Single atoms as highly selective active sites in heterogeneous catalysis

由于化石燃料储量的减少，从生物质生产燃料和化学品变得越来越重要。生物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，也是全世界可用的最重要的可再生能源之一。像呋喃甲醛这样的纤维素衍生化学品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原料和构件。因此，开发价格低廉、环境友好、性能稳定和持久的低温催化剂具有重大的工业意义。所描述的工作旨在开发一类原子高效的催化剂，用于生物基能源和精细化工行业的一类加氢反应。将研究两类不同的材料，这两类材料都是基于氧化物载体表面或相对便宜的金属纳米颗粒表面上少量孤立的催化活性金属中心金、钯和铂的催化性能。将研究氢在孤立位置上的活化及其在氧化物载体上的溢出，以确定有希望的低温加氢系统。主要的焦点将是糠醛、肉桂醛和丙烯醛的选择性加氢。将使用各种实验室和同步加速器技术来建立分子结构与加氢活性和单原子位置的选择性之间的关系。该项目开发的材料具有原子效率高和生产成本低的优点，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一性，单原子催化剂提高了对特定产品的选择性。氧化物载体上的精细分散可以提供一种相对廉价的替代传统使用的多相加氢催化剂的方法。

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.