Mechanism Study of Imidazole-Type Deep Eutectic Solvents for Efficient Absorption of CO.

Deep eutectic solvents (DESs) are a new class of green solvents that exhibit unique properties in various process applications. In this regard, this study evaluated imidazole-type DESs as solvents for carbon dioxide (CO) capture. A series of imidazole-type DESs with different ratios was prepared through one-step synthesis. The absorption capacity of CO in imidazole-type DESs was measured through weighing, and the effects of temperature, hydrogen bond acceptors, hydrogen bond donors, and water content were discussed. DESs absorbed the effects of CO. Im-MEA (1:2) was selected to linearly fit lnη and 1/ using the Arrhenius equation under variable temperature conditions, and a good linear relationship was found. The results show the best absorption effect for Im-MEA (1:4). At 303.15 K and 0.1 MPa, the absorption capacity of Im-MEA (1:4) was as high as 0.323 g CO/g DES; through five times of absorption-desorption after the cycle, the absorption capacity of DES was almost unchanged. Finally, the mechanism of CO absorption was studied using Fourier transform infrared and nuclear magnetic resonance spectroscopy. The absorption mechanism of imidazole-type DESs synthesized using imidazole salt and an amine-based solution was chemical absorption, and the reaction formed carbamate (-NHCOO) to absorb CO.