Application of electroless deposited thin-film palladium composite membrane in hydrogen separation

In recent years, there has been increased interest in developing inorganic and composite membranes for in-situ separation of hydrogen to achieve an equilibrium shift in catalytic membrane reactors. The productivity of these membrane reactors, however, is severely limited by the poor permeability and selectivity of available membranes. To develop a new class of permselective inorganic membranes, electroless plating has been used to deposit palladium thin-films on a microporous ceramic substrate. A palladium thin-film coating was deposited on a microporous ceramic disk (alpha-alumina, empty set 39 mm x 2 mm thickness, nominal pore size 150 nm and open porosity approximate to 42%) by electroless deposition. The film was evaluated by SEM and EDX analysis. A steady-state counter-diffusion method, using gas chromatographic analysis, was used to evaluate the permeability and selectivity of the composite palladium membrane for hydrogen separation at temperatures from 373 to 573 K. The pressure on the high pressure side of the membrane ranged from 170 to 240 kPa and the low pressure side was maintained at 136 kPa, The measured hydrogen permeabilities at 573 K were found to be 1.462 x 10(-9) mol.m/m(2).s.Pa-0.778, and 3.87 x 10(-8) mol.m/m(2).s.Pa-0.501 for palladium film thicknesses of 8.5 and 12 mu m, respectively. The results indicate that the membrane has both high permeability and selectivity for hydrogen and may find applications in high temperature hydrogen separation and membrane reactors.