Preservation of CO2 hydrate under different atmospheric conditions

A comprehensive understanding of the preservation of gas hydrates is important from a physicochemical point of view, and for practical applications such as gaseous CO2 storage and transport in the form of solid hydrate. We measured dissociation rates of CO2 hydrate under different gases, such as CO2, N2 and Xe, at 0.1 MPa and studied the effects of ambient gas pressure on CO2 hydrate-dissociation rate by powder X-ray diffraction method. The crystallographic structure of CO2 hydrate was refined to estimate the amount of CO2 gas in the hydrate. CO2 hydrates showed a self-preservation phenomenon, even in CO2 + N2 mixed gases such as flue gas, and it is estimated that the self-preserved CO2 hydrate holds more than 150 times the volume of hydrate crystal at 0.1 MPa and temperatures just below the melting point of ice. Small amounts of gas molecules, such as Xe, disturb the onset of CO2 hydrate self-preservation.