Role of Vanadium and Phosphorus in Substituted Keggin‐Type Heteropolyoxo Molybdates Supported on Silica SBA‐15 in Selective Propene Oxidation
Role of Vanadium and Phosphorus in Substituted Keggin‐Type Heteropolyoxo Molybdates Supported on Silica SBA‐15 in Selective Propene Oxidation
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DOI：
10.1002/cctc.201402970
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发表时间：
2015-04
期刊：
影响因子：
4.5
通讯作者：
R. Zubrzycki;J. Epping;T. Ressler
中科院分区：
文献类型：
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作者：
R. Zubrzycki;J. Epping;T. Ressler
将含钒的Keggin型杂多酸盐（[PV 2 Mo 10 O 40]5-）负载在二氧化硅SBA-15上（表示为PV 2 Mo 10-SBA-15）。通过使用原位X射线吸收光谱，在丙烯选择性氧化条件下研究了PV 2 Mo 10-SBA-15和合适的参比V2 Mo 10 Ox-SBA-15的结构演变和催化活性。在催化反应后进行负载的PV 2 Mo 10-SBA-15和参比H3 PO 4-SBA-15的31 P MAS NMR测量。PV 2 Mo 10-SBA-15在丙烯氧化条件下的热处理期间形成主要为四面体[MoOx]和[VOx]单元的混合物。V中心周围的平均局部结构的变化与Mo中心周围的平均局部结构的变化和催化活性的开始相吻合。此外，主要是四面体[MoOx]和[VOx]单元似乎是在催化条件下的紧密接近和相互作用。相反，在用单独的V和Mo源前体合成的参比材料V2 Mo 10 Ox-SBA-15中，Mo和V中心似乎彼此更加分离。在催化条件下，PV 2 Mo 10-SBA-15中P的结构环境对应于各种物质的混合物。P通过P → O → Si键和[MoOx]或[VOx]单元连接到载体材料SBA-15。显然，Keggin前体中V和Mo的接近是在载体材料上获得（Mo，V）氧化物物质的先决条件。
Vanadium‐containing Keggin‐type heteropolyoxo molybdate ([PV2Mo10O40]5−) was supported on silica SBA‐15 (denoted as PV2Mo10‐SBA‐15). The structural evolution and catalytic activity of PV2Mo10‐SBA‐15 and a suitable reference V2Mo10Ox‐SBA‐15 were investigated under selective propene oxidation conditions by using in situ X‐ray absorption spectroscopy. 31P MAS NMR measurements of supported PV2Mo10‐SBA‐15 and reference H3PO4‐SBA‐15 were performed after the catalytic reaction. PV2Mo10‐SBA‐15 formed a mixture of mainly tetrahedral [MoOx] and [VOx] units during thermal treatment under propene oxidation conditions. Changes in the average local structure around V centers coincided with the changes in the average local structure around Mo centers and the onset of catalytic activity. In addition, mainly tetrahedral [MoOx] and [VOx] units seemed to be in close proximity and interacted under catalytic conditions. Conversely, in the reference material V2Mo10Ox‐SBA‐15 synthesized with individual V and Mo source precursors, Mo and V centers appeared to be more separated from each other. The structural environment of P in PV2Mo10‐SBA‐15 under catalytic conditions corresponded to a mixture of various species. P was connected to both the support material SBA‐15 via POSi bonds and [MoOx] or [VOx] units. Apparently, the proximity of V and Mo in Keggin precursors was a prerequisite for obtaining (Mo,V) oxide species on the support material.