Effect of mechanochemical treatment on the structure and physicochemical properties of MoO3

Using X-ray phase analysis, IR spectroscopy, and derivatography we have shown that when molybdenum(VI) undergoes mechanochemical treatment in a planetary mill, along with an increase in the specific surface area changes also occur in the chemical composition and structure. The Mo-O-Mo bonds of the oxide lattice and the terminal Mo=O bonds are weakened and lengthened, evidence for which comes from IR spectroscopy data. Partial reduction of the molybdenum ions occurs with formation of the phase MoO2.8 in water, water-benzene, and water-alcohol medium. In the presence of ethanol, the Magnéli phase χ-4-Mo8O23 can be formed for a certain energy load according to a crystallographic shift mechanism. The presence of reduced phase and the increase in specific surface area promote an increase in the activity of the oxide in oxidation of benzene. Selective oxidation of benzene to maleic anhydride is favored by an increase in the relative content of the (020) crystallographic face. © 1999 Kluwer Academic/Plenum Publishers.