Changes in structure and catalytic properties of V2O5 caused by mechanochemical treatment

By means of x-ray phase analysis and tunneling microscopy, it has been shown that when vanadium(V) oxide in an ethanol medium is subjected to mechanochemical treatment in a planetary mill, it undergoes not only size reduction with an increase of surface area, but also a change of structure. Extension of the processing time increases the relative content of the vanadyl plane (010) by a factor of more than 5. It has been established by means of x-ray photoelectron spectroscopy that some of the surface vanadyl ions are reduced. Modification of the structure and composition of the surface of the vanadium oxide leads to changes in its catalytic properties in n-butane and benzene oxidation reactions. The approximately twofold increase of hydrocarbon conversion may be related to the increase of surface area of the specimen; this view is supported by the constancy of the specific rate of n-butane oxidation. The sharp increases that are observed in the selectivity of maleic anhydride formation (sixfold in the oxidation of n-butane, threefold in the oxidation of benzene) are related to the increased content of the vanadyl plane and the surface formation of groupings of vanadium differing in valence.