Mo-V-Te-(Nb)-O mixed metal oxides prepared by hydrothermal synthesis for catalytic selective oxidations of propane and propene to acrylic acid
Mo-V-Te-(Nb)-O mixed metal oxides prepared by hydrothermal synthesis for catalytic selective oxidations of propane and propene to acrylic acid
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DOI：
10.1016/s0926-860x(03)00381-8
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发表时间：
2003-09
影响因子：
5.5
通讯作者：
D. Vitry;Y. Morikawa;J. Dubois;W. Ueda
中科院分区：
文献类型：
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作者：
D. Vitry;Y. Morikawa;J. Dubois;W. Ueda
研究了水热制备的 Mo-V-Te-O 和 Mo-V-Te-Nb-O 混合金属氧化物催化剂上丙烷和丙烯选择性氧化成丙烯酸的情况。两种催化剂均获得了具有相同斜方层状结构的单相晶体材料，其特征是 XRD (Cu Kα) 图案中 6.6、7.9、9.0 和 22.2° 处有尖峰，因此铌不是创建该结构所必需的。然而，铌的添加导致催化剂形态发生明显变化。通过SEM观察到Mo-V-Te-O体系中长棒状晶体（30-50μm），而Mo-V-Te-Nb-O体系中观察到小圆柱状晶体（300-500nm长度）的聚集体。两种催化剂对丙烷和丙烯的氧化均具有很高的活性，并且在底物转化方面表现出几乎相同的催化性能。结果表明，铌对丙烷和丙烯的氧化活化没有影响。另一方面，在含铌催化剂中，两个反应中丙烯酸的选择性均增加了约 15-20%。当转化率较高时，这种效果更加明显。我们讨论了水热合成过程中活性斜方结构的形成以及铌对其结构形成和Mo-V-Te-O催化性能的作用。
Selective oxidations of propane and propene to acrylic acid were investigated over hydrothermally prepared Mo-V-Te-O and Mo-V-Te-Nb-O mixed metal oxide catalysts. Mono-phasic crystalline materials were obtained for both catalysts with the same orthorhombic layered structure characterized by sharp peaks at 6.6, 7.9, 9.0, and 22.2° in XRD (Cu Kα) patterns, so that niobium was not necessary for creating the structure. However, the addition of niobium resulted in a clear change in catalyst morphology. Long rod-shaped crystals (30–50μm) in the case of the Mo-V-Te-O system were observed by SEM, whereas aggregates of small cylinder-shaped crystals (300–500nm length) in the case of the Mo-V-Te-Nb-O system. Both catalysts were highly active for the oxidations of propane and propene and both showed almost the same catalytic performance in terms of substrate conversions. The results indicate that niobium was not influential in the oxidative activation of propane and propene. On the other hand, the selectivity to acrylic acid in both reactions increased by about 15–20% in the niobium-containing catalyst. This effect was much clearer at higher conversion. We discuss the formation of active orthorhombic structure during the hydrothermal synthesis and the role of niobium on the structure formation and on the catalytic performance of Mo-V-Te-O.