Thermodynamics Research Center / ThermoML | Fluid Phase Equilibria

ABSTRACT

A number of applications with ionic liquids (ILs) and hydrofluorocarbon gases have recently been proposed. Detailed phase equilibria and modeling are needed for their further development. In this work, vapor.liquid equilibrium, vapor.liquid.liquid equilibrium, and mixture critical points of imidazolium ionic liquids with the hydrofluorocarbon refrigerant gas, 1,1,1,2-tetrafluoroethane (R-134a) was measured at temperatures of 25 .C, 50 .C, 75 .C and pressure up to 143 bar. The ionic liquids include 1-hexyl-3-methyl-imidazolium bis(trifluoromethylsulfonyl)amide ([HMIm][Tf2N]), 1-hexyl-3-methylimidazolium hexafluorophosphate ([HMIm][PF6]), and 1-hexyl-3-methyl-imidazolium tetrafluoroborate ([HMIm][BF4]). The effects of the anion and cation on the solubilitywere investigated with the anion having greatest impact. [HMIm][Tf2N] demonstrated the highest solubility of R-134a. The volume expansion and molar volume were also measured for the ILs and R-134a. The Peng.Robinson Equation of State with van derWaals 2-parameter mixing rule with estimated IL critical pointswere employed to model and correlate the experimental data. The models predict the vapor.liquid equilibrium and vapor.liquid.liquid equilibrium pressure very well. However, the mixture critical points predictions are consistently lower than experimental values.