Mechanosynthesis and mechanochemical treatment of bismuth-doped vanadium phosphorus oxide catalysts for the partial oxidation of n-butane to maleic anhydride

摘要

Three Bi-doped vanadyl pyrophosphate catalysts were prepared via dihydrate route (VPD method), which con- sisted of different preparation methods including mechanosynthesis, mechanochemical treatment, and the conventional reflux method. The catalysts produced by the above three methods were characterized by x-ray diffraction (XRD), scanning electron microscopy (SEM), and temperature programmed reduction (TPR). Catalytic evaluation for the partial oxidation of n-butane to maleic anhydride (MA) was also carried out. The XRD patterns of all the Bi-doped catalysts showed the main peaks of pyrophosphate phase. Lower intensity peaks were observed for the mechanochemically treated Bi-doped catalyst (VPDBiMill) with two additional small peaks corresponding to the presence of a small amount of V5+ phase. The TPR profiles showed that the highest amount of active oxygen species, i.e, V4+–O- pair, responsible for n-butane activation, was removed from VPDBiMill. Furthermore, from the catalytic test results, the graph of selectivity to MA as a function of the conversion of n-butane demonstrated that VPDBiMill was the most selective catalyst. This suggests that the mechanochemical treatment of vanadium phosphate catalyst (VPDBiMill) is a potential method to improve the catalytic properties for the partial oxidation of n-butane to maleic anhydride.