Study on Liquid-Liquid Equilibrium Experiments and Correlation of Cyclohexane +Toluene + Imidazole Ionic Liquids Systems at several temperatures

Abstract In today's increasingly strong concept of sustainable development and environmental protection, it is of great significance to seek more environmentally friendly and safe separation technology. Toluene and cyclohexane are important organic solvents, and their separation and purification play important role in chemical industry, environmental protection, food, drug preparation and other fields. In this work, two ionic liquids (ILs) 1-butyl-3-methylimidazolium hexafluorophosphate ([BMIM][PF 6 ]) and 1-Hexyl-3-methylimidazolium hexafluorophosphate ([HMIM][PF 6 ]) were screened as extractants by COSMOthermX 2021 to separate toluene from cyclohexane. The liquid-liquid equilibrium (LLE) data of the ternary system for cyclohexane + toluene + [BMIM][PF 6 ]/[HMIM][PF 6 ] were measured at T = 298.15, 308.15 and 318.15 K, and the effect of the alkyl chain length on LLE was revealed. To assess the separation efficiency, we calculated the distribution coefficient (D) and selectivity (S) at different temperatures. Additionally, the Othmer-Tobias equation was used to test the reliability of the experimental data. The nonrandom two-liquid (NRTL) model is used to correlate the LLE data, and the model parameters were obtained using Matlab tools, and root-mean-square deviation (RMSD) values less than 0.018, indicating that experimental data agree with the regressed by the NRTL model.