Vapor Pressure Measurement of Ternary Systems LiCl + [Emim]Cl + H2O, LiBr + [Emim]Cl + H2O, and LiCl + [Emim]Br + H2O

1-Ethyl-3-methylimidazolium chlorine ([Emim]­Cl) and 1-ethyl-3-methylimidazolium bromide ([Emim]­Br) as an additive to working fluid [lithium bromide aqueous solution (H2O/LiBr) and lithium chloride aqueous solution (H2O/LiCl)] of absorption cycles were proposed. The vapor pressure of H2O + LiCl + [Emim]Cl (mass ratio LiCl/[Emim]Cl = 2) in the temperature from 314.79 to 435.48 K, H2O + LiCl + [Emim]Br (mass ratio LiCl/[Emim]Br = 2) in the temperature from 317.62 to 431.27 K, and H2O + LiBr + [Emim]­Cl (mass ratio LiBr/[Emim]Cl = 2) in the temperature from 303.10 to 409.91 K was measured by the boiling point method. The mass fractions of the absorbent were from 0.30 to 0.60. The experimental data were regressed using the Antoine-type equation, and the average absolute relative deviation (AARD %) between the experimental data and calculated values of three systems was 0.44, 0.51, and 0.54%. Compared with that of the previously reported ionic liquids, ([Emim]­Ac) as an absorbent for LiBr + H2O, vapor pressure of these four systems follows the order LiCl + [Emim]Cl + H2O < LiCl + [Emim]Br + H2O < LiBr + [Emim]Cl + H2O < LiBr + [Emim]­Ac + H2O. The proposed ternary systems have better water affinity and can be promising alternative working fluids in the absorption cooling system.