Using supported metal nanoparticles for the conversion of biomass derived molecules

The energy demand of the world is increasing and the depletion of its reserves of fossil fuels are making energy production more expensive. The challenge therefore falls on researchers to develop novel ways of meeting this increased energy demand which are both cost-effective and environmentally friendly. Utilisation of biomass will be vital in achieving this goal because of its abundance and availability. In particular, levulinic acid has been identified as a valuable chemical feedstock. It can be easily converted into γ-valerolactone, which has vast potential applications in both the fuel and chemicals industries. The work presented in this thesis primarily focusses on the hydrogenation of levulinic acid into γ- valerolactone. Hydrogenation of levulinic acid is well known, but catalysts that facilitate it usually incorporate expensive precious metals. In order for a process to become truly sustainable, the catalysts should also be sustainable. This requirement makes research into the use of cheap and abundant materials as catalysts desirable. The work presented in this thesis investigated the use of critical, precious metal catalysts compared with the cheaper, abundant, and non-critical base metals as potential replacements. An investigation into lactic acid hydrogenation to 1,2-propanediol as a model reaction for levulinic acid hydrogenation was also carried out. Chapter 3 provides comparative data of a 5 wt.% Ru/C catalyst prepared by the sol immobilisation method and a commercial 5 wt.% Ru/C catalyst. In Chapter 4, a variety of preparation parameters for the synthesis of 1 wt.% Ru/C catalysts were investigated, including the choice of Ru precursor, carbon support, and preparation method. 1 wt.% Ru/C from this chapter was set as the benchmark for base metals. The second half of this thesis describes an investigation into the use of base metals as potential catalysts for levulinic acid hydrogenation. Chapter 5 shows that Cu-ZrO2 catalysts were active for levulinic acid hydrogenation under much harsher reaction conditions compared with the benchmark (1 wt.% Ru/C). The synthesis of Cu-ZrO2 was optimised through variation of the various preparation parameters and a detailed investigation was performed. Chapter 6 shows that the incorporation of Ni into Cu-ZrO2 improved the activity of Cu-ZrO2, with a product yield of 100 % obtained after 90 minutes. This was attributed to an increased surface area and the formation of a Ni-Cu alloy. Modifying the preparation method further by adding a ball-milling step further increased the surface area of the catalyst and resulted in a product yield of 100 % after 30 minutes of reaction. It was found that there was more metal that required present in these catalysts, indicating a requirement of further work in order to produce catalysts with comparable catalytic activity