Kinetics and redox properties of vanadium phosphate catalysts for butane oxidation

The kinetics of butane oxidation over two vanadium phosphate catalysts of differing phosphorous to vanadium ratios (P/V = 1.0 and 1.1) were studied in order to assess the effects of phosphorous content on butane oxidation kinetics. These catalysts were prepared in an organic medium and demonstrated yields of maleic anhydride (MA) comparable to those claimed in commercial catalysts. The primary reaction products were MA and carbon oxides. The kinetic data were correlated by an eight parameter model which accounts for reaction inhibition by butane and MA. The PV1.0 catalyst was approximately twice as active as the PV1.1 catalyst, while the selectivities to MA were similar. Transient reaction experiments and redox titrations indicate that the redox processes taking place under reaction conditions are restricted to a near-surface region.