Reaction Kinetics of CO₂ in Aqueous Methyl- and Dimethylmonoethanolamine Solutions

In the present work, kinetics of the carbon dioxide (CO₂) reactions with N-methylmonoethanolamine (MMEA) and N,N-dimethylmonoethanolamine (DMMEA) is investigated by using a stirred-cell reactor. The reaction with the linear secondary amine, MMEA, is described by both the zwitterion and termolecular mechanisms, whereas the reaction with the tertiary amine, DMMEA, is described by the base-catalyzed hydration of CO₂. Densities and viscosities of both amines in aqueous solutions are measured at 298, 303, and 308 K over a wide range of amine concentrations. The investigated reactions are of the first order with respect to both CO₂ and amine. On the basis of the temperature dependence of the second-order rate constants, the activation energy is evaluated. It is found that the increase in temperature and amine concentration causes the expected increase in the values of the observed reaction rate constants.