Role of Lattice Oxygen of Metal Oxides in the Dehydrogenation of Ethylbenzene under a Carbon Dioxide Atmosphere

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• 作者：Kazuhiro Saito ; Kazumi Okuda ; Na-oki Ikenaga ; Takanori Miyake ; Toshimitsu Suzuki
• 刊名：Journal of Physical Chemistry A
• 出版年：2010
• 出版时间：March 25, 2010
• 年：2010
• 卷：114
• 期：11
• 页码：3845-3854
• 全文大小：521K
• 年卷期：v.114,no.11(March 25, 2010)
• ISSN：1520-5215

文摘

The mechanism for the dehydrogenation of ethylbenzene over V, Cr, and Fe oxides loaded on activated carbon, powdered diamond, Al₂O₃, and MgO was studied in the presence of CO₂. Vanadium oxide-loaded catalysts provided higher styrene yields under CO₂ than Ar flow. The transient response method was carried out to understand the reaction behaviors of lattice oxygen of various metal oxides on the support. The results showed that lattice oxygen of vanadium oxide (V═O) was consumed in the dehydrogenation reaction and that reduced vanadium oxide was reoxidized with CO₂. A similar redox cycle was observed on iron oxide-loaded activated carbon catalyst. Spectroscopic characterization revealed that vanadium oxide and iron oxide on the support were reduced to a low valence state during the dehydrogenation reaction, and that CO₂ could oxidize the reduced metal oxides. In contrast, chromium(III) oxide was not reduced during dehydrogenation. From these findings, the redox cycle over vanadium oxide- and iron oxide-loaded catalysts was concluded to be an important factor in promoting the catalytic activity with CO₂.