Enhanced Carbon Dioxide Capture Using a Mixed Amino Acid Salt Solution

This study investigated the carbon dioxide (CO2) absorption and desorption performance of a mixed amino acid solution (containing glycine (G), alanine (A), proline (P), and lysine (L), GAPL). These four amino acids were intentionally selected to reflect the chemical and structural variations (pKa and steric hindrance of amino groups) of amino acids. The single cycle CO2 capture experiment showed that the GAPL salt solution had 19% higher CO2 absorption (0.91 mol CO2/mol amino acids) compared to the absorption calculated by adding the proportional capacities of G, A, P, and L (0.77 mol CO2/mol amino acids). 13C NMR data delineated the effects of individual amino acids on carbamate and bicarbonate/carbonate formation and elucidated the distribution of captured CO2 in the GAPL salt solution. The recirculation experiment concluded that the GAPL salt solution had much better CO2 capture performance than the conventional monoethanolamine process. Less than 10% of the absorption and cyclic capacity of the GAPL salt solution was lost after ten cycles of CO2 capture. This study demonstrated an approach that blended amino acid solutions can be tailored and designed as new, efficient reagents to massively capture CO2 in a technically feasible, economically viable, and environmentally friendly manner.