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。它们在催化中的应用尤其重要，因为它们能够使用非均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浪费和能源消耗。此外，它们的结构特征和孔径可以很容易地调整，这使得沸石成为尺寸和形状选择反应的理想选择。虽然大多数关于沸石的研究都集中在结构-活性关系上，但运输-结构-活性关系仍未被探索，而且不易解开。虽然具有潜在的高信息量，但沸石中的扩散研究相当复杂，因为多种环境会产生不同的扩散机制（例如，晶内，晶间，颗粒内）。测量扩散最有效的方法之一是核磁共振，它将在这个项目中被利用，与核磁共振弛豫测量相结合，可以提供不同孔隙大小和位点之间质量传输的定量图。在这个项目中，主要目标是开发和应用方法来研究和量化具有潜在应用于工业催化过程的新型沸石催化剂的扩散，以确定沸石孔隙结构的系统变化-如孔径调整，形态变化，分层孔隙度的引入，通道长度的调整，双功能催化剂所需的金属纳米颗粒沉积-影响活性物质的扩散行为以及这如何反映到它们的催化性能。

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.