1996-02-01

Advanced Metallic Three-Way Catalysts with Optimized Washcoat Performance 960560

Our major challenge for future catalyst systems was to develop more thermally stable washcoats for close coupled operating conditions and for engines operating under high speed and load conditions. To design these future emission systems extensive research and development was undertaken to develop methods to disperse and stabilize the key catalytic materials for operation at much higher temperatures. Our second priority was to design catalysts that are more effective under low exhaust temperature exhaust conditions and have improved oxygen storage properties in the washcoats. Incorporating new materials and modified preparation technology a new generation of metallic catalyst formulations emerged, those being trimetallic K6 (Pt:Pd:Rh and bimetallic K7 (Pd+Pd:Rh). Our target was to combine the best property of Pt:Rh (good NOx reduction) with that of the good HC oxidation activity of Pd and to ensure that precious metal/support interactions were positively maintained. Both K6 and K7 concepts contain special catalyst structures with optimized washcoat performance which can be employed either individually or combined in a single or double brick converter configuration. Improvement in light-off, thermal stability and transient performance with these new catalyst formulations has clearly been shown in both laboratory and vehicular testing.

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