Phase equilibrium for ionic semiclathrate hydrate formed with CO₂, CH₄, or N₂ plus tetrabutylphosphonium bromide

The article describes the equilibrium conditions for the semiclathrate hydrates formed in the following three ternary systems, CO₂+tetrabutylphosphonium bromide+water system, CH₄+tetrabutylphosphonium bromide+water system, and N₂+tetrabutylphosphonium bromide+water system. The experiments were performed at temperatures between 282.6 and 291.6K, at pressures between 0.15 and 5.10MPa with tetrabutylphosphonium bromide aqueous solution of w_TBPB=0.35, where w_TBPB denotes the mass fraction of tetrabutylphosphonium bromide, respectively. The equilibrium pressure at a given temperature was lower in the order of CO₂, CH₄ and N₂ thereby indicating the possibility of capturing CO₂ from the CH₄+CO₂ and N₂+CO₂ mixtures.