High pressure phase behaviour of carbon dioxide and two ionic liquids based on a benzyl functionalized cation

The high pressure phase behaviour of a CO2 and 1-benzyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide, [BzMeIM][NTf2], binary system was experimentally measured at high pressure up to about 13.5 MPa and at a temperatures range of 293.2-323.2 K. The solubilities were determined by measuring the bubble point pressure of the binary mixture comprising CO2 and an ionic liquid using a phase equilibrium apparatus including a high pressure variable-view cell. The effect of a benzyl functional group in different cations, imidazolium and pyridinium, on the high pressure phase behaviour of the CO2 and 1-benzylpyridinium bis(trifluoromethylsulfonyl)imide, [BzPY][NTf2], binary system was also investigated within similar temperature and CO2 mole fractions ranges. The experimental data correlated well with the Peng-Robinson equation of state. In general, higher CO2 solubilities were obtained in [BzPY][NTf2] than those in [BzMeIM][NTf2] at similar temperature and pressure. This may be attributed to the difference in aromaticity in pyridinium and imidazolium cations.