Impact of Hydration on Supported V2O5/TiO2 Catalysts as Explored by Magnetic Resonance Spectroscopy,The Journal of Physical Chemistry C

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Impact of Hydration on Supported V2O5/TiO2 Catalysts as Explored by Magnetic Resonance Spectroscopy
The Journal of Physical Chemistry C ( IF 3.3 ) Pub Date : 2021-07-23 , DOI: 10.1021/acs.jpcc.1c04150
Nicholas R. Jaegers _{1,

2} , Yong Wang _{1,

2} , Jian Zhi Hu _{1,

2} , Israel E. Wachs ₃

Affiliation

Supported vanadium oxide catalysts are important industrial materials for a wide array of chemical transformations. The condition of surface hydration is of particular interest as a reflection of the state of freshly manufactured catalysts prior to their activation in catalytic reactors or under the conditions of photocatalysis where surface vanadia are exposed to moisture. Under such conditions, the surface vanadia species undergo structural changes, as evidenced by ⁵¹V magic-angle spinning nuclear magnetic resonance (⁵¹V MAS NMR) in this study. For low surface vanadia densities on titania, a modest trend toward the formation of dimeric and oligomeric vanadia species was observed under hydrated conditions when compared to the corresponding dehydrated catalyst, which contains a large abundance of monomeric vanadia species. The incorporation of tungsten oxide into the V₂O₅/TiO₂ catalyst with low surface vanadia density, however, is found to better stabilize the surface vanadia species on the titania support upon hydration than its tungsta-free counterpart. This stabilization is not an intrinsic property of more extensively oligomerized surface vanadia species in the presence of tungsten oxide, which is evidenced by the conditions of high concentrations of surface vanadia oligomers on titania that exhibit dramatic structural changes upon hydration. At high surface vanadia coverage under hydrated environments, the simultaneous observation of polycrystalline V₂O₅ nanoparticles and a mobile phase of surface vanadia species is apparent, where vanadia species are dissolved in a thin hydration layer on the titania support. These new findings have broad implications on the behavior of other metal-oxide species on high surface oxide supports under hydrated conditions.

中文翻译：

通过磁共振光谱研究水合作用对负载型 V2O5/TiO2 催化剂的影响

负载型氧化钒催化剂是用于多种化学转化的重要工业材料。表面水合的条件特别令人感兴趣，因为它反映了新鲜制造的催化剂在催化反应器中活化之前或在表面氧化钒暴露于水分的光催化条件下的状态。在这种条件下，表面钒物种会发生结构变化，如⁵¹ V 魔角自旋核磁共振所证明的（⁵¹V MAS NMR）在本研究中。对于二氧化钛上的低表面氧化钒密度，与含有大量单体氧化钒物质的相应脱水催化剂相比，在水合条件下观察到形成二聚和低聚氧化钒物质的适度趋势。V ₂ O ₅ /TiO _{2 中}氧化钨的掺入然而，发现具有低表面钒密度的催化剂在水合时比其不含钨的对应物更好地稳定二氧化钛载体上的表面钒物质。在氧化钨的存在下，这种稳定性不是更广泛低聚的表面氧化钒物质的固有特性，这由二氧化钛上高浓度的表面氧化钒低聚物的条件证明，其在水合时表现出显着的结构变化。在水合环境下高表面钒覆盖率下，同时观察多晶 V ₂ O ₅纳米颗粒和表面氧化钒物质的流动相很明显，其中氧化钒物质溶解在二氧化钛载体上的薄水合层中。这些新发现对水合条件下其他金属氧化物物质在高表面氧化物载体上的行为具有广泛的影响。

更新日期：2021-08-06

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