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首页> 外文期刊>Journal of Materials Science >Surface properties and epoxidation catalytic activity of Ti-SBA15 prepared by direct synthesis
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Surface properties and epoxidation catalytic activity of Ti-SBA15 prepared by direct synthesis

机译：直接合成制备的Ti-SBA15的表面性质和环氧化催化活性

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摘要

The influence of hydrothermal treatment time on the physicochemical properties and the catalytic activity in cyclohexene epoxidation of titanium-substituted SBA15 silicas prepared by direct one-step synthesis was systematically studied using a combination of N-2 physisorption at -196 A degrees C, X-ray diffraction, X-ray photoelectron spectroscopy, diffuse reflectance UV-Vis, and elemental analysis. The other synthesis parameters were chosen to illustrate the different chemical environments of the titanium species formed before, during, and after the precipitation of anatase TiO2. At the beginning of hydrothermal treatment, results showed that the titanium species are homogeneously dispersed in the silica framework. When anatase TiO2 clusters precipitate, they do so mainly on the external surface of the mesoporous material. At higher hydrothermal treatment times, the material showed a decreased catalytic activity even if essentially no variation in their specific surface area was then observed. This lower activity was shown to be due to a partial coverage of active tetrahedral Ti species by extraframework higher coordination TiO2 deposit.
机译：系统地研究了N-2物理吸附在-196 A℃，X-下的组合，研究了水热处理时间对直接一步合成的钛取代SBA15二氧化硅的理化性质和环己烯环氧化催化活性的影响。射线衍射，X射线光电子能谱，漫反射UV-Vis和元素分析。选择其他合成参数以说明在锐钛矿型TiO2沉淀之前，期间和之后形成的钛物种的不同化学环境。在水热处理开始时，结果表明钛物种均匀分散在二氧化硅骨架中。当锐钛矿型TiO2团簇沉淀时，它们主要在中孔材料的外表面上沉淀。在较高的水热处理时间下，该材料显示出降低的催化活性，即使随后基本上没有观察到它们的比表面积变化。该较低的活性被证明是由于框架外的较高配位的TiO2沉积物部分覆盖了活性四面体Ti物种。

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