An experimental and theoretical study on the effects of amine chain length on CO2 absorption performance

Abstract

AbstractTo explore the effect of amine chain length on CO2 absorption performance, the reaction kinetics of CO2 absorption in aqueous 1‐dimethylamino‐2‐propanol (DMA2P), 1‐diethylamino‐2‐propanol (DEA2P), 2‐(methylamino)ethanol (MAE), and 2‐(ethylamino)ethanol (EAE) solutions with different concentrations were explored using the stopped‐flow apparatus. Additionally, Density Functional Theory (DFT) calculations were conducted to examine the reaction mechanism and the free energy barrier of the elementary reactions underlying CO2 absorption in these four aqueous amine solutions. Kinetic models for CO2 absorption in tertiary amines and secondary amines were established, based on the base‐catalyzed hydration mechanism and the zwitterion mechanism, respectively, both of which perform well in predicting the relationship between k0 and the amine concentration. The free energy barrier obtained by DFT is consistent with the activation energy barrier trend obtained by experiment. In addition, the effect of chain length on the free energy barrier was investigated through the chemical bond and weak interaction analysis.