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.