Regenerable solid molecular basket sorbents for selective SO₂ capture from CO₂-rich gas streams

A series of molecular basket sorbents (MBSs) consisting of SBA-15 loaded with ethylene glycol (EG) derivatives and dimethyl sulfoxide (DMSO) are developed and investigated for sulfur dioxide (SO₂) capture from industrial tail gas streams. The EG derivatives and DMSO are successfully immobilized on the support via surface interaction with the silanol groups as evidenced by DRIFTS analysis. The mesoporous structure of SBA-15 is preserved after loading with different compounds, with no major morphology changes. The SO₂ sorption capacity increases with decreasing the molecular weight of EG derivatives. Furthermore, changing the terminal group of EG derivatives from hydroxyl (-OH) to methoxy (-OCH₃) improves SO₂ sorption capacity. DMSO-based MBS exhibits much higher SO₂ affinity (64 mg-SO₂/g-sorb.) than EG-based sorbents (<25 mg-SO₂/g-sorb.). DMSO/SBA-15 sorbents are able to selectively capture SO₂ in the presence of high CO₂ concentration (30 %) with a relative selectivity factor of 120. Pre-saturating the DMSO-based sorbents with water vapor does not affect SO₂ sorption capacity, and the sorbents possess good stability and regenerability. Moreover, the spent DMSO/SBA-15 sorbent could be further applied for H₂S removal for producing elemental sulfur via Claus reaction between H₂S and the adsorbed SO₂, providing an environmentally friendly and sustainable way of regenerating the spent DMSO/SBA-15 sorbents.