The Purification of Hydrogen

The purification or separation of hydrogen has traditionally been based on solid-state diffusion technology utilising noble metal membranes. The development of this technology, which has been centred around improved diffusion membrane materials based on the silver-palladium alloy system, is reviewed in this paper. It is shown that, despite the emergence of alternative techniques, diffusion technology based on silver-palladium membranes remains the most suitable technique for the production of high purity hydrogen, a product which is required increasingly in many high technology applications.