Density, Viscosity, and Vapor–Liquid Equilibrium of the Ternary System Water–1-Ethyl-3-methylimidazolium Acetate–1-Ethyl-3-Methylimidazolium Trifluoromethanesulfonate

Abstract

Mixtures of ionic liquids and water offer an interesting opportunity to replace corrosive and/or partly miscible working pairs like lithium bromide−water in absorption chillers. Such an alternative must feature both a high depression of the water vapor pressure and a low viscosity to be feasible. However, hitherto published literature data of binary systems of ionic liquids and water fulfill only one of the two criteria. A mixture of two different ionic liquids may exhibit a solution for this dilemma. In this work, a ternary system consisting of water, 1-ethyl-3methylimidazolium acetate ([EMIm][OAc], high reduction of vapor pressure), and 1-ethyl-3-methylimidazolium trifluoromethanesulfonate ([EMIm][OTf], low viscosity) was investigated. Experimental data for density, dynamic viscosity, and vapor−liquid equilibrium in the temperature range from 293.15 to 353.15 K at water mass fractions between 5% and 20% and different mass fractions of [EMIm][OTf] are presented. The viscosity of the ternary mixture measured with a falling ball viscometer range between 90.9 and 1.9 mPa•s at a relative mean deviation below 3.6%. The density measured with a glass pycnometer range between 1087 and 1285 kg•m −3 at a relative mean deviation of 0.33%. The water vapor pressure measured by infrared spectroscopy range between 293 and 15164 Pa. The relative mean deviation is below 15.1%. The water vapor pressure data are correlated using a nonrandom two liquid model. The thermodynamic properties show that the considered ternary system can indeed be used as a suitable working mixture in absorption refrigerators.

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

“…To make sure that the vapor pressure of the system was low enough, LiBr/[Emim]Ac mass ratio was set as 3 . Previous VLE researches of [Emim]Ac were mostly on its mixtures with water, glycol, and ILs. − By far, there is no literature on the VLE study of [Emim]Ac plus H 2 O plus LiBr system. To complete the VLE data of the ternary system and investigate its feasibility as an alternative working fluid in absorption cycles is the very motivation of our work.…”