The Ethylbenzene/Styrene Preferential Separation with Ionic Liquids in Liquid-Liquid Extraction

The objective of this work was to explore the feasibility of using ionic liquids (ILs), namely N-ethyl-N-methylmorpholinium dicyanamide, [EMMor][DCA], (3-hydroxypropyl)-1-methylmorpholinium dicyanamide, [N-C(3)OHMMor][DCA], 1-(3-hydroxypropyl)-3-methylimidazolium dicyanamide, [N-C3OHMIM][DCA], 1-(3-hydroxypropyl)pyridinium dicyanamide, [N-C3OHPy][DCA], (3-cyanopropyl)pyridinium dicyanamide, [N-C3CNPy][DCA], and (3-cyanopropyl)methylpyrrolidinium dicyanamide, [N-C(3)CNMPyr][DCA] for the separation of ethylbenzene and styrene. The liquid-liquid equilibrium (LLE) data in ternary systems of {IL (1)+styrene (2)+ethylbenzene (3)} at T=298.15K and ambient pressure is presented for the six ILs synthesized by us. The final chromatography analysis of the composition of tie-lines has shown that the studied ILs are not found in the raffinate phase and they show interesting results on the selectivity and solute distribution ratio for styrene extraction. A comparison of different ILs is presented for the studied separation problem. It was observed that the best separation selectivities were found for [N-C3CNPy][DCA] (S-Av=2.38) and [N-C(3)OHMMor][DCA] (S-Av=2.42) in comparison with other studied ILs in this work and those presented in the literature. While the data presented here are useful from a theoretical standpoint, the possibility of applications for these ILs in technological processes is questionable because of low solute distribution ratios, especially those calculated from the masses [N-C3CNPy][DCA] ((MAv)=0.08) and [N-C(3)OHMMor][DCA] ((MAv)=0.07). The experimental tie-lines were correlated with the non-random two liquid NRTL model.