Structure Sensitivity of Oxidative Dehydrogenation of Cyclohexane over FeOx and Au/Fe3O4 Nanocrystals

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• 作者：S. Goergen ; C. Yin ; M. Yang ; B. Lee ; S. Lee ; C. Wang ; P. Wu ; M. B. Boucher ; G. Kwon ; S. Seifert ; R. E. Winans ; S. Vajda ; M. Flytzani-Stephanopoulos
• 刊名：ACS Catalysis
• 出版年：2013
• 出版时间：April 5, 2013
• 年：2013
• 卷：3
• 期：4
• 页码：529-539
• 全文大小：726K
• 年卷期：v.3,no.4(April 5, 2013)
• ISSN：2155-5435

文摘

Shape-controlled nanoscale FeO_x and Au/Fe₃O₄ catalysts with an inverse spinel structure were prepared and tested for the oxidative dehydrogenation of cyclohexane. The reaction was studied in situ in SAXS/TPRx mode with isothermal steady-state holds. {111}-Bound Fe₃O₄ nanooctahedra are highly stable under reaction conditions at 300 掳C, but {100}-bound nanocubes begin to agglomerate above 250 掳C. The selectivity to cyclohexene and benzene over CO₂ depends strongly on the iron oxide shape and its interaction with the gold. When gold is added onto the iron oxide, the formation of benzene over cyclohexene is favored over both shapes. The highest benzene yield was measured on the Au/Fe₃O₄ octahedra. A parallel study of a commercial polycrystalline Au/Fe₂O₃ powder was conducted, and the activity and selectivity of this catalyst were compared with the nanoshapes. After leaching of the gold with a sodium cyanide solution and heat treatment, the atomically dispersed gold on the iron oxide surface selectively catalyzed the ODH of cyclohexane to benzene. Stabilization of cationic gold was found by in situ XANES conducted during the ODH reaction.

Keywords:

gold; iron oxide; oxidative dehydrogenation; cyclohexane; shape effect; benzene; structure selectivity