Liquid-liquid equilibria of hydrofluoroethers and ionic liquid 1-ethyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide

Binary liquid-liquid equilibria (LLE) in mixtures of five hydrofluoroethers and room-temperature ionic liquid, 1-ethyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide, have been measured for the first time using the volume-mass method. All five binary systems show large immiscibility gaps. The ionic liquid-rich side solutions become increasingly more soluble in HFE (hydrofluoroether) as the HFE normal boiling point decreases. Observed LLE are well correlated by use of the nonrandom two liquid (NRTL) solution model. The excess molar volumes of the HFE and ionic liquid rich side solutions are small and similar to ordinary binary mixtures which is opposite to what we have previously reported with hydrofluorocarbons (HFCs) in ionic liquids. Therefore, the insertion of an ether oxygen has changed the liquid structure of HFEs vs HFCs in ionic liquids.