Mercury emission from coal-fired power plants is a global problem that has garnered attention due to regulations limiting the emission from anthropogenic sources. The three forms of mercury that are all emitted include: elemental mercury (HgO), oxidized mercury (Hg2+), which can both then form particulate mercury. Since current HgO removal technology is not effective, and HgO is extremely toxic, new catalytic solutions are necessary to allow complete oxidation of HgO. The aim of the project was to understand the mechanism of heterogeneous catalyzed mercury oxidation from simulated flue gas streams using supported gold catalysts. It has been proposed in the literature that three mechanisms could potentially be responsible for mercury oxidation: the Langmuir-Hinshelwood, the Eley-Rideal, and the Mars-Maessen mechanisms. To investigate the possible reactions, the mercury saturator was placed either before or after the catalyst bed and in some experiments, the gold catalyst was pre-saturated with mercury. Numerous characterization and gas-phase analysis techniques were used to identify surface changes and species present at both the surface and in the gas stream. For the gold catalysts, it was found that pre-saturating the catalyst with mercury improved mercury oxidation. Based on this data, mercury adsorption is necessary to promote the reaction, not mercury in the gas phase. In addition, the catalysts more efficient at oxidizing mercury generally had increased CI2 production. The gold-mercury amalgam was seen in the STEM images, but only in the more complex gas compositions, not in the N2/Hg gas mixture. In addition to the gold catalysts, ruthenium catalysts supported on titania were tested due to their promotion of the Deacon process. Mercury oxidation and CI2 production was as high with the ruthenium catalysts as with the gold supported catalysts. It is possible that the titania supports are better at producing an oxidized form of mercury, such as HgCI2.
| Identifer | oai:union.ndltd.org:bl.uk/oai:ethos.bl.uk:677959 |
| Date | January 2015 |
| Creators | Morgan, Michelle Marie |
| Publisher | Queen's University Belfast |
| Source Sets | Ethos UK |
| Detected Language | English |
| Type | Electronic Thesis or Dissertation |
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