Reoxidation Performance Of Vanadium Phosphorus Oxide Catalyst For Selective Oxidation Of N-Butane To Maleic Anhydride

The partial oxidation of n-butane to Maleic Anhydride (MA) over vanadium phosphorus oxide (VPO) catalyst is still the only heterogeneously catalyzed, alkane-selective oxidation reaction in commercial use.Three kinds of VPO catalysts, used to the model reaction system, n-butane oxidation to MA were investigated. By the means of thermogravimetric unit, fixed bed micro-reactor, on-line chromatographic and mass spectroscopy, oxidation regeneration kinetics and the performance of steady-state reaction were probed. The best catalyst suitable to forced unsteady-state reaction was distinguished.At first, a simple, and accurate GC analysis method and the method for processing experimental data were established for n-butane selective oxidation to MA. An experimental set-up was built for investigating the steady-state operation of fixed bed reactor. Under steady-state conditions, the performances of three kinds of the VPO catalysts were evaluated and compared each other.Secondly, the thermal oxidation regeneration process and its reaction kinetics were investigated by temperature-programmed-oxidation (TPO). The best catalyst suitable to forced unsteady-state reaction was distinguished, combining steady-state performance.Thirdly, re-oxidation rate equation was deduced and identified. The results show that the re-oxidation process of the catalyst obeys the contracted core model controlled by phase border, and the rate-controlling step is chemical reaction. A model of oxidation regeneration process for VPO catalyst is developed for simulation and prediction purposes.Finally, using TGA unit and on-line mass spectroscopy (MS) transient measurement in fixed bed micro-reactor, the modulation of feed composition transient response experiments were completed and the stability of REDOX cycle was also examined.