Composite alumina membrane was prepared for the hydrogen separation from H₂-N₂ mixture gas. The membrane was formed in a porous alumina support by coating with boehmite sol mixture by Yoldas method with 5 wt% concentration of Pd in dry base. Sonication of the sol mixture increased the Pd dispersion compared to that of conventional impregnation method. In order to facilitate penetration of the sol, the inner side of the porous alumina support was maintained at the vacuum condition of 20 torr during the coating procedure. Tortuosity of the resulting membrane was increased from 10 to 20. The selectivity also increased up to 10 because of the activated diffusion by the Pd particles dispersed in the alumina membrane layer. Sealing between membrane housing and supported membrane was designed to endure high temperature operation and provided a way to develop alumina membrane module.