Kinetics of Carbon Dioxide Removal by Aqueous Alkaline Amino Acid Salts

Abstract

Aqueous solutions containing alkaline salts of carboxylic or sulfonic amino acids represent candidate solvents with good potential for carbon dioxide (CO2) capture. In the present work, the CO2 reactions with potassium salts of glycine (aminoacetic acid) and taurine (2-aminoethanesulfonic acid) in aqueous solutions are investigated using a stirred-cell reactor. The reaction pathways are comprehensively described using the zwitterion and the termolecular mechanism. The investigated reactions belong to the fast pseudo-first-order reaction regime systems. The second-order rate constant for the CO2 reaction with potassium glycinate is determined, and its value at 303 K is evaluated to be 6.29 m3/(mol s). The liquid-side mass-transfer coefficient is estimated, and its value (0.006 cm/s) is consistent with those typical for stirred-cell reactors. Finally, it is determined that potassium glycinate promotes the activity of tertiary amines (e.g., N,N-diethylethanolamine).