Recovery of low-concentration hydrogen using alloy LaNi5 based pressure swing adsorption

A cost-effective strategy for long distance hydrogen transportation entails its integration into existing natural gas pipelines. The demand for efficient separation of the minor component hydrogen poses a challenge for post co-transportation gas treatment to meet the specifications of various industrial applications. While porous materials for selective H2 adsorption are extremely rare, certain metal alloys known for their hydrogen storage property via reversible hydriding/dehydriding reaction show great promise for selective H2 separation. Despite the unfavorable and harsh reaction conditions of most metal hydrides, LaNi5 displays unique H2 adsorption properties at moderate temperatures and pressures, rendering it a promising material for hydrogen separation. Our experimental measurements reveal that LaNi5 exhibits rapid H2 update kinetics and a high adsorption capacity of 6.8 mol/kg at 25 °C and 600 kPa. Preliminary experiments based on a single pressure vessel were conducted to demonstrate that hydrogen gas can be successfully enriched from 56 % to 96.57 % via a roundtrip (adsorption and desorption) process. To explore the full potential of this process, a pressure swing hydride process akin to classical vacuum pressure swing adsorption (VPSA) was designed to recover the minor component H2 from the mixture, achieving high-purity CH4 and H2 (both >99 %) products at the same time with recoveries exceeding 90 %. The findings of this study underscore the feasibility and efficacy of metal hydride pressure swing adsorption to generate high-purity hydrogen and methane gases for the energy industry.