Design and development of nickel based catalysts for the hydrogenation of levulinic acid to fuels and fuel additives
Creators: name: Velisoju, Vijay Kumar
Publisher: name: RMIT University
Year: 2024

description: There is significant interest in the development of new routes for the production of renewable fuels, especially fuels for the transportation sector. Apart from first generation renewable fuels, there has been increased interest in the development of processes for generating renewable fuels using non-edible feedstocks such as lignocellulose. Of the various processes that have been developed for converting lignocellulose to fuels and fine chemicals, processes which involve the conversion of levulinic acid (LA) have received significant interest. Various processes have been investigated for conversion of LA into fuel compounds such as γ-valerolactone (GVL) and valeric acid (VA). These processes, however, have significant room for improvement in terms of economic and environmental efficiency. Hence there is significant interest in the development of new catalysts for the conversion of LA into fuel compounds. There are many reports on the hydrogenation of LA to GVL over noble and non-noble metal based catalysts in the liquid phase, whilst very few studies have been conducted on the aforementioned in the vapour phase. Therefore, with the aim of developing continuous processing of LA to fuels and fuel additives, detailed investigations were carried out in this thesis using non-noble metal based catalysts at an ambient pressure and moderate reaction temperatures.<br><br>In chapter III, the conversion of LA to GVL was investigated over a range of TiO2 supported Ni and noble metal (Pt, Pd, and Ru) based catalysts. Links between characteristics of the materials studied and activity observed were investigated using various characterization techniques such as XRD, pulse chemisorption, and pyridine adsorbed DRIFTS. Different Ni loaded catalysts were screened for LA hydrogenation to optimize the product yield and catalyst composition. The influence of catalyst synthesis, pre-treatment procedures and reaction parameters on activity and selectivity for GVL were investigated for the Ni/TiO2 catalyst.<br><br>In chapter IV, various oxides TiO2, SiO2, ZrO2, and Al2O3 were assessed as supports for Ni catalysed the conversion of LA to GVL. Among the tested materials, the Ni/TiO2 catalyst was found to have the highest activity and selectivity towards GVL formation. Based on the results obtained in this chapter, the presence of predominantly Lewis acidity on the catalyst surface favours GVL formation, whereas the presence of a significant amount of Brønsted acidity initiate ring opening of GVL to form other products such as VA.<br><br>In chapter V, the conversion of LA to VA ( a useful chemical in the production of valeric bio-fuels) was investigated using a modified form of the Ni/TiO2 studied in chapters III and IV. Based on the results obtained, it was decided to modify the Brønsted acidity of the highly active and stable Ni/TiO2 catalyst studied in previous chapters. Different W loaded Ni/TiO2 catalysts were prepared and extensively characterized by various adsorption and spectroscopic techniques to see the surface and bulk characteristics. Based on the results obtained in this work, it was found that the increased Brønsted acidity and strong metal-support interactions were most likely responsible for the high activity towards the desired product.