Isothermal reduction of V2O5 powder using H2 as oxygen carrier: Thermodynamic evaluation, reaction sequence, and kinetic analysis

V2O3 was prepared by reducing V2O5 powder using H-2 as the oxygen carrier. To initially determine reasonable experimental for the H-2-based reduction, oxygen potential and equilibrium calculations were performed. The reaction sequence of the V2O5 powder reduction was predicted by V=O phase diagram assessments and was then verified by XRD and XPS measurements under various experimental condition. It was observed that the reduction followed the path of V2O5-VnO(2n+1)(n = 3 and 6)-VO2-VnO(2n-1)(n = 7, 6, 5, 4, and 3)-V2O3. Isothermal reduction experiments and kinetic analysis were performed using thermogravimetric analysis (TGA) at 813 K, 823 K, and 833 K, under a pure H2 gas flow. The entire reduction process, from V2O5 to V2O3, obeyed the unreacted shrinking core model (with random instant nucleation and three-dimensional growth of nuclei) and was controlled by chemical reactions. Mathematical fitting showed that the reduction process could be described as G (alpha) = [-ln(1-alpha)]1/3, and the apparent activation energy was determined to be 47.11 kJ.mol(-1). (C) 2020 Elsevier B.V. All rights reserved.

Automated summary

V2O3 was prepared by reducing V2O5 powder using H-2 as the oxygen carrier. Oxygen potential and equilibrium calculations were performed to determine reasonable experimental conditions for the H-2-based reduction. The reduction process from V2O5 to V2O3 followed a specific sequence and was controlled by chemical reactions, with an apparent activation energy of 47.11 kJ.mol(-1).