Refcoal is a refined carbon source obtained by extraction of coal with dimethylformamide (DMF). During the coking process, Refcoal goes through a mesophase (fluid) stage to form an anisotropic coke. In contrast, oxidised Refcoal does not undergo such a mesophase stage during the carbonisation process. Thus it does not yield an anisotropic coke, but forms an isotropic coke. The objective of this study is to produce an anisotropic coke from oxidised Refcoal. For this purpose, diabietic acid, a hydrogen donor, was considered as a suitable additive. Coking was performed in sealed glass capillary tubes as diabietic acid proved to be volatile at the carbonisation temperature of 500 °C. The resultant cokes were analysed using thermogravimetric analysis, Raman spectroscopy and optical microscopy. The results show that the degree of anisotropy increased with diabietic acid content (3, 5 and 10 mass %). / Dissertation (MSc (Chemistry))--University of Pretoria, 2008. / Chemistry / MSc / Unrestricted

Synthetic graphite is an important industrial material, used in nuclear reactors, electrodes and many other applications. Graphitisation of coke is the solid-state transformation of the disordered carbon atoms into a well-ordered hexagonal graphite structure, requiring temperatures as high as 2 600 ºC. Catalytic graphitisation using metals or metal compounds allows the rearrangement of atoms to occur at lower temperatures. The extent of catalytic graphitisation is markedly dependent on the structural ordering of the parent coke, the catalyst concentration and the reaction conditions. Solvent extraction of coal using dimethylformamide (DMF) as a solvent yields a refined coal solution referred to as Refcoal solution. Cokes of solvent-refined Tshikondeni coal derivatives have been found to be graphitisable. The activity of acetylacetonate and hydroxyquinolinate complexes of Al, Ca, Cu, Fe and Zr for catalysing the graphitisation of Refcoal cokes at 1 600 and 2 000 ºC was investigated. The effect of residence time on the catalytic graphitisation of Refcoal cokes was investigated by heat-treating cokes for two and six hours at 1 600 °C. For iron(III)acetylacetonate, the effect of metal concentrations was studied. Samples were analysed using thermogravimetric analysis (TGA), scanning electron microscopy (SEM), X-ray diffraction (XRD), Raman spectroscopy and optical microscope techniques. The results show that calcium(II)acetylacetonate catalyses the graphitisation of Refcoal cokes. The degree of graphitisation increases with an increase in the iron concentration. However, iron promotes localised graphitisation, probably in the vicinity of the catalyst particles. / Dissertation (MSc (Chemistry))--University of Pretoria, 2008. / Chemistry / unrestricted