NMR Methods for Measuring Mass Transport in Zeolites used for Catalytic Applications

沸石是一类重要的多孔材料，在化学工业中作为催化剂、吸附剂、离子交换剂和分离介质具有不可缺少的作用。它们在催化中的用途特别重要，因为它们能够使用多相催化技术促进许多酸催化反应，避免在均相溶液中使用无机酸，从而最大限度地减少废物和能源消耗。此外，它们的结构特征和孔径可以很容易地调节，这使得沸石非常适合于尺寸和形状选择性反应。虽然大多数关于沸石的研究都集中在结构-活性关系上，但是运输-结构-活性关系仍然大多未被探索并且不容易解开。虽然潜在地高度信息化，但是由于多种环境产生不同的扩散机制（例如，晶内、晶间、颗粒内）。测量扩散的最有效方法之一是通过NMR，该方法将在本项目中使用，并结合NMR弛豫测量，可以提供不同孔径和站点之间质量传输的定量图。在该项目中，主要目标是开发和应用方法来研究和量化在具有工业催化过程中的潜在应用的新型沸石催化剂中的扩散，以确定沸石孔结构的系统性变化-例如孔径的调节、形态的变化、分级孔隙率的引入、通道长度的调节、双功能催化剂所需的金属纳米颗粒的沉积-影响反应性物质的扩散行为以及这如何反映到它们的催化性能上。

Zeolites are an important class of porous materials, which have an indispensable role in the chemical industry as catalysts, adsorbents, ion exchangers and separation media. Their use in catalysis is particularly important since they are able to promote many acid-catalysed reactions using heterogeneous catalysis technologies, avoiding the use of inorganic acids in homogeneous solution with consequent minimization of waste and energy consumption. In addition, their structural features and pore size can be easily tuned, which makes zeolites ideal for size and shape selective reactions. Whilst the majority of studies on zeolites has been focused on structure-activity relationships, the transport-structure-activity relationship remains mostly unexplored and is not easy to unravel. Although potentially highly informative, diffusion in zeolites is quite complex to study due to the multiple environments creating different diffusion regimes (e.g., intra-crystalline, inter-crystalline, intra-particle). One of the most powerful methods to measure diffusion is by NMR, which will be exploited in this project, in combination with NMR relaxation measurements that can provide quantitative maps of the different pore sizes and mass transport between sites. In this project, the main objective is to develop and apply methods to investigate and quantify diffusion in new zeolite catalysts with potential applications in industrial catalytic processes in order to establish how systematic changes in zeolite pore structure - such as tuning of pore size, changes in morphology, introduction of hierarchical porosity, tuning of channel length, deposition of metal nanoparticles needed for bi-functional catalyst - affect the diffusion behaviour of reactive species and how this reflects onto their catalytic performances.