Liquid-liquid equilibrium and modelling insight: molecular interaction analysis of water + methanol + dimethyl...

In this work, ternary liquid-liquid equilibrium (LLE) was measured for water (H₂O) + dimethyl carbonate (DMC) + 1-ethyl-3-methylimidazolium ([Emim][MeSO₃]) and methanol (MeOH) + DMC + [Emim][MeSO₃] mixtures at 293.15 K at atmospheric pressure. LLEs were modelled utilizing COnductor-like Screening MOdel for Real Solvents (COSMO-RS) and non-random two-liquid (NRTL) models. COSMO-RS was utilized to provide insight into interactions at molecular level through chemical potentials corresponding to the sigma profile and predicted excess enthalpies. The nature of COSMO-RS accuracy was qualitative, while NRTL had an accuracy of 0.013 and 0.030 root mean square deviation for LLE of H₂O + DMC + [Emim][MeSO₃] and MeOH + DMC + [Emim][MeSO₃] mixtures, respectively. Hydrogen bonding behavior explained favorable [Emim][MeSO₃]-H₂O and -MeOH interactions. These interactions might be mainly due to strong hydrogen bond donor interaction between [MeSO₃] anion-H₂O and -MeOH. The unfavorable [Emim][MeSO₃]-DMC interaction was explained by electrostatic repulsion, possibly arising from repulsion between [MeSO₃] anion and DMC oxygens.