Water in Zeolite Pores: Modelling of Water-Active Site Interactions

Abstract

Sustainably sourced biomass may have wide applicability as a renewable resource for the production of transportation fuels as well as many consumer products (plastics, car supplies, clothing). What is more, traditional – zeolite-based – catalysis has been successfully explored for performing such sustainable manufacturing processes. Nonetheless, new catalytic reactions introduce new difficulties. Fuel production (via high-temperature cracking of the oxygen-rich biomass molecules) involves water formation while converting biomass poly-alcohols into chemicals often requires an aqueous environment. In both cases, the presence of water in the traditional zeolite-based catalysts causes a reduction of activity over time.

In this PhD thesis we combine quantum mechanical and classical simulations to study water in zeolites, with the goal to develop guidelines to design more stable zeolite catalysts for the future applications. The project can be divided into two branches, involving two different simulation scales. In the first part, we investigate the reactivity of water towards the zeolite framework using density functional theory approach. Based on our results we propose a novel method of how to control the Al distribution and thus the catalyst stability. In the second part of the project, we explore the chemical transformations of the Brønsted acid site proton in the presence of water, with the aim to study the influence of water on the catalyst activity and reactivity. This thorough study provides information about the structure and location of water adsorbed in zeolites and can serve as a framework for further studies on the reactivity of the biomass compounds themselves.