Nanostructured palladium–iron membranes for hydrogen separation and membrane hydrogenation reactions

Hydrogen permselectivity and poisoning resistance of nanostructured palladium–iron alloy films were examined to evaluate these materials for potential membrane applications. At 200 °C, nanostructured palladium–iron films had hydrogen/helium selectivities of up to 35:1 and hydrogen fluxes of up to 10 sccm/cm2. The rate-limiting step for hydrogen transport was diffusion through the bulk metal. Hydrogen flux in the nanostructured palladium-based membranes decreased with increasing iron content. The nanocrystalline membranes had higher hydrogen fluxes than coarse-grained polycrystalline systems of similar compositions. Nanostructured membranes also exhibited better resistance to hydrogen sulfide poisoning than polycrystalline membranes. When applied for the hydrogenation of ethene, the palladium–iron nanocrystalline membranes displayed stable activities over long time periods.