Zeolite acidity strongly influences hydrogen peroxide activation and oxygenate selectivity in the partial oxidation of methane over M,Fe-MFI (M: Ga, Al, B) zeolites

Abstract

The partial oxidation of methane to oxygenates, primarily formic acid, over a series of Fe-MFI zeolites with different trivalent framework atoms is reported. Numerous characterization techniques were used to confirm the crystallinity, composition, textural properties, and iron coordination in these solid catalysts. Ammonia temperature-programmed desorption along with in situ Fourier-transform infrared spectroscopy of pyridine were used to probe the acidity strength of these samples. These catalysts were then studied in the partial oxidation of methane using H₂O₂ as the oxidant at mild conditions. The two key findings from this work are that higher iron loadings than reported previously can still result in active catalysts and that the presence of strong acidity is key to H₂O₂ activation and controls the product selectivity, favouring formic acid over methanol. The most active catalysts have TON values of 159 and 165.