| 负载型MoO3 /γ-Al2O3催化剂中晶格氧的丙烷氧化脱氢反应性能 |
| Reactivity of Lattice Oxygen in Supported MoO3 /γ-Al2O3 Catalysts for Oxidative Dehydrogenation of Propane |
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| 摘要: 采用X射线衍射(XRD)，氢气程序升温还原(H2-TPR)和无氧脉冲反应评价等研究了MoO3在γ-Al2O3载体表面的分散状态和负载型MoO3/γ-Al2O3催化剂晶格氧物种的丙烷氧化脱氢反应性能。结果表明在γ-Al2O3表面MoO3分散容量的实测值(4.73 Mo6+/nm2)与按照“嵌入模型”估算的理论分散容量(4.90 Mo6+/nm2)接近。在分散容量以下，键合在γ-Al2O3表面孤立的Mo-O-Al物种倾向于分散在相邻的空位上且通过Mo-O-Mo化学键相连形成聚合的表面MoOx物种。随着MoO3负载量增加，Mo-O-Al键合方式逐步转变为Mo-O-Mo键合方式，钼离子周围的氧离子活泼性下降，导致丙烷氧化脱氢反应活性下降。超过分散容量以上的Mo离子以晶相形式存在。由于钼离子表面利用率下降，尤其是多层的晶相氧化钼表面Mo-O-Mo物种难以与载体表面铝离子键合，导致与钼离子相结合的氧离子可移动性下降、反应活泼性降低，催化剂的丙烷氧化脱氢反应活性急剧下降。 |
| 关键词: MoO3 /γ-Al2O3 分散 晶格氧 丙烷 氧化 脱氢 |
| 基金项目: |
| Abstract: The dispersion state and catalytic properties of molybdenum ions on the surface of MoO3 /γ-Al2O3 catalysts were studied by means of X-ray diffraction(XRD), H2 Temperature-programmed reduction(H2-TPR) and pulse reaction test for propane oxidative dehydrogenation in absence of gaseous oxygen. It has been shown that the dispersion capacity of molybdenum oxide on γ-Al2O3 is about 4.73 Mo6+/nm2 and this value is close to the theoretical value(4.90 Mo6+/nm2) estimated by “Incorporation Model”. When the loading of MoO3 is below its dispersion capacity, the isolated Mo-O-Al species combined on γ-Al2O3 surface is easily dispersed on the neighbor vacant site by Mo-O-Mo bond to form polymerized surface MoOx species. With the increase of MoO3 loading, the Mo-O-Al bond converts to Mo-O-Mo bond, and the reactivity of oxygen anions around Mo ion decreases, which leads to the decrease of activity for oxidative dehydrogenation of propane. When the MoO3 loading is higher than the dispersion capacity, the excess Mo6+ ions form crystal phase, leading to the further decrease of activity for oxidative dehydrogenation of propane. |
| Keywords: MoO3 /γ-Al2O3 dispersion lattice oxygen ion propane oxidation dehydrogenation |
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| 赵小燕,许波连,范以宁.负载型MoO3 /γ-Al2O3催化剂中晶格氧的丙烷氧化脱氢反应性能[J].无机化学学报,2008,24(9):1489-1493. |
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