Reaction and Separation Mechanism in Zeolite Catalytic Membrane Reactor for Dehydrogenation

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An FAU-type zeolite membrane was formed on porous α-alumina support tube by hydrothermal synthesis method. Vapor permeation test of the membrane was carried out. Then dehydrogenation of cyclohexane was performed in the membrane reactor with the zeolite membrane. Finally, reaction and separation behaviors in the membrane reactor were simulated.Vapor permeation of benzene arid saturated C4-C7 hydrocarbons was studied. For the case of a single-component feed, permeance to cyclohexane was higher than that to benzene. Meanwhile high benzene/cyclohexane selectivity can be attributed to the high adsorption selectivity in favor of benzene and the blockage against cyclohexane. Similar results were obtained for the case of binary mixture of benzene and other saturated hydrocarbons.An FAU-type zeolite membrane was used for the catalytic dehydrogenation of cyclohexane in a membrane reactor packed with a Pt/Al_2O_3 catalyst. The conversion of cyclohexane in the membrane reactor increased beyond the thermodynamic equilibrium value due to the simultaneous removal of hydrogen and benzene from the reaction site.A simple mathematical model assuming isothermal operation and a plug flow pattern was developed to evaluate the performance of an FAU-type zeolite membrane reactor. The result of the simulation was in good agreement with the experimental result. As a result, the reduction in coke formation on the catalysts in the membrane reactor was clearly demonstrated.