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Since May 2000, PSA Peugeot Citroën has commercialized a wide range of diesel vehicles of different sizes (Peugeot 807, 607, 406 and 307; Citroën C8 and C5) equipped with a Diesel Particulate Filter (DPF) system using a Ceria-based Fuel-Borne Catalyst (FBC). More than 250000 vehicles have been sold in Europe. Based on extensive in-service feedback, an opportunity to further improve and optimize the technology was identified which will facilitate its extension to smaller passenger vehicles. The use of a more active FBC was identified as one of the key areas for improvement: with increased catalytic activity the FBC dosing rate is reduced and thus the rate of ash-build up in the DPF is limited. This could significantly extend the DPF interval maintenance. A new Ceria-based FBC (Ce-FBC) has been developed which demonstrates enhanced catalytic activity with limited exothermal peaks during DPF regeneration. This property is essential in preventing mechanical failure of the DPF.

This paper will discuss a number of different matters relating to the regeneration of catalyst coated diesel particulate filters such as: impact of the catalyst on the soot ignition temperature, soot combustion rate and NO2 generation. If catalytic coatings prove to be sufficient compared to certain fuel additives they could be used in second generation diesel particulate aftertreatment systems. Examples will be shown on how catalytic diesel particulate filters (“DPF”) can operate on a common rail passenger car diesel engine. Furthermore, an outlook is given on the future combination of particulate - and NOx - emission control for diesel passenger cars.

1 Although combustion system improvements allow extremely low level of particulate (EURO 4 particulate level is already achieved) the particulate filter appears to be the only solution to reduce solid particulate emission by two to three order of magnitude over the whole size range starting from 10 nm. This is the reason why an active particulate filter system has been developed. The major issue was to fill in the gap between particulate regeneration temperature (550°C) and the naturally low exhaust gas temperature of modern DI diesel engine (150°C to 200°C in city driving conditions). This low exhaust gas temperature is the result of overall efficiency improvement to reduce fuel consumption.