Single atoms as highly selective active sites in heterogeneous catalysis

由于化石燃料储量的减少，从生物质中生产燃料和化学品变得越来越重要。生物基工业的发展和可持续性将高度依赖于能够选择性地将功能化有机分子转化为化学中间体和商业产品的催化过程。在这方面，纤维素生物质是最丰富的生物质形式，也是世界上最重要的可再生能源之一。纤维素衍生的化学品如糠醛提供了非常重要的商业机会，因为它们可以用作合成各种产品的起始材料和构建块。因此，开发具有稳定和持久性能的廉价、环保的低温催化剂是一个重要的工业利益。所描述的工作旨在为一类氢化反应开发原子高效催化剂，这些反应是生物能源和精细化工工业的核心。将研究两种不同类型的材料，这两种材料都是基于少量分离的催化活性金属中心（金、钯和铂）在氧化物载体表面或相对便宜的金属纳米颗粒表面的催化性能。为了确定有前途的低温加氢系统，将研究氢在分离位点上的活化及其在氧化物载体上的溢出。糠醛、肉桂醛和丙烯醛的选择性加氢反应是研究的重点。各种实验室和基于同步加速器的技术将用于建立分子结构与氢化活性和单原子位点选择性之间的关系。该项目开发的材料具有原子效率和低生产成本的优点，因为只需要少量的贵金属。更重要的是，由于催化剂表面活性中心的均匀性，单原子催化剂对特定产物的选择性提高了。氧化物载体上的精细分散体可以提供一种相对便宜的替代传统上使用的多相加氢催化剂。

The production of fuels and chemicals from biomass becomes increasingly important due to the diminishing reserves of fossil fuels. The development and sustainability of bio-based industries will be highly dependent on catalytic processes capable of selectively transforming functionalised organic molecules to chemical intermediates and commercial products. In this respect, cellulosic biomass is the most abundant form of biomass and one of the most important renewable energy resources worldwide available. Cellulose derived chemicals like furfural offer very important commercial opportunities as they can be used as starting materials and building blocks to synthesize a variety of products. Therefore, there is a major industrial interest to develop cheap, environmentally friendly low temperature catalysts with stable and prolonged performance.The described work aims to develop atom efficient catalysts for a class of hydrogenation reactions that lie at the heart of the bio-based energy and fine chemicals industries. Two different classes of materials will be investigated both of which are based on the catalytic properties of small quantities of isolated catalytically active metal centres of gold, palladium and Pt on the surface of oxide supports or on the surface of relatively inexpensive metal nanoparticles. The activation of hydrogen on isolated sites and its spillover on the oxide support will be investigated in order to identify promising systems for low temperature hydrogenations. The reactions of principal focus will be the selective hydrogenation of furfural, cinnamaldehyde and acrolein. A variety of laboratory and synchrotron based techniques will be used to establish a relationship between molecular structure and hydrogenation activity and selectivity on single atom sites. The materials developed in this project offer the benefit of atom efficiency and low cost of production as only small amounts of precious metals are required. More importantly single atom catalysts offer improved selectivity towards specific products due to the homogeneity of the active center on the catalyst surface. Fine dispersions on oxide supports can provide a relatively cheap alternative to traditionally employed heterogeneous hydrogenation catalysts.