Exploiting links between nano-technology and heterogeneous catalysis: Shaped silver nano-particles as selective catalysts for partial oxidation of olefins to form chiral and..

所提出的工作的目的是探索成形的Ag纳米颗粒作为丙烯环氧化形成环氧丙烷和较大烯烃（即，苯乙烯）形成手性环氧化物。这些研究建立在密歇根大学Linic早期生产环氧乙烷的工作基础上。非均相Ag催化剂在商业上几乎专门用于该反应。环氧乙烷是合成乙二醇（防冻剂）、乙醇胺和洗涤剂的关键化学品。Linic的计算表明，Ag的特定面将对所需产物提供更高的选择性。新的合成策略，然后开发的形状特定的银纳米结构的合成。随着明确定义的银纳米结构可以是乙烯部分氧化的高选择性催化剂的证明，丙烯部分氧化为环氧丙烷的挑战是合乎逻辑的延伸。对于这种重要的大规模化学过程，没有选择性多相催化剂。PI表明，催化金属Ag颗粒的形状和它们的性能之间存在着关键的联系，并且影响性能的主要因素是颗粒的特定形状的表面终止。PI假设，Ag纳米立方体和纳米线催化剂，特别是终止于Ag（100）面，将显着更高的选择性，在丙烯的直接环氧化比传统的球形Ag颗粒，这是终止于（111）面。 PI假设，特定的金属银纳米结构，增强与手性改性剂，将是有前途的非均相催化剂较大的烯烃（例如苯乙烯）的不对称环氧化反应，形成手性环氧化物。目前，复杂且昂贵的均相催化剂用于手性氧化反应，因为它们提供比常规非均相固态催化剂更大的区域和立体选择性。拟议的研究项目试图建设性地整合纳米科学和多相催化领域，利用控制合成不同形状和不同表面终端的金属纳米颗粒的最新进展，设计高选择性的无机催化剂。这项研究的成功结果的变革性质是相当明显的。一种新的非均相催化环氧丙烷的路线具有大规模的商业意义。此外，开发用于手性烯烃环氧化反应的可行的非均相催化剂相对于其均相对应物将提供显著的优点，包括容易的产物分离、更长的催化剂寿命、更容易的催化剂再生以及可能利用更便宜和环境友好的氧化剂如氧气。

0966700LinicThe objective of the proposed work is to explore the potential of shaped Ag nano-particles as heterogeneous catalysts for the epoxidation of propylene to form propylene oxide and for the asymmetric epoxidation of larger olefins (i.e., styrene) to form chiral epoxides. The studies build on earlier work by Linic at the University of Michigan to produce ethylene oxide. Heterogeneous Ag catalysts are almost exclusively used for this reaction commercially. EO is a critical chemical used in the synthesis of ethylene glycol (antifreeze), ethanolamines, and detergents. Computations by Linic suggested that particular faces of Ag would offer higher selectivity to desired products. Novel synthetic strategies were then developed for the synthesis of the shape-specific Ag nano-structures. With the demonstration that well-defined Ag nano-structures can be highly selective catalysts for partial oxidation of ethylene, the challenge of propylene partial oxidation to propylene oxide is a logical extension. There are no selective heterogeneous catalysts for this important, large scale chemical process. The PI has shown that there exists a critical link between the shape of catalytic metallic Ag particles and their performance, and that the main factor affecting the performance is the shape-specific surface termination of the particles. The PI hypothesizes that Ag nano-cube and nano-wire catalysts, terminated specifically by the Ag(100) facet, will be significantly more selective in direct epoxidation of propylene than conventional spherical Ag particles, which are terminated by the (111) facet. The PI hypothesizes that specific metallic Ag nanostructures, enhanced with chiral modifiers, will be promising heterogeneous catalysts for asymmetric epoxidation of larger olefins (for example styrene) to form chiral epoxides. Currently, complex and expensive homogeneous catalysts are used for chiral oxidation reactions as they offer greater regio- and stereo-selectivity than conventional heterogeneous solid state catalysts. The proposed research project attempts to constructively integrate the fields of nanoscience and heterogeneous catalysis by taking advantage of recent advances in the controlled synthesis of metallic nano-particles of different shapes and different surface terminations to design highly selective inorganic catalysts. The transformative nature to the successful outcome of this study is quite apparent. A new heterogeneously-catalyzed route to propylene oxide has large scale commercial implications. Furthermore, developing viable heterogeneous catalysts for chiral olefin epoxidation reactions would offer significant advantages with respect to their homogeneous counterparts including easy product separation, longer catalyst lifetime, easier catalyst regeneration, and possible utilization of cheaper and environmentally friendlier oxidizing agents such as oxygen.