Effect of SO₂ on CO₂ Absorption in Flue Gas by Ionic Liquid 1-Ethyl-3-methylimidazolium Acetate

Significant efforts are being made to develop several novel solvents or materials for postcombustion CO 2 capture technology. Traditional amine solvents suffer from mass loses due to its volatility and poisoning by flue gas impurities. Ionic liquids (ILs) are considered to be promising alternatives for CO 2 capture due to their unique features, such as negligible vapor pressure. Despite the extensive research on CO 2 capture by ILs, few studies have investigated the effect of flue gas components on CO 2 absorption performance. Because of the large differences between CO 2 and SO 2 in the absorption capacity and partial pressure in flue gas, it is essential to study the role of SO 2 in CO 2 capture using ILs. This work focused on studying the effect of SO 2 with low concentration on postcombustion CO 2 capture by 1-ethyl-3-methylimidazolium acetate [C 2 mim][OAc] and explaining the microscopic mechanism through quantum chemical calculation. Results showed that the CO 2 absorption capacity was largely decreased by 25% in the presence of SO 2 . After 5 cycles of regeneration, the initial absorption capacity of CO 2 in [C 2 mim][OAc] remarkably decreased by 48%. Thus, the ionic liquid lost its excellent reversibility and regeneration property for CO 2 capture under continuous exposure to SO 2 . The quantum chemical calculation indicated that CO 2 could hardly compete with SO 2 for the main active sites in [C 2 mim][OAc]. In addition, the net charge transfer amount from acetate anion to CO 2 significantly decreased from −0.537 to −0.039 e in the presence of SO 2, which explained the decreased absorption capacity of CO 2 in [C 2 mim][OAc].