Molybdenum oxide supported on nanostructured MgO: Influence of the alkaline support properties on MoOx structure and catalytic behavior in selective oxidation
Molybdenum oxide supported on nanostructured MgO: Influence of the alkaline support properties on MoOx structure and catalytic behavior in selective oxidation
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DOI：
10.1016/j.micromeso.2013.05.032
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发表时间：
2013-11
影响因子：
5.2
通讯作者：
J. Scholz;Anke Walter;A. Hahn;T. Ressler
中科院分区：
文献类型：
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作者：
J. Scholz;Anke Walter;A. Hahn;T. Ressler
研究了碱性纳米载体材料负载的氧化钼的局部结构和催化活性。载体的性质对表面氧化物催化剂的结构有很大影响。支持材料是通过两种不同的路线制备的。将直接合成氧化镁的方法与包覆氧化镁的SBA-15进行了比较。采用X射线衍射仪和氮气物理吸附等方法对载体材料的结构进行了表征。两种材料均表现出较高的比表面积和较窄的孔径分布。包覆纳米氧化镁的SBA-15(MgO/SBA-15)具有与纯纳米氧化镁(Nano-MgO)相似的碱性，但在催化条件下更稳定。用X射线衍射仪、X射线衍射仪和DR-UV-Vis光谱对载体上高度分散的钼物种进行了表征。用气相色谱考察了该催化剂对丙烯选择氧化的催化活性。与SBA-15等更酸性的载体材料相比，碱性载体上存在着相当不同的物种。负载型氧化钼的结构主要由孤立的[MoO4]四面体组成，与Mo的负载量基本无关。与二氧化硅SBA-15负载的高聚合度钼物种相比，孤立的[MoO4]四面体担载的催化剂表现出较差的催化活性。
Local structure and catalytic activity of molybdenum oxide supported on alkaline, nanostructured support materials were investigated. The structure of the surface oxide catalysts was significantly affected by the properties of the support. The support material was prepared via two different routes. A direct MgO synthesis approach was compared to SBA-15 coated with magnesium oxide. The structure of the support materials was investigated by XRD and N2physisorption. Both materials exhibited a high specific surface area with a narrow pore size distribution. The MgO-coated SBA-15 (MgO/SBA-15) exhibited a similar alkaline character as pure nanostructured MgO (nano-MgO) but was more stable under catalytic conditions. The highly dispersed molybdenum species on the support was characterized by XRD, XAS and DR-UV–Vis spectroscopy. The catalytic activity for selective oxidation of propene was investigated by gas chromatography. A considerably different species was present on the alkaline support, compared to more acidic support materials like SBA-15. The structure of the supported molybdenum oxide consisted of predominantly isolated [MoO4] tetrahedra and was largely independent from Mo loadings. The supported catalysts with isolated [MoO4] tetrahedra exhibited only poor catalytic activity compared to the higher polymerized Mo species supported on silica SBA-15.