Development and Performance of Catalytic Diesel Particulate Filter Systems for Heavy-Duty Diesel Vehicles

Present and projected future stringent environmental regulations for PM emissions from diesel engines have required the development of reliable and economic after-treatment devices such as catalytic diesel particulate filters (DPF). Currently, the major concern in the catalytic DPF is a sufficiently high catalyst activity for soot oxidation which enables continuous regeneration of particulate wall-flow filter.

This paper reports on the development of a passive-type DPF system which adopts a catalyzed wall-flow filter for trapping and combustion of soot particulates. Engine bench tests and field-endurance tests for in-house performance evaluation showed sufficiently low regeneration temperature with > 90% PM removal efficiency with the use of 30 ppm S diesel fuel. Field tests such as fleet endurance tests were conducted, and the DPF system has shown > 90% PM reduction performance maintaining low backpressure under most driving conditions. Further development of soot oxidation catalyst was carried out to enhance the regeneration performances of the current DPF system. The best catalytic formulation for soot oxidation catalyst was obtained when platinum, transition metal oxides, and alkali metals were present with the optimum ratio. Engine bench test results have demonstrated that the newly developed DPF system has significantly better regeneration performance than the previous one.