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The aggressive reduction of future diesel engine NOx emission limits forces the heavy- and light-duty diesel engine manufacturers to develop means to comply with stringent legislation. As a result, different exhaust emission control technologies applicable to NOx have been the subject of many investigations. One of these systems is the NOx adsorber catalyst, which has shown high NOx conversion rates during previous investigations with acceptable fuel consumption penalties. In addition, the NOx adsorber catalyst does not require a secondary on-board reductant. However, the NOx adsorber catalyst also represents the most sulfur sensitive emissions control device currently under investigation for advanced NOx control. To remove the sulfur introduced into the system through the diesel fuel and stored on the catalyst sites during operation, specific regeneration strategies and boundary conditions were investigated and developed.

Currently, throughout the world combustion engine development is influenced by two primary concerns. First is the increasing concern for global warming, and second is the concern over particulate and oxides of nitrogen emissions, each of which affect the environment and human health because of the particles' toxicity and ground level ozone production, respectively. To address the global warming issue, in late 1997, various nations approved the Kyoto Protocol to reduce CO2 emissions because of its identified contribution to the greenhouse effect. The Diesel engine is the most efficient power plant for mobile and stationary purposes and, thus, Diesel engines are considered to be one alternative to gasoline engines to reduce fuel consumption and, thus, CO2 emissions. To address the emission concerns, the European Community and the U.S. Environmental Protection Agency (EPA) proposed emissions standards prescribing substantial reductions of NOX and PM emissions [1,2]1.