In Situ X‐ray Diffraction Studies on the Reduction of V₂O₅ and WO₃ by Using Hydrogen

Abstract

The reduction of metal oxides with hydrogen is widely used for the production of fine chemicals and metals both on the laboratory and industry scale. In situ methods can help to elucidate reaction pathways and to gain control over such synthesis reactions. In this study, the reduction of WO3 and V2O5 with hydrogen was investigated by in situ X‐ray powder diffraction with regard to intermediates and the influence of heating rates and hydrogen flow rates. Mixtures of V4O9, V6O13 and VO2 in two modifications were identified as intermediates on the way to phase‐pure V2O3. None of the intermediates occurs in a single phase and therefore cannot be prepared this way. In contrast, the intermediates of the WO3 reduction, H0.23WO3 and W10O29, appear consecutively and can be isolated. For both reactions, the heating and flow rates have little influence on the formation of intermediates.

In Situ X-ray Photoelectron Spectroscopy Study of Initial Stages of Tungsten Trioxide Reduction by Low-Energy Hydrogen Bombardment

“…The annealing of WO 3 in a hydrogen atmosphere at temperatures higher than 1000 K leads to the complete removal of oxygen and the formation of metallic tungsten. 40 Indeed, the most common technological method for preparing tungsten metal powder is the hydrogen-driven reduction of WO 3 . 41 In this process, the insertion of large amounts of H atoms at elevated temperatures into the WO 3 matrix leads to the removal of the O atoms via the formation of H 2 O molecules.…”

“…The annealing of WO 3 in a hydrogen atmosphere at temperatures higher than 1000 K leads to the complete removal of oxygen and the formation of metallic tungsten . Indeed, the most common technological method for preparing tungsten metal powder is the hydrogen-driven reduction of WO 3 .…”