Oxidative degradation of amine solvents for C02 capture
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This thesis focuses on the oxidative degradation of amine solvents used in coal-fired power plant flue gas CO2 capture. The relationship between amine structures and their oxidative degradation was studied at low temperature absorber conditions in order to identify stable amines that should be more rigorously screened. Amongst primary amines, those with three carbons separating the amino group from the neighboring electron-withdrawing group (such as PDA and MPA) showed resistance to oxidation, while those with even number of carbons (such as MEA, EDA, and DGA®) were susceptible to oxidation. Secondary amines did not follow the same observations. Tertiary amines resisted oxidation regardless of the structural characteristics mentioned above. The production of major oxidation products such as formate, oxalate and nitrite closely track parent amine degradation. Formate and oxalate are produced in certain ratios, and the ratio is different depending on the amine. Amine loss and formate also approach a certain ratio over time. The mechanism of oxidation is currently not well understood, and these observations are important to understanding the mechanisms of oxidation, production of nitrosamines from oxidation, and explaining why certain structures are resistant or susceptible to oxidation.