Separation of ethylbenzene/styrene systems using ionic liquids in ternary LLE

In this work, we studied the applicability of six imidazolium-based ionic liquids (ILs) with different anions dicyanamide, [DCA] − and tricyanomethanide, [TCM] − in the separation of ethylbenzene/styrene compounds. Experimental values for liquid–liquid equilibrium (LLE) were obtained for various binary and ternary mixtures of {IL (1) + styrene (2) + ethylbenzene (3)} at T = 298.15 K and ambient pressure. Six ILs have been studied: 1-ethyl-3-methylimidazolium dicyanamide, [EMIM][DCA], 1-ethyl-3-methylimidazolium tricyanomethanide, [EMIM][TCM], 1-allyl-3-methylimidazolium dicyanamide, [AMIM][DCA], 1-butyl-3-methylimidazolium dicyanamide, [BMIM][DCA], 1-butyl-3-methylimidazolium tricyanomethanide, [BMIM][TCM] and 1-benzyl-3-methylimidazolium dicyanamide, [BzMIM][DCA]. The ionic liquids were chosen after a literature analysis and measurements of activity coefficient at infinite dilution in many ILs. The ILs chosen have shown very good results in terms of selectivity and solute distribution ratio. The chromatography analysis revealed that the ILs used as an entrainers were not present in the aromatic hydrocarbon-rich layer after the experiment. This is convenient for planned new technology, because it eliminates the step needed for the separation of the solvent. A comparative study of the separation effectiveness of the [AMIM][DCA] in comparison with other reported ILs was chosen as the best solvent for the intended separation process. The non-random two liquid NRTL model was used successfully to correlate the experimental tie-lines and to calculate the phase composition error in mole fraction in the ternary systems.