M.Sc. (Chemistry) / Catalyst deactivation is a process that plays an important role in many catalytic processes. The forming of coke is in this respect the most common cause for deactivation. The research that has been done here has tried to give some insight into the mechanism of cokeforming with the help of Fourier Transform Infrared Spectroscopy (F)'IR). For this purpose a cobalt catalyst on an alumina carrier was used. The influence of the reaction time, the carbon monoxide to hydrogen ratio and the temperature on the rate and amount of coke formed was determined. A cell was developed that could be heated up to 500°C and could simultaneously be used in FTIR-spectroscopy in situ research. This enabled the determination of spectra at certain time intervals. In this way the development of the characteristic bands could be followed. Two other methods were used to support the transmission spectra : Diffuse Reflectance Spectroscopy and the burning of the coke from the catalyst. The latter was done to determine the amount of coke that had formed on the catalyst surface during the run. The amount of coke decreased with an increase of the hydrogen to carbonmonoxide ratio in the feed. Temperature also had a marked influence on coke formation: It decreased at higher temperatures. As expected the amount of coke increased with reaction time. In general the coke contained only a small hydrogen content. In conclusion it may be mentioned that the results obtained can contribute to the characterization of coke formed on Fischer-Tropsch catalysts.
| Identifer | oai:union.ndltd.org:netd.ac.za/oai:union.ndltd.org:uj/uj:4304 |
| Date | 12 March 2014 |
| Creators | Brands, Marcel |
| Source Sets | South African National ETD Portal |
| Detected Language | English |
| Type | Thesis |
| Rights | University of Johannesburg |
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