Diesel Oxidation Catalysts with Ultra-Low NO ₂ Emissions Supported by Nano-Washcoat on Sintered Metal Fibers

Diesel oxidation catalysts with ultra-low NO₂ emissions have been developed based on palladium-tungsten (Pd-W). The catalysts are supported by aluminum-yttrium oxides (Al₂O₃-Y₂O₃) nano-washcoat on sintered metal fibers. Elemental composition analysis was performed using Energy Dispersive Spectroscopy (EDS) to quantify the distribution of the Al₂O₃-Y₂O₃ nano-washcoats and Pd-W catalysts on the surface of the metal fibers. Initially, emissions measurements were conducted to evaluate the performance of Pd-W catalysts using small coated samples of sintered metal fibers. The results show that the catalysts selectively oxidize CO into CO₂ and reduce NO₂ into NO, resulting in over 90% reduction in CO emissions and up to 85% reduction in NO₂ emissions. Scale-up of an Active Diesel Particulate Filter (ADPF) was then tested on a Cummins 5.9L ISB diesel engine using the US-FTP transient test cycle and the ISO 8178 8-mode test cycle. The results of both test cycles yielded similar emissions reductions of 54% and 57% in CO, 84% and 81% in HC, 95% and 91% in PM, for the US-FTP and 8-mode test cycles, respectively. Both test cycles result in 100% reduction in NO₂. In conclusion, the results of this study show that the application of the new Pd-W catalysts can lead to new generation of ADPFs with ultra-low NO₂ emission, which are suitable for some applications such as school buses and underground mining equipment.