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Silicon carbide diesel particulate filter (DPF) is now recognized as the most effective and robust way to reduce not only the mass but also the number of emitted particles on diesel passenger cars. Widespread use of expensive catalytic platinum-containing coatings has contributed to increased harmful NO₂ emissions. A novel low-cost palladium-base metal coating, BMC-211, was developed which assists soot regeneration by oxygen transport and which actively removes NO₂ still having comparable passive and active soot regeneration properties. The novel coating was tested against a traditional commercial platinum coating on a modern series-produced car, on chassis dynamometer and on engine test bench.

Nitrogen dioxide (NO2) concentrations in European city street air have not decreased after year 2000 in spite of stringent Euro 3 and Euro 4 NOx limits for diesel passenger cars. NO2 emissions from modern diesel vehicles are caused by platinum catalysed Diesel Oxidation Catalysts (DOC) and platinum catalysed Diesel Particulate Filters (cDPF). The NO2 formed on DOC and cDPFs are used for passive soot regeneration but the excess of NO2 out of the filter is not controlled. A Euro 4 diesel passenger car equipped with a DOC and a palladium base metal cDPF was compared with DOC plus a platinum based cDPF using NEDC test cycle with both cold and hot start, FTP-75, and Artemis test cycles. Emissions of NO2 and NOx were measured online in the raw exhaust, and with standard bag sampling method. Relative to cold NEDC the NOx and NO2 levels increased with a warm engine.