Thermodynamic and structural analyses of pure SF6 and SF6+N2 gas hydrates formed in various reaction media

Abstract

SF6 is one of the most potent greenhouse gases due to its remarkably high global warming potential which is 23900 times larger than that of CO2 and long lifetime in the atmosphere. Accordingly, SF6 should be captured from the emission sources of industries. In this study, hydrate-based SF6 separation was suggested as a novel method. Three-phase (hydrate (H)-liquid water (Lw)-vapor (V)) equilibria of pure SF6 and SF6+N2 hydrates formed in various reaction media (bulk water, hollow silica, and porous silica gel) were measured to determine hydrate stability conditions. The inclusion of SF6 in the hydrate phase resulted in significant equilibrium pressure reduction. The reaction media used in this study did not affect the stability conditions of SF6 and SF6+N2 hydrates. The separation efficiency of SF6 was examined through gas chromatography. The structures of the pure SF6 and SF6+N2 hydrates were identified via powder X-ray diffraction and were found to be sII for all cases. The experimental results obtained in this study will be helpful to understand the hydrate-based SF6 separation process.