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The drive towards improved fuel economy and lower emissions for Diesel vehicles requires the development of catalysts capable of converting not only carbon monoxide (CO) and hydrocarbon (HC), but also particulate matter (PM) and nitrogen oxides (NOx) in a lean exhaust environment. This paper reviews the approaches that are being considered for this purpose, for light duty Diesels, together with factors that may influence catalyst performance such as components in the fuel and quality of the lubricant.

The low exhaust gas temperatures experienced on light duty Diesel vehicles present a very challenging environment for the successful operation of catalytic aftertreatment. To meet the future more severe legislation, Diesel engines are being developed with greater combustion efficiencies and advanced fueling control. These engine developments may produce lower particulate matter (PM) and nitrogen oxides (NOx) emissions, but increased hydrocarbon (HC) and carbon monoxide (CO) emissions may occur. As a result of these engine changes exhaust gas temperatures may reduce still further. These factors demand catalysts with high oxidation activity at low temperatures. This paper reviews oxidation catalyst technology developed for light duty Diesel vehicles and the factors affecting their performance. Results obtained on synthetic gas rigs, bench engines and vehicles are presented. A discussion oh the effect of the level of sulfur (S) present in Diesel fuel on aftertreatment is given.