Heterogeneous epoxidation of alkenes containing allylic hydrogen on Cu-based catalysts

烯丙基烯烃的非均相环氧化是一项艰巨的任务，因为不稳定烯丙基氢的容易提取引发烯烃的完全燃烧并阻止选择性氧化。最近，研究表明，铜在烯烃环氧化反应中，特别是在烯丙基烯烃环氧化反应中，比广泛使用的银具有更高的选择性。本项目的目的是了解烯丙基烯烃环氧化的微观机制明确的铜单晶表面和这些机制与铜基负载催化剂的反应性和选择性在实际条件下操作的连接。本研究的主要重点将在于结构参数的作用，如烯烃的吸附几何形状，附近的烯属双键和烯丙基氢的表面，催化剂表面的微观结构等的活性和选择性对环氧化的调查。此外，将研究可能的替代环氧化途径，其不包括用原子氧氧化烯烃的常见步骤。实验将在Lambert教授（英国剑桥大学）的小组中进行。

Heterogeneous epoxidation of allylic alkenes represents a demanding task, since the easy abstraction of labile allylic hydrogen triggers total combustion of the alkene and prevents selective oxidation. Recently, it was shown that copper is intrinsically much more selective than widely used silver for both alkene epoxidation in general and for the difficult case of allylic alkenes in particular. The present project aims at an understanding of the microscopic mechanisms of allylic alkenes epoxidation on well-defined Cu single crystal surfaces and a connection of these mechanisms with the reactivity and selectivity of Cu-based supported catalysts operated under practical conditions. The main focus of this study will lie on investigation of the role of structural parameters such as alkene adsorption geometry, vicinity of the olefinic double bond and of the allylic hydrogen to the surface, the microscopic structure of the catalyst surface etc. in the activity and selectivity towards epoxidation. Additionally, possible alternative epoxidation pathways will be investigated, which do not include a common step of alkene oxidation with atomic oxygen. The experiments will be carried out in the group of Prof. Lambert (University of Cambridge, England).