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The selective oxidation of bio-derived platform chemicals over supported gold catalysts

Douthwaite, John 2016. The selective oxidation of bio-derived platform chemicals over supported gold catalysts. PhD Thesis, Cardiff University.
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Abstract

A fundamental limitation effecting the exploitation of bio-fuels is that they are not currently economically competitive with conventional fossil fuels. The development of novel chemical processes to convert bi-products from these reactions into high value chemicals could be one method to reduce the economic deficit between these two industries. Glycerol and furfural are produced as bi-products in the production of 1st and 2nd generation bio-fuels. This thesis explores the potential of using supported Au catalysts for the oxidation of these bio-derived compounds for the synthesis of high value chemicals. The reaction conditions were found to significantly affect the product distribution and the reaction rate for the aerobic, liquid phase oxidation of glycerol over a AuPt/TiO2 catalyst. Mechanistic studies suggested that glycerol acid and tartronic acid are primary products in this reaction. This study also implied that C-C scission leading to the unfavourable formation of C1 and C2 products occurred from glyceraldehyde, dihydroxyacetone and glyceric acid. Au nanoparticles supported on hydrophobic supports were found reduce C-C scission, and the incorporation of Pd and Pt to a Au/BN catalyst was found to further increase desirable C3 selectivity. Additional work confirmed that the in-situ formation of H2O2 was primarily responsible for C-C cleavages, which led to the postulation that Dakin oxidation was the mechanistic process by which it proceeds. Supported trimetallic AuPdPt nanoparticles were found to be active for the oxidation of glycerol under base free conditions. The catalyst was found to significantly influence the activity of these particles. It was determined that a Au/TiO2 catalyst could selectively oxidise furfural to produce reasonable yields of furoic Acid. Polymerisation of the substrate was found to inhibit catalytic performance which was suggested to be a result of the polymers binding irreversibly to the catalyst. Optimisation of the catalyst and experimental procedure was found to reduce this unfavourable polymerisation, which led to the production of furoic acid yields in excess of 89% using a AuPd/Mg(OH)2 catalyst. Further tests indicated that the size of the metal nanoparticles and the Au:Pd ratio significantly affected catalytic performance for this reaction. Mechanistic studies identified the presence of three reactions; the direct oxidation of furfural, the oxidative dehydrogenation of furfuryl alcohol and the Cannizzaro reaction. A kinetic study allowed for the determination of the activation energies corresponding to each of these pathways, which ultimately highlighted the potential of using a catalyst for this reaction on an industrial scale.

Item Type: Thesis (PhD)
Status: Unpublished
Schools: Chemistry
Subjects: Q Science > QD Chemistry
Date of First Compliant Deposit: 19 August 2016
Last Modified: 04 Jun 2017 09:21
URI: http://orca-mwe.cf.ac.uk/id/eprint/93926

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