In recent reports, we measured the vapor−liquid−liquid equilibria (VLLE) of trifluoromethane (R-23) and pentafluoroethane (R-125) with a room-temperature ionic liquid (RTIL), 1-butyl-3-methylimidazolium hexafluorophosphate [bmim][PF6], using a volume−mass measurement method along various isotherms. In the present work, we complete similar investigation of VLLE for the methane and ethane series of hydrofluorocarbons (HFCs) in [bmim][PF6]. Compounds studied here are fluoromethane (R-41), 1,1,1,2-tetrafluoroethane (R-134a), 1,1,1-trifluoroethane (R-143a), 1,1-difluoroethane (R-152a), and fluoroethane (R-161) in [bmim][PF6]. Observed VLLE behaviors are consistent with the earlier predictions by our equation-of-state (EOS) model, which showed partial immiscibilities in the HFC-rich side solutions, indicating type-III or type-V mixtures according to the Konynenburg−Scott classification. Thus, the present study as well as those with R-23 and R-125 reasonably validate our EOS model. In addition, very large negative excess molar volumes have been observed for all the studied systems, similar to that observed for mixtures with R-23 and R-125.

Solubility behaviors of CFC-113 (CFCl 2 -CF 2 Cl), CFC-113a (CCl 3 -CF 3 ), CFC-114 (CF 2 Cl-CF 2 Cl), CFC-114a (CFCl 2 -CF 3 ), HCFC-123 (CHCl 2 -CF 3 ), HCFC-123a (CHClF-CF 2 Cl), HCFC-124 (CHFCl-CF 3 ), HCFC-124a (CHF 2 -CF 2 Cl), HFC-134 (CHF 2 -CHF 2 ), and HFC-134a (CH 2 F-CF 3 ) in room-temperature ionic liquid 1-ethyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide ([emim][Tf 2 N]) have been investigated using a gravimetric microbalance method from (283 to 348) K or volumetric and cloud-point methods. In the case of the perhalogenated compounds (CFC-113, CFC-114, and their isomers), the solubility behavior between isomers in the ionic liquid is practically identical with large immiscibility gaps. This suggests that the (present) ionic liquid cannot be used for these isomer separations. However, the monohydrogen substituted halocarbons (HCFC-123, HCFC-124, and their isomers) begin to show some difference (liquid-liquid immiscibility gap) in the ionic liquid. The isomer effect on the solubility in the ionic liquid becomes significant for the dihydrogen-substituted halocarbons (HFC-134 and HFC-134a), and these isomers can be separated using [emim][Tf 2 N] as an entrainer in an extractive distillation. This observation is consistent with our earlier findings for various HFCs in ionic liquids.