Mesoporous Silicas as Versatile Supports to Tune the Palladium-Catalyzed Selective Aerobic Oxidation of Allylic Alcohols
Mesoporous Silicas as Versatile Supports to Tune the Palladium-Catalyzed Selective Aerobic Oxidation of Allylic Alcohols
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DOI：
10.1002/cctc.201200301
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发表时间：
2013-04-01
期刊：
影响因子：
4.5
通讯作者：
Wilson, Karen
中科院分区：
文献类型：
--
作者：
Parlett, Christopher M. A.;Bruce, Duncan W.;Wilson, Karen
表面活性剂模板为合成具有有序、可调介孔结构的高比表面积二氧化硅提供了一种简单的途径。利用这些材料作为钯纳米颗粒的多用途催化剂载体，在温和条件下对烯丙醇进行了有氧选择性氧化（selox）。通过初始湿浸渍SBA-15、SBA-16和KIT-6合成的Pd/介孔二氧化硅家族，通过氮孔隙度测定、CO化学吸附、漫反射红外傅立叶变换光谱、x射线衍射、x射线光电子能谱、x射线吸收光谱和高分辨率透射电镜进行了表征，并在液相烯丙醇selox中对Pd/无定形SiO2标准进行了基准测试。从无定形到二维平行和三维互穿多孔二氧化硅网络的转变赋予了显著的selox速率增强，并与活性氧化钯位点的更高表面密度相关。溶解氧对氧化钯的原位稳定至关重要，因此维持了高活性，而使用钯金属对竞争性氢解途径中所需醛selox产物的选择性是由钯金属指导的。
Surfactant templating offers a simple route to synthesize high-surface area silicas with ordered, tunable mesopore architectures. The use of these materials as versatile catalyst supports for palladium nanoparticles has been explored in the aerobic selective oxidation (selox) of allylic alcohols under mild conditions. Families of Pd/mesoporous silicas, synthesized through incipient wetness impregnation of SBA-15, SBA-16, and KIT-6, have been characterized by using nitrogen porosimetry, CO chemisorption, diffuse reflection infrared Fourier transform spectroscopy, X-ray diffraction, X-ray photoelectron spectroscopy, X-ray absorption spectroscopy, and high-resolution TEM and benchmarked in liquid phase allylic alcohol selox against a Pd/amorphous SiO2 standard. The transition from amorphous to two-dimensional parallel and three-dimensional interpenetrating porous silica networks conferred significant selox rate enhancements associated with higher surface densities of active palladium oxide sites. Dissolved oxygen was essential for insitu stabilization of palladium oxide, and thus maintenance of high activity on-stream, whereas selectivity to the desired aldehyde selox product over competing hydrogenolysis pathways was directed by using palladium metal.