Thermophysical and thermodynamic properties of binary liquid systems of [BMIM]+[MeSO4]−ionic liquid with carboxylic acids.

Abstract

The thermophysical properties of binary mixtures of 1-butyl-3-methylimidazolium methyl sulphate [BMIM]⁺[MeSO₄]⁻ ionic liquid (IL), with acetic acid or propionic acid were determined via measurements of density (ρ) and speed of sound (u) in the range of mole fractions from 0.1 to 1.0 at various temperatures from T = (293.15 - 313.15) K at 5 K interval under atmospheric pressure of 0.1 MPa. From these measured values, the thermodynamic parameters, namely, isentropic compressibility ( ), deviation in isentropic compressibility (Δ ), excess molar volume ( ) and intermolecular free length ( ) were computed. It was observed that  and Δ  decreased with increasing the temperature. Furthermore, their values were negative throughout the whole range of binary compositions. The measured data and variations in derived thermodynamic values suggest that significant interactions occur when the ionic liquid forms a binary mixture with a carboxylic acid. These derived thermodynamic parameters ( ,  and Δ ) were correlated using the Redlich-Kister polynomial equation to generate binary factors and standard errors.