Methane Activation on In-Modified ZSM-5: The State of Indium in the Zeolite and Pathways of Methane Transformation to Surface Species

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• 作者：Anton A. Gabrienko ; Sergei S. Arzumanov ; Ilya B. Moroz ; Igor P. Prosvirin ; Alexander V. Toktarev ; Wei Wang ; Alexander G. Stepanov
• 刊名：Journal of Physical Chemistry C
• 出版年：2014
• 出版时间：April 17, 2014
• 年：2014
• 卷：118
• 期：15
• 页码：8034-8043
• 全文大小：428K
• 年卷期：v.118,no.15(April 17, 2014)
• ISSN：1932-7455

文摘

Methane activation pathways as well as methane involvement in the reaction of ethylene aromatization on In-modified H-ZSM-5 zeolite (In/H-ZSM-5) have been studied with solid-state NMR spectroscopy. The state of indium in In/H-ZSM-5 in dependence of the zeolite activation procedure, reductive or oxidative, has been analyzed with X-ray photoelectron spectroscopy (XPS). On the basis of ¹H MAS NMR analysis of the evolution of the quantity of Br酶nsted acid sites (BAS) and XPS analysis of the state of indium in dependence of zeolite activation procedure, it has been inferred that indium exists in the form of either In⁺ or InO⁺ isolated cationic species in the zeolite. Methane interaction with different indium cationic species has been analyzed with ¹³C MAS NMR spectroscopy. In⁺ species has been concluded to be inactive, whereas InO⁺ species provides dissociative adsorption of methane to afford primarily the oxyindium鈥搈ethyl species. The secondary products of oxyindium鈥搈ethyl species transformation are oxyindium鈥搈ethoxy, ethane, formate, and acetaldehyde species. Methane can be involved in the reaction of ethylene aromatization on In-modified zeolite H-ZSM-5. This involvement is provided by the reaction of the surface oxyindium鈥搈ethoxy species with simple aromatic molecules formed from ethylene. Preliminarily, oxyindium鈥搈ethoxy species are generated by the interaction of oxyindium鈥搈ethyl species with InO⁺ cations.