Hydrogen purification from underground storage via pressurized adsorption: Impact of adsorbent properties and operating parameters on methane separation

Abstract

This study compared methane adsorption/desorption for hydrogen purification over a pressure range of 1–60 bar at room temperature. The main aim of this work was comparing methane adsorption performance of two commercial activated carbons (GAC and CAC) with different porous properties. GAC, with lower mesoporosity (24 %) and a surface area of 896 m²/g, demonstrated superior methane capacity and longer breakthrough times at high pressures and low CH₄ concentrations. Conversely, CAC, with higher mesoporosity, exhibited faster adsorption kinetics, especially at lower pressures and higher CH₄ concentrations. The Gompertz model best described dynamic adsorption, while the Bohart-Adams capacity was 0.44 kmol/m³ for CAC and 0.63 kmol/m³ for GAC at 60 bar. Langmuir and BET models showed a maximum monolayer capacity of 4 mmol/g for GAC, with an isosteric heat of 15.48 kJ/mol from the Dubinin-Radushkevich model. Optimal desorption used a H₂ purge-to-feed ratio of 0.16 and 4 bara pressure.