Liquid-liquid equilibria in binary mixtures of 1,3-propanediol plus ionic liquids [bmim][PF6], [bmim][BF4], and [emim][BF4]

Binary liquid-liquid equilibria (LLE) in mixtures of 1,3-propanediol and three ionic liquids have been measured using the volumetric and cloud-point methods. The room-temperature ionic liquids studied are 1-butyl-3-methylimidazolium hexafluorophosphate [bmim][PF6], 1-butyl-3-methylimidazolium tetrafluoroborate [bmim][BF4], and 1-ethyl-3-methylimidazolium tetrafluoroborate [emim][BF4]. All three binary systems show upper critical solution temperatures (UCSTs), with about 299 K for [bmim][BF4], about 310 K for [emim][BF4], and about 360 K for [bmim][PF6]. The limited solubility behaviors with UCSTs are similar to the cases of various monoalcohols with ionic liquids reported in the literature. Observed LLE are well correlated by use of the nonrandom two liquid (NRTL) solution model.