Reducing the energy penalty and corrosion of carbon dioxide capture using a novel nonaqueous monoethanolamine-based biphasic solvent

Abstract To advance carbon dioxide (CO2) capture technology by simultaneously reducing the energy penalty and mitigating equipment corrosion, a novel nonaqueous biphasic solvent comprising monoethanolamine (MEA), 2-amino-2-methyl-1-propanol (AMP), dimethyl sulfoxide (DMSO), and N,N,N',N'',N''-pentamethyldiethylenetriamine (PMDETA) was proposed for CO2 capture in this study. The performance testing results demonstrated that the MEA-AMP-DMSO-PMDETA (M-A-D-P) biphasic solvent with the optimal composition could realize a high CO2 loading of 0.88 mol·mol-1 and that its rich phase stored 95.3% of the absorbed CO2 but constituted only 56.8% of the total volume. 13C NMR analysis and quantum chemical calculations showed that both MEA and AMP could absorb CO2 to form carbamate and carbamic acid species, with the latter being the dominant reaction product. Since the products were polar and could form hydrogen bonds with polar DMSO, the two had satisfactory mutual solubility, while less polar PMDETA was isolated, thereby leading to a phase change. After phase separation, only the CO2-rich phase required regeneration. Consequently, M-A-D-P significantly reduced the sensible heat and vaporization heat by 63.1% and 94.8%, respectively, compared to the benchmark MEA solution. Moreover, the results of the corrosion test demonstrated that M-A-D-P was virtually noncorrosive to carbon steel; thus, it clearly outperformed the MEA solution. Therefore, the novel M-A-D-P biphasic solvent may be a promising candidate for advancing energy-efficient and noncorrosive CO2 capture.