New Low Cost and High Performance Catalyst-Single Layer Pd/Rh Catalyst Development

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. After engine bench aging, the new single layer Pd/Rh catalyst shows better sweep test performance especially under lean exhaust conditions. Improved light-off behavior is achieved under rich exhaust conditions as compared to the reference double layer Pd/Rh catalyst which is certified for a LEV applications. In vehicle tests the newly developed single layer and the reference Pd/Rh catalyst show equivalent emission results after severe engine bench aging. These findings suggests the possibility of using the new single layer Pd/Rh catalyst for more demanding future emission requirements and replace more complex double layer Pd/Rh catalyst technologies.