Temperature-Dependent Double-Step CO 2 Occlusion of K 2 CO 3 under Moist Conditions

Abstract

In this study, CO₂ occlusion of K₂CO₃ was examined at different temperatures under moist conditions. The CO₂ occlusion rate increased with increasing temperatures, whereas the saturated occlusion amount decreased. The highest occlusion amount (i.e. 6.48 mmol·g⁻¹) was obtained at 313 K. Results of X-ray powder diffraction analysis showed that the formation of bicarbonate as a result of the K₂CO₃ decomposition with CO₂ and H₂O involved two reactions with K₄H₂(CO₃)₃·1.5H₂O as an intermediate. It was determined that the lower saturated occlusion amount at higher temperatures originated from the exothermic property of the second reaction. Because the equilibrium constant for the bicarbonate formation is smaller at higher temperatures, the reaction does not proceed as quickly or efficiently according to Le Châtelier's principle. Therefore, the CO₂ occlusion of K₂CO₃ is suitable for the saturated occlusion amount at lower temperatures.