Palladium-based micromembranes for hydrogen separation: Device performance and chemical stability

The performance of a perforated micromembrane device employing thin palladium-based films for hydrogen purification is reported. The perforated support provides mechanical strength, allowing the use of nanometer film thicknesses (200 nm) that significantly reduce internal diffusion resistance, and allows efficient heating of the active film. Steady-state operation of pure and 23 wt % silver-alloyed palladium films at 350degreesC, with a feed hydrogen partial pressure of 10.1 kPa (Deltap(H2), = 9.6 kPa), results in hydrogen fluxes of 3-4 mol/m(2)/s and hydrogen-to-argon selectivities approaching 1000:1, much larger fluxes than typically achieved with conventional macroscopic equipment. Chemical resistance to ammonia, carbon dioxide, and carbon monoxide is also reported. Ammonia and carbon dioxide are both found to have a minimal effect upon the device performance. Exposure to carbon monoxide results in a loss of hydrogen permeation, with silver-palladium films showing a partially recoverable loss of similar to40% initial hydrogen flux at a carbon monoxide concentration of 9000 ppm. Our results demonstrate that these microdevices could be part of an integrated portable hydrocarbon to electrical power system.