摘要
VPO are well-known catalysts for the oxidation of n-butane to maleic anhydride. The catalytic behavior is influenced by several factors, such as the phase composition and the vanadium oxidation state of VPO catalysts. These catalysts have been characterized by means of XRD and XPS, but it is difficult to detect the presence of low concentrations of VOPO<sub>4</sub> phases
