Preparation of Double Layer Membrane Combined with Palladium Metal and FAU Zeolite for Catalytic Membrane Reactor

The preparation of a double-layer membrane by the combination of Pd metal and FAU zeolite was attempted to enhance the catalytic activity of the membrane reactor. The membrane was successfully synthesized on a porous alpha-Al2O3 support tube by the hydrothermal synthesis of the FAU zeolite layer followed by chemical vapor deposition of the Pd layer. The thicknesses of the FAU and Pd layers were ca. 5 mu m and 1 mu m, respectively. The membrane functioned efficiently as a hydrogen separation membrane without deterioration, due to the rigid connection of each layer. During the model reaction, such as the reaction of benzene and permeated hydrogen species from Pd membrane, the inner surface of the Pd layer that was in contact with the FAU layer exhibited high hydrogenation activity, in contrast to the outer surface. Scanning electron microscope observations reveal that one of the reasons for this observed difference is the roughness of the inner surface. Loading of Pd particles in the micropores of FAU zeolite layer by ion-exchange treatment resulted in enhancement of the hydrogenation activity. The FAU zeolite layer is suitable for loading of the highly dispersed active metal particles. The combination of Pd metal membrane and fine metal particles has potential for acceleration of catalytic membrane reactions.