Experimental Verification of Methane Replacement in Gas Hydrates by Carbon Dioxide

Abstract

If the conversion of methane hydrate to carbon dioxide hydrate with the net recovery of methane could occur, this would be quite attractive as an innovative method of both methane production and carbon dioxide storage. In this study, the swapping phenomenon occurring in gas hydrates and its potential application to carbon dioxide sequestration was demonstrated through stability condition measurements and ¹³C NMR spectroscopic analysis. The hydrate phase equilibria for the ternary CH₄ + CO₂ + water mixtures were measured to determine the hydrate stability conditions of the mixed gas hydrates. Through ¹³C NMR measurements, it was found that carbon dioxide has a preference for the large cages in the sI hydrate and carbon dioxide is a relatively poorer guest when carbon dioxide competes with methane in occupying the small cages of the sI hydrate. From the NMR spectra and direct dissociation, it wasconfirmed that about 70% of methane is recoverable after reaction with carbon dioxide.