Deactivation of commercial three-way catalysts: effect of the thermal ageing

Sammanfattning: This licentiate thesis is a summary of my study on thermal deactivated commercial threeway catalysts (TWCs). The experiments were performed using gasoline and a E85 fuelmixture of 85 vol.% ethanol and 15 vol.% gasoline. Gas composition, temperature, spacevelocity and stoichiometry were kept to levels similar to automotive conditions. Theeffect of hydrothermal ageing on mono- and bimetallic commercial TWCs wasinvestigated. The analysis showed clear deactivation of the aged samples and theinfluence on TWC’s properties, such as: light-off temperature, specific surface area(BET), noble metal dispersion, oxygen storage capacity (OSC), oxygen storage capacitycomplete (OSCC) and labile oxygen storage capacity (LOSC). Water inhibition has beeninvestigated and confirmed for the performance of NOx reduction of the fresh catalyst. Xrayphotoelectron spectroscopy (XPS) was used to measure changes in the oxidation stateof the Pd and Rh present in the washcoat of the catalyst before and after hydrothermalageing. An element map SEM-EDX analysis was performed in order to characterize thedesign and morphology of the catalysts, as well as their surface’s composition anddistribution. In this work, theoretical and methodological contributions to deactivation ofthe catalysts are presented.