Absorption and Conversion of SO(2) in Functional Ionic Liquids: Effect of Water on the Claus Reaction

[Image: see text] The absorption of SO(2) from flue gas and its conversion to chemicals is important in the industry. Functional ionic liquids (ILs) have been broadly used to absorb SO(2) in flue gas, but seldom convert it to chemicals. As we know, water is inevitable in a desulfurization process. In this work, three functional ILs (monoethanolaminium lactate-[MEA][Lac], 1,1,3,3-tetramethylguanidinium lactate-[TMG][Lac], tetraethylammonium lactate-[N(2222)][Lac]) with or without water were used as absorbents to absorb SO(2) in flue gas, and then the absorbed SO(2) in the absorbents was converted to sulfur via a Claus reaction. The result shows that the three ILs can efficiently absorb SO(2) and convert it to sulfur. But the addition of water in the ILs can reduce the conversion of absorbed SO(2), and the conversion increases with increasing the acidity of absorbents. To explain this phenomenon, we studied the Claus reaction in H(2)SO(3), NaHSO(3) and Na(2)SO(3) aqueous solutions. It turns out that the conversion of the Claus reaction is related to the species of S (IV) in the order of the oxidability: H(2)SO(3) > HSO(3)(–) > SO(3)(2–), and their proportions dependent on the pH of solutions. On the basis of the absorption mechanism of SO(2) in functional ILs aqueous solution, H(2)S reacts with HSO(3)(–) and SO(3)(2–) with weaker oxidability, resulting in the lower conversion. Importantly, we found that the addition of lactic acid could increase the conversion of SO(2) via the Claus reaction.