Studies on the preparation of Pd/alumina/porous stainless steel membranes for hydrogen separation

The focus of this article is to study preparation procedures used to make s upported palladium (Pd) membranes for hydrogen separation. We first modifie d the outside surface of a commercial porous stainless steel (PSS) tube by polishing and coating with a thin layer of alumina. This alumina layer serv es to flatten the surface and also to act as a diffusion barrier between th e Pd and PSS substrate. After modification, the Pd layer is then deposited using an electroless plating technique. Permeation analysis results indicat e that the average pore size decreases from the original 17 mum to about 1. 5 mum after modification. A dense Pd film can be obtained after only four t imes of electroless deposition. The selectivity of this Pd/Al2O3/PSS tube ( length 5 cm, outside diameter 0.95 cm) is 110 for H-2/N-2, and the hydrogen permeance is 2.2 x 10(-7) mol/m(2)-s-Pa at 350 degreesC under a transmembr ane pressure difference of 1.0 x 10(5) Pa.