Density, viscosity and phase equilibria study of {ethylsulfate-based ionic liquid + water} binary systems as a function of temperature and composition

• The [EMPIP][EtSO4], [EMMOR][EtSO4], [EMPYR][EtSO4] and its aqueous mixtures have been studied.
• The density, dynamic viscosity and SLE have been determined.
• The excess molar volumes and viscosity deviations have been calculated.
• The NRTL, Wilson, UNIQUAC, Redlich–Kister and VFT equations have been used to correlate the experimental data.

This paper is a continuation of our investigation on physicochemical and thermodynamic properties of ionic liquids and its aqueous solutions. In this work the density, ρ and dynamic viscosity, η have been determined for binary mixtures of the ionic liquids: 1-ethyl-1-methyl-piperidinium ethylsulfate, [EMPIP][EtSO4], 1-ethyl-1-methylmorpholinium ethylsulfate, [EMMOR][EtSO4] and 1-ethyl-1-methylpyrrolidinium ethylsulfate, [EMPYR][EtSO4] with water at wide temperature and composition range at atmospheric pressure. From experimental values of the density, ρ and dynamic viscosity, η the excess molar volumes, VE and viscosity deviations, Δη were calculated and correlated using Redlich–Kister polynomial equation. The (solid + liquid) phase equilibria, SLE for the tested binary mixtures have been determined by well-known dynamic method at a wide range of composition and temperature at atmospheric pressure. For comparison, the SLE data for {[EMPYR][EtSO4] + water} binary mixtures have been determined using DSC technique. The experimental SLE data have been correlated by means of NRTL, UNIQUAC and Wilson equations. Additionally, the basic thermal properties of the pure ILs, that is, the glass-transition temperature, Tg,1 as well as the heat capacity at the glass-transition temperature, ΔCp(g),1, melting temperature, Tm and enthalpy of melting, ΔmH have been measured using a differential scanning microcalorimetry technique (DSC). Decomposition of the ILs was detected by the simultaneous TG/DTA experiments. The choice of the ionic liquids allowed to determine the effect of cation structure on physicochemical and thermodynamic properties.