Selection of Ionic Liquids as Entrainers for the Separation of Ethyl Acetate and Ethanol

This work tries to explore the relation between molecular structures of ionic liquids (ILs) as entrainers and separation performance on ethyl acetate (1) and ethanol (2). The vapor-liquid equilibrium (VLE) data have been measured for ethyl acetate (1) + ethanol (2) containing ILs at 101.32 kPa. The ionic liquids investigated were 1-butyl-3-methylimidazolium tetrafluoroborate ([BMIM](+)[BF4](-)) and 1-methyl-3-octylimidazolium tetrafluoroborate ([OMIM](+)[BF4](-)), as well as 1-ethyl-3-methylimidazolium tetrafluoroborate ([EMIM](+)[Br-4](-)) that has been studied in our previous work, All the ILs could give rise to the salting-out effect. It was found that, at low IL concentration, the separation ability of ILs is in the order [EMIM](+)[BF4](-) > [BMIM](+)[BF4](-) > [OMIM](+)[BF4](-), while at high IL concentration (x(3) = 0.10-0.30) the separation ability of ILs is in the order [OMIM](+)[BF4](-) > [EMIM](+)[BF4](-) > [BMIM](+)[BF4](-) due to the difference of polarity of the three ILs and demixing effect. [EMIM](+)[triflate](-) was included as entrainer and compared with the tetrafluoroborate-based ILs. The measured ternary data were correlated using the NRTL model.