Abstract
Keywords -NOx aftertreatment systems; NOx storage catalyst; SCR-catalyst; Diesel Engines; Tier2 Bin5
The main focus of powertrain development is shifting gradually to the improvement of fuel economy and the reduction of CO2 emissions. Lean burn combustion approaches such as the diesel engine or stratified spray-guided gasoline direct injection technology are an important element in achieving those goals due to the good fuel economy associated with these engine concepts.
A substantial success factor for both types of engines is the further improvement of innovative exhaust gas aftertreatment solutions able to convert nitrogen oxides, or NOx under oxidizing conditions. The NOx storage catalyst or lean NOx trap (LNT) has become the most widely adopted choice for engines with gasoline direct injection systems and also for the current diesel Bluetec systems from Daimler.
In the heavy duty sector, as well as for the introduction of heavy passenger vehicles for the BIN5 legislation in the USA, urea-SCR technology is already in use in series production or is being developed for series production.
In this paper, requirements and trends for future NOx aftertreatment technologies are being discussed. Ongoing development work focusing on improving the durability and sulfur resistance of LNT formulations will be presented and discussed. The most important development targets for both NOx aftertreatment technologies are an extension of the active temperature window as well as an improvement of the high-temperature stability of the individual catalyst components.
In addition, the cost associated with the introduction of new technologies present a challenge which has to be met in cooperation between OEMs and the supplier industry.