Method and system for the purification of exhaust gas from an internal combustion engine

1. Method for the purification of exhaust gas from an internal combustion engine, comprising

reducing the content of soot in the exhaust gas by passing the gas through a filter;

subsequently reducing the content of nitrogen oxides in presence of ammonia or a precursor thereof in contact with a catalyst being active in NH 3 -SCR;

periodically regenerating the filter by burning of soot captured in the filter and thereby increasing temperature of the exhaust gas up to 850° C. and water vapour content up to 100% by volume; and

passing the exhaust gas from the filter through the catalyst during the regeneration of the filter, wherein the catalyst comprises a hydrothermally microporous stable zeolite and/or zeotype having the AEI type framework and being promoted with copper, and maintains 80% of the initial reduction of nitrogen oxides at 250° C. after the catalyst has been exposed to a water vapour content of 100% in the exhaust gas for 13 hours.

2. The method of claim 1 , wherein the atomic copper to aluminium ratio is between about 0.01 and about 1 for the zeolite and the atomic copper to silicon ratio is between 0.01 and about 1 for the zeotype.

3. The method of claim 1 , wherein the atomic ratio of silicon to aluminium is between 5 and 50 for the zeolite and between 0.02 and 0.5 for the zeotype.

4. The method of claim 1 , wherein 80% of the initial reduction of nitrogen oxides at 250° C. is maintained after the catalyst has been exposed to a temperature of 750° C.

5. The method of claim 1 , wherein at least 80 to 90% of the initial microporosity is maintained after aging at 600° C., and at least 30 to 40% is maintained after aging at 750° C.

6. The method of claim 3 , wherein the catalyst is an aluminosilicate zeolite SSZ-39 and/or silicoaluminum phosphate SAPO-18.