Synthesis of Pd-Ag alloy membranes and their application in membrane reactors for hydrogen production and purification

Pd-Ag based membranes, self-supported and supported on porous α-Al2O3, have been studied for hydrogen selective separation. In the case of the self-supported membranes the Pd-Ag permeator tube was prepared by cold-rolling and diffusion welding technique; magnetron sputtering technique was employed for the synthesis of the membrane supported on porous α-Al2O3. The results have shown that the self supported Pd-Ag membranes are infinitively H2-selective and the H2-permeation rate through this membrane is in accordance with Sieverts´ law for detect-free meal membranes; hence, an ultra-pure hydrogen stream can be obtained. The Pd-Ag membrane supported on porous α-Al2O3 is not completely selective towards H2, but requires much less metal since it is much thinner (ca. ~50 vs. 1 µm). In this work, it was studied the water-gas shift on Pd-Ag membrane reactor, but it was also illustrated another application of palladium membranes, in the ethanol steam reforming. The use of the self-supported Pd-Ag membrane leads to enhance the H2 yield in both reactions, providing much better performances than conventional reactors.Patricia Pérez is grateful to Fundação para a Ciência e a Tecnologia (FCT) for the doctoral grant (reference: SFRH/BD/73673/2010). The authors also acknowledge financing from FCT through the project PTDC / EQU -ERQ/098730/2008