Patent ID: 6684628
Filing Date: 2004-02-03
Classification: F01N,F02D,Y02T

Abstract:
A process for checking the operability of a nitrogen oxide storage catalyst which is used to remove the nitrogen oxides contained in the exhaust gas stream from a lean burn engine and which contains at least a nitrogen oxide storage material, a catalytically active component and optionally an oxygen storage material, wherein the lean burn engine is operated with cyclic alternation of the air/fuel mixture from lean to rich and the nitrogen oxides contained in the exhaust gas are stored by the nitrogen oxide storage material in the presence of lean exhaust gas in the storage phase and is desorbed and converted in the presence of rich exhaust gas in the regeneration phase comprising:determining the nitrogen oxide storage capacity of the nitrogen oxide storage catalyst at the exhaust gas temperatures which are within the range in which the oxidation of nitrogen monoxide to nitrogen dioxide is kinetically controlled, and at exhaust gas temperatures which are within the range in which the oxidation of nitrogen monoxide to nitrogen dioxide is thermodynamically controlled and, wherein damage to the catalytically active components is detected if the nitrogen oxide storage capacity in the kinetically controlled temperature range is lowered while no change of the nitrogen oxide storage capacity in the thermodynamically controlled temperature range is detected, and damage to the storage materials is detected if the nitrogen oxide storage capacity is lowered in the thermodynamically controlled temperature range.