Absorption of SO2 by thermal-stable functional ionic liquids with lactate anion

The capture of SO2 by ionic liquids (ILs) has drawn much attention due to the unique properties of ILs. Among the ILs, guanidinium- and alkanolaminium-based ILs have been widely studied by many groups experimentally or theoretically. However, the thermal stability of the ILs is low, and the degradation of the ILs may occur during the desorption process of SO2 at high temperatures. In this work, 1-butyl-3-methylimidazolium lactate ([Bmim]L) with high thermal stability was synthesized and was used to absorb SO2. It has been found that the IL can absorb large amounts of SO2 and the solubility of SO2 in the IL decreases with the increase of temperature; the absorption of SO2 by the IL is reversible, and the IL can be reused for the absorption of SO2 without obvious loss of absorption capacity. The comparison of [Bmim]L with other ILs based on lactate anion suggests that the cations of ILs have a significant influence on the absorption and desorption behaviors of SO2 while the length of the alkyl chains has no obvious influence on the solubility of SO2 in imidazolium-based ILs with lactate anion. The imidazolium-based ILs with lactate anion are promising absorbents for the removal of SO2 from the flue gas.