Effect of Ⅲ B metals (Sc, Y, La and Ce) on active components regulation of VPO catalyst in n-butane selective oxidation

•The Ⅲ B elements were used to modify the VPO catalyst, and the similarities and differences between VPO catalysts were investigated to better understand the catalytic mechanism.•The addition of sc and Y reduces the V5+/V4+ ratio of VPO catalyst, thereby reducing the surface acidity. The suitable acidity and the increasement of lattice oxygen content ultimately improve the MA yield.•The high V5+/V4+ ratio of La- and Ce-VPO catalysts results in an excess of strong acid sites, resulting in a decrease in MA yield despite the high lattice oxygen content.