Catalytic oxidation reactions using hydrogen peroxide

Sharp, Gregory 2023. Catalytic oxidation reactions using hydrogen peroxide. PhD Thesis, Cardiff University. Item availability restricted.

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Abstract

The research within this thesis has focussed principally on two reactions: the selective oxidation of benzyl alcohol via in-situ hydrogen peroxide (H2O2) synthesis, and the catalytic wet peroxide oxidation of phenol. Additionally, investigations involving the direct synthesis of H2O2 from H2 and O2 were conducted in relation to the selective oxidation of benzyl alcohol in order to gain better insight into the individual reaction pathways. The selective oxidation of benzyl alcohol via in-situ H2O2 synthesis has been investigated previously in the literature and provides a lower temperature alternative to aerobic oxidation methodologies, which typically require reaction temperatures in the range of 80-120 oC, whilst oxidation via in-situ generated H2O2 allows for operation at temperatures approaching 50 oC. Furthermore, by generating H2O2 in-situ, the limitations of using commercial H2O2 produced through the anthraquinone auto-oxidation process can be mitigated. In this work, investigations have focussed on optimising the support material for a Pd-based heterogeneous catalyst, incorporating secondary and tertiary metals alongside Pd and synthesising catalysts through different preparation methodologies with the objective of increasing benzyl alcohol conversion and limiting catalyst deactivation. Particular attention has been given to Pd, FePd and AuPd supported catalyst, with FePd and AuPd catalysts representing the most promising candidates for future development. Pd-based heterogeneous catalysts represent a ubiquitous and well-studied class of catalysts for the direct synthesis of H2O2, with factors including nanoparticle size, the influence of support material, the oxidation state of Pd and the effects of secondary metal alloying having received previous research attention. It should be noted that the direct synthesis of H2O2 utilises lower reaction temperatures (20 oC in this Thesis) compared to the selective oxidation of benzyl alcohol (50 oC) and that the degradation of H2O2 is promoted at higher temperatures. In collaboration with Selden Research Ltd. the development of novel disinfectants using catalysis was undertaken, with the intention of developing chemical disinfectants that incorporate benign and non-toxic components that naturally degrade after use. The catalytic wet peroxide oxidation of phenol has been used in this work as a model reaction system to develop and maximise the oxidative ability of a mixture containing ascorbic acid and sodium percarbonate, which operates as a source of H2O2. This was used in conjunction with a heterogeneous source of a Fenton-type metal catalyst. This work was conducted under the assumption that reaction systems that delivered higher levels of conversion of phenol may also offer high efficacy when used as a disinfectant. Investigations have focussed on selecting the optimal Fenton-type catalyst, optimising the concentrations of each component of the reaction mixture, and examining the effects of pH on both the extent of catalytic metal leaching and towards the overall conversion of phenol.

Item Type:	Thesis (PhD)
Date Type:	Completion
Status:	Unpublished
Schools:	Chemistry
Date of First Compliant Deposit:	2 May 2024
Last Modified:	02 May 2024 16:02
URI:	https://orca.cardiff.ac.uk/id/eprint/168673

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