Combined Effect of Temperature and pK_a on the Kinetics of Absorption of Carbon Dioxide in Aqueous Alkanolamine and Carbonate Solutions with Carbonic Anhydrase

In present work the absorption of carbon dioxide in aqueous N-methyldiethanolamine, N,N-dimethylethanolamine, and triisopropanolamine solutions with and without the enzyme carbonic anhydrase has been studied in a stirred cell reactor at temperatures varying between 278 and 313 K, at an alkanolamine concentration of 1 kmol m^-3 and carbonic anhydrase concentrations ranging from 0 to 2.4 kg m^-3, respectively. The experimental data from these experiments have been used to fit the obtained rate constant for the enzymatic CO₂ hydration to the Brønsted relation: ln(k) = A(pK_a) + B + C/T. In addition to the carbon dioxide absorption in the three tertiary alkanolamines, the absorption of carbon dioxide in next three solvents had been studied: 0.3 kmol m^-3 potassium carbonate, 0.3 kmol m^-3 sodium carbonate, and 0.2 kmol m^-3 2-amino-2-methyl-1-propanol. The kinetics from these solvents are well predicted by the relation fitted to the data of the tertiary amines only.