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 13 C nuclear magnetic resonance (NMR) spectroscopy was used to study carbon dioxide (CO 2 ) 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 13 C 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 CO 2 , the formation of AEEA carbamate on primary amine is comparatively faster than that on secondary amine. During the CO 2 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 CO 2 /mol amine (CO 2 loading) of the blended amines decreases.