Theoretical study of stability zones of mixed H2 + CO2 gas hydrates CS-I and CS-II

Abstract

Using the original approach that utilizes statistical thermodynamic theory that has been developed in our group the phase p-T diagram and hydrate phase composition have been calculated for “CO2 + H2 + H2O”. Depending on the CO2 content in the gas phase two hydrates types can be formed: CS-I and CS-II. It has been found that increasing CO2 content in the gas phase drastically reduces hydrate formation pressure and in the same time reduces hydrogen uptake by the hydrate. While pure H2 hydrates have CS-II structure, addition of more than 2 mol.% of CO2 into the gas phase makes CS-I hydrate structure more stable, that displays worse maximum hydrogen content. These results could be helpful for practical use of hydrates for efficient CO2 utilization and H2 transportation.