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Persistent URL http://purl.org/net/epubs/work/67342707
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Record Id 67342707
Title Investigating the dynamics of species relevant to the partial oxidation of methane using neutrons & muons
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Abstract The partial oxidation of methane over copper loaded zeolites represents a rapidly evolving field of research due to the growing understanding of the complex challenges associated with optimising and implementing an industrially-viable process. However, there is a paucity of literature regarding the dynamics of the various species involved in this reaction within Cu-loaded zeolite catalysts. This study investigates such dynamics, focusing on methane, methanol, water and copper within zeolites mordenite, SSZ-13 and ZSM-5. Quasielastic neutron scattering enabled insights into the dynamics of water, methane and methanol within the Cu-doped zeolites. At low temperatures, water was found to be immobile; however, as the temperature was increased, rotational and translational dynamics were observed, particularly at 300 K. Methanol adsorbed onto the three zeolites displayed non-Arrhenius behaviour, with varying jump lengths, residence times and diffusion constants. These results have implicated multiple, concurrent processes taking place, such as clustering around cationic sites and methoxylation, influenced by the presence of copper. Probing the dynamics of methane resulted in no observable motions, likely due to challenges in methane adsorption or inherently low uptake under the experimental conditions used. Neutron diffraction complemented the findings by revealing how the zeolitic framework responds to the adsorption of water and methane. The former induced significant structural changes characterised by anisotropic expansion and contraction of the zeolite framework; whilst the latter resulted in minimal observable changes. Muon spectroscopy is presented as a novel approach for the study of metal ion dynamics within zeolite hosts. Transverse and longitudinal field measurements showed significant differences in muon relaxation rates between the pure and Cu-doped zeolites, suggesting dynamic processes associated with the copper ions. The formation of muonium and its temperature-dependent interaction with Cu(II) species highlighted the electronic and magnetic influences of copper ions; and temperature dependent longitudinal field measurements have indicated processes involving copper dynamics or the redox behaviour thereof. The integration of neutron and muon techniques presents a comprehensive approach to understanding the behaviour of various species within microporous materials, paving the way for enhanced methane-to-methanol conversion processes and broader applications in catalysis.
Organisation ISIS , ISIS-EMU , ISIS-IRIS , ISIS-TOSCA , ISIS-ENGIN-X , STFC
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Language English (EN)
Type Details URI(s) Local file(s) Year
Thesis PhD, University of Glasgow, 2024. https://theses.gla.ac.uk/84759/ 2024