PROMOTION OF HYDROGEN PERMEATION ON METAL-DISPERSED ALUMINA MEMBRANES AND ITS APPLICATION TO A MEMBRANE REACTOR FOR METHANE STEAM REFORMING

A mesoporous membrane for selective separation of hydrogen was prepared using the sol-gel method. Some metal salts such as RuCl3, Pd(NH3)4Cl2, RhCl3, and H2PtCl6 were added to the boehmite sol and coated on a porous alumina substrate before firing at 500-degrees-C. It was found that the permeability of hydrogen and the separation factor for a hydrogen-nitrogen gaseous mixture of these metal dispersed membranes exceeded the limitations of the Knudsen diffusion mechanism. Although the gas permeation through a neat alumina membrane is governed by the Knudsen diffusion, the metals dispersed in alumina membranes were effective in promoting hydrogen permeation. These metal dispersed alumina membranes were also used in a membrane reactor for methane steam reforming at low temperature. In the temperature range of 300 to 500-degrees-C, the membrane reactor attained a methane conversion twice as high as the equilibrium value of the packed bed catalytic reactor system as a result of the selective removal of hydrogen from the reaction system.