SO2 absorption in acid salt ionic liquids/sulfolane binary mixtures: Experimental study and thermodynamic analysis

Two new simple acid salt ionic liquids (ASILs), tetraethylammonium diglutarate ([N 2222 ][diglutarate]) and dimethylethanolammonium diglutarate ([DMEA][diglutarate]) were synthesized and the ASILs/sulfolane binary mixtures containing 40   wt% ASILs were prepared for SO 2 absorption in this work. The SO 2 absorption rate is found to be quite fast with an equilibrium time within 2   min, due to the low viscosity of the mixtures. The solubilities of SO 2 in the two binary mixtures were measured under the pressure range of 0–1   bar and the temperature range of 303.15–333.15   K and results demonstrate the binary mixtures could trap as much as 6.836–7.624   mol SO 2 /kg absorbents at 1   bar and 303.15   K. The solubilities are 0.826–0.954   mol SO 2 /kg absorbents at a pressure as low as 0.004   bar, which is important for capturing SO 2 from the flue gas with low content of SO 2 . Thermodynamic analysis based on a Reaction Equilibrium Thermodynamic Model (RETM) was used to calculate the Henry’s law constants, reaction equilibrium constants, chemical absorption capacity, physical absorption capacity and thermodynamic functions of SO 2 absorption in the mixtures. The calculated absorption enthalpy are −53.73 and −47.15   kJ/mol for the two binary mixtures, respectively. The ASILs/sulfolane binary mixtures are shown to be an attractive alternative to pure ILs to be applied in SO 2 absorption due to the large absorption capacity and low absorption enthalpy, as well as the fast absorption rate.