Experimental measurement of gas hydrate phase equilibria in the CO2+TBPB + THF system in the presence and absence of NaCl aqueous solution

In this study, the effects of mixed promoters of tetra n-butyl phosphonium bromide (TBPB) and tetrahydrofuran (THF) in the presence and absence of NaCl aqueous solution on the formation of CO2 hydrates are investigated. The experimental data, which have been obtained using the isochoric pressure-search method, are reported in the temperature and pressure ranges of (278 to 295) K and (1.1 to 4.5) MPa, respectively. The results show that addition of the (TBPB + THF) mixture to the system causes a synergism of gas hydrate formation promotion effect compared to the pure water system. The effect of TBPB and NaCl in different concentrations on the equilibrium phase behavior of corresponding hydrates have been also studied. It is found that the thermodynamic inhibition effect of NaCl increases as a function of hydrate formation pressure. In addition, it is observed that addition of 0.03 mass fraction of NaCl to the 0.05 mass fraction TBPB aqueous solution improves CO2 hydrate formation conditions leading the phase diagram shift to more stable regions.