Computation of liquid-liquid equilibrium of organic-ionic liquid systems using NRTL, UNIQUAC and NRTL-NRF models

Ionic liquids (ILs) with their limitless combination of cations and anions can offer an optimal solvent for a specific purpose especially separation processes. Among ionic liquids, alkyl-sulfate derivatives are the most promising Its to be applied in industrial processes. The present work investigates liquid-liquid equilibrium phase behavior of 12-ILs comprising sulfate-based anions. Computation of liquid-liquid equilibrium for 36 ternary systems is carried out using three local composition models, namely non-random two liquid (NRTL), non-random two liquid non-random factor (NRTL-NRF) and universal quasi chemical (UNIQUAC) activity coefficient models. All the interaction parameters of the three models are regressed using an optimization program based on Simplex method of Nelder and Mead. Comparison of the results is expressed by root mean square deviation (rmsd) between the experimental and calculated compositions. It is demonstrated that the NRTL-NRF model presents very good satisfactory results with rmsd values of about 1.05 so that this model is highly appropriate to calculate thermodynamic properties of ionic liquid solutions. (C) 2012 Elsevier BM. All rights reserved.