Room-Temperature Oxidation of Methane by 伪-Oxygen and Extraction of Products from the FeZSM-5 Surface

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• 作者：Eugeny V. Starokon ; Mikhail V. Parfenov ; Larisa V. Pirutko ; Sergei I. Abornev ; Gennady I. Panov
• 刊名：Journal of Physical Chemistry C
• 出版年：2011
• 出版时间：February 10, 2011
• 年：2011
• 卷：115
• 期：5
• 页码：2155-2161
• 全文大小：869K
• 年卷期：v.115,no.5(February 10, 2011)
• ISSN：1932-7455

文摘

Room-temperature oxidation of methane to methanol by 伪-oxygen is of great mechanistic interest for both conventional and biomimetic oxidation catalysis. This work was carried out using new-generation FeZSM-5 samples that have the O_伪 concentration of 100 渭mol/g. This value exceeds 3鈭?5 times the O_伪 concentration on the earlier studied samples, thus providing more precise quantitative measurements related to the reaction mechanism. Fourier transform infrared spectroscopy data confirmed an earlier conclusion that CH₄ + O_伪 surface reaction proceeds by the hydrogen abstraction mechanism. This mechanism leads to hydroxy and methoxy groups residing on 伪-sites. The methanol formation takes place by hydrolysis of (Fe-OCH₃)_伪 groups at the step of extraction. For the first time dimethyl ether (DME) was identified in the reaction products, its amount comprising 6鈭?% of the methane reacted. In distinction to methanol, DME is readily extracted both by dry solvents (acetonitrile, tetrahydrofuran, ethanol) and their mixtures with water. A reliable extraction procedure was developed, which provides a 75% recovery of the methane oxidation products (methanol + DME). The missing products are shown to remain on the catalyst surface and can be quantitatively recovered in the form of CO_x at heating the sample. A mechanism involving CH₃^{鈥?/sup> radicals formed in the H-abstraction step is suggested to explain the reaction stoichiometry CH₄:O_伪 = 1:1.75 and a deficit of the carbon balance at extraction.}