Comparative kinetics of carbon dioxide (CO2) absorption into EAE, 1DMA2P and their blends in aqueous solution using the stopped-flow technique

The amine blends as the potential carbon dioxide (CO2) capture absorbents have been received much attention in recent years, but this amines interaction mechanism remains unclear. In the present work, the kinetics of CO2 absorption into aqueous solutions of a secondary amine (Ethylethanolamine, EAE), a tertiary amine (1-Dimethylamino-2-propanol, 1DMA2P) and their blend were investigated by using a stopped-flow setup. The kinetic data of aqueous EAE solution can be interpreted well by the zwitterion mechanism, and the reaction rate of 1DMA2P can be fitted well using the base-catalyzed hydration mechanism. Experimental results showed that the pseudo first-order rate constants (k0) of EAE/1DMA2P is much higher than the calculated values of individual EAE and 1DMA2P using the parallel reaction mechanism. It has been accepted that the tertiary amine (i.e. 1DMA2P) can attract the CO2 from the zwitterion to release the free EAE molecules or the 1DMA2P as a base join the reaction of the CO2 and EAE. Then, the reaction pathway was proposed and the kinetic model with acceptable AARD% values of 6.642 was developed. Therefore, it can be concluded that the addition of EAE into 1DMA2P with low energy consumption can importantly enhance the absorption performance to solve the contradiction between low absorption heats and high CO2 absorption rates.