CHAPTER 4: Alkali-metal-carbonate-based CO₂ Adsorbents

The capacity and kinetics of CO₂ sorption for Na₂CO₃ and K₂CO₃ under moist conditions were studied to determine the mechanism for CO₂ capture under ambient conditions. Bicarbonate formations of Na₂CO₃ and K₂CO₃ were examined by thermogravimetric analysis under various CO₂ concentrations and humidity, and the accompanying structural changes of Na₂CO₃ and K₂CO₃ were exhibited by X-ray diffraction (XRD). Also, morphological changes were observed during the reaction by scanning electron microscopy (SEM). The structural and morphological changes during the reactions were then related to the kinetic and exothermic properties of the CO₂ sorption of Na₂CO₃ and K₂CO₃ together with H₂O from XRD and SEM measurements. The modification of Na₂CO₃ and K₂CO₃ for improvement in regeneration temperature and CO₂ occlusion kinetics were also examined by substitution of different metal ions or formation of nanostructured materials.