Search Results

1 In this paper results obtained with different particulate matter (PM) reduction technologies are presented. Diesel oxidation catalysts (DOC) are well known as a reliable PM reduction technology which can efficiently remove the soluble organic fraction (SOF) but which has no effect on the solid particles in PM. A drawback is that in combination with high sulfur fuel, oxidation of SO2 to SO3 by the DOC can occur, resulting in an increase of PM emissions. An alternative technology that is proven to significantly reduce soot emissions comprises diesel particulate wall-flow filters. High filtration efficiencies of up to 90% and beyond are feasible. The main obstacle is the combustion of the trapped soot. As shown in this paper, the application of a catalyst coating to the filter aids the filter regeneration by lowering the balance-point temperature. The main disadvantages of wall-flow filters are an increase in back-pressure and possible plugging caused by oil-ash accumulations.

The combustion efficiencies of diesel oxidation catalysts (DOC) targeted for use in the heat-up role of active diesel particulate filter (DPF) systems are investigated. Light-off tests using synthetic gases and fuel injection studies on light and heavy duty engines, both before and after thermal aging, are carried out. These evaluations are used to demonstrate differences in activity between closely related Pt-only and Pt/Pd formulations. Post-mortem analyses are conducted to determine the basis for the performance differences observed during the fuel injection studies. These analyses include measurement of the accumulation of carbonaceous compounds on catalyst surfaces which are associated with incomplete combustion of the injected fuel. Aging cycles developed for DOC+DPF systems incorporating heat-up by in-exhaust fuel injection on heavy-duty diesel engines are presented. The impact of these aging cycles on the performance of a Pt/Pd catalyst are summarized.