Fast and Efficient CO<sub>2</sub> Absorption in Non-aqueous Tertiary Amines Promoted by Ethylene Glycol
Meisi Chen, Mengjia Li, Feng Zhang, Xingbang Hu, Youting Wu
Abstract
With the catalytic induction of ethylene glycol (EG), anhydrous N,N-dimethylethanolamine (DMEA) shows CO2 absorption performance via chemical binding and physical storage under normal pressure. Among the absorbents, pure DMEA and EG can hardly absorb CO2 directly, but when the zwitterionic alkylcarbonates are formed between CO2 and DMEA-EG, which can be characterized by 13C NMR and FTIR spectroscopy, the absorption rate of CO2 is improved. With the increase in the CO2 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–CO2 is unstable at higher temperatures. In other words, DMEA–EG–CO2 can be easily regenerated upon appropriate depressurization or heating. The corresponding thermodynamic calculations prove that the regenerative energy of DMEA–EG–CO2 is −27.33 kJ/mol, far less than that of other absorbent systems.