CO₂ Absorption on Na₂ZrO₃:  A Kinetic Analysis of the Chemisorption and Diffusion Processes

Abstract

The kinetics analysis of carbon dioxide (CO 2 ) chemisorption on sodium zirconate (Na 2 ZrO 3 ), which implies a sodium diffusion process, was investigated. Initially, Na 2 ZrO 3 was analyzed by X-ray diffraction, scanning electron microscopy, and N 2 adsorption, to characterize the material. Finally, the material was thermally analyzed under a CO 2 flux. Later, different isothermal experiments were performed under a CO 2 flux to study kinetically the CO 2 chemisorption on Na 2 ZrO 3 . Results showed that there is a sintering effect of the sample during the heating process. This effect produced, at low temperatures, a decrease in the CO 2 chemisorption efficiency. However, at high temperatures, once the sodium diffusion was activated, the sintering effect did not interfere with the CO 2 chemisorption process. Modeling the CO 2 chemisorption on Na 2 ZrO 3 (in terms of a double process: chemisorption and sodium diffusion) allowed us to estimate the activation energy for these processes, 33 866 J/mol (chemisorption) and 48 009 J/mol (diffusion), which demonstrated that the diffusion process is the limiting step.