Study on Metal Hydride Performance for Purification and Storage of Bio-H₂

Abstract

Biomass-derived hydrogen (Bio-H₂) has been attracting much attention as a low environmental load type of hydrogen. Among the potential applications of Bio-H₂, use as a fuel for polymer electrolyte membrane fuel cells (PEMFCs) would require the removal of contaminants. Therefore, we propose the use of metal hydride for the purification and storage of Bio-H₂. Metal hydride can store a larger volumetric amount of hydrogen than that under high-pressure or liquefied, and the hydrogenate is processed at near atmospheric pressure and room temperature. In addition, by exploiting the selective hydrogen absorption properties of metal hydride, we have successfully reduced the concentration of methane as well as carbon monoxide and carbon dioxide in the hydrogen using a lanthanumrich mischmetal alloy, the storage performance of which was evaluated in our previous study. Pressure swing adsorption was used to reduce the contaminant concentration, which was measured as 3% methane. For practical application, the influence of methane on the hydrogen absorption performance of the metal hydride is examined and the hydrogen recovery rate over the hydrogen absorption and desorption processes is evaluated.