Synthesis and functional verification of the unsupported active phase of VxOy catalysts for partial oxidation of n-butane

We studied unsupported VxOy nanoparticles prepared by a novel nonaqueous route in the selective oxidation of n-butane to maleic anhydride. The evolution of the electronic and geometric structure of the material was characterized by X-ray photoemission spectroscopy, electron energy-loss spectroscopy, transmission electron microscopy, and electron diffraction before and after the reaction at different temperatures. A change from a water-mediated C-C bond cracking functionality of the catalyst forming acetic acid to an oxidizing functionality resulting in maleic anhydride was observed. It was found that the particles underwent a radical modification of the geometric and electronic structure that finally resulted in V2O5 crystals. Experimentally derived conclusions are related to some conceptual claims from the literature. (c) 2005 Elsevier Inc. All rights reserved.