Catalysts and inhibitors for oxidative degradation of monoethanolamine

MEA solutions were subjected to oxidative degradation at both low and high gas rates. Solutions were degraded with 100 mL/min of 98%O-2/2%CO2 with mass transfer achieved by vortexing. Solutions were analyzed for degradation products by IC and HPLC. In a parallel apparatus 7.5 L/min of 15%O-2/2%CO2 was sparged through solution, with additional mass transfer achieved by vortexing. A Fourier Transform Infrared (FTIR) analyzer collected continuous gas-phase data on volatile products. Hydroxyethyl-formamide (HEF) and hydroxyethylimidazole (HEI) are the major liquid-phase oxidation products. In the presence of Fe2+ and Cu2+, HEF, HEI, and MEA losses increase by a factor of 3 compared to Fe2+ alone. Cr3+ and Ni2+, two metals present in stainless steel alloys, resulted in MEA losses that are 55% greater. In terms of oxidative degradation potential (greatest to lowest): Cu2+ > Cr3+/Ni2+ > Fe2+ > V5+. Inhibitor A reduces the formation of known products by 90% when catalyzed by Fe2+ and Cu2+ and by 99% with Cr3+/Ni2+. Inhibitor B reduces product rates by 97% and MEA losses by 75%, while a 100:1 ratio of EDTA to Fe2+ completely inhibits oxidation. (C) 2009 Elsevier Ltd. All rights reserved.