Study on CO₂ absorption performance of ternary DES formed based on DEA as promoting factor

In this study, we used tetraethylammonium chloride (TEAC), diethanolamine (DEA), and N -methyldiethanolamine (MDEA) to prepare ternary DES and binary DES to absorb CO 2 . We found that their formation was due to the hydrogen bond interaction between hydrogen bond acceptor and hydrogen bond donor (HBD). Surprisingly, TEAC/MDEA/DEA can react with CO 2 , but TEAC/MDEA cannot react with CO 2 . Unexpectedly, after adding DEA to TEAC/MDEA, the ternary TEAC/MDEA/DEA DES can react with CO 2 . Nuclear magnetic resonance spectroscopy and Fourier infrared spectroscopy results showed that the accidental CO 2 absorption behavior mainly depended on the HBD DEA, because the imine group in DEA reacted with CO 2 to form carbamate, thereby absorbing CO 2 , while the hydroxyl group on MDEA and the hydroxyl group of DEA did not interact with CO 2 . Through thermal stability analysis, TEAC/MDEA/DEA system with the molar ratio of 1:3:4 is more stable. We further studied the influence of molar ratio, temperature, water content, and other factors on the absorption of CO 2 by ternary DES. In addition, TEAC/MDEA/DEA (1:3:4) was regenerated at 80°C, and the absorption capacity of DES was almost unchanged after five absorption–desorption cycles.