Advanced Electron Microscopy Studies of Zeolite-Supported Bifunctional Catalysts

Abstract

The results described in this PhD research answer fundamental questions related to catalysts that are used for specific industrial purposes. These catalysts consist of a support material on which metal nanoparticles are deposited. Different facets of these catalysts were investigated. It was found that the heterogeneities, i.e. the non-uniform distribution of the metal nanoparticles (platinum) on the support material (zeolite), is related to the local chemical composition of the support material. It is shown that the heterogeneous distribution of platinum can influence the catalytic activity. By choosing the synthesis conditions carefully, this heterogeneity could be controlled, and therefore the catalytic activity improved. Thereby the amount of metal can be optimized, important in view of economic as well as ecologic aspects. Besides this part of the research, a new technique, namely liquid cell transmission electron microscopy, has been used to study these catalysts in liquid phase. This technique allows for imaging materials and processes in liquid, which can lead to new insights. By using this technique it was found that the composition of the support material is important during the experiments, as it can have a significant influence on the stability of the material during the measurements. In addition, nucleation and growth of platinum metal nanoparticles on the support material was investigated. This led to the insight that it is important in which liquid the measurements are performed, as it had a direct influence over the growth.