Green photo-oxidation of styrene over W-Ti composite catalysts

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• 作者：Mario J. Mu帽oz-Batista ; Anna Kubacka ; Rafal Rachwalik ; Bel茅n Bachiller-Baeza ; Marcos Fern谩ndez-Garc铆a
• 关键词：Photo-catalysis ; Partial oxidation ; Styrene ; Titania ; Tungsten
• 刊名：Journal of Catalysis
• 出版年：January, 2014
• 年：2014
• 卷：309
• 期：Complete
• 页码：428-438
• 全文大小：2300 K

文摘

A series of WO₃-TiO₂ composite catalysts with variable quantities of tungsten was prepared by a single-pot microemulsion procedure and evaluated in the gas-phase selective photo-oxidation of the aromatic hydrocarbon styrene. Samples improve the performance of TiO₂ by a factor ca. 3 and increase significantly the selectivity to valuable products (as styrene oxide) upon UV and, more importantly, sunlight-type excitation. Optimum performance in terms of both activity and selectivity was achieved under a sunlight-type renewable energy source. A complete structural (bulk and surface) and electronic characterization using Transmission Microscopy, X-ray diffraction (XRD), X-ray Photoelectron (XPS), Raman, and UV-visible spectroscopies and calorimetry with the help of the ammonia probe molecule was carried out. The study was able to detect and quantify the presence of different W entities as a function of the tungsten content of the catalysts. Three species were found to be present throughout the series; oligomeric W species and WO₃ nanoparticles in close contact with anatase-TiO₂ and non-contacting WO₃ platelets. From a spectro-kinetic analysis carried out with the help of electron paramagnetic resonance (EPR), we provide evidence that these W-containing species play different roles in reaction. Activity and selectivity improvements with respect to the bare titania are intimately related with presence of oligomeric W species at anatase surfaces.