Characterization of thin wall Pd–Ag rolled membranes

Abstract A thin wall Pd–Ag tube (thickness 50 μm ) obtained by a procedure of cold-rolling and annealing of thin metal foils has been characterized in long-term tests for determining the hydrogen permeability under operating condition of a temperature range from 300°C to 400°C and transmembrane differential pressure from 50 to 100 kPa . During testing, the physical and mechanical stability of the rolled membranes have been observed and high hydrogen fluxes have been measured. The long-term tests have also shown the modification of the surface structure of the membrane due to the hydrogen–metal interaction and the thermal cycling: as a consequence, an increase of the mass transfer properties of the hydrogen through the material (diffusivity and solubility) has been observed and the membrane tube has attained very high performances in about 3 months of operation in terms of hydrogen permeability. Furthermore, the tests have demonstrated that these Pd–Ag membranes have the capability to separate hydrogen from gas mixtures with a complete hydrogen selectivity and can be used to produce ultra-pure hydrogen for applications in energetic fields in membrane reactors by molecular reforming in membrane reactors (i.e. isotopic hydrogen separation, fuel cell, etc.).