Efficient and stable silica-supported iron phosphate catalysts for oxidative bromination of methane

FePO4/SiO2 was employed for the oxidative bromination of methane (OMB) for the first time. A methane conversion of 50% and total selectivity of 96% for CH3Br plus CO (CH3Br:CO ≈ 1) were obtained at 570 °C. Comparison experiments were designed to investigate the roles of O2, HBr and the catalysts. Powder X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), Fourier-transform infrared spectroscopy (FTIR) and 57Fe Mössbauer spectroscopic studies were conducted on the catalysts. It was confirmed that the FePO4 components of the fresh catalyst transformed quickly to stable active species during the induction period, and the active components of the stable catalyst have been found to consist of near-equimolar α-Fe3(P2O7)2 and Fe2P2O7. The reaction over the FePO4/SiO2 catalyst was proposed to follow a redox route based on the results of comparison experiments and associated characterization.