Experimental and modelling of the vapor-liquid equilibria of [Cnmim]Br(n = 2, 3, 4) + H2O systems

Abstract

Mixtures of ionic liquids (ILs) and water are considered as promising working pair fluids for absorption refrigeration systems (ARS), and they have been the subject of intensive research in recent years. The performance of these mixtures as working fluids directly depends on the phase behavior and thermodynamic properties. In this work, the vapor-liquid equilibrium (VLE) data of three binary systems of 1-ethyl-3-methylimidazolium bromide and water ([C2mim]Br + H2O), 1-propyl-3-methylimidazolium bromide and water ([C3mim]Br + H2O) and 1-buthyl-3-methylimidazolium bromide and water ([C4mim]Br + H2O) have been measured by using the boiling method at pressures ranging from 7.96kPa to 50.10kPa and mole fractions of ILs ranging from 0.02 to 0.50. The thermodynamic models NRTL and e-NRTL are used to correlate the experimental data and a good agreement between the models and the data is obtained. It is found from VLE data that the addition of ILs in water leads to a dramatic decrease of the saturated vapor pressure of the system, and the systems exhibit a high deviation from Raoult's law. Therefore, the three IL + water binary systems have a great potential as working pairs for ARS. In addition, shorter alkyl chains of the IL cation leads to a stronger ability ([C2mim]Br+ > [C3mim]Br+ > [C4mim]Br+) to absorb water.