New synthesis method of Pd membranes over tubular PSS supports via "pore-plating" for hydrogen separation processes

Abstract

A new synthesis method to prepare Pd membranes by novelty modified electroless plating over tubular porous stainless steel supports (PSS) has been developed. This new pore plating method basically consists on feeding both plating solution and reducing agent from opposite sides of support, allowing the preparation of totally hydrogen selective membranes with a significantly lower Pd consumption than the corresponding to the conventional electroless plating procedure. In the latter, both reducing agent and plating solution are added simultaneously in one side of the PSS support. This new plating method has been applied over raw commercial PSS supports and air calcined supports in order to generate a Fe-Cr oxide intermediate layer. A completely dense Pd membrane with a thickness in the range 11-20 m directly over tubular porous stainless steel tubes with a high roughness has been achieved. The permeation properties of the membranes have been tested at different operating conditions for pure feed gases: retentate pressure (1 - 4 bar) and temperature (350 - 450ºC). All membranes present good permeance reproducibility after several thermal cycles and a complete hydrogen ideal selectivity, since complete retention of nitrogen is maintained for all tested experiment conditions, ensuring 100% purity in the hydrogen permeate flux. The permeance of both membranes is maintained in the range of 1-3 ·10-4 mol·m-2·s-1·Pa-0.5.