Measurement and modeling of hydrogen transport through high-flux Pd membranes

The permeability of H2-selective palladium membranes fabricated with microsystem technol. has been studied. The permeation expts. have been carried out at temps. between 623 and 873 K at H2 feed partial pressures of 0.2-1.0 bar. At 823 K, a permeance based on the free membrane area of 18 mol H2/m2 s bar0.58 has been measured for a Pd membrane with a thickness of 0.5 mm. From the permeation expts. the rate detg. transport step and the stability of the membranes have been detd. At 873 K the H2/He selectivity decreases rapidly, indicating the formation of pinholes at higher temps. From a combination of expts. and computer simulations the limiting transport step has been detd. to be H-atom diffusion through the membrane at elevated temps. and H2 surface reactions at the retentate side at lower temps