Microstructural Thermal Evolution of the Na2CO3 Phase Produced during a Na2ZrO3-CO2 Chemisorption Process

Na2ZrO3 was synthesized by a solid-state reaction, and a CO2 chemisorption process was evaluated as a function of temperature to determine whether structural and/or microstructural modifications occurred during the reaction process. This study was performed using the following techniques: thermogravimetry, X-ray diffraction, scanning and transmission electron microscopy, and N-2 adsorption. The results clearly show that Na2CO3-ZrO2 was produced on the external shell of Na2ZrO3 during the CO2 chemisorption process. The microstructural properties varied as a function of temperature. The Na2ZrO3-CO2 chemisorption reaction was not limited at T <= 550 degrees C because the Na2CO3-ZrO2 external shell contained mesopores. CO2 diffused through the mesoporous shell, and the reaction continued. Conversely, if the CO2 chemisorption occurred at T > 550 degrees C, the mesoporosity on the Na2CO3-ZrO2 external shell was not observed, and the chemisorption was kinetically controlled by the diffusion of CO2 through the sodium crystal phases.