CataRaman: Watching Catalysts in situ using Total Internal Reflection Raman Spectroscopy

研究挑战：直到最近，大多数研究固体催化剂的方法都是在低压/低温条件下进行的-与化学发生所需的方法非常不同。因此，能够在典型催化剂操作条件下洞察情况的新技术对于理解这些重要过程如何在分子水平上工作非常有价值。在光学光谱学领域，几乎没有真正的表面敏感技术，尽管原则上非常适合在操作条件下研究材料(许多材料和反应物，如气体，对光比电子或软X射线更透明)。由于感兴趣的催化化学通常只发生在催化剂表面，表面敏感性对于研究这些材料是非常重要的。要了解固体催化剂表面发生的化学作用，更容易研究定义明确的均匀尺寸、结构和组成的材料。这消除了在材料表面的不同部分上有许多相互竞争的过程的问题。以可伸缩的方式制造这些均匀材料的方法通常仅限于使用纳米颗粒的胶体合成，然后沉积到二氧化硅等氧化物上。这是光谱研究的一个问题，因为合成过程中必然会涉及阻止颗粒团聚的添加剂--这些添加剂很难去除，会留在金属颗粒的表面，而且可能会产生光谱信号，掩盖在催化剂表面反应的分子的光谱信号。及时性/英国重要性：90%的石化工业流程使用固体催化剂；多相催化剂制造每年价值2500亿美元。仅在英国，大宗商品化学品的年营业额就达到184亿GB。目前，化学工业(以及许多其他行业间接使用的)使用的碳基原料的99%来自石油和天然气。将现有的化学过程转换为更可持续的原料的压力要求开发具有显著不同性质的新催化剂。要做到这一点，需要更多地了解这些材料的实际工作原理，允许合理设计催化材料和工艺，从而能够更高效、更可持续地制造商品化学品。这对英国来说尤其重要，不仅是为了确保制造业的未来，也是为了应对能源挑战，既要对现有技术进行绿化，又要提供新的、更可持续的替代工艺。项目目标：该项目旨在使用一种新的先进的光谱技术来研究固体催化剂在制备过程中和实际操作条件下的情况。该项目将专注于高碳烯烃的环氧化化学--这是一种重要的反应，用于生产用于表面活性剂、液压油、除冰剂、塑料和纤维等产品的战略中间体。这一反应是目前新催化技术的一个重要目标，因为它目前使用的是非绿色氧化剂，对环境有害，原子效率低。创新的解决方案：该项目将采用最近开发的光谱工具TIR(全内反射)拉曼光谱，并首次将其应用于固体催化剂的现场研究。这提供了一种新的工具，可以在反应条件下从催化剂表面获得本质上对表面敏感的拉曼光谱。为了促进这一点，通过使用有机金属化学直接在二氧化硅表面制备纳米颗粒，将获得尺寸、结构和组成均匀的定义良好的材料。这避免了在这种合成中经常使用的合成试剂的使用，从而允许在清洁的纳米颗粒上进行吸附光谱分析。

Research Challenge:Until recently, most methods for studying solid catalysts have been under low pressure / low temperature conditions - very different from those required for the chemistry to occur. Thus, new techniques that allow insight under typical catalyst operating conditions are very valuable in understanding how these important processes work at a molecular level. In the area of optical spectroscopy very few truly surface-sensitive techniques exist, despite in principal being very well suited to studying materials under operational conditions (many materials and reactants such as gases are more transparent to light than electrons or soft X-rays). Since the catalytic chemistry of interest typically only occurs at the catalyst surface, surface-sensitivity is very important for studying these materials. To understand the chemistry occurring on a solid catalyst's surfaces it is easier to study materials of a well defined uniform size, structure and composition. This eliminates the problem of having many competing processes on different parts of the material's surface. Methods for making these uniform materials in a scalable way (to allow enough material for realistic high pressure catalyst testing) are generally limited to using colloidal synthesis of nanoparticles and subsequent deposition onto an oxide such as silica. This is a problem for spectroscopic studies, because the synthesis necessarily involves additives to stop particle agglomeration - these are hard to remove, remain on the surface of the metal particles and are likely to give rise to spectroscopic signals obscuring those of the molecules reacting at the catalyst surface. Timeliness / UK Importance: Solid catalysts are used in 90% of all petrochemical-based industrial processes; heterogeneous catalyst manufacture is worth $250bn annually. Commodity chemicals in the UK alone turnover £18.4bn annually. Currently, 99% of carbon-based feedstocks used by the chemicals industry (and indirectly by many others) are derived from petroleum and natural gas. The pressure to switch existing chemical processes to more sustainable feedstocks requires the development of new catalysts with significantly different properties. To do this requires a greater understanding of the way these materials actually work, allowing rational design of catalytic materials and processes, and thus enabling more efficient and sustainable manufacturing of commodity chemicals. This is important to the UK specifically not only in securing the future of the manufacturing sector but also addressing the energy challenge by both 'greening' current technologies and providing new more sustainable, alternative processes. Project Aims: This project aims to use a new advanced spectroscopic technique to studying solid catalysts both during their preparation and under realistic operating conditions. The project will focus on epoxidation chemistry of higher olefins - an important reaction for producing strategic intermediates that are used in products such as surfactants, hydraulic fluids, de-icers, plastics and fibres. This reaction is an important current target for new catalytic technology as it currently uses non-green oxidants that are environmentally harmful and atom inefficient. Innovative Solution:This project will take TIR (Total Internal Reflection) Raman spectroscopy, a recently developed spectroscopic tool, and apply it to study solid catalysts in situ for the first time. This provides a new tool that allows intrinsically surface sensitive Raman spectra to be acquired from a catalyst surface under reaction conditions. To facilitate this, well defined materials in terms of uniform size, structure and composition will be obtained by using organometallic chemistry to prepare nanoparticles directly on a silica surface. This avoids the use of synthetic agents often used in this kind of synthesis allowing spectroscopy of adsorbates on clean nanoparticles.