Evaluation and Development of CO₂ Absorbents by Thermal Analysis

Abstract

Single phase specimen of polycrystalline Ba₂Fe₂O₅, which has been a candidate for CO₂ absorbents, was prepared by solid state reaction method under N₂ flow. Ba₂Fe₂O₅ showed weight increase above 450 °C under CO₂ flow, which was originated from CO₂ absorption. The weight decrease due to CO₂ desorption was observed above 1100 °C under CO₂ flow. Thermogravimetry (TG) and X-ray diffraction measurements have revealed that Ba₂Fe₂O₅ can reversibly react with CO₂, which is represented as Ba₂Fe₂O₅ + CO₂ ⇄ BaCO₃ + BaFe₂O₄. Thermodynamic calculation of this reaction was carried out, showing agreement with the results obtained by TG measurements. The reaction kinetics of CO₂ absorption by Ba₂Fe₂O₅ was investigated by TG under various P(CO₂)'s. The calculated Ellingham diagram of the reaction was found to show agreement with the variation in the equilibrium temperature of the reaction with P(CO₂). The results of the morphology observation, specific surface area analysis and TG measurement suggested that CO₂ absorption mechanism was described by a superficial reaction, a diffusion-controlled process, and a sintering reaction as the reaction proceeds. The kinetics of CO₂ absorption for the diffusion-controlled process has been analyzed with the Jander function.