摘要
Sterically hindered amines in non-aqueous solvents are promising for CO2 capture due to their high solvent capacity and potential for reducing energy consumption. However, reaction kinetics are depressed in common alcohol-based organic solvents, limiting their applications. This study investigates the reaction kinetics of sterically hindered amines: 2-amino-1-propanol (2-AP), diethanolamine (DEA), and 2-amino-2-methyl-1-propanol (AMP) in semi-aqueous N-methyl-2-pyrrolidone (NMP) using a stopped-flow apparatus. NMP significantly enhances reaction kinetics for all tested amines, increasing the second-order rate constant for AMP by over 40 times compared to alcohol-based solvents and 3 times compared to aqueous solutions. This enhancement is explained by the zwitterion mechanism, where the increased amine activity in NMP substantially accelerates both zwitterion formation and zwitterion deprotonation by amines, outweighing the reduced contribution to deprotonation from water. NMR spectroscopy indicates that the solvent capacity of sterically hindered amines in semi-aqueous NMP outperforms that of conventional monoethanolamine, despite the decreased availability of water for carbamate hydrolysis. This study demonstrates that sterically hindered amines in semi-aqueous NMP can leverage the benefits of non-aqueous solvents while enhancing reaction kinetics. These findings will advance solvent development and contribute to cost-effective CO2 capture processes.