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

Abstract

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.

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