Phase equilibria for the ionic semiclathrate hydrate formed with tetrabutylphosphonium chloride plus CO2, CH4, or N2

This paper presents the phase equilibrium conditions for the semiclathrate hydrates in the systems of (CO2, CH4 or N2 + tetrabutylphosphonium chloride + water). The experiments were performed by isochoric method within the range of temperature from (283.0 to 291.8) K and pressure from (0.19 to 5.02) MPa with mass fraction of tetrabutylphosphonium chloride aqueous solution 0.36. The presence of tetrabutylphosphonium chloride increases the phase equilibrium temperatures of CO2, CH4 or N2 hydrates by at least 8 K at a given pressure. The gas separation performance in tetrabutylphosphonium chloride hydrate systems was compared with that in other semiclathrate hydrate systems, based on the measured phase equilibrium conditions.