Toyota’s Diesel Aftertreatment Strategy for Future Emission Compliance

Authors

Dr. T. Fukuma, T. Asanuma, Dr. N. Ohashi, M. Inoue, K. Ishibashi, Toyota Motor Corporation, Shizuoka

Year

2008

Print Info

Fortschritt-Berichte VDI, Reihe 12, Nr. 672

Summary

Toyota introduced the diesel particulate and NOx reduction (DPNR) system based on the Toyota D-CAT concept in the European market in 2003 and continued the development of enhancing the system’s efficiency to comply with future low emission requirements.


Further important improvements have been made to the NOx catalyst material to increase the thermal resistance, and to improve the efficiency of the desulfurization methodology. The high thermal resistance of the NOx catalysts by Pt-O-Ce bond, results in the suppression of precious metal sintering to obtain higher catalytic activity after aging, especially under lower temperature conditions. The desulfurization performance is enhanced in several ways, such as by the adoption of TiO2 catalyst support material, by keeping overall temperature uniformity in the catalyst and by using rich combustion reduction control in addition to the exhaust port injection. Through these improvements, a NOx conversion efficiency was achieved over 70% in the new European driving cycle (NEDC) after aging and which could be further raised up with a Sulfur Trap catalyst.


The comparison of the improved NSR with Urea SCR is carefully investigated to decide the future strategy, considering NOx reduction efficiency, fuel penalty, system cost, system weight, vehicle packaging and development scale. As a result it was concluded that the NSR is an optimal solution for passenger cars in C and D segment.