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Title: Heterogeneously catalysed selective hydrogenations in the liquid phase
Author: McManus, Iain James
ISNI:       0000 0004 5371 2343
Awarding Body: Queen's University Belfast
Current Institution: Queen's University Belfast
Date of Award: 2014
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Heterogeneous catalysis is widely used in industry for the synthesis of chemicals. However, achieving a high selectivity to the desired products can be a challenge. Numerous factors influence the selectivity of a reaction, including the solvent used. The effect of solvent on the hydrogenation of the aromatic ketone over a Pt/Titania catalyst was, therefore, investigated, The solvent was found to have a major effect on the rate and the selectivity of the reaction. This effect was found not to be due to empirical or physical properties of the solvent. Alkane solvents gave fast reactions which favoured ring hydrogenation, aromatics gave slower reactions which favoured carbonyl hydrogenation and alcohols favoured carbonyl hydrogenation. The rate in alcohol solvents depended on whether the solvent was a primary alcohol or secondary alcohol, with secondary alcohols giving much faster reactions, In addition, water had a major effect on the rate and selectivity of alcohol solvents. The aromatic solvents were found to be site blocking the active sites, The alcohols form a layer on the catalyst surface, which in the case of the primary alcohol solvents prevents the substrate from reaching the active sites. Reactions were performed over Pt/silica sintered Pt/titania and Pt supported on anatase and rutile. The reaction was found to be structure sensitive and oxygen vacancies were found to play a role in determining the selectivity of the reaction. The selective hydrogenation of a number of compounds over OMS-2 and catalysts based on OMS-2 was investigated. It was found the OMS-2 is an active hydrogenation catalyst, even without an added metal, though the reactions were usually slower. Chloronitrobenzene was not dehalogenated by OMS-2. Due to the results obtained over this catalyst, the mechanism of nitrobenzene hydrogenation was investigated. It was found that two mechanisms occlllTed, which depended on the catalyst and conditions used.
Supervisor: Not available Sponsor: Not available
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
EThOS ID:  DOI: Not available