Experimental investigation of CO2 absorption enthalpy in conventional imidazolium ionic liquids

Ionic liquids (ILs) have elicited considerable attention in the field of gas absorption and separation due to their unique properties. In addition to absorption capacity and absorption rate, absorption enthalpy is an important indicator for sorbent evaluation. In this work, the absorption enthalpy of CO2 in several kinds of ILs was measured directly using a Calvet calorimeter. The effects of anions, cationic alkyl chain length, and temperature on absorption properties were discussed. Results showed that anions influenced CO2 absorption enthalpy considerably. 1-Butyl-3-methylimidazolium acetate presented the most appropriate enthalpy for CO2 absorption compared with the other ILs investigated with different chain lengths. Absorption enthalpy was dependent on temperature, and the isosteric absorption enthalpy decreased with an increase in temperature. This work provides a useful basis for the appropriate selection of alternative forms of IL sorbents for post-combustion CO2 capture technology. (C) 2018 Society of Chemical Industry and John Wiley & Sons, Ltd.