Formation of metal oxide cluster lattice and catalytic oxidation properties

金属氧化物催化剂根据其本体结构分为两大类。一种是如在普通金属氧化物中观察到的那样，其中金属-氧键简单地在三维中顺序形成的氧化物。另一种是所谓的聚氧乙烯酸盐，类似于杂多化合物，它是由金属多面体构建的离散簇合物。然而，第三类是作为第一和第二之间的中间，因为最近发现的三维氧化物固体与团簇单元。第三个是非常重要的催化剂，必须控制每一个基本的反应步骤，在烷烃的选择性氧化，换句话说，高度功能化的金属氧化物表面，可以创建与孤立的簇晶格似乎是必不可少的实现烷烃的催化选择性氧化，这是公认的是一个非常困难的反应。在本研究计划中，催化活性的金属氧化物表面已经设计和生产的自组织过程与结构构建单元，这是适合于形成簇晶格。我们通过使用离散的Mo 132（所谓的大球）来合成MoVSbOx催化剂，选择所述大球是因为它在其离散结构中具有金属八面体的5元环单元。我们成功地合成了具有正交结构的高结晶MoVSbOx。这一结果有力地支持了单元合成在复杂金属氧化物中形成团簇晶格的有效性。该技术也被应用到Mo-V-Ox系统中，我们成功地获得了具有与MoVSbOx相同正交结构的晶体材料。通过Rietveld分析对这些材料的结构进行了分析和细化。通过这些固体氧化物对丙烷选择氧化制丙烯酸的催化试验，阐明了簇合物晶格在反应步骤中的作用以及各组分的作用。

Metal oxide catalysts were classified into two large categories in terms of their bulk structure. One is the oxides in which metal-oxygen bonds are simply formed sequentially in three-dimension as observed in normal metal oxides. The other one is so-called polyoxometalate, like hetempolycompounds, which was formed by the construction of discrete clusters with metal polyhedra. However, third category which is as an intermediate between the first and the second are revealed, because three-dimensional oxide solid with cluster units has been found recently. The third one is found to be very important for catalysts which have to control every elemental reaction step in the alkane selective oxidation In other words, highly functionalized metal oxide surface which can be created with isolated cluster lattice seems to be indispensable for achieving catalytic selective oxidation of alkanes which is recognized as a highly difficult reaction. In this research project, catalytically active metal oxide surface has been designed and produced by self-organization process with structure building units which are suitable for the formation of cluster lattice. We synthesized MoVSbOx catalysts by using discrete Mo 132 so-called big-ball, which was selected because it has 5-member ring unit of metal octahedra in its discrete structure. We succeeded to synthesize highly crystallized MoVSbOx with orthorhombic structure. This result strongly supports the effective ness of unit synthesis to create cluster lattice in complex metal oxides. This technique was also applied to Mo-V-Ox system and we obtained successfully crystalline materials with the same orthorhombic structure that MoVSbOx had. The structure of these materials was analyzed and refined by Rietveld analysis. By the catalytic test of these solid oxides for propane selective oxidation to acrylic acid, the effect of cluster lattice in the reaction steps and the role of constituents were clarified.