Title page for ETD etd-06112008-134204


Document Type Master's Dissertation
Author Nyathi, Mhlwazi Solomon
Email s25480279@tuks.co.za
URN etd-06112008-134204
Document Title Catalytic graphitisation of refcoal cokes
Degree MSc (Chemistry)
Department Chemistry
Supervisor
Advisor Name Title
Prof W W Focke Supervisor
Keywords
  • refcoal
  • coke
  • carbonisation
  • catalytic graphitisation
  • catalyst
  • graphite
Date 2008-04-23
Availability unrestricted
Abstract

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 C. 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 C 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.

University of Pretoria 2007

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