Novel catalyst systems for deNOx

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Silver catalysts for NOx storage and reduction using hydrogen

Gasification technologies are being developed to enable a feed of biomass to be converted to a fuel that has a high CO and H2 content; which may then be used in stationary gas engines to supply energy in the form of electricity and heat on a local level. This creates an opportunity to develop more effective, economic solutions for the clean-up of emissions from such engines, in line with the Waste Incineration Directive (WID).Ammonia or urea selective catalytic reduction (NH3-SCR) is the current industrial practice for NOx control from stationary sources. NOx Storage and Reduction (NSR) processes (Takahashi et al. (1996)), where NOx species are ‘trapped’ before they are subsequently reduced through alternate lean and rich-burn cycles, also use ammonia as the reductant of choice. In an ideal system it would not be necessary to supply an additional feedstock for the treatment of emissions. Hydrogen may also be used as a reductant in these processes, and as it is already present in the application of interest it negates the need for the production of additional chemicals and their associated costs.Novel silver catalyst systems supported on honeycomb monolith structures, and prepared through impregnation methods, have been investigated in a flow reactor with online mass spectrometer analysis. The catalysts have demonstrated promising performance for the treatment of NOx using hydrogen in the NSR process, by selectively converting stored NOx species to H2O and N2. The affinities of the catalysts for the reaction species have been further characterized through Temperature Programmed Desorption (TPD) studies.The possible impact of a novel catalyst support structure known as ‘KK Leaves’, which consist of very thin layers (0.2-0.8 μm) of alumina produced through a freeze drying process (Kolaczkowski et al. (2006)), will also be discussed. In further future work it may also be possible to combine the SCR and NSR processes, using hydrogen as the reductant, creating a hybrid design to further improve the efficiency of the NOx treatment system.Kolaczkowski, S. T. and Kim, S. (2006). Novel Alumina `KK Leaf Structures' as Catalyst Supports. Catalysis Today, Vol. 117, No. 4, pp. 554-558.Takahashi, N., Shinjoh, H., et al. (1996). The New Concept 3-Way Catalyst for Automotive Lean-Burn Engine: NOx Storage and Reduction Catalyst. Catalysis Today, Vol. 27, No. 1-2, pp. 63-69.<br/

Novel catalyst systems for deNOx

Technologies are being developed to enable a feed of biomass to be gasified, producing a fuel that has a high CO and H2 content; which may then be used in stationary gas engines to supply energy in the form of electricity and heat. This creates an opportunity to develop more effective, economic solutions for the clean-up of emissions from such engines, in line with the European Waste Incineration Directive (WID).Ammonia or urea selective catalytic reduction (NH3-SCR) is the current industrial practice for NOx control from stationary sources. NOx Storage and Reduction (NSR) processes, where NOx species are ‘trapped’ before they are subsequently reduced through alternate lean and rich-burn cycles, also use ammonia as the reductant of choice.Hydrogen may also be used as a reductant in these processes, and as it is already present in the application of interest, it negates the need for the additional chemicals and their associated costs. The development of a catalyst material which can facilitate the reduction of NOx using hydrogen is the primary aim of this research, and recent work has focused on investigation of the performance of various catalysts in these processes. It may also be possible to combine the SCR and NSR processes, using hydrogen as the reductant, to create a hybrid design further improving the efficiency of the NOx treatment system.<br/