Panchal, Monik;
(2023)
Multiscale Imaging and In Situ Analysis of Catalysts used for Emission Control.
Doctoral thesis (Ph.D), UCL (University College London).
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Abstract
Air pollutant emission standards and limits were established as a measure to control pollution levels. This has led to novel solutions to meet the ever- tightening standards, especially towards the size and quantity of particulate matter (PM), particularly ash, emissions. Recent emission standards by the European Union (EU6c), have focused on reducing the PM emissions from gasoline engines. Gasoline particulate filters (GPF) technologies which use a three-way catalyst (TWC) washcoat applied onto the particulate filter, are expected to be implemented to comply with regulatory limits. Challenges with this system include understanding the role of the ash deposition on the catalyst washcoat and how it affects the catalytic performance. Thus, by observing how the ash interacts within particulate filters, the distribution of metal catalyst and how the regeneration of the catalyst affects performance are key towards improving aftertreatment technology. This project is focused on the analysis of GPF containing mainly PdRh/CeZrOx - La/Al2O3 (TWC) catalyst, using synchrotron-based techniques and imaging, to understand the effect of ageing (simulating use of >100 000 km) and ash deposition on the system. This project explored using Operando XAS, which was utilised to understand the evolution of Pd during operation conditions and found that with the presence of ash the light-off temperature for CO oxidation and NO reduction increased. On aged GPF’s, various length scale imaging techniques were performed on the same sample (to retaining spatial resolution), such as XRM, EPMA, FIB-SEM, XRF and AC-STEM and correlated. Nanoprobe XRF mapping and AC-STEM-EDS, suggest formation of large Pd species upon ageing and further co-location of Zn species (introduced by ash deposition) about engine aged ash containing samples. Further, the use of spatially resolved Zn K- edge XANES highlighted that multiple zinc compounds were present from the ash, which reacted with the catalyst upon ageing, forming a zinc spinel analogue.
| Type: | Thesis (Doctoral) |
|---|---|
| Qualification: | Ph.D |
| Title: | Multiscale Imaging and In Situ Analysis of Catalysts used for Emission Control |
| Open access status: | An open access version is available from UCL Discovery |
| Language: | English |
| Additional information: | Copyright © The Author 2023. Original content in this thesis is licensed under the terms of the Creative Commons Attribution-NonCommercial 4.0 International (CC BY-NC 4.0) Licence (https://creativecommons.org/licenses/by-nc/4.0/). Any third-party copyright material present remains the property of its respective owner(s) and is licensed under its existing terms. Access may initially be restricted at the author’s request. |
| Keywords: | Catalysis, Chemistry, Electron Microscopy, Emission Control, EXAFS, Gasoline Particulate Filters, Imaging, In situ, Multilength Scale, Operando, Synchrotron, XANES, XAS, XRF |
| UCL classification: | UCL UCL > Provost and Vice Provost Offices > UCL BEAMS UCL > Provost and Vice Provost Offices > UCL BEAMS > Faculty of Maths and Physical Sciences UCL > Provost and Vice Provost Offices > UCL BEAMS > Faculty of Maths and Physical Sciences > Dept of Chemistry |
| URI: | https://discovery.ucl.ac.uk/id/eprint/10171955 |
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