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Thermal spreading of WO_3 onto zirconia support

机译：WO_3在氧化锆载体上的热扩散

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摘要

This study focused on preparation of tungsten oxide supported on zirconia by thermal spreading. The prepared samples were characterized by infrared spectroscopy, UV-vis diffuse reflection spectroscopy, X-ray diffraction, and also by methanol dehydration reaction. It was observed that isolated octahedral tungsten dispersed species and dispersed polytungstate were formed on zirconia surface, although some WO_3 that remained after the thermal treatment could also be detected. The presence of these species led to an increase of the number of Lewis sites and the generation of Broensted acid sites. High calcination temperatures promoted the creation of Broensted sites as a consequence of polytungstate species formation. The activity on methanol dehydration was also determined by the concentration of these species, whereas the isolated WO_x species were found poorly active. The correlation observed between the catalytic performance and the tungsten dispersed species, as revealed by spectroscopic techniques, evidenced the occurrence of thermal spreading of WO_3 on ZrO_2. The results presented in this work show that WO_3 thermal spreading on ZrO_2 may be effectively accomplished as predicted by thermodynamics.
机译：这项研究的重点是通过热扩散法制备氧化锆负载的氧化钨。通过红外光谱，紫外可见漫反射光谱，X射线衍射以及甲醇脱水反应对制备的样品进行表征。观察到在氧化锆表面上形成了分离的八面体钨分散物质和分散的多钨酸盐，尽管也可以检测到热处理后残留的一些WO_3。这些物质的存在导致路易斯位点数量的增加和布朗斯台德酸位点的产生。由于多钨酸盐物种的形成，高的煅烧温度促进了布朗斯台德位点的形成。甲醇脱水的活性也由这些物质的浓度确定，而分离出的WO_x物质活性差。光谱技术表明，催化性能与钨的分散种类之间存在相关性，证明了WO_3在ZrO_2上的热扩散。这项工作提出的结果表明，如热力学所预测的，WO_3在ZrO_2上的热扩散可以有效完成。

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