The catalytic converter on a European diesel car must operate under extremely variable conditions, ranging from very low temperature during city-driving to high temperature during Autobahn-driving. Therefore, the development of new catalyst technology for European applications requires simultaneous achievement of properties that have long been considered incompatible.
In this paper, it is shown how extremely good low temperature activity for CO and hydrocarbons (and VOF), negligible storage of sulfates, and very good thermal durability were obtained simultaneously with an appreciable reduction of NOx. Through the systematic analysis of basic catalytic phenomena, under conditions of relevance to the real-world application, it was possible to control the interaction between support, stabilizers and promoters with the precious metal package in an efficient way. The large-scale manufacturing aspects formed an important part of the development program.
The resulting catalysts were characterized for performance by means of a stage-wise evaluation scheme, including model exhaust of varying complexity, engine bench studies and CVS evaluation on vehicles.