Carbon dioxide capture with alkanolamines has been in use since longtime, where monoethanolamine is the most studied absorbent for post combustion. 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.

A wide range of technologies exist for separation and capture of CO₂ from gas streams, of which a large number is based on absorption into solvents. Alkanolamines have been used as absorbents for several decades, MEA being the most studied absorbent. In the absorption processes, problems relating to degradation may be significant, causing not only loss of amine but also corrosion, foaming, fouling and plugging of the equipment, in addition to environmental problems. MEA itself is an accepted chemical regarding marine environment, as is supported by ecotoxity and bidegradation measurements.

Degradation may occur thermally with CO₂ present, or through oxidative degradation, depending on the conditions. In order to prevent degradation, it is important to understand the degradation mechanisms, which in turn requires knowledge of both the reaction stoichiometry and kinetics. 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.

Thermal degradation has been studied for a long time, but degradation studies for an oxidizing environment, as in flue gas, are more limited. Oxidative degradation of alkanolamines is believed to take place through radical formation, and the process has been found to be catalysed by iron. The specific mechanisms are still not fully understood and there are primarily two different mechanisms suggested that give the same degradation products

Anabell Rose
Journal of Bioremediation & Biodegradation
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