A microporous membrane for selective separation of hydrogen was prepared using the sol-gel method. Boehmite sor containing a metal salt, such as RuCl3, Pd(NH3)(4)Cl-2, RhCl3, H2PtCl6, Ni(NO3)(3), Co(NO,)3, Fe(NO3)(3) or Cu(NO3)(2), was coated on a porous alumina substrate before firing at 900 degrees C. It was found that the permeability of hydrogen and the separation factor for the gaseous hydrogen/nitrogen mixture using metal-dispersed membranes, such as Ru-, Rh-, Pd-, Ni-, and Pt-Al2O3 membranes, exceeded the value expected from the Knudsen diffusion mechanism. Although the gas permeation through the neat alumina membrane was governed by the Knudsen diffusion, the metal particles dispersed in the alumina membranes were effective in promoting hydrogen permeation.