Department of Chemistry and Material Science (DCMS)

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    FEASIBILITY STUDY FOR YELLOW OLEANDER BIODIESEL PRODUCTION USING EGGSHELL-DERIVED NANOCATALYST SYNTHESIZED BY BOTTOM-UP TECHNIQUE
    (Technical University of Kenya, 2023-10) MASIME, JEREMIAH ODHEK
    The global energy demand is expected to rise by 53% by 2030, depleting crude oil reserves by 2052. This increase in energy demand growth has led to increased CO2 emissions, environmental degradation, and the need for alternative fuels. Researchers are exploring biofuel production using Yellow Oleander seeds, a non-edible plant with high oil content. Heterogeneous base catalysts are preferred for biodiesel production due to their non-toxic, high surface area, reusable, and superior stability, while nanocatalysis increases catalytic activity. The eggshell-derived nanocatalyst was prepared using the bottom-up technique and characterized using TG/DTG/DSC, BET/BJH, XRD, FTIR, XRF, TEM, SEM, and EDX. Response surface methodology was used to optimize biodiesel production from yellow oleander by analyzing physicochemical properties, performance, combustion, and emission characteristics in a 4-stroke engine and life cycle analysis. Yellow oleander oil yielded 64.53 ± 0.53 % under optimal conditions, including 80°C temperature, a petroleum ether solvent, 180 minutes, oilseed particle size, and 1:6 solid-to-solvent ratio, following second-order kinetics. The activation energy, enthalpy of extraction, and entropy were ΔEa = + 33.03 kJ/mol, ΔH = + 38.27 kJ kg-1, and ΔS = + 0.097 kJ/mol.K, respectively. The Gibbs free energy decreases at high temperatures, causing the extraction process to become spontaneous. Using XRD diffractograms, the particle size was determined to be 13.86 ± 0.987 nm. The spherical nature of the nanocatalyst particles was revealed by the SEM and TEM images. From BET analysis, the surface area, average pore diameter, and pore volume were; 5.54 ± 0.48 m2g-1, 18.57 ± 2.16 nm, and ≈ 0.016 ± 0.0 to 0.017 ± 0.0 cm g-1, respectively. The eggshell-derived nanocatalyst, a mesoporous material with a large specific surface area, was found to be beneficial for the transesterification reaction process. The response surface methodology yielded 93.70% of yellow oleander biodiesel under optimal conditions, including a reaction time of 40 minutes, a mild temperature of 60°C, and a 3.68 wt% catalyst loading. The FTIR spectrum of yellow oleander oil and biodiesel showed consistent carboxylate regions. The oil and biodiesel's physical and chemical properties align with ASTM D6751 standards. Engine performance, combustion, and emission behavior were evaluated. B20 was found to be the blend with properties close to that of petrodiesel. The study assessed the production costs and energy balance of a biodiesel plant, revealing an energy balance of 6.94 and an estimated production cost of KES 99.90/L (US$ 0.68)/L). The market price for a biodiesel blend of yellow oleander with 20% biodiesel (B20) was 186.75 KES/L (US$ 1.27 /L). This study synthesized a cost-effective, long-lasting nanocatalyst using waste egg shells to produce yellow oleander biodiesel, which meets ASTM D 6751 specifications and can be used in diesel engines.
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    SEARCH FOR BIOLOGICALLY ACTIVE SUBSTANCES FROM OKINAWA MARINE ORGANISMS -ISOLATION AND STRUCTURES OF THE COMPOUNDS WHICH INHIBIT THE DIVISION OF THE FERTILIZED SEA URCHIN EGGS
    (2005-09) NOSE, HOLLlNESS MANYAMA
    Ethyl acetate extracts of 75 Okinawa marine organisms were screened by the fertilized sea urchin egg assay. Among them 51 specimens showed potent cytotoxity and 20 specimens exhibited moderate activity. The constituents of five marine organisms (three sponges, one soft coral and one alga) whose ethyl acetate extract displayed strong inhibition of various cleavages of fe11ilized sea urchin eggs were examined. Bioassay guided fractionation of these extracts led to the isolation of twelve compounds of which eight (1, 2, 3A, 3B, 4A, 4B, 5 and 6) were new. The structures were established by 1D and 2D NMR spectroscopy and mass spectroscopy. Compounds 1 and 2 inhibited the first cleavage of the fertilized sea urchin eggs at 1 ppm. Compounds 3A, 3B, 4A, 4B and 8 inhibited the development of the fertilized sea urchin eggs at the blastula stage.
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    THEORETICAL EVALUATION OF PYRAZOLYL-BASED IRON, COBALT, NICKEL AND PALLADIUM COMPLEXES AS ETHYLENE OLIGOMERIZATION CATALYSTS
    (TUK, 2025-11) KIDIGASAMSON GUREMA
    encouragement. iv ABSTRACT Transition metal complexes in catalysis have gained a lot of interest for a decade now. Because of the widespread importance and applications of transition metal complexes in catalytic reactions of industrial importance, it is desirable to theoretically design and evaluate their catalytic activities. This dissertation involves a series of modeling investigations that have been designed to probe the influence of the electronic structure of the metal cation, the nature of the ligand, as well as the effect of chelation and steric interactions on the activity of the catalysts for ethylene oligomerization reactions. A series of transition metal cations, Fe2+, Co2+, Ni2+, and Pd2+ chelated by 2-(3, 5-dimethyl-pyrazol-1-yl)-ethanol and 1-(2-chloro-ethyl)-3, 5-dimethyl-1H-pyrazole ligands have been investigated as ethylene oligomerization catalysts. Six chelates in total were studied: Fe1, Co1, Ni1, Pd1, Co2, and Ni2. Electronic structure calculations were employed to determine stable low-energy structures, energetics, and chemical reactivity’s of the transition metal complexes. Density Functional Theory (DFT) was employed to gain a conceptual understanding of the structures of the initial metal complexes in solution that are likely to be pre-catalysts in the ethylene oligomerization reaction. A further goal was to analyze the electronic factors and ligand effects that impact on the chemical reactivity order of the six metal complexes within the context of DFT simulations. Theoretical studies used B3LYP and B3PW91 DFT methods and LanL2DZ basis set for metal atoms and 6-311+G (2d, p) basis set for all the remaining atoms. Theoretical studies of the Ni1 and Ni2 metal complexes were compared to the previous experimental studies of analogous complexes. The ground-state structures of all the six metal complexes show that the ligands bind in a fashion consistent with the simple valence shell electron pair repulsion model, where minor distortions from the idealized geometries are correlated with the structure of the ligands and more significant distortions with the valence electron configuration of the metal cation. The nature of the metal cation and ligand moiety had a discernible impact on the global chemical reactivity’s parameters of the six metal complexes. The chemical potential, the electrophilicity indices, the charge, and the electronegativity values suggest that Ni1 is the best catalyst in the series. Comparison between theory and experiment further confirm that Ni1 is indeed the best catalyst of the six catalysts studied for ethylene oligomerization reaction. Both electronic and steric factors correlate with the metal-ligand distances, and appear to be significant factors underpinning the reactivity of the six metal complexes. Thus, the results showcase the importance of using theoretical simulations to design catalysts rapidly and the ability to develop potentially active catalysts for ethylene oligomerization reaction through a thorough analysis of the global chemical reactivity parameters.