The increasing volume of air pollutants such as carbon monoxide (CO), hydrocarbons (HC) and nitrogen oxides (NOx) has become a seriious global environmental problem. The main source of man-made NOx emissions is the transportation sector. In addtion to these emissions, the increasing carbon dioxide (CO2) concentration in the atmosphere and its contribution to the greenhouse effect is also of general concern. Therefore the development of combustion engines with improved fuel economy is of social interest. The main sources for man-made NOx emission is the transportation sector which accounts for systems into the market are urgently needed. The SNR-technique is a new NOx aftertreatment system for lean burn gasoline and diesel applications. The objective of SNR is NOx removal from lean exhaust gas by NOx adsorptionand subsequent selective external recirculation and decompstion of NOx in the combustion process