Efficient Regeneration of SO2-Absorbed Functional Ionic Liquids with H2S via the Liquid-Phase Claus Reaction

Functional ionic liquids (ILs), which have high absorption capacities of low-concentration SO2 through chemical interaction, have been widely studied. However, the absorbed SO2 in functional ILs is normally desorbed with high-temperature and steaming treatment, which is harmful to the stability of absorbents and causes high-energy consumption. In this work, functional ILs (monoethanolaminium lactate-[MEA]L, 1,1,3,3-tetramethylguanidinium lactate-[TMG]L, tetraethylammonium lactate-[N2222]L) mixed with ethylene glycol (EG) or H2O were used to capture low-concentration SO2, and then H2S was added to regenerate the absorbents via the liquid-phase Claus reaction. It was found that the reaction of H2S with SO2 in the absorbents proceeded fast and the absorbed SO2 was almost completely converted to solid sulfur (S8) under mild conditions without the addition of any catalysts. The effects of temperature, H2S initial pressure, and solvent on the Claus reaction in the functional ILs were investigated, and the optimal reaction conditions were obtained. The recycle experiments showed that the activity of the functional ILs for the Claus reaction was not decreased after being reused three times. The Claus reaction between H2S and SO2 in functional ILs provides a promising method for the efficient regeneration of functional ILs and SO2 resource utilization.