The three-way catalyst (TWC) greatly reduces emissions of hydrocarbons, carbon monoxide and nitrogen oxides from gasoline powered vehicles. However up to 80% of all hydrocarbons are emitted in the first 120 seconds after the engine is started, before the TWC achieves light-off. Catalysts which are active at lower temperatures offer a potential solution to this ‘cold-start’ problem. Co3O4 is one of the most active transition metal oxide catalysts for the total oxidation of hydrocarbons. In this work the synthesis of bulk and supported cobalt oxide catalysts has been investigated. The catalysts were thoroughly characterised and tested for the total oxidation of propane, a model hydrocarbon. Variables in the mechanochemical synthesis and precipitation of bulk Co3O4 were studied. Cobalt hydroxycarbonate hydrate synthesised by both techniques was found to give rise to active and stable Co3O4 catalysts upon calcination. Small Co3O4 crystallites, high surface areas, weak Co3+-O bonds, and the absence of contaminants were found to be required for high propane oxidation activity. Deposition precipitation, wet impregnation and powder blending methods were investigated for supporting Co3O4 on a high surface area, non-porous silica. Wet impregnation from cobalt nitrate was found to be the most effective method of synthesising supported Co3O4 with minimal formation of undesired cobalt silicates. Activity increased with increased cobalt weight loading but supported catalysts displayed lower activity than bulk catalysts.
| Identifer | oai:union.ndltd.org:bl.uk/oai:ethos.bl.uk:649424 |
| Date | January 2014 |
| Creators | Pinnell, Rebecca |
| Publisher | Cardiff University |
| Source Sets | Ethos UK |
| Detected Language | English |
| Type | Electronic Thesis or Dissertation |
| Source | http://orca.cf.ac.uk/73543/ |
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