CO2 capture from CH4–CO2 mixture by gas–solid contact with tetrahydrofuran clathrate hydrate

Abstract

This study evaluated the CO2 separation characteristics for gas–solid contact between CH4 and CO2 mixtures and stoichiometric tetrahydrofuran (THF) hydrate to elucidate system temperature and pressure effects on clathrate hydrate gas separation performance. The CO2 molecules in the system were incorporated selectively into the hydrate phase during the gas–solid contact at lower temperatures. The CO2 selectivity for gas uptake was higher at higher-pressure conditions at a constant temperature. Results suggest that greater driving force for gas uptake to stoichiometric THF hydrate crystals contributes to improved CO2 selectivity from the CH4–CO2 mixture. Effects of the driving force on CO2 separation from CH4–CO2 mixture contrasted against those of gas–liquid systems using THF aqueous solution or liquid water. The different effects are expected to derive from differences in gas uptake process between gas–solid and gas–liquid systems and differences in cages for competition for gas uptake.