Global phase behavior of imidazolium ionic liquids and compressed 1,1,1,2-tetrafluoroethane (R-134a)

Authors

  • Wei Ren,

    1. Dept. of Chemical and Petroleum Engineering, NSF-ERC Center for Environmentally Beneficial Catalysis, University of Kansas, Lawrence, KS 66045
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  • Aaron M. Scurto

    Corresponding author
    1. Dept. of Chemical and Petroleum Engineering, NSF-ERC Center for Environmentally Beneficial Catalysis, University of Kansas, Lawrence, KS 66045
    • Dept. of Chemical and Petroleum Engineering, NSF-ERC Center for Environmentally Beneficial Catalysis, University of Kansas, Lawrence, KS 66045
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Abstract

Novel processes involving ionic liquids with refrigerant gases have recently been developed. Here, the complete global phase behavior has been measured for the refrigerant gas, 1,1,1,2-tetrafluoroethane (R-134a) and 1-n-alkyl-3-methyl-imidazolium ionic liquids with the anions hexafluorophosphate [PF6], tetrafluoroborate [BF4] and bis(trifluoromethylsulfonyl)imide [Tf2N] from ∼0°C to 105°C and to 33 MPa. All of the systems studied were Type V from the classification scheme of Scott-van Konynenburg with regions of vapor-liquid equilibrium, miscible/critical regions, vapor-liquid-liquid equilibrium, and upper and lower critical endpoints (UCEP and LCEP). The effect of the alkyl chain length has been investigated, for ethyl-([EMIm]), n-butyl-([BMIm]), and n-hexyl-([HMIm]). With increasing chain length, the temperature of the lower critical end points increases and pressure at the mixture critical points decrease. With a common cation, the temperature of the LCEP increased and the mixture critical point pressures decreased in the order of [BF4], [PF6], and [Tf2N]. © 2008 American Institute of Chemical Engineers AIChE J, 2009

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