Comprehensive Study of the Kinetics of the Oxidative Degradation of CO2 Loaded and Concentrated Aqueous Monoethanolamine (MEA) with and without Sodium Metavanadate during CO2 Absorption from Flue Gases

A comprehensive mechanistic-based kinetic study of the oxidative degradation of CO2 loaded MEA, with and without a corrosion inhibitor (NaVO3), was performed in a stainless steel rotary-type autoclave with MEA concentrations of 11.4 and 17.9 mol %, NaVO3 concentration of 0.1 mol %, O2 pressures of 250 and 350 kPa, and CO2 loading ranging from 0 to 0.44 (mol of CO2)/(mol of MEA) at temperatures of 328-393 K (typical absorber and stripper temperatures). The results showed that the presence of NaVO3 and increases in MEA concentration, temperature, or O2 pressure resulted in an increase in the MEA degradation rate. In contrast, an increase in CO2 loading led to a decrease in the degradation rate. The general mechanistic rate model obtained to represent all the systems investigated was of the following form: - rMEA = {k11[MEA]a[O2]b}/{k2 + k3[O2]c + k5[CO2]e}. This rate model shows that, in a CO2 loaded system, the loaded CO2 acts as a degradation inhibitor. In addition, the order of reaction with respect to MEA (a) for all the systems investigated was ~1.