Thermogravimetric analysis of kinetic characteristics of K2CO3-impregnated mesoporous silicas in low-concentration CO2
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The requirement for self-sustained and long-duration human operations in confined spaces including submarines, spacecrafts, or underground citadels has made ambient removal of low-concentration CO2 a critical technology. Mesoporous silica materials have been regarded as promising carriers to support active components for CO2 sorption. The CO2 sorption kinetic of mesoporous silica-supported adsorbent is an important parameter to be assessed. In this paper, K2CO3-impregnated mesoporous silicas were prepared by impregnating K2CO3 on MCM-41, SBA-15, and silica gel (SG) in ethanol solution, respectively. The CO2 sorption experiments were performed in a simulated confined space atmosphere of 1.0 % CO2, 2.0 % H2O, and 293–333 K using thermogravimetric analysis. The kinetic performances of the sorbents were evaluated by fitting the experimental data to the shrinking core model. K2CO3/SG exhibited the optimum carbonation kinetic performance. The apparent activation energies for chemical reaction-controlled region and internal diffusion-controlled region are 3.95 and 64.87 kJ mol−1, respectively. To obtain the specific carbonation kinetic mechanism, a double exponential model was used to simulate the carbonation process of K2CO3/SG. The apparent activation energies for H2O diffusion–hydration and CO2 diffusion–carbonation stages are 8.40 and 4.32 kJ mol−1, respectively. H2O diffusion–hydration is the rate limiting step in the whole carbonation process.
KeywordsThermogravimetric analysis Carbonation kinetic K2CO3-impregnated mesoporous silicas Low-concentration CO2
Financial support from the National Natural Science Foundation of China (No. 51206155), the Science Foundation of Key Laboratory of Energy Thermal Conversion and Control of Ministry of Education, and the Fundamental Research Funds for the Central Universities of China (WK2320000023) is sincerely acknowledged.
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