Effect of alcohol chain length on carbon dioxide absorption into aqueous solutions of alkanolamines

To identify structural factors of alkanolamine molecule which influence the CO2 absorption properties, we systematically investigated the CO2 absorption into aqueous solutions of 2-(ethylamino)ethanol (EAE), 3-ethylamino- 1-propanol (EAP), 4-ethylamino-1-butanol (EAB), 2-(propylamino)ethanol (PAE) and 2-(butylamino)ethanol (BAE). It was shown that the CO2 loading exhibited a clear dependence on the alcohol chain length by quantitative 13C nuclear magnetic resonance measurements. In contrast, it did not differ significantly among EAE, PAE and BAE. The results support the idea that the hydroxyl functional group of alkanolamine has a specific effect on the CO2 absorption reactions in the aqueous solutions by intramolecularly interacting with the central amino moiety.