Method for purifying exhaust gas of a diesel engine

A method for purifying the exhaust of a diesel engine, comprising:

• catalytically oxidizing nitrogen monoxide, hydrocarbons and carbon monoxide in the exhaust gas from a diesel engine to form an exhaust gas comprising nitrogen dioxide by contacting the exhaust gas with an oxidation catalyst when the air/fuel ratio of the exhaust gas is lean in fuel;
• collecting carbon particulates contained in the exhaust gas in a diesel particulate filter;
• removing nitrogen oxides out of the exhaust gas by sorbing the nitrogen oxides in an absorbent when the air/fuel ratio of the exhaust gas is lean in fuel;
• periodically regenerating the diesel particulate filter by raising the temperature of the exhaust gas by activating an electric heater attached to said oxidation catalyst to a temperature high enough to promote the reaction between nitrogen dioxide and the carbon particulates contained in the diesel particulate filter so as to result in a regenerated diesel particulate filter and an exhaust gas rich in carbon oxides and nitrogen monoxide;
• removing nitrogen monoxide from the filter regeneration out of the exhaust gas;
• periodically regenerating the absorbent by intentionally shifting the air/fuel ratio of the exhaust gas to a fuel rich air/fuel ratio thereby temporarily terminating the catalytic oxidation of the hydrocarbons and carbon monoxide in the exhaust gas set forth in the first step and passing the resulting hydrocarbon and carbon monoxide rich exhaust gas into the absorbent where a reaction occurs between the hydrocarbons and carbon monoxide and the nitrogen oxides released in the absorbent to convert the nitrogen oxides into nitrogen.