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Zirconium dioxide (zirconia) is a well-known material often being a major component in the washcoat systems of three-way catalysts (TWC) and diesel oxidation catalysts. One important characteristic of zirconia containing washcoats is an improved aging stability which is required to meet the more and more stringent emission standards. In the last few years the utilization of zirconia became even more important - especially for high sophisticated three-way washcoat systems. This was due to the development of high temperature stable oxygen storage components, containing cerium dioxide (ceria) in combination with different other oxides - one very promising candidate being zirconia. In the present work the results of a research program are discussed, focusing on the influence of zirconia in combination with ceria and additional rare earth promoters on the stability of the oxygen storage characteristics.

Research programs were completed for the development of improved Pd-containing three-way catalysts, which were targeting on the future emission control standards for passenger cars. The influence of newly developed washcoat components as well as an improved precious metal location in special architectured washcoats on the catalyst performance is demonstrated by model gas and engine tests. The most promising catalyst systems were evaluated on different vehicles in U.S. and E.U. driving cycles. The results obtained in this study clearly indicate the potential of Pd-based technologies to be a cost effective alternative for Pt/Rh converters.