Mechanism Study of Imidazole-Type Deep Eutectic Solvents for Efficient Absorption of CO₂

Abstract

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 (CO2) capture. A series of imidazole-type DESs with different ratios was prepared through one-step synthesis. The absorption capacity of CO2 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 CO2. Im-MEA (1:2) was selected to linearly fit lnη and 1/T 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 CO2/g DES; through five times of absorption–desorption after the cycle, the absorption capacity of DES was almost unchanged. Finally, the mechanism of CO2 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 CO2.

Role of intermolecular interactions in Deep Eutectic solvents for CO2 capture: Vibrational spectroscopy and quantum chemical studies

“…The H-bonding network influences the viscosity of the DES, which is an essential factor in deciding how easily CO 2 can diffuse through the solution before reacting. 21,65 Experimental techniques, such as infrared spectroscopy (FT-IR), provide valuable insights into H-bonding.…”

Role of Ionic Solvents in the Electrocatalytic CO2 Conversion and H2 Evolution Suppression: From Ionic Liquids to Deep Eutectic Solvents

“…During the last decades, 30-50 wt % monoethanolamine (MEA) aqueous solutions have been industrially used for the CO 2 capture, mainly thanks to the reversible chemical formation of carbamates. [34,39] Recently, amine-based DES containing in their composition different di-and monoethanolamines, [41,42] functionalized-DES possessing CO 2 affinity groups, [43] as well as imidazole-based DES, [44] have been developed for enhancing the CO 2 capture capacity with respect to traditional MEA solutions. [20,45] This is because these novel DES are able to display both a chemical reaction and additional Van der Waals interactions with CO 2 , which notably enlarge the amount and efficiency of the mechanisms for the CO 2 capture, with respect to the use of molecular solvents or imidazolium-based ILs.…”

Advances in CO2 Absorption by Deep Eutectic Solvents

“…CO 2 Absorption by DESs of Imidazole as HBA and Amines as HBD. Shi et al 65 synthesized DESs using Im and 67 synthesized DESs for CO 2 absorption using 1H-1,2,4-triazole (Tz) as HBA and 1,5diazabicyclo[4.3.0]non-5-ene (DBN) as HBD in different ratios. The results indicate that Tz-DBN (1:3) has the highest absorption capacity, 1.90 mol of CO 2 /mol of DES.…”

“…Shi et al synthesized DESs using Im and 4CH 3 -Im as HBAs and DEA and MEA as HBDs in different ratios and determined their CO 2 absorption capacity. The results showed that Im-MEA (1:4) had the best absorption capacity (see Table for detailed data).…”