Absorption of CO₂ into Aqueous Potassium Salt Solutions of l-Alanine and l-Proline

Aqueous potassium salt solutions of l -alanine and l -proline were investigated as carbon dioxide (CO 2 ) absorbents. The CO 2 absorption capacities and absorption heats (−Δ H abs ) of the aqueous amino acid salts were measured in a semi-batch absorption system and differential reaction calorimeter (DRC). The solution experiments tested concentrations of 2.5 M and were carried out at 298 and 313 K. The 13 C and 1 H nuclear magnetic resonance (NMR) spectra were used to identify the species distributions in the CO 2 -loaded absorbents. The absorption properties were compared to those of the commercial monoethanolamine (MEA) absorbent, revealing that the CO 2 loading capacity was higher than that of MEA (0.68 mol of CO 2 /mol of solute for the potassium salt of l -alanine > 0.5 mol of CO 2 /mol of solute for MEA). The absorption heat was lower than that of MEA at 298 K (53.26 kJ/mol of CO 2 for the potassium salt of l -alanine < 81.77 kJ/mol of CO 2 for MEA).