Process for checking the operatability of a nitrogen oxide storage catalyst

摘要

A process is disclosed for checking the operatability 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. 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 burn exhaust gas (storage phase) and is desorbed and converted in the presence of rich exhaust gas (regeneration phase). The process is characterised in that, in order to determine possible damage to the catalytically active component, the nitrogen oxide storage capacity of the nitrogen oxide storage catalyst is determined at exhaust gas temperatures which are within the range in which the oxidation of nitrogen monoxide to nitrogen dioxide is kinetically controlled, while no change in the nitrogen oxide storage capacity is detected in the thermodynamically controlled range and, to determine possible damage to the storage materials, the nitrogen oxide capacity of the nitrogen oxide storage catalyst is determined at exhaust gas temperatures which are within the range in which the oxidation of nitrogen monoxide to nitrogen dioxide is thermodynamically controlled.