Experimental investigation of incipient equilibrium conditions for the formation of semi-clathrate hydrates from quaternary mixtures of (CO2 + N2 + TBAB + H2O)

The three-phase (vapour + liquid + solid) equilibrium conditions for semi-clathrates formed from three mixtures of (CO2 + N2), in aqueous solutions of tetra-butyl ammonium bromide (TBAB), were measured in an isochoric reactor. The experiments were conducted at temperatures between (281 and 290) K, at pressures between (1.9 and 5.9) MPa and in aqueous TBAB solutions of wTBAB = (0.05, 0.10, and 0.20). The experimental results obtained in this study were compared with previously obtained results for gas hydrates, formed from the same three mixtures of (CO2 + N2) and it was observed that semi-clathrates formed at a substantially lower pressure than did gas hydrates.

► Thermodynamic equilibrium data for TBAB semi-clathrates formed from gas mixtures of CO2/N2.
► Isochoric technique used for determining the equilibrium point.
► The amount of CO2 in the gas phase decreased during the experiment.
► Semi-clathrates were found to form at milder conditions than gas hydrates.