The Design of Flow-Through Diesel Oxidation Catalysts

Progress made in reducing engine-out particulate emissions has prompted a revival in the design of flow-through oxidation catalysts for diesel engine applications. Effort in this area has focused primarily in the area of SOF control for the further reduction of particulate emissions. The work reported here covers some of the catalyst design parameters important for SOF and gas phase pollutant control. This is illustrated with both laboratory reactor and engine evaluation data for several formulary and operating parameters. Platinum-based catalysts are shown to be generally the most active, but they require treatments or additives to reduce the inherently high activity of platinum for the oxidation of SO₂ present in the exhaust. The effect of additives and their loading on the oxidation activity of Pt/alumina for HC, CO, SOF and SO₂ oxidation is discussed in detail and additives are identified which reduce SO₂ oxidation with minimal effect on HC, CO or SOF oxidation activity. Aged performance for light duty applications is discussed for the best catalyst formulation that resulted from this work.