Fossil fuels such as coal, oil and natural gas are, by the nature of their formation. a finite resource. Fossil fuel resources will eventually deplete or become uneconomical to use. If mankind is to maintain or improve its current quality of life over future generations, alternative means of producing usable energy and materials must be found. One feasible approach is bio-refining, which uses biomass to produce usable energy and materials from renewable sources. It has been stated that the main factor against the viability of a bio-refinery is the lack of available technology. The work described within this thesis aimed to enhance the technology in two areas within a potential bio-refinery; the depolymerisation of lignin to produce platform chemicals and the polymerisation of rac-lactide to produce bio-plastics. Chapter 2 contains the synthesis of a range of novel zinc(II) and aluminium(II1) heterogeneous silica tethered initiators for the ROP of rac-lactide were synthesised as well as their homogeneous silsesquioxane analogues. The heterogeneous complexes produced polylactide of reasonable molecular weight in a well controlled fashion. with Si-(L-HO)Al showing a degree of stereocontrol (Pr=0.32). ICP-AES analysis showed a reduction in the metal content of the polymer produced by heterogeneous initiators. A polymer synthesised by the heterogeneous Si-(LtBUO)AI complex contained 431 ppm Al compared to 2500 ppm Al when its homogeneous analogue, Al(tbuO)Me2, was used. A novel tetrametallic zinc(II) complex, Zn4(L HO)4(OMe)2Me2, was synthesised, demonstrating serendipitous oxygen insertion into the Zn-Me bond. Chapter 3 involved the synthesis and characterisation of a range of novel zinc(U) complexes based on a β-ketoiminate ligand system with varying steric properties. These were also active for the synthesis of polylactide from rac-lactide but exhibited no stereocontrol. The complexes were active in the industrial preferred melt conditions. Chapter 4 details analytical processes to assess the depolymerisation of lignin under oxidative conditions and a range of model lignin compounds were synthesised. Various approaches were utilised, based on heterogeneous and homogeneous•catalysts. The catalytical coupling of two -OH groups to form an ether moiety was observed in the presence of a Re(VII) complex and H20 2• A range of cobalt and vanadium complexes were synthesised and two solid state structures, CoSaLtBuOO and V(LTBUOO)O, were determined, these were screened for the depolymerisation of lignin and model compounds.
| Identifer | oai:union.ndltd.org:bl.uk/oai:ethos.bl.uk:601644 |
| Date | January 2012 |
| Creators | Di Iulio, Carlo |
| Contributors | Jones, Matthew |
| Publisher | University of Bath |
| Source Sets | Ethos UK |
| Detected Language | English |
| Type | Electronic Thesis or Dissertation |
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