CO2 capture with alkanolamines has been in use since 1930, where MEA is the most studied absorbent for postcombustion. In order to prevent degradation, it is important to understand the degradation mechanisms, which in turn requires knowledge of both stoichiometry and kinetics of the reactions. The stability of the degradation products is a starting point when exploring possible mechanisms, and can be determined from the Gibbs free energy of the net reaction. In the present work, quantum mechanical calculations and continuum solvation models are used to calculate the reaction energy for different oxidative degradation reactions and to verify the suggested mechanism for thermal degradation of MEA with CO2. The suggested total reaction mechanisms for thermal degradation with CO2 were found to be energetically favorable, and oxalic acid, oxalamide and 1-(2-hydroxyethyl)-imidazole (HEI) were found to be of the most probable oxidative degradation products.
