A 13C NMR study of carbon dioxide absorption and desorption in pure and blended 2-(2-aminoethylamine)ethanol (AEEA) and 2-amino-2-methyl-1-propanol (AMP) solutions

Quantitative 13C nuclear magnetic resonance (NMR) spectroscopy was used to study carbon dioxide (CO2) absorption and desorption, at 313 and 393 K, respectively, from 30 wt% aqueous 2-(2-aminoethylamine)ethanol (AEEA), 30 wt% 2-amino-2-methyl-1-propanol (AMP) and 20 wt% AEEA + 10 wt% AMP solutions. The 13C NMR results indicate that the main AEEA species are free amine, protonated amine, primary carbamate and secondary carbamate, and the main AMP species are free amine and protonated amine. There is no evident indication that dicarbamate species of AEEA and carbamate of AMP are formed. When AEEA absorbs CO2, the formation of AEEA carbamate on primary amine is comparatively faster than that on secondary amine. During the CO2 desorption process, the AEEA carbamate on secondary amine is produced by an endothermic reaction, which reduces the overall efficiency of desorption. Six cycles of absorption-desorption tests are performed to measure the feasibility of regenerated amine solutions for reuse and the absorption amount of them remains essentially constant during the second to the sixth absorption-desorption experiments. Compared with pure AEEA solution, the recyclability of blended amines, AEEA + AMP, improves while the mol CO2/mol amine (CO2 loading) of the blended amines decreases.