Novel Nonaqueous Liquid-Liquid Biphasic Solvent for Energy-Efficient Carbon Dioxide Capture with Low Corrosivity

To address the problems of the relatively high energy penalty and corrosivity of aqueous biphasic solvents, a novel nonaqueous biphasic solvent composed of 2-((2-aminoethyl)amino)ethanol (AEEA), dimethyl sulfoxide (DMSO), and N,N,N',N″,N″-pentamethyldiethylenetriamine (PMDETA) was proposed for CO₂ capture. With optimization, this novel AEEA-DMSO-PMDETA (A-D-P) biphasic solvent could achieve a high CO₂ loading of 1.75 mol·mol^-1, of which 96.8% of the absorbed CO₂ was enriched in the lower phase with only 49.6% of the total volume. ¹³C NMR analysis and quantum calculations revealed that A-D-P could absorb CO₂ to form not only carbamate but also carbamic acid species, which were stabilized by DMSO via hydrogen-bonding interactions. Most products were highly polar and preferred to dissolve in polar DMSO rather than the less polar PMDETA, thus leading to the phase change. The thermodynamics results showed that the heat duty of A-D-P was only 1.66 GJ·ton^-1 CO₂ (393.15 K), which was significantly lower than that of the benchmark MEA (3.59 GJ·ton^-1 CO₂) and the reported aqueous biphasic solvents. Moreover, A-D-P presented a noncorrosive behavior to steel after CO₂ saturation, clearly showing its superiority over MEA and the aqueous biphasic solvents. Therefore, with superior properties of energy savings and noncorrosiveness, the A-D-P biphasic solvent could be a promising candidate for CO₂ capture.