Keywords: hydrogen purification, palladium, membrane, Sievert', s Law, porous stainless steel, palladium alloys, stainless steel membranes, nitrogen diffusion, hydrocarbon fuels, fuel cells
Hydrogen purification with palladium and palladium alloys on porous stainless steel membranes
Hydrogen purification membranes have been prepared via a simultaneous electroless plating of Pd and Ag on a 0.5 ?m media grade Porous Stainless Steel (PSS). Effects of the electroless bath temperature, composition, annealing time and temperature were studied while developing the Pd coating. Very low but measurable N2 fluxes were seen, ranging from 0.010 to 0.020 cm?/cm?-min at temperatures varying from 300?C to 400?C. As no helium flux was observed, it appears that nitrogen diffused, albeit much more slowly, through the same interstitial sites that hydrogen did. H2 permeances varying from (1.9?3.1) ? 10?2 cm?/cm?-min-Pa0.5 were recorded between temperatures from 350?C to 550?C. Sievert's Law was seen to hold true at all temperatures. Short term stability and reproducibility of the H2 permeance were confirmed. The activation energy (Ed) for H2 permeance in the Pd-Ag layer was calculated from the permeance data to be 9 ? 1 kJ/mol.