Potentials for NOx and CO2 reduction of combined NSC + passive SCR system in Diesel passenger car application

The stringent pollutant and CO₂ emission limitation in upcoming legislation norms for Diesel passenger car applications force the introduction of exhaust aftertreatment systems with maximum purification and energetic efficiency. The state-off-the-art technologies for NO_x reduction, NO_x storage and reduction catalyst (NSC) and selective catalytic reduction catalyst (SCR), show challenges for robust performance under strongly extended emission relevant operation conditions from cold start to high engine load and speed. One technical solution is the combination of NSC and passive SCR. This paper presents the experimental results obtained in the EUproject “Powerful”. On engine test bench and demonstrator vehicle, an exhaust aftertreatment system combining NSC, passive SCR and fuel reformer technology was developed and experimentally investigated steady-state and on road. The engine independent NSC operation offers potentials for lowered fuel consumption penalty by avoiding engine rich operation. The intrinsic NH₃ formation during the NSC regeneration is used for additional NO_x conversion on the passive SCR and reduces NO_x and CO₂ emission.