Phase Equilibrium and Transport Properties of the Ionic Liquid 1-Ethyl-3-methylimidazolium Bis(trifluoromethylsulfonyl)amide and Compressed Difluoromethane and Pentafluoroethane

Global phase behavior, high-pressure vapor-liquid equilibrium (VLE), density, viscosity, and thermal conductivity have been measured for binary mixtures of the ionic liquid (IL) 1-ethyl-3-methylimidazolium bis-(trifluoromethylsulfonyl)-amide ([EMIm]-[Tf2N]) with either of the hydrofluorocarbon (HFC) gases, pentafluoroethane (R-125) or difluoromethane (R-32), at temperatures from 298.15 to 398.15 K and pressures to 4 MPa. At all VLE conditions investigated, R-32 is more soluble than R-125 at a given temperature and pressure. These systems are modeled with the NRTL activity coefficient model and Peng-Robinson equation of state. The mixture liquid viscosity decreases drastically with increasing compositions of dissolved gas. The thermal conductivity of both systems remains dominated by that of the IL until very high compositions of dissolved solute are achieved (>80% mol HFC). Simple mixing rules between the pure component properties can cause large, and potentially costly, errors in engineering design, as illustrated for examples in required pumping power and necessary surface area in a heat exchanger.