Walter Anke, Herbert Rita, Hess Christian, Ressler Thorsten
Institut für Chemie, Technische Universität Berlin, Berlin, Germany.
Chem Cent J. 2010 Feb 11;4:3. doi: 10.1186/1752-153X-4-3.
The local structure of vanadium oxide supported on nanostructured SiO2 (VxOy/SBA-15) was investigated by in situ X-ray absorption spectroscopy (XAS). Because the number of potential parameters in XAS data analysis often exceeds the number of "independent" parameters, evaluating the reliability and significance of a particular fitting procedure is mandatory. The number of independent parameters (Nyquist) may not be sufficient. Hence, in addition to the number of independent parameters, a novel approach to evaluate the significance of structural fitting parameters in XAS data analysis is introduced. Three samples with different V loadings (i.e. 2.7 wt %, 5.4 wt %, and 10.8 wt %) were employed. Thermal treatment in air at 623 K resulted in characteristic structural changes of the V oxide species. Independent of the V loading, the local structure around V centers in dehydrated VxOy/SBA-15 corresponded to an ordered arrangement of adjacent V2O7 units. Moreover, the V2O7 units were found to persist under selective oxidation reaction conditions.
通过原位X射线吸收光谱（XAS）研究了负载在纳米结构SiO2上的氧化钒（VxOy/SBA-15）的局部结构。由于XAS数据分析中潜在参数的数量通常超过“独立”参数的数量，因此必须评估特定拟合程序的可靠性和重要性。独立参数的数量（奈奎斯特数）可能不足。因此，除了独立参数的数量外，还引入了一种新的方法来评估XAS数据分析中结构拟合参数的重要性。使用了三种具有不同V负载量（即2.7 wt%、5.4 wt%和10.8 wt%）的样品。在623 K的空气中进行热处理导致V氧化物物种发生特征性结构变化。与V负载量无关，脱水的VxOy/SBA-15中V中心周围的局部结构对应于相邻V2O7单元的有序排列。此外，发现V2O7单元在选择性氧化反应条件下持续存在。
