Lothar Mussmann

Impact of Aging and NOX/Soot Ratio on the Performance of a Catalyzed Particulate Filter for Heavy Duty Diesel Applications

Particulate filters are currently the method of choice for reducing soot levels in diesel exhaust to the extremely low levels required for meeting future emission standards. For cost effective, reliable and manageable soot regeneration, the Catalytic Diesel Particulate Filter (CDPF) has proven to be one of the most promising solutions for maintaining filter performance. The activity of the CDPF can help lower soot ignition temperature thereby promoting active, oxygen-based filter regeneration. It can also facilitate passive regeneration of a filter at temperatures below 400 °C through formation of NO 2 by catalyzing the oxidation of NO. There are two important factors which affect the passive regeneration of a CDPF. One is the influence of NOx/soot ratio. The other is the deterioration of the catalytic function upon aging. Together they determine the quantity of NO 2 available for soot oxidation. In the first part of this publication the impact of model gas, engine and field aging on the catalytic performance of a state of the art CDPF (A) and newly developed CDPF (B) will be reported. A correlation is developed between aging methods and the thermal durability of these two CDPF technologies. In the second part of this paper the influence of NO x concentration on the regeneration of diesel particulate filters will be investigated on a heavy duty engine bench. Both coated and uncoated filters in fresh and aged state will be evaluated at temperatures typical of passive NO 2 and oxygen-based soot regenerations.