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

Abstract

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 Bronsted relation: ln(k) = A(pKa) + 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.