(448a) Triple Function Ru Catalysts for Low-Temperature Co Oxidation, Voc Combustion and Scr-Denox

For emissions control of multicomponent exhaust gas streams, catalytic converters have to perform three functions: the catalytic oxidation of carbon monoxide to carbon dioxide, the destruction of Volatile Organic Carbon compounds (VOC's), and NOx abatement. State-of-art catalysts for CO oxidation are based on CuMn2O4 (hopcalite), for VOC combustion on Pt/alumina, and for DeNOx either supported noble metals (Rh, Pt, Pd) or redox metals (V, Mn) are commonly employed. Extensive research has focused on the improvement of catalytic activity at low temperatures. We have applied high-throughput and combinatorial approaches to the discovery of more efficient catalysts for low temperature CO oxidation, VOC combustion and DeNOx. The screening approach was based on a hierarchy of qualitative and semi-quantitative primary screens for the discovery of hits, and quantitative secondary screens for hit confirmation, lead optimization and scale-up. Parallel IR thermography and fast serial scanning mass spectrometry were the primary screens for CO oxidation and SCR-DeNOx, respectively, using wafer-formatted libraries of 256 catalysts with CO/O2/N2 and sulfur- and water-free NH3/NO/O2/Ar model feeds. Multi-channel fixed bed reactors equipped with imaging reflection FTIR spectroscopy or GC were used for scale up as well as VOC screening using propylene/O2/N2 model feed. RuCo, RuSn and RuCu families of active hits were discovered and optimized for CO oxidation and the effect of doping was investigated for supported and bulk mixed oxide catalysts [1]. RuCoCe and RuCoCeY compositions have previously been shown to compare favorably with the Pt/Al2O3 benchmark for combined CO oxidation/VOC combustion and to lower the light off temperature in CO/propylene/O2 mixed feed [2]. For NH3-SCR-DeNOx over alumina supported metals, the activity ranking at 300C was given by Ru > Co ~ Cu > V ~ Fe > Mn, whereas Cu was the most active at 250C [3]. Therefore, Ru based compositions such as Ru-Co and Ru-Cu systems could lead to novel multi-functional classes of catalysts suitable for 3-way catalytic converters.

[1] S. Cypes et al., ?High Throughput Screening of Low Temperature CO Oxidation Catalysts in IR Thermography Reactor?, in: Special Issue of ?High Throughput Screening and Combinatorial Chemistry?, Ed. Jozsef Margitfalvi, 2006 (submitted). [2] A. Hagemeyer et al., ?Novel Ru-Co Catalysts for Combined Low Temperature CO Oxidation/VOC Combustion?, ACS Spring National Meeting, Atlanta, GA, March 26-30, 2006. [3] G. Streukens et al., ?Discovery of Novel Catalytic Materials for Emissions Control using High Throughput Scanning Mass Spectrometry?, 4th International Conference on Environmental Catalysis, Heidelberg, Germany, June 5-8, 2005.