Method for reducing emission of nitrogen oxide in a motor vehicle having a lean burning internal combustion engine

A method for reducing nitrogen dioxide emissions in a lean burning internal combustion engine having a connected exhaust gas purification system that includes an SCR catalytic converter for reducing nitrogen oxides with ammonia under oxidizing conditions, and a device arranged upstream of the SCR catalytic converter for enriching the exhaust gas with ammonia and/or a reagent enabled for splitting off ammonia said SCR catalytic converter having adsorption centers for nitrogen oxides;

• said method comprising:
• above an operating temperature at which the SCR catalytic converter can reduce significantly nitrogen oxides with ammonia under oxidizing conditions, exhaust gas supplied to said SCR catalytic converter is enriched with ammonia;
• and
• below said operating temperature, the exhaust gas supplied to the SCR catalytic converter is enriched with a material which adsorbs at least partially on said adsorption centers, in such a manner that adsorption of nitrogen oxides on said adsorption centers is inhibited, wherein
• for inhibiting adsorption of nitrogen oxides at said adsorption centers, the exhaust gas is enriched with hydrocarbons,
• said exhaust gas purification system includes an oxidation-catalytically effective exhaust gas purification component connected upstream of the SCR catalytic converter;
• and
• enrichment of the exhaust gas with hydrocarbons is ended when
• the SCR catalytic converter has a predeterminable charge with hydrocarbons, the predeterminable charge with hydrocarbons being an amount sufficient to inhibit adsorption of nitrogen oxides at the adsorption centers.