Alternatives to palladium in membranes for hydrogen separation: Nickel, niobium and vanadium alloys, ceramic supports for metal alloys and porous glass membranes

Palladium-based membranes have been widely studied in terms of their use in hydrogen separation processes. The high permeability and selectivity of these membranes mean that they are suitable for a variety of applications, although these are limited by the high cost of the precious metal. In order to reduce the cost, several researchers have considered the use of thin metal film membranes, as well as low-cost metals and their alloys, as an alternative to Pd. This chapter focuses on the development of membranes based on metals, such as Ni, Nb, V and Ti, which are promising substitutes for Pd alloys. The main issues related to the synthesis of these membranes and the effect of alloying on their chemical and physical properties are described. Properties relating to hydrogen solubility and permeability, as well as embrittlement under hydrogenation cycling, are also reported. Finally, this chapter discusses ceramic and glass porous membranes. Ceramic porous membranes are examined in terms of their applications as support for new metal alloys, while the use of glass porous membranes in gas separation and in membrane reactors is treated in detail.