CATALYST FOR REDUCING NITROGEN OXIDES

The present invention relates to a nitrogen oxide storage catalyst comprising a support body and washcoat layers A, B, C and D, wherein - washcoat layer A is disposed on the support body and contains cerium oxide, an alkaline earth metal compound and/or an alkali metal compound, and also platinum or platinum and palladium in a weight ratio of > 5:1; - washcoat layer B is disposed on washcoat layer A and contains cerium oxide, and also platinum or platinum and palladium in a weight ratio of > 5:1, and is free of alkali metal compounds and compounds of calcium, strontium and barium; - washcoat layer C is disposed on washcoat layer B and comprises cerium oxide-supported palladium or palladium and platinum in a weight ratio of > 2:1, and rhodium; - washcoat layer D is disposed on washcoat layer C and comprises platinum or platinum and palladium; and to a method of converting NOx in exhaust gases from motor vehicles that are operated with lean-burn engines.