CNR-Institute of Molecular Sciences and Technologies, Via C. Golgi 19, Milan, Italy.
Phys Chem Chem Phys. 2013 Aug 28;15(32):13354-62. doi: 10.1039/c3cp51570b.
Niobium-containing silica materials obtained by deposition via liquid-phase grafting or dry impregnation of niobocene(iv) dichloride are active and selective catalysts in the epoxidation of alkenes in the presence of aqueous hydrogen peroxide. The generation of the catalytically-active Nb species was followed step-by-step, and investigated using a combined DR-UV-Vis, NIR, Raman, XRD, XANES and EXAFS analyses. At the end of the grafting procedure, the nature of the surface active species can be described as an oxo-Nb(v) site, tripodally grafted onto the silica surface in close proximity to other Nb(v) centres. The liquid-phase methodology provides a better dispersion of the metal sites onto the siliceous support than the dry-impregnation approach. The niobium-silica catalysts were then tested in the epoxidation of cyclohexene and 1-methylcyclohexene, as model substrates.
采用铌茂（IV）二氯化物液相接枝或干法浸渍法制备的含铌硅材料是在水相过氧化氢存在下烯烃环氧化的活性和选择性催化剂。通过分步 DR-UV-Vis、NIR、拉曼、XRD、XANES 和 EXAFS 分析，对催化活性 Nb 物种的生成进行了跟踪研究。接枝过程结束时，表面活性物种的性质可以描述为一个氧-Nb（V）位，以三脚架的形式紧密靠近其他 Nb（V）中心接枝到硅表面上。液相方法比干法浸渍法能更好地将金属位分散在硅载体上。然后，这些铌硅催化剂被用于环己烯和 1-甲基环己烯的环氧化反应，作为模型底物进行了测试。
