Catalytic Activity and Regeneration Property of a Pd Nanoparticle Encapsulated in a Hollow Porous Carbon Sphere for Aerobic Alcohol Oxidation
Catalytic Activity and Regeneration Property of a Pd Nanoparticle Encapsulated in a Hollow Porous Carbon Sphere for Aerobic Alcohol Oxidation
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DOI：
10.1021/la102824s
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发表时间：
2010-11-16
期刊：
影响因子：
3.9
通讯作者：
Matsumura, Michio
中科院分区：
文献类型：
--
作者：
Harada, Takashi;Ikeda, Shigeru;Matsumura, Michio
采用由钯（Pd）纳米颗粒和中空碳壳（Pd@hmC）组成的核-壳复合物作为催化剂用于各种醇的有氧氧化。核壳结构的合成通过连续涂层的Pd纳米粒子与硅质和碳层，然后通过去除中间硅质层。使用TEM和N-2吸附-脱附测量的结构表征表明，由此获得的Pd@hmC由直径为3-6 nm的Pd纳米颗粒核和具有发育良好的中孔（约1.5 μ m）的中空碳壳组成。2.5 nm的直径）和（约.直径为0.4- 0.5nm）系统。与一些Pd负载的碳相比。Pd@hmC在常压O2-氧化苯甲醇合成苯甲醛的反应中表现出很高的催化活性。Pd@hmC复合物也表现出高水平的催化活性，用于其他伯苄醇和烯丙醇的有氧氧化成相应的醛。侧碳壳中发达的孔系统的存在使得底物和产物都能够有效地扩散以到达中心Pd纳米颗粒。导致如此高的催化活性。由于每个Pd纳米颗粒通过碳壳与相邻颗粒的物理隔离，这种核-壳结构还提供了Pd纳米颗粒对聚结和/或聚集的高热稳定性：Pd@hmC的这种特定性质导致通过催化反应后回收的样品的高温热处理可能再生这些有氧氧化的催化活性。
A core-shell composite consisting of a palladium (Pd) nanoparticle and a hollow carbon shell (Pd@hmC) was employed as a catalyst for aerobic oxidation of various alcohols. The core-shell structure was synthesized by consecutive coatings of Pd nanoparticles with siliceous and carbon layers followed by removal of the intermediate siliceous layer. Structural characterizations using TEM and N-2 adsorption-desorption measurements revealed that Pd@hmC thus-obtained was composed of a Pd nanoparticle core of 3-6 nm in diameter and a hollow carbon shell with well-developed mesopore (ca. 2.5 nm in diameter) and micropore (ca. 0.4-0.5 nm in diameter) systems. When compared to some Pd-supported carbons. Pd@hmC showed a high level of catalytic activity for oxidation of benzyl alcohol into benzaldehyde using atmospheric pressure of O-2 as an oxidant. The Pd@hmC composite also exhibited a high level of catalytic activity for aerobic oxidations of other primary benzylic and allylic alcohols into corresponding aldehydes. The presence of a well-developed pore system in the lateral carbon shell enabled efficient diffusion of both substrates and products to reach the central Pd nanoparticles. leading to such high catalytic activities. This core-shell structure also provided high thermal stability of Pd nanoparticles toward coalescence and/or aggregation due to the physical isolation of each Pd nanoparticle from neighboring particles by the carbon shell: this specific property of Pd@hmC resulted in possible regeneration of catalytic activity for these aerobic oxidations by a high-temperature heat treatment of the sample recovered after catalytic reactions.