CHAPTER 4: Ultrathin and Thin Film Pd/Ag Membranes for Hydrogen Production

The successful implementation of membrane reactors for hydrogen production heavily depends on: (i) the advances in the production of thin membranes with high hydrogen fluxes and high hydrogen permselectivity resistance to high temperatures and long-term stability at affordable costs; and (ii) the design of innovative reactor concepts to avoid (or reduce) mass and heat transfer resistances. The integration of membranes in multifunctional reactors creates additional requirements for membranes as interactions at different levels between the catalyst/module and the membrane surface can occur. In this chapter, we describe the latest developments on thin film (<5 µm) Pd-based membranes and achievements in membrane reactors for the production of H₂ from different feedstocks. The trend in Pd-based membranes development is toward thinner membranes, particularly binary and ternary alloys. The requirements to be fulfilled by H₂ permselective membranes for their integration in packed or fluidized bed membranes reactors are discussed as well as the selection of the material for the supports, interdiffusion barriers, and selective layers. Particular attention is paid to improvements on the sulfur resistance of Pd-based membranes, resistance to hydrogen embrittlement, and stability at high temperature.