Final Activity Report Summary - PLASCAT (Plasma-assisted catalysis for the removal of volatile organic compounds from waste gas stream)
In the field of environmental clean-up, there is always a search for new energy efficient technologies for the destruction of pollutants in waste gas streams from arrange of industrial processes. The use of a heated catalyst to achieve this aim is an established method involving a continual search for new and more robust catalysts that can tolerate the, often hostile, processing environments. A relatively new technique involves passing the waste gas through plasma, in which a discharge produces energetic electrons that create excited and reactive species breaking down the pollutants and transforming them into benign species, such as water and carbon dioxide, which can be safely discharged into the atmosphere. Recently, the techniques of plasma and catalysis were synergistically combined to produce a very promising technology that offered enhanced rates of pollutant destruction with more control over the end products. The combined plasma-catalyst processing took place at much lower temperatures than for catalysis alone, giving increased energy efficiency and hence improved catalyst performance in terms of resistance to poisoning, coking or sintering.
In this project, experiments were conducted on some pollutants such as benzene and toluene that were commonly used as solvents in industry and were not easily destroyed. Using a range of catalysts and different placements of the catalysts with respect to the discharge, the temperature was varied in order to investigate the mechanism of the plasma activation of the catalyst. Kinetic studies showed that, in some cases, the plasma brought about a lowering of the energy barriers to destruction. Two mechanisms were distinguished by their different temperature behaviours, namely one in which the plasma directly activated the surface of the catalyst producing reactive surface sites and giving a slight temperature dependence and a second in which the role of the plasma was to create reactive species which were then adsorbed onto the surface causing breakdown of the pollutant which had a strong temperature dependence.
These results gave fundamental information about how plasma catalysis worked, would enable scientists to further optimise the process improving its efficiency, selectivity and energy input and would allow catalyst to be optimised for this type of process.
In this project, experiments were conducted on some pollutants such as benzene and toluene that were commonly used as solvents in industry and were not easily destroyed. Using a range of catalysts and different placements of the catalysts with respect to the discharge, the temperature was varied in order to investigate the mechanism of the plasma activation of the catalyst. Kinetic studies showed that, in some cases, the plasma brought about a lowering of the energy barriers to destruction. Two mechanisms were distinguished by their different temperature behaviours, namely one in which the plasma directly activated the surface of the catalyst producing reactive surface sites and giving a slight temperature dependence and a second in which the role of the plasma was to create reactive species which were then adsorbed onto the surface causing breakdown of the pollutant which had a strong temperature dependence.
These results gave fundamental information about how plasma catalysis worked, would enable scientists to further optimise the process improving its efficiency, selectivity and energy input and would allow catalyst to be optimised for this type of process.