Kinetics and Structural Changes in CO2 Capture of K2CO3 under a Moist Condition

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• 作者：Hongchao Luo ; Hideyuki Chioyama ; Stephan Th眉rmer ; Tomonori Ohba ; Hirofumi Kanoh
• 刊名：Energy & Fuels
• 出版年：2015
• 出版时间：July 16, 2015
• 年：2015
• 卷：29
• 期：7
• 页码：4472-4478
• 全文大小：529K
• ISSN：1520-5029

文摘

The capacity and kinetics of CO₂ capture of K₂CO₃ were studied to determine the mechanism for CO₂ sequestration under ambient conditions. Bicarbonate formation of K₂CO₃ was examined by thermogravimetric analysis under various CO₂ concentrations in the presence of water vapor, and the accompanying structural changes of K₂CO₃ were demonstrated by X-ray diffraction (XRD). Morphological variations were observed during the reaction in the presence of different CO₂ concentrations through scanning electron microscopy (SEM). Structural changes and morphological variations, which occurred during the course of the reaction, were then connected to the kinetic and exothermic properties of the CO₂ capture process from XRD and SEM measurements. The XRD results showed that the bicarbonate formation process of K₂CO₃ could be divided into three reactions, such as the formation of K₂CO₃路1.5H₂O from K₂CO₃, the subsequent formation of K₄H₂(CO₃)₃路1.5H₂O from K₂CO₃路1.5H₂O, and the slow formation of KHCO₃ from K₄H₂(CO₃)₃路1.5H₂O. The SEM observations showed that the morphology of the particles at all three stages played a crucial role in the kinetic behavior for CO₂ sorptivity of K₂CO₃. CO₂ capture of K₂CO₃ was inhibited under a concentrated CO₂ atmosphere during the initial stage, consisting of the first and second reactions, but the formation of KHCO₃ from K₄H₂(CO₃)₃路1.5H₂O was thermodynamically favorable upon the increase of the CO₂ concentration.