Phosphatation of Zeolites: A Combined Spectroscopy, Microscopy and Catalysis Study

Abstract

The scope of this dissertation is to gain a fundamental understanding of phosphorus interaction with zeolites. These interactions can be either promotional or poisonous. Therefore, the main focus of this PhD thesis will be on the understanding of the physicochemical effects that occur upon phosphorus modification of zeolites. The ultimate goal is to elucidate if and what kind of bonds phosphorus forms with zeolite framework atoms, what the nature and location of phosphorus species are, and how these influence the acidity, the accessibility, the shape-selective character and the hydrothermal stability of zeolites. To achieve this goal we have used a combination of spectroscopic and microscopic techniques, complemented with catalytic testing to study a variety of zeolites to which different pre-, and post-treatments have been applied. It was found that phosphorus forms reversible and irreversible bonds with framework and extra-framework aluminum. These interactions lead to lower acid site number and strength, change the size of channel intersections and promote the stability of framework aluminum. The insights gained in this thesis will help with more rationalized designs of phosphated zeolites, which can be used for a variety of applications, such as biomass conversion, bio-alcohol dehydration, methanol-to-hydrocarbon reactions, and hydrocarbon cracking.