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Dimethyl ether(DME) is easily reformed into H2, since the chemical structure of DME does not feature direct C-C bonds, in contrast to diesel fuel. We have researched reforming catalysts for effectively generating H2 from the exhaust gases of a DME engine. The objective of this study is to evaluate the de-NOx performance of a combined system of RC(Reforming Catalyst) and LNT(Lean NOx Trap) for a DME engine according to reforming catalysts. The H2 generation of the reforming catalyst was observed under various conditions. CAT-A, CAT-B and CAT-C were prepared as reforming catalysts, and OC(Oxidation Catalyst) and LNT (Lean NOx Trap) were examined as commercial catalysts. The CAT-A catalyst has a higher amount of acid sites compared to the CAT-B and CAT-C catalysts. The CAT-A which is a mixing of mordenite and γ-Al2O3, has the highest H2 yield. However, the H2 yield decreased in the reforming reaction when CO2, NO and O2 coexisted.

Particulate matter emissions can jeopardize good health. Diesel particulate matter (PM), of diameters less than 10,000nm, was measured from a high-speed direct injection (HSDI) diesel engine by using an electrical low pressure impactor (ELPI). Results were obtained for the smoke level and the PM level (masses and numbers) from this engine by using the ELPI and the Bosch smoke meter, and the results were compared. The effects of a diesel oxidation catalyst (DOC) were also investigated. Under a high speed and high load condition, HSDI diesel engine exhausts a considerable mass of particulate matter with diameter over 100nm, and considerable number of PM from 7 to 100nm at the same driving condition. DOC showed reduction in the total mass of PM, but showed increase in the number of ultra fine PM. At low temperature, before light-off temperature of the soot, the DOC adsorbs the PM, and oxidizes the PM after the light-off temperature. Finely-sized PM could be created during oxidation.