Concerns over dwindling fossil fuel reserves, and the impact of CO2 emissions on climate change, is driving the quest for alternative feedstocks to reduce dependence on non-renewable sources of fuels and chemicals. Biomass offers the only renewable source of organic molecules for the manufacture of bulk, fine and speciality chemicals necessary to secure the future needs of society. In this regard, conversion of biomass derived C6 sugars to 5-hydroxymethylfurfural (HMF), the latter a potential, bio-derived platform chemical, is of significant current interest. However, commercial implementation of HMF as a chemical intermediate is impeded by high production costs. A heterogeneously catalysed route to directly convert glucose into HMF in aqueous media thus remains highly sought after. In this thesis, the telescopic conversion of glucose to fructose and then HMF has been explored over a family of bifunctional sulfated zirconia catalysts possessing tuneable acid–base properties. Characterisation by acid–base titration, XPS, XRD and Raman reveal that sub-monolayer SO4 coverages offer the ideal balance of basic and Lewis– Brønsted acid sites required to respectively isomerise glucose to fructose, and subsequently dehydrate fructose to HMF. Here we demonstrate that systematic control over the Lewis–Brønsted acid and base properties of SZ enables one-pot conversion of glucose to HMF in aqueous media, employing a single bi-functional heterogeneous catalyst. Further improvements in catalytic performance have been achieved through the synthesis of monolayer grafted ZrO2/SBA-15 catalysts in which conformal layers of ZrO2 are grown from Zr propoxide. Analysis reveals 1-3ML can be achieved; subsequent sulfation yields a catalyst with 1.25 to 2 times the activity of bulk SZ. These catalysts also exhibit remarkable water tolerance with retention of pore structure upon hydrothermal treatment at 170 °C for 6 h. All catalysts find application in esterification,with optimum activity for samples treated with 0.1 M H2SO4.
| Identifer | oai:union.ndltd.org:bl.uk/oai:ethos.bl.uk:646321 |
| Date | January 2014 |
| Creators | Osatiashtiani, Amin |
| Publisher | Cardiff University |
| Source Sets | Ethos UK |
| Detected Language | English |
| Type | Electronic Thesis or Dissertation |
| Source | http://orca.cf.ac.uk/73287/ |
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