaction order and rate constant in each step were obtained. It was concluded that the benzene conversion is first order with respect to benzene, and with respect to hydrogen, it is second order at low pressure, fraction order at middle pressure and zero order at high pressure. While the cyclohexene hydrogenation to cyclohexane is zero order with respect to cyclohexene, and with respect to hydrogen, it is second order at low pressure, fraction order at middle pressure and zero order at high pressure. Based on these results, the kinetic equations of benzene hydrogenation to cyclohexene in each step were given. The kinetic equations were also confirmed based on the experimental data. The reason for the reaction order in each step was also discussed.