Quaternary (liquid + liquid) equilibria for systems of imidazolium based ionic liquid + thiophene + pyridine + cyclohexane at 298.15K: experiments and quantum chemical predictions

Abstract

1-Ethyl 3-methylimidazolium acetate [EMIM][OAc], 1-ethyl 3-methylimidazolium ethylsulfate [EMIM][EtSO₄] and 1-ethyl 3-methylimidazolium methylsulfonate [EMIM][MeSO₃] are found to be effective for the selective removal of a five member ring sulfur compound, viz. thiophene, and a six member ring nitrogen compound, viz. pyridine from a hydrocarbon, viz. cyclohexane at room temperature and atmospheric pressure. The liquid liquid equilibrium (LLE) data for the quaternary mixtures of ionic liquid (1) + thiophene (2) + pyridine (3) + cyclohexane (4) are experimentally determined. The experimental tie line data are successfully correlated with the Non Random Two Liquid (NRTL) and UNIversal QUAasi-Chemical (UNIQUAC) models, which provide a good correlation of the experimental data with root mean square deviation (RMSD) values less than unity for all the studied systems. The results suggest that the structure and size of the anion greatly affects the extractive performance of ionic liquids. The reliability of experimental data is ascertained by applying the quantum chemical based COnductor like Screening Model-Segment Activity Coefficient (COSMO-SAC) model. The goodness of the fit is determined by calculating the RMSD values. The RMSD values obtained for [EMIM][OAc], [EMIM][EtSO₄] and [EMIM][MeSO₃] are 10.4%, 8.1% and 12.2%, respectively.