A technique that is becoming more widespread in usage and popularity, ball milling has been used successfully in the pretreatment of sodium lignosulphonate (NaLS), a waste biomass material. The ball milled material produced higher yields of commercially valuable aromatic products, particularly vanillin in an industry standard copper-catalysed aerobic oxidation reaction. Through the optimisation of the parameters of this pretreatment technique both for NaLS alone and NaLS with sodium hydroxide and calcium oxide as additives, the vanillin yield after oxidation of the pretreated material could be increased by over 100 %. The generation of vanillin in NaLS in the solid state during ball milling was also observed for the first time confirming that mechanochemical transformation of the NaLS was taking place. Despite the difficulties associated with the analysis of such a heterogeneous and complex biopolymer, SEM imaging, GPC analysis and 2-D NMR analysis were used to identify some of the major chemical and physical changes occurring in the material during mechanochemical pretreatment. An HPLC analytical method for accurate measurement of the main oxidation products was also developed. The effect of using milling media of a different material on the pretreatment and subsequent oxidation reactions revealed that this pretreatment is transferable between different types and scale of equipment but that the results are sensitive to both materials of construction and storage conditions for analytical samples. The extrapolation of this pretreatment technique to other reactions of NaLS, hydrogenolysis for example, and to other biomass substrates was also investigated but with varying degrees of success, indicating that the mechanochemical changes can be subtle and highly reaction specific. Initial attempts at providing more mechanistic information were made through the synthesis and transformations of some simple lignosulphonate model compounds. These provided confirmation that the mechanistic scenario is complex and that several pathways are likely to be operating in parallel in the transformations of both model and polymer substrates.
| Identifer | oai:union.ndltd.org:bl.uk/oai:ethos.bl.uk:679263 |
| Date | January 2014 |
| Creators | McKinnie-Hill, J. S. |
| Publisher | Queen's University Belfast |
| Source Sets | Ethos UK |
| Detected Language | English |
| Type | Electronic Thesis or Dissertation |
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