Polymer Immobilised Ionic Liquid Supported Catalysts: Synthesis, Characterisation and Applications

Abstract

Due to increasing demand for synthetic commodities, to reduce the overall environmental impact of existing chemical processes, a sustainable approach is required. In order to accomplish this, it will be necessary to use highly efficient, durable, and scalable catalyst technologies which are low in energy consumption and waste production. In addition, bio-renewable feedstock will also be required due its abundancy and availability. In this regard, chapter 1 provides an overview of the unique physicochemical properties and concepts of ionic liquids (ILs). The incorporation of ILs can produce functional materials, which in turn, can be used for the sustainable conversion of bio-renewable feedstock. Chapter 2 discusses the rational design and synthesis of a range of ruthenium nanoparticle (RuNP) catalysts, in which, the catalysts were tested in the hydrogenation of the benchmark substrate acetophenone. The overall aim of this work was to investigate the effect of the interactions between the ruthenium and the polymer support on the catalyst performance and selectivity. The resulting catalysts were highly active and selective in the hydrogenation of a range of 𝛼, 𝛽-unsaturated ketones, aldehydes, and the study was extended to include bio-derived substrates. In total four reactions were tested, namely the hydrogenation of acetophenone, furfural, levulinic acid and ethyl levulinate. The low ruthenium loadings and the reusability of these heterogenous catalysts, in addition to the use of water as the co-solvent/solvent, has provided a sustainable hydrogenation method, which is among one of the highest reported on comparison with the literature. Chapter 3 covers the application of the RuNPs for the hydrazine-mediated reduction of a broad range of nitroaromatics to their corresponding aromatic amines under mild conditions with low catalyst loadings. Chapter 4 details the synthesis of a set of imidazolium polystyrene-based Brønsted acid catalysts immobilised with peroxophosphotungstate anions. These efficient and selective catalysts were tested, as catalysts for the alcoholysis of furfuryl alcohol to produce alkyl levulinates, under batch as well as continuous flow regimes. Such generated levulinates are highly desirable as bio-renewable fuel additives.