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Global phase behavior of imidazolium ionic liquids and compressed 1,1,1,2‐tetrafluoroethane (R‐134a)
Author(s) -
Ren Wei,
Scurto Aaron M.
Publication year - 2009
Publication title -
aiche journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.958
H-Index - 167
eISSN - 1547-5905
pISSN - 0001-1541
DOI - 10.1002/aic.11657
Subject(s) - ionic liquid , hexafluorophosphate , tetrafluoroborate , chemistry , vapor pressure , refrigerant , alkyl , critical point (mathematics) , binodal , thermodynamics , imide , phase (matter) , vapor–liquid equilibrium , organic chemistry , phase diagram , chromatography , physics , mathematical analysis , mathematics , gas compressor , catalysis
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 [PF 6 ], tetrafluoroborate [BF 4 ] and bis(trifluoromethylsulfonyl)imide [Tf 2 N] 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 [BF 4 ], [PF 6 ], and [Tf 2 N]. © 2008 American Institute of Chemical Engineers AIChE J, 2009