An efficient iron phosphorus oxide catalyst for selective oxidation of n-butane to maleic anhydride: Phase regulation enhances catalytic performance

Vanadium phosphorus oxide (VPO) is regarded as the most efficient catalyst for the selective oxidation of n- butane towards maleic anhydride (MA). However, to a certain extent, its industrial applications are restricted by the “trade-off” effect between n -butane conversion and MA selectivity. Here, an iron phosphorus oxide (FePO) catalyst was synthesized using a modified molten salt method and characterized. The optimum Fe 0.25 PO catalyst achieved considerable catalytic performance with n -butane conversion of 59.77 %, MA selectivity of 59.07 %, and MA yield of 35.31 %. Various characterizations revealed the relationship between the catalytic performance and physicochemical properties such as the crystal structure, surface P/Fe ratio, oxygen species, and surface acidity. The results indicated that the ordered Fe(PO 3 ) 3 structure was the primary active phase for the Fe 0.25 PO catalysts, in which the abundant exposure of Fe 3+ sites and active oxygen species contributed to improving the reactivity and n -butane conversion. In addition, acid sites distribution, Lat-O/Sur-O, Fe 3+ /Fe 2+ , P/Fe, and O/Fe are critical factors for determining the activity and MA selectivity. The exploration of FePO catalysts offers a guideline for the development of high-performance catalysts to replace VPO for n -butane selective oxidation to MA.