The project was concerned with the investigation of the electrochemical oxidation of various phenols, and to develop a viable reaction system for the production of the respective hydroquinones. Current production routes utilizing phenol as starting material have the limitations of using large amounts of acids, having to be stopped at low conversions and producing a mixture of the hydroquinones and catechols. Of the possible routes to the respective hydroquinones from the various phenols, the electrochemical oxidation of these phenols offers commercial and environmental advantages and hence formed the theme of the investigation. The synthetic possibilities proved to be more prevalent in a system when the electrochemical oxidation of these phenols was performed in an aqueous medium utilizing an organic co-solvent. Results obtained during this investigation made it possible to make certain predications about the mechanism taking place. This was found to depend on the anode material used for the oxidation. The results showed that the process developed for the electrochemical oxidation of these phenols, yields mainly the para-isomers of the respective hydroquinones and benzoquinones in good yields and selectivities, with fair current efficiencies and good mass balances at high conversions. For example: * Phenol (batch) 8 F: 345% current efficiency, 70% hydroquinone, 6% catechol, 9% benzoquinone, 9% phenol and 94 mass balance. * 2-Tert-butylphenol (flow) 10 F: 37% current efficiency, 65% hydroquinone, 33% benzoquinone, 2% phenol and 100% mass balance. * 2,6-Di-tert-butylphenol (flow) 11 F: 23% current efficiency, 92 % hydroquinone, 6% benzoquinone, 1% phenol and 99% mass balance. The developed electrochemical oxidation system offers the following advantages over previous and current methods: simplified isolation and extraction procedures, smaller amounts of acid usage, reasonably selective synthesis of the para-isomer and a less corrosive system all at high conversions.
| Identifer | oai:union.ndltd.org:netd.ac.za/oai:union.ndltd.org:nmmu/vital:10367 |
| Date | January 2005 |
| Creators | Rautenbach, Daniel |
| Publisher | Nelson Mandela Metropolitan University, Faculty of Science |
| Source Sets | South African National ETD Portal |
| Language | English |
| Detected Language | English |
| Type | Thesis, Doctoral, DTech (Science) |
| Format | ix, 232 leaves ; 30 cm, pdf |
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