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 CO 2 loaded MEA, with and without a corrosion inhibitor (NaVO 3 ), was performed in a stainless steel rotary-type autoclave with MEA concentrations of 11.4 and 17.9 mol %, NaVO 3 concentration of 0.1 mol %, O 2 pressures of 250 and 350 kPa, and CO 2 loading ranging from 0 to 0.44 (mol of CO 2 )/(mol of MEA) at temperatures of 328−393 K (typical absorber and stripper temperatures). The results showed that the presence of NaVO 3 and increases in MEA concentration, temperature, or O 2 pressure resulted in an increase in the MEA degradation rate. In contrast, an increase in CO 2 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: − r MEA = { k 1 1 [MEA] a [O 2 ] b }/{ k 2 + k 3 [O 2 ] c + k 5 [CO 2 ] e }. This rate model shows that, in a CO 2 loaded system, the loaded CO 2 acts as a degradation inhibitor. In addition, the order of reaction with respect to MEA ( a ) for all the systems investigated was ∼1.