Below the room temperature measurements of solubilities in ester absorbents for CO2 capture

Six ester absorbents were selected for CO2 capture, such as methyl benzoate, methyl heptanoate, ethyl hexanoate, butyl butyrate, triethyl phosphate and tributyl phosphate. CO2 solubilities in these absorbents were determined under temperatures of 273.15-283.15 K, and pressures up to 1.2 MPa. Henry's constants of CO2 + the selected absorbent systems at 273.15 K and 283.15 K were calculated and compared with those at higher temperature. It seemed that decreasing the absorption temperature is obviously beneficial for enhancing absorption performance. In order to assess the absorption capacity for different physical absorbents, Henry's constants and volumetric solubilities of the selected absorbents were compared with ionic liquids, common solvents and the selected absorbents in our previous work. The result showed that tributyl phosphate and triethyl phosphate were found to be relatively good absorbents by mole and volumetric fraction respectively, and they have potential value for CO2 capture. Moreover, thermodynamic properties such as entropy of solution, enthalpy of solution and Gibbs free energy of solution for the selected systems were calculated and assessed to study the absorption behavior.