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

摘要

The capacity and kinetics of CO2 capture of K2CO3 were studied to determine the mechanism for CO2 sequestration under ambient conditions. Bicarbonate formatioft 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 MID results showed that the bicarbonate formation process of K2CO3 could be divided into three reactions, such as the formation of K2CO3 center dot 1.5H(2)O from K2CO3, the subsequent formation of K4H2(CO3)(3)center dot 1.5H(2)O from K2CO3 center dot 1.5H(2)O, and the slow formation of KHCO3 from K4H2(CO3)(3)center dot 1.5H(2)O. 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 CO, atmosphere during the initial stage, consisting of the first and second reactions, but the formation of KHCO3 from K4H2(CO3)(3)center dot 1.5H(2)O was thermodynamically favorable upon the increase of the CO2 concentration.