Sulfolane-based biphasic solvent with high water-balance robustness and degradation resistance for industrial CO2 capture

Chemisorption with biphasic solvents is a promising low-energy strategy for separating CO2 from industrial flue gas, however, amine degradation and changes in water content can considerably impede the phase-splitting performance. To the issues, tetramethylene sulfone (TMS) was selected as separating agent to prepare a biphasic solvent with polyamine triethylenetetramine (TETA) with a TETA:TMS:H2O ratio of 2:6:2 (denoted as 20 T-60TMS). The CO2 loading of the blended phase and the volume fraction of the rich phase were 2.56 mol/L and 35.4%, respectively; the total regeneration heat duty was 2.36 GJ/tCO2. The proposed biphasic solvent exhibited better resistance to oxidative degradation and thermal degradation than did previously reported solvents, attributed to the beneficial effect of TMS. Additionally, the degradation products did not substantially reduce the phase separation performance after a 360 h thermal degradation test. A dynamic phase-splitting evaluation revealed that the 20 T-60TMS solvent was robust to changes in water content. Theoretical calculations confirmed that the introduction of TMS weakened the hydrogen bond between TETACOO−/TETAH+ and H2O, engendering enhanced TETACOO− and TETAH+ self-aggregation, forming a strong hydrogen bond network, and achieving fast phase separation. This work provides a novel biphasic solvent with excellent tolerance and stability for CO2 capture from flue gas.