Deep eutectic solvents formed by EmimCl plus lactams: Effective SO2 capture and conversion into sulphur via DESs-mediated Claus process

Abstract Sulfur dioxide (SO2) is not only a notorious polluting gas, but it can also be recycled as the sulfur resource to synthesize high value-added chemicals. In this work, we have demonstrated an effective strategy for the SO2 capture and conversion using deep eutectic solvents (DESs) as the green medium. These DESs formed by 1-ethyl-3-methylimidazolium chloride (EmimCl) plus lactams, which exhibited an extremely high SO2 loading capacity with up to 1.323 g SO2 per gram DES and excellent reversibility. The FTIR, NMR and calculation results showed that the absorption of SO2 by investigative DESs is a physical process. Particularly, the absorbed SO2 can be rapidly converted in situ to sulphur via the DESs-mediated Claus process under mild conditions without any additives. Good to excellent yields of sulphur were obtained and DESs can be reused repeatedly. This DESs-mediated Claus process provides a promising method for the efficient regeneration of DESs and SO2 resource utilization.