Water-lean monophasic absorbents containing secondary alkanolamines and dimethyl sulfoxide for energy-efficient CO2 capture

Water-lean amine absorbents have potential in reducing regeneration energy consumption for post-combustion CO2 capture. In this work, dimethyl sulfoxide (DMSO) was proposed as a cosolvent to develop water-lean monophasic absorbents for capturing CO2 in the simulated flue gas treatment. CO2 absorption and desorption performance has been investigated for nonaqueous/water-lean systems involving three secondary alkanolamines and compared with the conventional monoethanolamine (MEA). Effect of water content in these absorbents on reaction products, regeneration energy consumption and capture performance was also discussed. Interestingly, the DMSO-based amine blends can maintain the monophasic state before and after CO2 absorption at the investigated conditions. Water-lean absorbent of 2-(butylamino)ethanol (BAE)/DMSO/H2O was proposed for energy-efficient CO2 capture, due to the observed high cyclic capacity and super-low energy consumption. Increasing water content in the absorbents can slightly improve the absorption capacity and cyclic capacity, but significantly increased the regeneration energy. Maintaining the water content not higher than 10 mass% can reduce the regeneration energy by 48–55% compared with the benchmark aqueous 30% MEA (4.05 MJ kg−1 CO2), which makes the proposed absorbent as a compelling candidate in the conventional CO2 capture process without major process modification.