PATHWAYS AND REACTION PRODUCTS FOR THE OXIDATIVE DEGRADATION OF CO_2 LOADED AND CONCENTRATED AQUEOUS MEA AND MEA/MDEA MIXTURES DURING CO_2 ABSORPTION FROM FLUE GASES

摘要

The products and pathway for the oxidative degradation of CO_2-loaded and concentrated aqueous solution of MEA/MDEA mixture (i.e. MEA-MDEA-H_2O-CO_2 system) were evaluated and compared with those for MEA-H_2O-CO_2 system in a stirred cell reactor at temperatures in the range of 55-120℃, overall amine concentration in the range of 5-9 mol/L, MDEA/MEA ratio of 0-0.4, CO_2 loading in the range of 0-0.53 mol/mol total amine and O_2 pressure of 250 kPa. Results showed that fewer degradation products were obtained for the MEA-H_2O-O_2 system for both the CO_2 loaded and CO_2-free cases as compared with the MEA-MDEA-H_2O-O_2 system. Also, fewer degradation products were obtained with the CO_2-loaded case than the CO_2-free case for both the MEA-H_2O-O_2 and MEA-MDEA-H_2O-O_2 systems. Our overall results tend to indicate that, under our experimental conditions, MDEA is more prone to oxidative degradation and, when used in a mixture with MEA, is preferentially degraded to protect MEA. Our results further show that even in an initially O_2 free environment, O_2 is produced as a by-product of CO_2-induced degradation, thereby eventually generating an oxidative degradation environment for the two systems.