Kinetic study on CO2 absorption by aqueous secondary amine + tertiary amine blends: Kinetic model and effect of the chain length of tertiary amine

Abstract

To study the reaction kinetic of CO2 absorption in aqueous secondary amine + tertiary amine blends, 1-Diethylamino-2-propanol (DEA2P) and 1-Dimethylamino-2-propanol (DMA2P) were selected to form aqueous amine blended solutions with 2-(Ethylamino) ethanol (EAE), respectively. The reaction kinetics of CO2 absorption in aqueous EAE/DEA2P solutions and EAE/DMA2P solutions were explored using the stopped-flow apparatus, and the reaction mechanism was then explored by Density Functional Theory (DFT) calculations. Based on the zwitterion mechanism and the base-catalyzed hydration mechanism, experimental reaction kinetics models were established. It was found that in secondary amine + tertiary amine blends, tertiary amines played the key role of the proton acceptor in step of zwitterion deprotonation. With the increase of the chain length of tertiary amine, the CO2 absorption rate increased. Through analysis, it was found that the main reason for the increased CO2 absorption rate was the presence of H-bond or the stronger proton affinity of N atom.