Phase Equilibrium Characteristics of CO2 and Ionic Liquids with [FAP]− Anion Used for Absorption-Compression Refrigeration Working Pairs

Abstract

The study of the phase equilibrium characteristics of CO2-ionic liquids (ILs) as new absorption-compression type refrigeration working pairs is of great importance. Three kinds of ILs, i.e., [emim][FAP], [bmim][FAP] and [hmim][FAP], were chosen as potential absorbents. The solubility of CO2 in these ILs was measured experimentally within 0 to 5.0 MPa at temperatures of 293.15 K to 333.15 K, and the effects of temperature, pressure, IL anion and cation structure and stirring action on CO2 solubility were also discussed and analyzed. The results showed that the longer alkyl chains in an identical IL family, the alkyl fluoride group in IL anions and the stirring action by a magnetic stirrer had positive effects on the solubility of CO2. In the three ILs, [hmim][FAP] possessed the best performance for CO2 absorption; the solubility of CO2 reached 0.7641 at a pressure of 5 MPa and temperature of 293.15 K, the maximum solubility measured in this work. The CO2-[hmim][FAP] binary mixture is recommended as a potentially applicable working pair for CO2 absorption-compression refrigeration systems.