Currently, the major sources of fuel, energy, and chemicals are nonrenewable fossil resources such as petroleum, natural gas, and coal. Additionally, petroleum is used for the production of most transportation fuels and for the production of about 95% of organic chemicals. However, the production and use of non-renewable fossil fuels are unsustainable. For economic and environmental sustainability, there is a need to search for new and/or renewable resources and technologies for energy, fuels, and chemicals production that have the potential of effectively substituting fossil resources. In this context, lignocellulosic biomass is one of the candidates that meet these requirements due to its abundance and renewability. Lignocellulosic biomass-derived sugars can be chemically converted into 5-(hydroxymethyl)furfural (HMF), a versatile platform chemical that can used to generate intermediates for the production of biofuels and chemicals. In this dissertation novel catalytic processes for converting monosaccharides into HMF are described.
In chapter one, a literature review of the significance of HMF and the chemical intermediates derived from HMF is presented. The chapter also describes some of recent developments in the catalytic production of HMF from lignocellulosic sugars using homogeneous and heterogeneous catalysts. Chapter two discusses the catalytic activity of dimethylaluminum complexes bearing (aminomethyl)phenolate ligands that I developed for converting glucose to HMF in ionic liquids. A systematic study on the effects of modification of the aluminum ancillary ligands on the efficiency of glucose conversion is presented. High HMF yield were obtained with substitution of an aryl substituent on the amino groups of the (aminomethyl)phenolate ligands.
In an effort to improve HMF yield, the effects of modifying the ligands on the phenolate moiety of the (aminomethyl)phenolate ligands were investigated in chapter three. Using bulky ortho-phenoxide substituents achieved high HMF yields. The selectivity for HMF production with respect to fructose dehydration was also discussed, together with spectroscopic characterization of the polymeric humins produced from the dehydration reactions. In chapter four a study of the structural differences of poor vs. effective dimethylaluminum complexes bearing (aminomethyl)phenolate ligands is described.
Insights from this study shows that different precatalyst intermediate could be formed depending on the aluminum complex used, which in turn affects HMF selectivity of dehydration reactions. The isomerization of glucose to fructose using aluminum complexes in N-methyl-2-pyrrolidone (NMP) is discussed in chapter five. Using NMR spectroscopy on isotopically labeled glucose, a mechanism for glucose isomerization to fructose is presented. Finally, chapter six gives a summary and describes potential future directions for the research detailed in this dissertation.
| Identifer | oai:union.ndltd.org:uky.edu/oai:uknowledge.uky.edu:chemistry_etds-1107 |
| Date | 01 January 2018 |
| Creators | Saang'onyo, Daudi Sayialel |
| Publisher | UKnowledge |
| Source Sets | University of Kentucky |
| Detected Language | English |
| Type | text |
| Format | application/pdf |
| Source | Theses and Dissertations--Chemistry |
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