Fast and Efficient CO₂ Absorption in Non-aqueous Tertiary Amines Promoted by Ethylene Glycol

With the catalytic induction of ethylene glycol (EG), anhydrous N, N -dimethylethanolamine (DMEA) shows CO 2 absorption performance via chemical binding and physical storage under normal pressure. Among the absorbents, pure DMEA and EG can hardly absorb CO 2 directly, but when the zwitterionic alkylcarbonates are formed between CO 2 and DMEA-EG, which can be characterized by 13 C NMR and FTIR spectroscopy, the absorption rate of CO 2 is improved. With the increase in the CO 2 loading as the mass fraction of EG in DMEA–EG, 80 wt % EG captures up to 0.72 mol/mol at 293 K and 101 kPa via chemical binding and physical storage. The amount that is chemically bound and physically stored is directly dependent on temperature; within the range of 293–323 K, an absorption–regeneration cycle can be formed in a closed vessel because the zwitterion DMEA–EG–CO 2 is unstable at higher temperatures. In other words, DMEA–EG–CO 2 can be easily regenerated upon appropriate depressurization or heating. The corresponding thermodynamic calculations prove that the regenerative energy of DMEA–EG–CO 2 is −27.33 kJ/mol, far less than that of other absorbent systems.