Browsing by Author "Hamad, Fatma"
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Item Potential Biological Applications of Bio-Based Anacardic Acids and Their Derivatives(2015) Hamad, Fatma; Mubofu, Egid B.Cashew nut shells (CNS), which are agro wastes from cashew nut processing factories, have proven to be among the most versatile bio-based renewable materials in the search for functional materials and chemicals from renewable resources. CNS are produced in the cashew nut processing process as waste, but they contain cashew nut shell liquid (CNSL) up to about 30–35 wt. % of the nut shell weight depending on the method of extraction. CNSL is a mixture of anacardic acid, cardanol, cardol, and methyl cardol, and the structures of these phenols offer opportunities for the development of diverse products. For anacardic acid, the combination of phenolic, carboxylic, and a 15-carbon alkyl side chain functional group makes it attractive in biological applications or as a synthon for the synthesis of a multitude of bioactive compounds. Anacardic acid, which is about 65% of a CNSL mixture, can be extracted from the agro waste. This shows that CNS waste can be used to extract useful chemicals and thus provide alternative green sources of chemicals, apart from relying only on the otherwise declining petroleum based sources. This paper reviews the potential of anacardic acids and their semi-synthetic derivatives for antibacterial, antitumor, and antioxidant activities. The review focuses on natural anacardic acids from CNS and other plants and their semi-synthetic derivatives as possible lead compounds in medicine. In addition, the use of anacardic acid as a starting material for the synthesis of various biologically active compounds and complexes is reported.Item Solid Base Catalysed Transesterification of Triglycerides for Biodiesel Synthesis(2015-06) Tajuddin, N. A.; Hamad, Fatma; Elimbinzi, E.; Nyandoro, Stephen S.; Mubofu, Egid B.; Wilson, Karen; Lee, Adam F.The quest for sustainable resources to meet the demands of a rapidly rising global population represents one of this century’s grand challenges. Biomass offers the most readily implemented, and low cost, solution for transportation fuels, and the only non-petroleum route to organic molecules for the manufacture of bulk, fine and speciality chemicals and polymers required to meet future societal demands. However, careful selection of biomass is critical to ensure such renewable resources are sustainable, and despite initial promise, first-generation bio-based fuels and chemicals (derived from edible plant materials) caused controversy over competition between land-use for fuel crops versus traditional agricultural cultivation. So called 'second generation' bio-based fuels and other chemical materials should thus use biomass sourced from non-edible crop components, e.g. from agricultural or forestry waste, or alternative non-food crops which require minimal cultivation. Crops belonging to the Euphorbiaceous family, which includes the Castor plant Ricinus communis in Tanzania, are advantageous for such applications, growing in the wild in large quantities across tropical and sub-tropical countries. The development of new catalytic routes to convert Castor seed oil to fuels and chemicals would also provide a valuable boost to the agronomy and chemical industries in Tanzania. Castor oil is mainly comprised of triricinoleate (90 %), trilinoleate (4 %) and trioleate (3 %), which upon transesterification would not only offer a valuable source of fatty acid esters, but also have potential for use a fatty acid based surfactants in the preparation of mesoporous catalyst support materials. Here we report on the application of Castor oil as a renewable soft template to synthesise amine-functionalised mesoporous silicas via a post-synthesis grafting method with 3-(aminopropyl)triethoxysilane. Resulting materials were characterized by X-ray diffraction (XRD), Nitrogen physisorption, thermogravimetry (TG), X-ray photoelectron spectroscopy (XPS) and diffuse reflectance infrared fourier transform spectroscopy (DRIFTS), and appear well-suited as mesoporous solid bases for catalytic processes. A comparison of the transesterification of castor oil and relevant model triglycerides using the resulting mesoporous solid base and hydrotalcite catalysts will be presented.Item Wet Oxidation of Maleic Acid By Copper(II) Schiff Base Catalysts Prepared Using Cashew Nut Shell Liquid Templates(2011-05) Hamad, Fatma; Mubofu, Egid B.; Makame, Yahya M. M.Novel heterogeneous copper(II)Schiff basecatalysts have been successfully prepared using a Cashew Nut Shell Liquid (CNSL) templating agent. The preparation of catalyst supports was via a one-pot route and afforded aminopropyl-functionalized Micelle Templated Silica (MTS-AMP). The MTS-AMP support was then condensed with pyridine-2-carboxyaldehyde, 2-hydroxybenzaldehyde, 2-hydroxynaphthaldehyde to produce the corresponding Schiff bases. In each case, the Schiff base was complexed with copper(II) acetate solution at room temperature. The supports and heterogeneous catalysts were porous with pore diameters of up to 25 nm and grain sizes of up to 1.0 μm as revealed by Nitrogen Physisorption Study and Scanning Electron Microscopy (SEM) respectively. The maximum copper loading was about 3% w/w for heterogeneous catalysts supported on CNSL based supports whereas the maximum loading of about 2% w/w was obtained for coppercatalysts prepared using commercially available dodecylamine and hexadecylamine templates. The catalysts were tested on the oxidation of maleic acid at room temperature using H2O2 as an oxidant and the catalysts had an excellent catalytic efficiency with a yield of up to 90% and turn over number of about 1000 in ten minutes. The performance of catalysts depended on the type of ligands, the template used to prepare the catalyst support and on the method of catalyst preparation. Catalysts prepared using CNSL templates were more efficient than those prepared using the commercially available templates. The catalysts prepared by a stepwise approach were robust and gave good results while those prepared by an imprinting approach leached out after one reaction cycle.