Abstract: Process for preparing a two layer metal palladium or palladium alloy composite membrane consisting of a porous substrate support and a palladium or palladium alloy membrane by rinsing/washing and drying the porous substrate support, treating the porous substrate support with a pore filler in order to decorate the pores of the support and the disfigurements of the substrate surface, sensitizing and activating with a palladium solution the decorated substrate support, and plating the resulting support with a palladium solution to form the two layer composite membrane, drying. The resulting composite membrane is subjected to a post-processing where the pore fillers residing in the pore-channels of the porous substrate are partly removed or reduced in volume through heating.

Abstract: The present invention relates to a metal palladium composite membrane or an alloy palladium composite membrane in which essentially the metal palladium membrane or alloy palladium membrane exists substantially on the outer surface of the porous substrate support, with little or no presence in the pore channels of the support, and to process for its preparation. The process comprises the steps of treating the porous substrate with a pore filler before plating it with a palladium solution to form the composite membrane.