Hydrate-based pre-combustion capture of carbon dioxide in the presence of a thermodynamic promoter and porous silica gels

Abstract

In this study, the feasibility of the hydrate-based pre-combustion capture of carbon dioxide in the presence of a thermodynamic promoter and porous silica gels was examined through stability condition measurements, gas uptake measurements, and microscopic analyses. When a fuel gas mixture of H-2 (60%) and CO2 (40%) was used for gas hydrate formation, the addition of tetrahydrofuran (THF) yielded significantly enhanced hydrate stability conditions. Silica gels with a nominal diameter of 100.0 nm demonstrated increased gas consumption during gas hydrate formation, indicating higher conversion of water into gas hydrate. With only one step of hydrate formation, CO2 concentrations of higher than 90% were achieved in the hydrate phase for all cases. It can be concluded that the hydrate phase composition is affected primarily by the cage occupancies of guest gases in the hydrate lattices whereas the vapor phase composition is strongly influenced by the conversion of water to gas hydrate and also partially by the cage occupancy of CO2 in the hydrate phase. From powder X-ray diffraction (PXRD) patterns and Raman spectra, it was confirmed that the H-2 (60%) + CO2 (40%) gas mixture forms structure I hydrate and the inclusion of THF induces the formation of structure II hydrate.