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 CO2-loaded monoethanolamine (MEA) were performed in a stainless steel rotary-type autoclave with MEA concentrations of 5 and 7 mol/L, O2 pressures of 250 and 350 kPa, and a CO2 loading ranging from 0 to 0.44 mol of CO2/mol of MEA at temperatures of 55-120 (degree) 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, O2 pressure, MEA concentration, and CO2 loading on MEA degradation. The results showed that an increase in the temperature or O2 pressure resulted in an increase in degradation for both the MEA-H2O-O2 and MEA-H2O-O2CO2 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-H2O-O2 > MEA-H2O-O2-CO2 > MEAH2O-CO2. 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.