Advanced Three-Way Catalysts - Optimisation by Targeted Zoning of Precious Metal

Emissions from (and cost of) three-way catalysts can minimised by targeted application of PGM along the catalyst's length rather than the conventional homogeneous distribution. Experiments are described demonstrating pollutant conversion as a function of catalyst length during the European MVEG-B cycle. It is shown that most pollutant conversion occurs on the front portion, and that therefore the most effective catalysts have the majority of the PGM content there. Further analysis of the three legislated pollutants CO, HC and NOx leads to insights about the optimum distribution of Pt, Pd and Rh within the catalyst. In advantageous circumstances bi or trimetallic systems can be partially replaced with Rh-only systems with significant cost and backpressure benefits. Further experiments comparing zoned catalysts with current catalysts whose PGM is homogeneously distributed are described, demonstrating additional performance benefits.