A new kinetic model for CO2 capture on sodium zirconate (Na2ZrO3): An analysis under different flow rates

In this work, it is presented a kinetic study for CO2 capture on Na2ZrO3 as a function of temperature (250-550 degrees C) and CO2 flow rate (5, 60, and 120 mL/min). We discuss the relevance of a new kinetic model able to fit the experimental data and propose a consecutive reaction model for CO2 capture under low, moderate, and high CO2 flow rates. The proposed model considers that a Na2CO3-ZrO2 layer is formed at the particle surface level, and then, the capture process is later enhanced by Na+ ions diffusion, but its improvement depends entirely on the surface capture. This kinetic approach allowed a better fit for CO2 capture results, describing well the variations obtained as a function of the different flow rates tested between 250 and 550 degrees C. Thermogravimetric and kinetic data showed that the CO2 capture was benefited as the CO2 flow rate increased from 5 to 120 mL/min. However, high flow rates (60 and 120 mL/min) achieved similar capture efficiencies (sigma approximate to 90 %), only once the CO2 sorption-desorption equilibrium was reached. In addition, through the Eyring model analysis, the activated state energy was calculated, being within the range of 0.84 and 1.20 eV for the surface capture and between 0.89 and 1.02 eV for bulk capture (related to Na+ diffusion). In the final section, it was discussed the CO2 sorption desorption process takes place at both, low temperature and flow rate, and how such a process inhibits or triggers high-temperature CO2 capture.

Automated summary

This work presents a kinetic study of CO2 capture on Na2ZrO3 as a function of temperature and CO2 flow rate. A new kinetic model is proposed and discussed, which considers the formation of a Na2CO3-ZrO2 layer and the enhancement of the capture process by Na+ ions diffusion. The results show that the CO2 capture efficiency is improved as the CO2 flow rate increases. The activated state energy for surface capture and bulk capture are calculated using the Eyring model. The study also discusses the impact of CO2 sorption desorption process at low temperature and flow rate on high-temperature CO2 capture.