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As legislation tightens in the Heavy Duty Diesel (HDD) area it is essential to develop systems with high activity and excellent durability for both Particulate Matter (PM) and NOx control. The Continuously Regenerating Trap (CRT™) system controls hydrocarbon (HC), CO and PM emissions from HDD vehicles with efficiencies of over 90%, and has demonstrated very good field durability over distances exceeding 700,000 km. The system is widely used in Europe, and is demonstrating the same high performance and excellent durability within field applications in North America. The Continuously Regenerating Trap (CRT™) system has been developed and patented by Johnson Matthey [1]. Throughout this paper this system will be referred to as the Continuously Regenerating Diesel Particulate Filter, CR-DPF. The CR-DPF comprises an oxidation catalyst, optimised for NO2 generation from the engine-out NOx, and a downstream DPF.

The proposals to further lower particulate matter (PM) standards for heavy duty diesel powered vehicles throughout the world have increased interest in diesel particulate filter based aftertreatment solutions such as the Continuously Regenerating Trap (CRT™). This system has been applied to thousands of heavy duty diesel vehicles in Europe as a retrofit technology over the last six years to meet various local and governmental requirements. For example, the Swedish environmental zones require that all heavy duty diesel vehicles must have better than Euro 2 emissions or at least 80% PM and 60 % hydrocarbon conversion to operate within the cities of Stockholm, Gothenburg and Malmo. The legislated EU PM limit will be decreased from 0.1 g kW-1 hr-1 to 0.02 g kW-1hr-1 over the European Steady-state Cycle (ESC) in 2005.