Defect-Free Palladium Membranes on Porous Stainless-Steel Support

Defect-free Pd membranes were prepared by an electroless plating technique on porous stainless-steel tubes. The effective surface of Pd membranes was up to 75 cm². The helium flux was not detected at room temperature and pressure difference of 3 atm. At 350&C hydrogen permeances of up to 8 m³/(m² · h→ · atm^0.5) were obtained. At a pressure difference of 1 atm and 350°C, selectivity coefficients as high as J(H₂/J(N₂) = 5,000 were observed. Fluxes of gases, impermeable through the Pd, were quantitatively described as a combination of Knudsen diffusion and viscous flow through the gaps created in the Pd layer at high temperatures. The stability of the prepared membranes at temperatures up to 700°C was investigated. The membranes were stable at 350°C over a period of 1,100 h, with no significant changes in the steady-state hydrogen flux and with a recrystallization texture and aggregation of Pd grains.