Application and Improvement of NOx Storage and Reduction Technology to Meet Real Driving Emissions

Strategies to achieve RDE requirement for diesel passenger car are introduced in this paper focusing on NOx storage and reduction (NSR) technologies. High NOx conversion performance with advanced NSR technologies which make use of reducing agents like NH3 or intermediate reductants created from HC (Bisaiji et al. in SAE Int J Fuels Lubr 5:380-388, 2012) dosing, is demonstrated by vehicle tests. The mechanisms to create reducing agents are discussed in detail. MS analysis identified the key elements to produce reductant species for diesel NOx after-treatment by adsorbed intermediate reductants (DiAir), focusing on the effect of oxygen on the catalyst surface and the catalyst formulation. It was found that surface oxygen has an important role to make intermediate reductants during HC dosing for DiAir. Moreover, the role of Ce component in oxidizing the injected HC and create intermediate reductants effectively became clear. Furthermore, high CO oxidation performance of NSR after ageing in comparison with diesel oxidation catalyst is shown and the mechanism is discussed. Oxidation performance is also important for diesel vehicles because the catalyst temperature is further reducing due to CO2 reduction. The potential to meet next stringent legislation is shown in this paper from the view point of not only NOx reduction but also CO oxidation by an advanced NSR system.