Oxidation Inhibitors for Copper and Iron Catalyzed Degradation of Monoethanolamine in CO₂ Capture Processes

Abstract

This study examines the effect of a number of additives on the oxidative degradation of monoethanolamine (MEA) in the presence of dissolved Cu. Additives were selected from three categories: O2 scavengers and reaction inhibitors, chelating agents, and stable salts. Three proprietary inhibitors have been identified that significantly inhibit the rate of degradation at concentrations below 100 mM. Inhibitor A is a stable compound, while Scavengers B and C are stoichiometrically degraded to products that must be removed in an industrial application. Hydroquinone, ascorbic acid, manganese sulfate, and potassium permanganate all increased the rate of oxidative degradation. EDTA (ethylene-diamine-tetraacetic acid) was an effective chelating agent but lost inhibiting capacity over time. Phosphate was a weak chelating agent. Heat stable salts, including potassium chloride, potassium bromide, and potassium formate, were also ineffective oxidation inhibitors. Potassium formate was the strongest of the stable salts tested and decreased degradation by 15% at 0.55 M.