Department of Chemistry and Material Science (DCMS)

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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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    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.