Hydrogen Direct Adsorptive Separation: Development Status and Trends

Metal hydrides are promising hydrogen storage materials. As a result of their high volume adsorption density and excellent adsorption selectivity, they have also been proposed for use in hydrogen purification; that is, as hydrogen adsorbents for the direct separation of hydrogen from complex mixed gases. In this review, the properties of metal hydride adsorbents are reviewed, including their thermodynamic properties and susceptibility to poisoning by impurity gases. The differences and similarities between common pressure swing adsorption (PSA) techniques and PSA using metal hydride adsorbents are analyzed on the basis of which the principles for cycle procedure design are given. The potential utility of metal hydrides for hydrogen purification has been demonstrated by some lab- and pilot-scale tests, which are also introduced here. On the basis of this review and analysis, elevated-temperature PSA techniques using metal hydrides appear to be a feasible direction for the development of hydrogen purification processes.