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

点击翻译按钮获取中文摘要

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.