Phase behavior of vinyl fluoride in room-temperature ionic liquids [emim][Tf2N], [bmim][N(CN)2], [bmpy][BF4], [bmim][HFPS] and [omim][TFES

Abstract

We have measured for the first-time the gas solubility of vinyl fluoride (VF, H2CCHF) in room-temperature ionic liquids (RTILs), 1-ethyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide [emim][Tf2N], 1-butyl-3-methylimidazolium dicyanamide [bmim][N(CN)2], 1-butyl-4-methylpyridinium tetrafluoroborate [bmpy][BF4], 1-butyl-3-methylimidazolium 1,1,2,3,3,3-hexafluoropropanesulfonate [bmim][HFPS] and 1-octyl-3-methylimidazolium 1,1,2,2-tetrafluoroethanesulfonate [omim][TFES] at isothermal conditions from about 278 to 373K using a volumetric view cell. The observed pressure–temperature-composition (PTx) data have been analyzed by use of a generic RK (Redlich–Kwong) equation-of-state (EOS) model, which has been successfully applied in our previous works. The interaction parameters have been determined using our measured VLE (vapor–liquid–equilibrium) data. EOS model predictions suggest that these systems show VLLE (vapor–liquid–liquid equilibrium) and demonstrate Type III and Type V phase behavior, according to the classification of van Konynenburg and Scott. The global phase behavior of VF has also been compared with our measured data for ethylene (C2H4, H2CCH2) in 1-ethyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide. The addition of a fluorine atom in VF significantly increases the gas solubility due to hydrogen bonding with the ionic liquid. Henry's law constants were calculated and compared at about room temperature (298K). Enthalpies and entropies of absorption were determined by considering the temperature effects on gas solubilities.