Study on the efficient production of sulfur from SO2-contaning ionic liquid via the liquid-phase claus reaction

Sulfur dioxide (SO2) in the smelting flue gas is an irritating and toxic gas, and its efficient capture and conversion into sulfur is the goal of green development for non-ferrous smelting industry. In this paper, the absorption and conversion performance of SO2 in tetramethylguanidine acetate (TMGAc) was investigated by coupling the Claus reaction technique mediated by an ionic liquid absorbent. The experimental results show that TMGAc prepared by simple acid-base neutralization has a high SO2 absorption capacity (saturation adsorption capacity is 1.06 gSO2·g-1ILs), which is superior to that of conventional ionic liquid absorbents. When H2S gas is introduced at room temperature, the captured SO2 can be rapidly in situ converted to sulfur (sulfur yield up to 99%). High-temperature melting was used to separate the reaction product from the solid-liquid, and a combination of XRD, SEM and EDS analyses indicated that the product was S8. After five cycles, the sulfur yield maintains more than 90%. The mechanism of SO2 absorption by TMGAc was proposed by IR and NMR characterization methods, and the transformation mechanism of SO2 in the presence and absence of water was investigated. This study not only provides a basis for the efficient desulfurization of ionic liquids, but also provides ideas for SO2 resourcing and re-cycling, and helps the green and high-quality development of non-ferrous smelting industry.