Process for heating a catalytic converter and/or particle filter mounted in an exhaust system of a diesel internal combustion engine of a vehicle, a motor vehicle in particular, to a desulfation and/or decarbonization temperature and a catalytic converter, a nitric oxide storage catalytic converter in particular, for exhaust systems of internal combustion engines

Abstract

The invention relates to a process for heating a catalytic converter, a nitric oxide storage catalytic converter and/or particle filter in particular mounted in an exhaust system of a diesel internal combustion engine of a vehicle, to a desulfation and/or decarbonization temperature, a process in which the catalytic converter is heated to a desulfation and/or decarbonization temperature at the beginning of the desulfation and/or decarbonization phase as regeneration phase. A rich exhaust gas flow is delivered periodically to the catalytic converter for the purpose of direct heating of this catalytic converter to a regeneration temperature, in such a way that the unburnt exhaust gas components, hydrocarbons and carbon monoxides in particular, react to the oxygen stored in the catalytic converter and the thermal energy released in the process heats the catalytic converter to a regeneration temperature. A catalytic converter is also proposed in which the oxygen storage component is unevenly distributed over the catalytic converter in the direction of flow of the exhaust gas, in such a way that, as viewed in the direction of flow, the highest oxygen storage capacity is present at the exhaust gas inlet of the catalytic converter as viewed in the direction of flow.

1 . A process for heating a catalytic converter, a nitric oxide storage catalytic converter or particle filter in particular, mounted in an exhaust system of a diesel internal combustion engine of a vehicle, a motor vehicle in particular, to a desulfation and/or decarbonization temperature, wherein the catalytic converter is heated to a desulfation and/or decarbonization temperature as a regeneration temperature at the commencement of the desulfation and/or decarbonization phase as regeneration phase, characterized in that a rich-fuel exhaust gas flow is introduced into the catalytic converter periodically for the purpose of direct heating of such catalytic converter to a regeneration temperature, in such a way that the unburned exhaust gas components, hydrocarbons and carbon monoxides in particular, react to the oxygen stored in an oxygen accumulator of the catalytic converter and the thermal energy released heats the catalytic converter to a regeneration temperature.  
     
     
         2 . The process as claimed in  claim 1 , wherein a lean and a rich exhaust gas flow are alternately delivered to the catalytic converter for the purpose of heating to a regeneration temperature as a function of the extent of charging the oxygen storage component of the catalytic converter, in such a way that switching from a lean to a rich exhaust gas flow is always effected at a first switching moment at which the oxygen storage component has been fully charged, and in such a way that switching from a rich to a lean exhaust gas flow is always effected at a second switching moment at which the oxygen storage component is more or less empty.  
     
     
         3 . The process as claimed in  claim 2 , wherein a large increase in the lambda value of the order of at least λ=1, preferably of at least λ=1.5, is effected as a lambda stroke on transition from rich to lean exhaust gas flow and also on transition from lean to rich exhaust gas flow.  
     
     
         4 . The process as claimed in  claim 3 , wherein consecutive lambda strokes are always equal at least as regards extent.  
     
     
         5 . The process as claimed in  claim 3 , wherein 
 the lambda value of the rich exhaust gas flow is at the maximum λ=0.6, preferably more or less λ=0.8 to 0.95, and    the lambda value of the lean exhaust gas flow is at the minimum λ=1.2, preferably more or less λ=1.5 to 3.5.    
     
     
         6 . The process as claimed in  claim 1 , wherein, in order to achieve uniform heating of the catalytic converter in the direction of flow of the exhaust gas, which direction is preferably axial, the oxygen storage component is not equally distributed over the catalytic converter, in such a way that, as viewed in the direction of flow, the greatest oxygen storage capacity is present at the exhaust gas inlet of the catalytic converter.  
     
     
         7 . The process as claimed in one of  claim 1 , wherein the catalytic converter is a main catalytic converter, preferably an underbody catalytic converter upstream from which at least one preliminary catalytic converter, preferably a three-way catalytic converter, is mounted.  
     
     
         8 . The process as claimed in  claim 7 , wherein the lambda value of the engine is set at approximately λ=1 in order to minimize the exothermic reaction in the preliminary catalytic converter.  
     
     
         9 . The process as claimed in one of  claim 1 , wherein a fuel is subsequently injected into the rich exhaust gas flow coming from the internal combustion engine for the purpose of additional enrichment of such exhaust gas flow.  
     
     
         10 . A catalytic converter, a nitric oxide storage catalytic converter for exhaust systems of internal combustion engines of vehicles, motor vehicles in particular, especially for use in the processes claimed in  claim 1 , with an oxygen storage component, characterized in that the oxygen storage component of the exhaust gas is distributed unevenly over the catalytic converter, preferably in the axial direction, in such a way that the greatest oxygen storage capacity is present at the exhaust gas inlet of the catalytic converter as viewed in the direction of flow.  
     
     
         11 . The catalytic converter as claimed in  claim 10 , wherein a particle filter is integrated into the catalytic converter.