Kinetics of the reaction of CO2 with aqueous potassium salt of taurine and glycine

The kinetics of the reaction between CO2 and aqueous potassium salts of taurine and glycine was measured at 295 K in a stirred-cell reactor with a flat gas-liquid interface. For aqueous potassium taurate solutions, the temperature effect on the reaction kinetics was measured at 285 and 305 K Unlike aqueous primary alkanolamines, the partial reaction order in amino acid salt changes from one at low salt concentration to approximately 1.5 at salt concentrations as high as 3,000 mol.m(-3). At low salt concentrations, the measured apparent rate constant (kapp) for potassium glycinate is comparable to the values in literature. In the absence of reliable information in the literature on the kinetics and mechanism of the reaction, the applicability of the zwitterion and termolecular mechanism (proposed originally for alkanolamines) was explored. For the zwitterion mechanism, the forward second-order reaction rate constant (k(2)) of the CO2 reaction with amino acid salt seems to be much higher than for alkanolamines of similar basicity, indicating that the Bronsted plot for amino acid salts might differ from that of alkanolamines. The contribution of water to the deprotonation of zwitterion seems to be more significant than reported values for aqueous secondary alkanolamines.