MSc, School of Chemistry, Faculty of Science, University of the Witwatersrand, 2011 / In this work, a detailed study of the evaluation of gold-based catalysts supported on
manganese oxides for the oxidation of volatile organic compounds (VOCs) has been
undertaken. Model catalysts were prepared by deposition-precipitation methods to
establish the effect of the support on the catalytic activity of the gold catalysts. The catalysts
were characterised by X-ray diffraction, transmission electron microscopy, N2–physisorption
measurements and temperature programmed reduction techniques. The activity of the
catalysts for VOC oxidation reactions were tested in a continuous flow fix bed glass reactor.
The products were analysed by GC/TCD and GC/FID.
The catalysts Au/TiO2, Au/Al2O3, Au/ZnO and Au/MnO2 were used for the VOC oxidation
reaction. 2-propanol, 2-butanol and toluene were used as VOCs for the study. These were
chosen because they are important indoor pollutants given their wide laboratory use and
high volatility. Toluene was found to be the most difficult to oxidise, followed by 2-propanol.
The effect of calcination temperature and preparation procedure was evaluated for the
gold/manganese oxide catalysts. Au/b-MnO2 catalysts prepared by deposition-precipitation
showed some catalytic performance which was less than the performance shown by
Au/MnOx, prepared by co-precipitation. g-MnO2 proved to be more efficient in the oxidation
of 2-propanol than pyrosulite phase MnO2. The addition of gold to any metal oxide support
was found to enhance the oxidation of VOCs. Gold-based catalysts were more active than
the Ce/MnO2 catalyst.
Catalytic tests showed that Au/CeO2 was the superior catalyst for the total oxidation of
toluene, 2-propanol and 2-butanol. Ceria is a highly reducible oxide and the formation of
gold–ceria interactions produced an even more easily reduced material.
University of the Witwatersrand, Johannesburg ii
| Identifer | oai:union.ndltd.org:netd.ac.za/oai:union.ndltd.org:wits/oai:wiredspace.wits.ac.za:10539/10408 |
| Date | 13 September 2011 |
| Creators | Kwenda, Ellen |
| Source Sets | South African National ETD Portal |
| Language | English |
| Detected Language | English |
| Type | Thesis |
| Format | application/pdf |
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