High-pressure phase behaviors of CO2 + 1-propanol + ionic liquid ternary systems

In this work, the vapor–liquid equilibria for CO2 + 1-propanol + 1-butyl-3-methylimidazolium trifluoromethanesulfonate ([Bmim][Tfo]) and CO2 + 1-propanol + 1-butyl-3-methylimidazolium terafluoroborate ([Bmim][BF4]) systems were measured at 318.15 K and at 9.0 MPa, 13.0 MPa, and 17.0 MPa. It was demonstrated that the anions of the ILs affected the phase behaviors of the ternary systems considerably. CO2 + 1-propanol + [Bmim][Tfo] system has smaller two-phase region than CO2 + 1-propanol + [Bmim][BF4] system at all the pressures. Increase of pressure resulted in decrease of the two-phase regions. The solvent power of supercritical carbon dioxide (scCO2) + 1-propanol mixture for the ILs increased with increasing 1-propanol concentration, and the solubility of the ILs in the vapor phases was considerable as the mole fraction of 1-propanol in the vapor phase was large enough. The distribution coefficient of 1-propanol in CO2 + 1-propanol + [Bmim][Tfo] is smaller than that in CO2 + 1-propanol + [Bmim][BF4].