Carbon dioxide solubility in ionic liquids: [Guad-(6,6),(1,1),(1,1)][DCA] and [Guad-(6,6),(1,1),(1,1)][TCM] at high pressure

Abstract

This work is the continuation of our study of the applicability of two new synthesized ionic liquids (ILs) for the absorption of carbon dioxide using the "static–synthetic" method. Experimental vapor–liquid equilibrium (VLE) data were obtained for three binary systems of IL + CO2 at (298.15, 313.15 and 323.15) K and pressures ranged from 0.1 MPa to 2 MPa. New solubility data are presented for two new ILs, 2,2-dihexyl-1,1,3,3-tetramethylguanidinium dicyanamide, [Guad-(6,6),(1,1),(1,1)][DCA] and 2,2-dihexyl-1,1,3,3-tetramethylguanidinium tricyanomethanide, [Guad-(6,6),(1,1),(1,1)][TCM]. The CO2 solubility in these ILs was higher than ILs with imidazolium and pyrrolidinium cations and [DCA] and [TCM] anions presented in the literature. The experimental phase equilibrium data were modelled using the Peng-Robinson equation of state and extended Van der Waals mixing rule. Additionally, the glass transition temperature, heat capacity change at the glass transition temperature, density and viscosity of new ILs were measured.