Desulfurizing a nitrogen oxide storage catalyst, for use in e.g. engines with direct fuel injection, comprises exposing the catalyst to a rich gas atmosphere during repeated periods, most of which are performed at low temperature

摘要

Method for desulfurizing a nitrogen oxide storage catalyst in the exhaust system of an internal combustion engine, comprises performing at least 70% of the desulfurization periods at an exhaust gas temperature which is less than a limiting temperature that is at most 50 K above the temperature at which up to 70% of the maximum amount of sulfur storable in the catalyst is removed within 3 minutes. Method for desulfurizing a nitrogen oxide (NOx) storage catalyst in the exhaust system of an internal combustion engine, in which the catalyst is exposed during repeated periods to a rich gas atmosphere with an air/fuel ratio below 1 and a variable desulfurization temperature at least equal to a minimum desulfurization temperature, comprises performing at least 70% of the desulfurization periods, which are initiated by actively increasing the catalyst temperature, as low-temperature desulfurization periods at a first exhaust gas temperature, measured upstream of the catalyst, which is no greater than a limiting temperature that is no more than 50 K above the temperature at which up to 70% of the maximum amount of sulfur storable in the catalyst is removed within 3 minutes. An Independent claim is also included for apparatus comprising means for performing the desulfurization periods as above.