Degradation of N-methyldiethanolamine desulfurization solution at high temperature and by sulfur dioxide, carbon dioxide, and oxygen blends

• CO2 and SO2 were considered as influence factors on degradation of MDEA.
• Temperature, SO2, CO2, and O2 were analyzed comparatively.
• Physical properties and desulfurization performance of MDEA were analyzed.
• Effects of degradation products on foaming behavior and foam stability were observed.

The effects of O2, SO2, CO2, and heating on the degradation and physical properties of 50 wt% MDEA solutions were evaluated systematically in a stirred reactor. The results showed that the degradation rate decreased in the order MDEA-O2 > MDEA-SO2 > MDEA-CO2, indicating the detrimental influence of the presence of O2 in the solvent. The results also showed that the degradation rate presented an upward trend with the increase of temperature. In addition, the degradation under different conditions caused the decrease of the pH value and surface tension of the solution. Also, a higher degradation rate resulted in a higher foaming tendency and foam stability, especially for MDEA-O2. Furthermore, the degradation products of MDEA-O2 all promoted foaming behavior and foam stability. Among these products, carboxylic acid had more influence on foaming than the other products.

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