Absorption characteristics of amine-based deep eutectic solvents for CO2 capture

Deep eutectic solvent (DES) has the potential to replace aqueous amines for carbon capture. However, the reported DESs fail to absorb CO 2 equivalent to that absorbed by aqueous amines. To combine the excellent performance of amines and DESs, 9 amine-based DESs were prepared. The tetraethylammonium chloride was selected as the hydrogen bond acceptor, while ethanolamine, diethanol amine and triethanolamine were selected as the hydrogen bond donors. The molar ratios range from 1:4 to 1:6. Their properties were analyzed, including the structure, the thermal behavior and the potential corrosion. It has been determined that all DESs show a large liquid range (200 ∼ 600 K). Furthermore, the absorption characteristics of 9 DESs were studied. It has been found that the absorption capacity of DES3 and DES5 can reach up to 0.4066 and 0.3752 mol CO 2 /mol absorbent respectively, even 3 ∼ 6 times amount compared with the corresponding aqueous amines. At the laboratory level, the heat duty for the desorption process at 413.15 K of DES1 is 21.31 % of that for that of 30 wt% MEA at 393.15 K. For DES5, this value is 6.70 %. Besides, these DESs can maintain their splendid performance in absorption–desorption after 5 cycles. Meanwhile, the thermal stability and viscosity of the rich-absorbents were analyzed. Rich-absorbents are stable. Furthermore, effects of water have been inspected. The added water reduces the viscosity but confines the absorption capacity. For balance, the addition of 10 wt% water is recommended. Finally, the absorption mechanism was revealed. Both the physical and chemical absorption promote the absorption capacity of DESs.