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

Abstract

Thermophysical properties, namely, density (ρ) and speed of sound (u) of binary mixtures of 1-butyl-3-methylimidazolium methyl sulphate [BMIM][MeSO₄] ionic liquid (IL), with acetic acid or propionic acid have been measured in the mole fraction range from 0.1 to 1.0 at temperature ranging from 293.15 to 313.15 K at a 5 K interval, under atmospheric pressure of 101 kPa. From these measured values, the derived thermodynamic parameters, such as, isentropic compressibility (κ_s), deviation in isentropic compressibility (Δκ_s), excess molar volume (V<img src='http://www.niscair.res.in/jinfo/em2.gif' border=0>) and intermolecular free length (L_f) have been calculated. It is observed that V<img src='http://www.niscair.res.in/jinfo/em2.gif' border=0> and Δκ_s decrease with increasing the temperature. Furthermore, these values are negative in the whole range of binary compositions. The measured data and variations in derived thermodynamic values suggest that significant interactions occur when the IL forms a binary mixture with carboxylic acids. These derived thermodynamic parameters (V<img src='http://www.niscair.res.in/jinfo/em2.gif' border=0>, L_f and Δκ_s) are correlated byusing the Redlich-Kister polynomial equation to generate binary factors and standard errors.