Eco-Friendly Deep Eutectic Solvents Blended with Diethanolamine Solution for Postcombustion CO2 Capture

Deep eutectic solvents (DESs) are the new generation of green promising CO2-capturing solvents, owing to their desirable properties, good stability, and environmental-friendly features. In this study, a novel hybrid solvent has been developed based on DESs for CO2 separation from a simulated flue gas flow. DESs: chlorine chloride (ChCl)-monoethanolamine (MEA), glyceline [1 ChCl/2 glycerol (Gly)], and piperazine-activated glyceline (glyceline/Pz) were added to the diethanolamine (DEA) solution in the concentration range of 10-30 wt %. The CO2 absorption performances of the DES-DEA hybrid solvents were studied from the solubility and mass transfer points of view. Hydrodynamic studies revealed that the addition of DES results in a smaller bubble Sauter mean diameter. Moreover, partial replacement of water with ChCI-MEA or glyceline/Pz increased the CO2 capture capacity, effective time, empirical enhancement factor, and overall mass transfer coefficient. On the contrary, with increasing glyceline concentration, the enhancement factor and overall mass transfer coefficient decreased under the studied operating conditions, although the CO2 solubility did not change. Moreover, C-13 NMR analysis was used to characterize carbon-based species in DES-DEA systems before and after CO2 absorption. Finally, the results of TGA measurements demonstrate that the addition of Gly-based DESs makes more stable hybrid solvents, which could be regenerated.