A study of isotopic exchange of hydrogen and deuterium in a LaNi₃Al₂ hydride bed

An experimental study was carried out on the isotopic exchange of hydrogen and deuterium in a LaNi₃Al₂ hydride bed. The exchange capacity of the LaNi₃Al₂ hydride for deuterium, the overall mass-transfer coefficient and the height equivalent to a theoretical plate (HETP) were obtained from the analysis of effluent curves for a pulse or step change of an influent deuterium concentration. The exchange capacity for deuterium was found to be almost constant between 200 and 300°C and was around 1.7 in a D/metal ratio. The rate of the isotopic exchange was independent of the total hydrogen pressure, and a value of 31.8 kJ/mol was obtained for its activation energy. The minimum HETP value obtained was 0.5 cm at 300°C and is smaller than that of a cryogenic distillation column for hydrogen isotopic separation.