Catalytic membrane reaction for methane steam reforming using porous silica membranes

Catalytic membranes, which have hydrogen permselectivity over other gaseous molecules and catalytic activity for methane steam reforming, were prepared by 2 different procedures and applied to methane steam reforming at 450-500degreesC. Type A catalytic membranes were manufactured by the preparation of a hydrogen separation layer from silica-zirconia colloidal sols, followed by the application of a nickel catalyst coating. Type B catalytic membranes were prepared via the impregnation of a nickel catalyst inside the a-alumina porous substrates, followed by the application of a coating on the hydrogen separation layer. Hydrogen permselectivity over nitrogen was degraded by coating the catalyst layer, as in the Type A membranes, and in addition, methane conversion decreased with time probably because of catalyst sintering or carbon deposition. Type B catalytic membranes showed a steady conversion for a longer period than did Type A, and the permeability ratio of hydrogen to nitrogen was approximately 200; therefore, Type B was found to be the effective route to preparing catalytic membranes. Methane steam reforming through the use of catalytic membranes revealed that methane conversion beyond the equilibrium conversion levels could be achieved either by sweeping the permeate stream or by pressurizing the feed stream at 6 bar and not using sweeping gas.