Liquid–liquid equilibria for quaternary systems of imidazolium based ionic liquid + thiophene + pyridine + iso-octane at 298.15 K: Experiments and quantum chemical predictions

In this work, 1-ethyl 3-methylimidazolium acetate [EMIM][OAc], 1-ethyl 3-methylimidazolium ethylsulphate [EMIM][EtSO4] and 1-ethyl 3-methylimidazolium methylsulphonate [EMIM][MeSO3] were investigated as green solvents for the simultaneous separation of thiophene and pyridine from iso-octane at 298.15 K and atmospheric pressure. The liquid–liquid equilibrium (LLE) data for the quaternary mixture of 1-ethyl 3-methylimidazolium acetate (1) + thiophene (2) + pyridine (3) + isooctane (4), 1-ethyl 3-methylimidazolium ethylsulphate (1) + thiophene (2) + pyridine (3) + isooctane (4) and 1-ethyl 3-methylimidazolium methylsulphonate (1) + thiophene (2) + pyridine (3) + isooctane (4) systems were experimentally determined at ambient conditions. The effectiveness of the simultaneous extraction of thiophene and pyridine from iso octane was evaluated by selectivity and distribution coefficient values. The experimental tie-line data were accurately correlated with the non-random two liquid (NRTL) and UNIversal QUAasi-Chemical (UNIQUAC) models, which provides a good correlation of the experimental data with root mean square deviation (RMSD) values lesser than unity for all the studied systems. The reliability of experimental data was further ascertained by applying the Quantum chemical based COnductor like Screening MOdel for Real Solvents (COSMO-RS) model. The predictions were compared with the RMSD, i.e. 7.4% ([EMIM][OAc]), 4.49% ([EMIM][EtSO4]) and 8.26% ([EMIM][MeSO3]). These results show that [EMIM][OAc], [EMIM][EtSO4] and [EMIM][MeSO3] ionic liquid can be used as an alternative solvent for the simultaneous separation of thiophene and pyridine from hydrocarbon stream via LLE processes at ambient conditions.

► Use of [EMIM][OAc], [EMIM][EtSO4] and [EMIM][MeSO3].
► Simultaneous extraction of thiophene and pyridine from isooctane.
► Application of NRTL, UNIQUAC and COSMO-RS model.