Pathways for the Formation of Products of the Oxidative Degradation of CO₂-Loaded Concentrated Aqueous Monoethanolamine Solutions during CO₂ Absorption from Flue Gases

Oxidative degradation experiments involving CO 2 -loaded monoethanolamine (MEA) were performed in a stainless steel rotary-type autoclave with MEA concentrations of 5 and 7 mol/L, O 2 pressures of 250 and 350 kPa, and a CO 2 loading ranging from 0 to 0.44 mol of CO 2 /mol of MEA at temperatures of 55−120 °C in order to elucidate the pathways for the formation of degradation products under typical absorber and stripper conditions and to evaluate the effects of temperature, O 2 pressure, MEA concentration, and CO 2 loading on MEA degradation. The results showed that an increase in the temperature or O 2 pressure resulted in an increase in degradation for both the MEA−H 2 O−O 2 and MEA−H 2 O−O 2 −CO 2 systems. However, an increase in the MEA concentration gave the opposite effect for all of the systems. The number of products and the extent of degradation decreased in the following order: MEA−H 2 O−O 2 > MEA−H 2 O−O 2 −CO 2 > MEA−H 2 O−CO 2 . The gas chromatograph/mass spectrometer method was used to identify the degradation products, which were then used to propose pathways for their formation that are consistent with the products and the operating conditions.