ETD Collection

Permanent URI for this collectionhttps://wiredspace.wits.ac.za/handle/10539/104


Please note: Digitised content is made available at the best possible quality range, taking into consideration file size and the condition of the original item. These restrictions may sometimes affect the quality of the final published item. For queries regarding content of ETD collection please contact IR specialists by email : IR specialists or Tel : 011 717 4652 / 1954

Follow the link below for important information about Electronic Theses and Dissertations (ETD)

Library Guide about ETD

Browse

Filters

1993 - 199912010 - 20111

Settings

Subject: search.filters.subject.Chemistry, Physical and theoretical

Search Results

Now showing 1 - 2 of 2
  • No Thumbnail Available
    Item
    The deactivation of silico-aluminophosphate catalysts during methanol conversion reactions
    (1993) Cornel, Veronica May
    This dissertation focusses on the deactivation of SAP0-34 and modified SAPOs during methanol conversion under various conditions, in comparison to H-ZSM-5. SAPO-34 was found to deactivate rapidly during methanol conversdon. This was shown by the decrease in activity, surface area and pore volume of the catalyst. The deposited "coke" was analysed by in situ diffuse reflectance infra-red Fourier Transform spectroscopy,solid-state magic angle spinning nuclear magnetic resonance, gas chromatography mass spectroscopy (GCMS) of the HF- and dichloromethane-extracted to "coke"; and GCMS of the organic specfes released during regeneration of the catalyst and trapped in resin capillary inlet tubes.The "coke" consisted of alkylated aromatics and naphthalenes which probably formed on the surface or in the large cavities of SAPO-34. The amount of "coke" deposited during methanol conversion increased with reaction temperature, decreased with dilution of the methanol with water or nitrogen. and decreased with increased pressure, Incorporation of Ni into the SAPO framework did not decrease the rate of deactivation, but the "coke" that Has deposited was less bulky than that deposited in SAPO-34. Modification of the SAPO-34 with trlmethyl silylchloride decreased the rate at deactivation of the catalyst.
  • No Thumbnail Available
    Item
    Methane decomposition : characterization of the carbon produced and possible use in direct carbon fuel cells
    (2011-12-15) Salipira, Ketulo Lackson
    Investigations into methane conversion (both catalytic and non-catalytic) and characterization of the carbon produced for use in high efficiency DCFCs were performed. Under non-catalytic processes, a high methane conversion (> 80%) was achieved at 1200 oC at flow rates of between 10-60 ml/min. Analysis of the carbon using Raman spectroscopy showed that the carbon was highly disordered and the degree of disorder increased with increase in methane flow rate (from aD/aG = 1.54 at 10 ml to aD/aG = 2.24 at 60 ml/min). Further analysis of the carbon using thermogravimetric analysis (TGA) demonstrated that the carbon produced at higher flow rates e.g. 100 ml/min were easily oxidized (746 oC) compared with those produced at lower flow rates (10 ml/min, 846 oC). Therefore, a high temperature coupled with high flow rates (60-100 ml/min) produced carbon with desired qualities (high disorder, low crystallinity and more thermally reactive) for DCFC uses. In the catalytic decomposition of methane, Ni supported on TiO2 and a 1:1 mixture of TiO2/Al2O3 gave high and stable methane conversions of about 60% at only 600 oC compared to 1200 oC required for the non-catalytic conversion. These catalysts were found to be the best catalyst systems of the tested catalysts. Considering the thermal oxidation and crystallinity data which are some of the properties of the carbon required for direct carbon fuel cells (DCFCs), the carbon produced can potentially be used in DCFC systems.