Effect of the Nuclearity and Coordination of Cu and Fe Sites in Beta Zeolites on the Oxidation of Hydrocarbons

Cu- and Fe-zeolites can activate oxygen for oxidative reactions of methane and stable hydrocarbon molecules. Here, we analysed the activity of Cu- and Fe- sites with various nuclearities and coordination in *BEA zeolites towards complete oxidation of methane, toluene and ethanol by molecular oxygen. Spectral analysis of the interaction of methane with the individual Cu and Fe sites and a kinetic study show that the oxidation of methane is catalysed by different active sites with different activation energies. In the low temperature region (225 - 325 °C), the activity is primarily caused by reactive bridging oxygen atoms in dimeric Cu and Fe clusters. Isolated Fe3+-oxo ions in octahedral coordination and Cu2+ partially charge-balanced by the framework with less rigid redox states contribute to the activity at higher temperatures, ≥ 350 °C. The isolated Fe3+-oxo ions tetrahedrally coordinated to framework oxygen and the bare Cu2+ ions charge-balanced exclusively by the framework are strongly stabilized and ...