An Investigation of the Reduction and Reoxidation of Isolated Vanadate Sites Supported on MCM-48

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• 作者：Jason L. Bronkema and Alexis T. Bell
• 关键词：Vanadate ; Silica ; Reduction ; Oxidation
• 刊名：Catalysis Letters
• 出版年：2008
• 出版时间：April, 2008
• 年：2008
• 卷：122
• 期：1-2
• 页码：1-8
• 全文大小：628.0 KB

文摘

The reduction and subsequent reoxidation of isolated vanadate species supported on silica was investigated using temperature-programmed reduction and oxidation, along with in-situ XANES and Raman spectroscopy. Approximately 70–80 % of the vanadium was reduced to V3+ after reduction in H₂ at temperatures up to 923 K. Upon reduction, the vanadyl oxygen was removed and the three remaining V–O bonds are lengthened by 0.2 ?. The vanadate species are rapidly reoxidized when exposed to O₂, with the amount of oxygen uptake matching well with the amount removed during reduction. In-situ Raman spectroscopy during reoxidation in 18O₂ showed that significant scrambling occurs between gas phase oxygen and surface oxygen species during the reoxidation of the vanadate species.