(178c) Phase Equilibria Of Halocarbon Isomers In Room-Temperature Ionic Liquids

Vapor-liquid equilibria (VLE) and liquid-liquid equilibria (LLE) of binary mixtures of chlorofluorocarbon (CFC), hydrochlorofluorocarbon (HCFC), and hydrofluorocarbon (HFC) isomers [1-10] with room-temperature ionic liquids: [bmim][PF6] (1-butyl-3-methylimidazolium hexafluorophosphate), [bmim][BF4] (1-butyl-3-methylimidazolium tetrafluoroborate), [emim][BF4] (1-ethyl-3-methylimidazolium tetrafluoroborate) and [emim][Tf2N] (1-ethyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide) have been investigated using a gravimetric microbalance method or volumetric and cloud-point methods at a temperature range of 283 ? 348 K. In the case of the perhalogenated isomers: CFCl2-CF2Cl (CFC-113), CCl3-CF3 (CFC-113a), CF2Cl-CF2Cl (CFC-114), CFCl2-CF3 (CFC-114a) the solubility behavior between isomers in the ionic liquid is practically identical with large immiscibility gaps. However, the mono-hydrogen substituted halocarbons: CHCl2-CF3 (HCFC-123), CHClF-CF2Cl (HCFC-123a), CHFCl-CF3 (HCFC-124), CHF2-CF2Cl (HCFC-124a) 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 hydrofluorocarbons: CHF2-CHF2 (HFC-134), CH2F-CF3 (HFC-134a) and even diastereomers (threo and erythro) of 2,3-dihydrodecafluoropentane CF3CHFCHFCF2CF3 (HFC-4310mee) were found to have different miscibility characteristics. For two cases, the deuterated isotope effect was studied (CDCl3, CF3CDFCDFCF2CF3) and found to have only a minor effect on the solubility, but did show slightly higher miscibility than the non-deuterated isomers. Large immiscibility (LLE) gaps of the perhalogenated compounds (CFC-11, CFC-113, CFC-113a, CFC-114, CFC-114a) have been drastically reduced by the (only one) hydrogen (or deuterium) substitution of these compounds. The HCFCs (HCFC-123 and HCFC-123a + [bmim][PF6] or [emim][Tf2N]; HCFC-124 and HCFC-124a + [emim][Tf2N]) and HFC (HFC-134a + [bmim][PF6] or [emim][Tf2N]) were found to have lower critical solution temperatures (LCSTs) and belong to the Type-V fluid behavior according to the classification of van Konynenburg and Scott [11,12]. Negative values of the excess molar volume in the ionic liquid-rich side solution have been observed for all cases and in some systems these values are noticeably large (i.e. HFC-134a + [emim][Tf2N] from -9 to -15 cm3 mol-1). This observation is consistent with our earlier findings for various HFCs in ionic liquids. Experimental VLE and LLE data have been well correlated by the use of equation of state (EOS) and solution activity (NRTL) models.

[1] M.B. Shiflett and A. Yokozeki, Ind. Eng. Chem. Res. (2007) submitted. [2] M.B. Shiflett and A. Yokozeki, Fluid Phase Equilibr. (2007) submitted. [3] M.B. Shiflett and A. Yokozeki, J. Chem. Eng. Data (2007) submitted. [4] M.B. Shiflett and A. Yokozeki, AIChE J. 52(3) (2006) 1205-1219. [5] M.B. Shiflett, M.A. Harmer, C.P. Junk, A. Yokozeki, J. Chem. Eng. Data. 51(2) (2006) 483-495. [6] M.B. Shiflett, M.A. Harmer, C.P. Junk, A. Yokozeki, Fluid Phase Equilibr. 242 (2006) 220-232. [7] M.B. Shiflett and A. Yokozeki, Ind. Chem. Eng. Res 45(18) (2006) 6375-6382. [8] M.B. Shiflett and A. Yokozeki, J. Phys. Chem. B 110(29) (2006) 14436-14443. [9] M.B. Shiflett and A. Yokozeki, J. Chem. Eng. Data 51(5) (2006) 1931-1939. [10] A. Yokozeki and M.B. Shiflett, AIChE J. 52(11) (2006) 3952-3957. [11] R.L. Scott and P.H. van Konynenburg, Discus. Faraday Soc. 49 (1970) 87. [12] P.H. van Konynenburg and R.L. Scott, Phil. Trans. A298 (1980) 495.