Experimental and Cubic Plus Association Equation of State modelling study of phase equilibria of 1-Ethyl-3-methylimidazolium methanesulfonate + methanol + dimethyl carbonate + water binary and quaternary mixtures: The role of ionic liquids vapor pres

• The VLE was measured for methanol + water + DMC + [Emim][MeSO 3 ] quaternary mixture. • The CPA successfully modelled phase equilibria and [Emim][MeSO 3 ] vapor pressure. • CPA parameters fitted with [Emim][MeSO 3 ] vapor pressure enhanced modelling accuracy. Understanding the phase equilibria of ionic liquids (ILs) in mixtures related to dimethyl carbonate (DMC) synthesis is important for enhancing the yield of DMC by absorbing the water produced during the reaction. 1-Ethyl-3-methylimidazolium methanesulfonate ([Emim][MeSO 3 ]) shows promise as a water absorbent for this application. This study investigates the phase equilibria of binary and quaternary mixtures containing [Emim][MeSO 3 ], water, methanol, and DMC at 102 kPa. Vapor-liquid equilibrium (VLE) and liquid-liquid equilibrium (LLE) were measured using the circulation still and cloud point method. The Cubic Plus Association (CPA) equation of state (EOS) was used for modelling, using two parameterization strategies for [Emim][MeSO 3 ]. The first strategy used density and vapor pressure (CPAρP), whereas the second strategy used density and isobaric heat capacity (CPAρC). The CPAρP parameter set demonstrated generally higher accuracy in modelling binary and quaternary mixtures. It slightly improved VLE modelling of the H 2 O + [Emim][MeSO 3 ] mixture and enhanced LLE modelling of DMC + [Emim][MeSO 3 ] mixture over the CPAρC parameter set, with AAD values of 0.01 and 0.12 for the mole fraction of [Emim][MeSO 3 ]. For the quaternary mixture, the CPAρP parameter set outperformed the CPAρC parameter set in modelling the relative volatility of methanol with AAD values of 0.11 and 0.17. The results provide insights into phase equilibria modelling for mixtures involving [Emim][MeSO 3 ], water, methanol, and DMC. Including the vapor pressure of [Emim][MeSO 3 ] in the parameter regression improved the accuracy of the CPA model enhancing its ability to realistically simulate phase equilibria, which is essential for designing water absorbent for DMC synthesis.