Ph.D, Faculty of Science, University of the Witwatersrand, 2011 / 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.
| Identifer | oai:union.ndltd.org:netd.ac.za/oai:union.ndltd.org:wits/oai:wiredspace.wits.ac.za:10539/10896 |
| Date | 15 December 2011 |
| Creators | Salipira, Ketulo Lackson |
| Source Sets | South African National ETD Portal |
| Language | English |
| Detected Language | English |
| Type | Thesis |
| Format | application/pdf |
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