Challenges and Opportunities of Urealess NH3-SCR for Small Diesel Passenger Cars
Pyung-Soon Kim, Hyundai Motor Company
The need for improved fuel economy from mobile sources is becoming larger in automotive industries combined with the tight upcoming CO2 regulations worldwide. Lean combustion technologies such as diesel engine offer significant improvement in fuel economy; however the control of NOx emissions in oxygen-rich combustion has been a difficult challenge to meet strict emission standards such as LEVIII and EU6c. The selective catalytic reduction of NOx by urea (urea-SCR) is one of the most promising technologies for NOx emission control for diesel engine exhaust and has recently been commercialized. However, not only the periodic urea refill by drivers, but this system isn't very cost and volume efficient for small passenger vehicles. An attractive strategy for NOx treatment would involve the use of NH3 produced on-demand over PGMs in Lean-NOx Trap (LNT) catalyst paired with SCR catalyst. For the minimum fuel economy penalty during the rich operation, the selectivity of stored NOx into NH3 needs be enhanced by improving LNT formulations. Our work will discuss the benefits and challenges of the urealess ammonia SCR system in small diesel vehicles to meet future NOx emission targets.