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In order to meet recent and future stringent hydrocarbon emission regulations of passenger cars, the use of Pd-containing catalysts is of growing interest. This is especially true for Pd/Rh and Pt/Pd/Rh catalysts. To optimize the function of the individual precious metals, most high-performance catalysts have a double layer configuration. This double layer avoids undesired interactions between Pd and Rh after reacting with exhaust gas at a high temperature level. Of course, these double layer technologies lead to a more complex capacity utilization coating process during the manufacture of the catalyst. The present work summarizes the results of a research program targeting the development of a high-performance single layer Pd/Rh catalyst technology. The starting point was the functional improvement of Pd and Rh only catalysts then subsequently combining the best of these technologies.

The following paper highlights the results of a vehicle emission improvement program with emphasis on two main points: In the initial phase, various combinations of Pd and Pt-based three-way catalyst technologies were evaluated on a TLEV and a LEV calibrated vehicle in order to generate ULEV exhaust gas levels. One goal in this portion of the study was to achieve technical equivalence between a viable Pd-based technology and a newly developed Pt-based technology. A combination of the Pd- and Pt-based technologies was able to meet the ULEV and part of the ULEV II regulations in the test vehicle after a catalyst aging cycle that resembles 50,000 miles of vehicle driving. In the later phase, a mathematical algorithm based on the original TLEV and LEV vehicle data was developed in order to conduct computer modeling of the exhaust gas aftertreatment system. This algorithm described the kinetic behavior of the individual catalysts over a broad range of reaction conditions.

The LEV II and SULEV/PZEV emission standards legislated by the US EPA and the Californian ARB will require continuous reduction in the vehicles' emission over the next several years. Similar requirements are under discussion in the European Union (EU) in the EU Stage V program. These future emission standards will require a more efficient after treatment device that exhibits high activity and excellent durabilty over an extended lifetime. The present study summarizes the findings of a joint development program targeting such demanding future emission challenges, which can only be met by a close and intensive co-operation of the individual expert teams. The use of active systems, e.g. HC-adsorber or electrically heated light-off catalysts, was not considered in this study. The following parameters were investigated in detail: The development of a high-tech three-way catalyst technology is described being tailored for applications on ultra thin wall ceramic substrates (UTWS).