3. Electronic Theses and Dissertations (ETDs) - All submissions
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Item Applications of mesostructured carbonaceous materials as supports for fischer-tropsch metal catalyst(2007-02-21T12:32:55Z) Mbileni, Charity NonkululekoMesoporous MCM-48 was synthesized and used as a template to synthesize mesoporous carbon (MC) materials. Polystyrene, the carbon source, together with sulfuric acid and toluene were added to the template (160 oC for 6 h) and this procedure generated a low surface area carbon supported/MCM-48 material. A repeat addition and carbonization step was needed to form the precursor carbon/MCM-48 material that was pyrolysed at 900 oC to generate graphitic mesoporous carbon materials. After removal of the silica template, mesoporous carbons were characterized by XRD, HR-TEM, Raman spectroscopy and surface area analysis. The effect of the amount of polystyrene as well as the role of the pyrolysis temperature on the final product was investigated. This synthesis methodology can readily be controlled to produce partially ordered graphitic mesoporous carbon supports with predictable pore width and surface area. The methane selectivity was low (below 6%) and stable, and the overall olefin fraction was found to be good for all the supported catalysts studied. The potassium promoter increased the hydrocarbon chain growth to C68 giving α-1 and α-2 both between 0.79 and 0.90 for all supported catalysts with an exception of MCM-48 supported Fe catalyst that selectively produced hydrocarbons up to C28.Item Evaluation of humic acids as potential acid catalysts for transalkylation(2006-03-27) Skhonde, M PTransalkylation, a process of transfer of alkyl groups from one aromatic compound to another is carried out on acidic catalysts such as zeolites. The porous nature of zeolites is a prohibiting factor for transalkylation involving highly conjugated aromatic compounds. The study looks at the production of humic acids as well as their evaluation as potential acid catalysts for transalkylation. Optimisation of the production of humic acids was carried out through determination of a suitable coal type using air oxidation. Slurry phase oxidation was used to enhance and optimise coal oxidation and the production of humic acids. From the characterisations and test reactions carried out, humic acids do show some catalytic properties; however the study also showed that the strength of the acid sites is not strong enough to induce transalkylation reactions. Investigations of using humic acids as catalysts for other reactions such as oxidative dehydrogenation of ethylbenzene to form styrene, is recommended.