Experimental and Theoretical Thermokinetic Analysis of the Na3VO4–CO2 Reaction System under Different Physicochemical Conditions

Abstract

Sodium vanadate (Na₃VO₄) was synthesized, structural and microstructurally characterized as well as tested as possible carbon dioxide (CO₂) captor through thermodynamic calculations in addition to thermogravimetric dynamic and isothermal analyses. Ceramic structural characterization evidenced the formation of the Na₃VO₄ crystal phase, while microstructural features evidenced dense agglomerates with a poor specific surface area, although the synthesis temperature (600 °C) was not as high as that for other sodium ceramics. Na₃VO₄ was investigated for the CO₂ capture process through dynamic and isothermal experiments in the presence or absence of oxygen. All of these experiments showed that Na₃VO₄ possesses interesting CO₂ capture properties in a specific temperature range (520 and 600 °C). Isothermal product characterization allowed us to elucidate the reaction pathway, implying the Na₄V₂O₇ formation, as possible reactive intermediate. In fact, reaction path evolution was supported with theoretical thermodynamic data. Moreover, the kinetic analysis, performed using the Avrami-Erofeev mathematical model and subsequent thermodynamic data obtention, probed the positive influence of the temperature in both the CO₂ superficial and bulk chemical sorption processes, while oxygen addition did not enhance the superficial process. Additionally, as would be expected, kinetics were enhanced as a function of the CO₂ concentration.