Energy-efficient non-aqueous biphasic solvent for carbon capture: Absorption mechanism, phase evolution process, and non-corrosiveness

High latent heat and corrosivity related to H2O inhibit the application of aqueous biphasic absorbents for CO2 capture. An energy-efficient non-aqueous biphasic solvent DETA-EG-PMDETA (D-E-P) was developed with EGassisted CO2 absorption, interesting phase-transition behavior, and non-corrosiveness. EG could increase the absorption capacity through direct alcoholysis of carbamate and the complex reaction among EG, DETA, and CO2. When EG:PMDETA = 3.5:6.5, the CO2 saturated loading was as high as 2.02 mol/mol. Unlike common biphasic solvents, flue gas saturated-absorbent presented a denser CO2-rich phase with larger CO2 loading (6.01 mol/L) and smaller volume (26.7%), and more convenient homogeneous desorption, whereas the pure CO2-saturated absorbent exhibited an EG-diluted CO2-rich phase (4.34 mol/L, 43.5%) and heterogeneous desorption. Benefiting from low vapor pressure, vaporization enthalpy, and heat capacity of EG, and greatly reduced regeneration volume, the Q(latent) (0.0208 GJ/t CO2) and Q(sen) (0.12797 GJ/t CO2) were considerably decreased, resulting in a regeneration energy of 1.87 GJ/t CO2. It's significantly lower than 30 wt% MEA and other aqueous biphasic absorbents. In addition, because the carbamate hydrolysis and CO2 hydration could not take place in non-aqueous absorbent, the content of H+ was considerably limited, leading to a non-corrosive feature, and the corrosion rate was only 3.70 E-3 mm/a.