Vapor Pressure Measurement for the Ternary System of Water, Lithium Bromide, and 1-Ethyl-3-methylimidazolium Acetate

To improve the performance of an absorption system, ionic liquids (ILs) have been chosen as additives to conventional working fluid (lithium bromide aqueous solution) in recent years. In this paper, 1-ethyl-3-methylimidazolium acetate ([Emim]Ac) was added to lithium bromide aqueous solution (mass ratio LiBr/[Emim]Ac = 3) to measure the vapor–liquid equilibrium (VLE) data of the ternary system. The experiment was conducted by means of boiling point method, at temperatures between 303.94 K and 405.41 K and mass fractions of absorbent between 0.20 and 0.60. The experimental data were regressed using an Antoine-type equation, and the average absolute relative deviation (AARD%) between the experimental and calculated values was 0.34%, which showed excellent accuracy and consistency. The experimental ternary system was compared with the conventional LiBr + H2O system and two other ternary systems from the literature; the result revealed that the experimental ternary system had lower vapor pressures, which will benefit the process of releasing latent heat in absorption cycles.