Selective mild oxidation of methane to methanol or formic acid on Fe–MOR catalysts
- 5 November 2019
- journal article
- research article
- Published by Royal Society of Chemistry (RSC) in Catalysis Science & Technology
- Vol. 9 (24), 6946-6956
- https://doi.org/10.1039/c9cy01640f
Abstract
Controllable methane oxidation directly into value-added products under mild conditions remains a challenge. Herein, an active Fe/MOR catalyst was synthesized via simple solid-state ion exchange, and its activity in the selective oxidation of methane with H2O2 in the aqueous phase was intensively investigated. The octahedral dimeric Fe3+ species [Fe2(μ-O)2] in the extra framework was confirmed as the initial active site by X-ray photoelectron spectroscopy, X-ray absorption near-edge structure and extended X-ray absorption fine structure, UV-vis diffuse-reflectance spectroscopy, and high-angle annular dark-field scanning transmission electron microscopy in combination with DFT calculations. The DFT calculations indicated that methanol formation via methyl peroxide (CH3OOH*) on [Fe2(μ-OH)2O2] is the most favorable pathway compared to the direct formation of methanol via CH3O*. The formed CH3OH is easily further oxidized by hydroxyl radicals (˙OH) resulting in non-selective methane oxidation. In contrast, the Fe/MOR catalyst could lead to a high methanol selectivity of 71.3% in the presence of homogeneous Cu2+ precursor, which efficiently suppressed the over-oxidation of methanol, and a high formic acid selectivity up to 81–82% at a slightly higher reaction temperature by mildly shifting the oxidation of methanol and formaldehyde to the target product.Keywords
Funding Information
- National Natural Science Foundation of China (21576119, 21878127, 21706098, 21606108, 21802054)
- Fundamental Research Funds for the Central Universities (JUSRP11813, JUSRP11709, JUSRP51720B)
- Natural Science Foundation of Jiangsu Province (BK20180587)
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