Electronically Mediated Reactions in Metal Thermal Reduction of Molybdenum and Tungsten Oxide Compounds

Resumo

The reduction of tungsten and molybdenum oxide compounds (WO₃, MoO₃, MgWO₄, MgMoO₄, and CaMoO₄) with calcium vapor at 800–860°С and a residual argon pressure of 5–10 kPa has been studied. As previously during the reduction with magnesium vapor, the spatial separation of the reaction products was observed, namely, the major portion of the calcium oxide formed in the reaction was deposited outside the reaction zone. A specific feature of the reduction of MgWO₄ and MgMoO₄ is that the magnesium is first replaced by calcium. The resulting magnesium metal acts as a reducing agent, and the magnesium oxide, along with calcium oxide, forms a crust on the surface of the reaction mass. Analysis of the experimental results shows that the reduction of oxide compounds with magnesium and calcium vapors at a residual argon pressure of more than 5 kPa proceeds via the electronically mediated reaction mechanism without direct physical contact between the reactants.