Evaluation of Cellulosic Materials for the Enzymatic Production of Bioplastics

There is an increasing awareness of the benefits that continuous flow processes provide for the synthesis of platform chemicals, using the biorefinery approach. Continuous flow bio-oxidations offer advantages over traditional chemical batch oxidations through faster rates, higher selectivity, green oxidants and cascade reactions. This thesis explores different methods for continuous flow bio-oxidation of hydroxymethylfurfural (HMF) a sugar-derived building block that has potential use in bioplastics. To evidence improved sustainability, life-cycle analysis (LCA) techniques that look at the impact of production on the environment are essential in determining whether the new processes will be beneficial in the long-term.

The objectives of this thesis were: to improve upon existing bio-oxidative techniques and then apply them to continuous flow to further bridge the gap between academic and industrial research. This includes: introducing continuous oxidations for furan-based intermediates; developing reactors for foam production and transport of solid particulate; and analysing the techniques for their environmental impact. To establish a green route for the synthesis of FDCA from HMF, a variety of green oxidisers were tested. CAL-B lipase gave the highest yield and was developed further into a continuous flow bio-oxidation. Production of the precursor DFF in continuous flow required resolving common solubility issues. Protein-stabilised aqueous foams were able to transport insoluble particulate out of a reactor, whilst air could generate the foam and simultaneously supply the oxidation. To determine the feasibility of each developed process, a life-cycle assessment was conducted. A cradle-to-gate approach was used and compared to both a platinum catalysed synthesis of FDCA and petroleum derived terephthalic acid. Although the environmental impacts for the two FDCA processes are similar, significant improvement is needed to compete with the petroleum industry. The liquid foam reactor looks promising for up-scaling production but requires further evaluation of the DFF to FDCA setup before a full telescoped process can be developed.