As a new type of solvent with immeasurable vapor pressure, room-temperature ionic liquids are being used for chemical separation and unique reaction media. Solvent phase behavior is an important factor in the attractiveness of using ionic liquids in these applications as well as in new applications such as absorption cooling or heating.
The absorption refrigeration cycle has been in use in various forms for more than 100 years. Although the vapor compression cycle is now used for most air-conditioning and refrigerating applications, the well-known refrigerant-absorber systems (H2O/LiBr and NH3/H2O) are still being used for certain applications, particularly in the field of industrial applications or large-scale water chiller systems. Recently, more attention has been directed toward recovery of waste heat using the NH3/H2O system (Erickson, D. C., et al (ASHRAE Trans., 2004, 110). Inherent drawbacks to using LiBr and NH3 as refrigerants include the corrosiveness of LiBr and the toxicity and flammability of NH3. In the late 1950s, there were proposals of new refrigerant-absorbent pairs for the absorption cycle using fluoroalkane refrigerants with organic absorbents (Eiseman, B. J. [ASHRAE J., 1959, 1:45]; Mastrangelo, S. V. R. [ASHRAE J., 1959, 1:64]). Such studies continue actively even at the present time, especially among academic institutions (Nezu, Y., et al. [Natural Working Fluids 2002, IIR Gustav Lorentzen Conf. 5th, China, Sep. 17-20, 2002, 446-453]; Fatouh, M. and Murthy, S. S. [Renewable Energy, 1993, 3:31-37]; Bhatt, M. S., et al. [Heat Recovery System & CHP, 1992, 12:225-233]).
Although WO 05/113,702 discloses the use of ionic liquids in absorption refrigeration applications, a need still remains for refrigeration pairs that are characterized by a well-balanced set of properties.