Deactivation and Regeneration of an Ionic Liquid during Desulfurization of Simulated Flue Gas

Room-temperature ionic liquids (ILs) are widely investigated to absorb SO2 from mixed gases or simulated flue gases and can capture a large amount of SO2, which can be recovered easily by heating and vacuum treatment. However, after many circulations of SO2 absorption from flue gas, the capacity of SO2 in ILs decreases. The main reason may be the oxidation of SO2, and the oxidized SO2 becomes sulfuric acid when water presents in flue gas. Sulfuric acid in the ILs influences the regeneration of ILs and further absorption of SO2 by the ILs. In this work, the effect of sulfuric acid in a task-specific IL, monoethanolammonium lactate ([MEA]L), on the absorption of SO2 and the regeneration of [MEA]L from a mixture containing sulfuric acid were studied. It was found that when sulfuric acid was added into the IL, the absorption capacity of SO2 in [MEA]L decreased greatly. However, when NaOH, CaO, or CaCO3 was added into the mixture of [MEA]L and sulfuric acid, [MEA]L could be regenerated and sulfuric acid was formed into its corresponding salts and precipitated for removal.