Calorimetric and Volumetric Study on Binary Mixtures 2,2,2-Trifluoroethanol + (1-Butyl-3-methylimidazolium Tetrafluoroborate or 1-Ethyl-3-methylimidazolium Tetrafluoroborate)

This work was motivated by the fundamental interest in the study of mixtures containing ionic liquids and fluorinated alcohols but also by the possibility of the use of these mixtures in refrigeration applications. The study of the thermophysical properties of these mixtures will contribute to evaluate the reliability as an absorbent of several ionic liquids with the refrigerant 2,2,2-trifluoroethanol. Thus, densities, ρ, over the temperature ranges from (283.15 to 323.15) K and (293.15 to 323.15) K of 2,2,2-trifluoroethanol (TFE) + 1-butyl-3-methylimidazolium tetrafluoroborate ([C1C4im][BF4]) and 1-ethyl-3-methylimidazolium tetrafluoroborate ([C1C2im][BF4]) were measured at atmospheric pressure, respectively. Excess molar volumes, V m E, were calculated from the density values of the mixtures and of the pure compounds. In addition, mixing enthalpies (or excess molar enthalpies), Δmix H, were measured for both systems at atmospheric pressure and at (293.15 and 333.15) K. Densities of [C1C4im][BF4] + TFE are lower than those for [C1C2im][BF4] + TFE. For both systems, mixing enthalpies are positive, being higher for [C1C4im][BF4] + TFE. Excess molar volumes were positive in the case of [C1C4im][BF4] + TFE between (283 and 323) K and slightly negative at 333 K, whereas for [C1C2im][BF4] + TFE they were negative in the (293 to 333) K temperature range. In light of the results reported herein, the system containing [C1C2im][BF4] is preferred to [C1C4im][BF4] for refrigeration by absorption. Nevertheless, other properties should be taken into account for the final choice of a refrigerant/absorbent pair.