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>Role of polyoxometalate precursors and supports in the selective oxidation of methane into formaldehyde using supported metal oxide subnanocluster catalysts
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Role of polyoxometalate precursors and supports in the selective oxidation of methane into formaldehyde using supported metal oxide subnanocluster catalysts
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机译：Role of polyoxometalate precursors and supports in the selective oxidation of methane into formaldehyde using supported metal oxide subnanocluster catalysts
The direct synthesis of useful chemicals from methane (CH4) is desirable; however, the products are prone to nonselective overoxidation, leading to the formation of CO2. A previous study developed a supported iron oxide subnanocluster catalyst with high thermal stability using iron-containing polyoxometalates (POMs) as precursors to selectively produce formaldehyde (HCHO) and CO. Herein, we investigated various supported POM-based catalysts to further improve the selectivity to HCHO via CH4 oxidation, specifically by suppressing the pyrolysis and overoxidation of HCHO. After examining various metal-containing POM precursors and supports, we found that catalysts prepared using mononuclear- and dinuclear-iron-containing POM precursors supported on SiO2 with a high specific surface area were effective and yielded relatively high quantities of HCHO. In situ diffuse reflectance infrared Fourier transform spectroscopy (DRIFTS) measurements under HCHO flow demonstrated that the pyrolysis and oxidation of HCHO were suppressed on SiO2, while the pyrolysis of HCHO was promoted on Al2O3. Furthermore, in situ DRIFTS measurements conducted at different temperatures revealed that HCHO was not decomposed or oxidized at 500 °C in the absence of catalysts.
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