Vapor Pressure Measurement for the Water + 1,3-Dimethylimidazolium Chloride System and 2,2,2-Trifluoroethanol + 1-Ethyl-3-methylimidazolium Tetrafluoroborate System

Abstract

The combination of ionic liquids (ILs) and refrigerants to be used for absorption cooling has been proposed in recent years. In this paper, the boiling point method was adopted to measure the vapor pressure for water + 1,3-dimethylimidazolium chloride ([DMIm]Cl) and 2,2,2-trifluoroethanol (TFE) + 1-ethyl-3-methylimidazolium tetrafluoroborate ([EMIm]BF4) systems. The measured ranges of the vapor pressure and the mass fraction of ILs were from (1 to 100) kPa and from 0.4 to 0.85 for the H2O + [DMIm]Cl system and from (3 to 100) kPa and from 0.35 to 0.9 for the TFE + [EMIm]BF4 system, respectively. The Antoine type equation and the NRTL model were selected to correlate the experimental data. For the H2O + [DMIm]Cl system and the TFE + [EMIm]BF4 system, the average relative deviations in pressure of the Antoine type equation are 0.84 % and 0.61 % respectively, and the average relative deviations in pressure of the NRTL model are 2.42 % and 1.65 %, respectively. Particularly, the parameters α in the NRTL model for the two systems in this work are minus. The activity coefficients of H2O and TFE in the liquid phases of H2O + [DMIm]Cl and the TFE + [EMIm]BF4 systems are much lower than 1. It shows that the H2O and TFE are strongly affinitive to the relative ILs selected in this work, and the two systems might be used as alternative working fluids for absorption cooling cycles.