Method of desulfation of nox-adsorbers

Abstract

The invention relates to a method of desulfation of NOx-adsorbers ( 11 ) in a diesel exhaust system, comprising the steps of periodically increasing the temperature of the electrically conductive substrate ( 18 ) of the NOx-adsorber ( 11 ) above the decomposition temperature of the adsorbed S-comprising compounds by providing electric current to the electrically conductive substrate ( 18 ).

1 . A method of desulfation of NOx-adsorbers in a diesel exhaust system, comprising the steps of 
 providing an electrically conductive substrate comprising metal fibers, an oxidizing catalyst, a reducing catalyst and a NOx-adsorbing compound;    executing a loading step, passing the exhaust gasses from said diesel exhaust system through said electrically conductive substrate, at least partially oxidizing S-comprising compounds and at least partially adsorbing said oxidized S-comprising compounds as adsorbed S-comprising compounds on said NOx-adsorbing compound;    executing a desulfation step by increasing the temperature of said electrically conductive substrate above the decomposition temperature of said adsorbed S-comprising compounds by providing electric current to said electrically conductive substrate.    
     
     
         2 . A method of desulfation of NOx-adsorbers in a diesel exhaust system as in  claim 1 , said electrically conductive substrate is heated above 700° C.  
     
     
         3 . A method of desulfation of NOx-adsorbers in a diesel exhaust system as in  claim 1 , said process further comprising the step of providing an electrically regeneratable metal fiber soot filter upstream from said electrically conductive sustrate.  
     
     
         4 . A method of desulfation of NOx-adsorbers in a diesel exhaust system as in  claim 1 , said process comprising the additional step of desadsorbtion and reducing N-comprising compounds, being adsorbed by said NOx-adsobring compound by providing hydrocarbons and/or CO for the reduction of the adsobed N-comprising compounds, and increasing the temperature of said N-comprising compounds above the desadsorbtion temperature of said N-comprising compounds adsorbed on the NOx-adsorber during said loading step.  
     
     
         5 . A method of desulfation of NOx-adsorbers in a diesel exhaust system as in  claim 4 , said hydrocarbons and/or CO being provided by regeneration of said electrically regeneratable metal fiber soot filter.  
     
     
         6 . A method of desulfation of NOx-adsorbers in a diesel exhaust system as in  claim 4 , increasing temperature temperature of said N-comprising compounds above the desadsorbtion temperature of said N-comprising compounds adsorbed on the NOx-adsorber during said loading step is obtained by providing electric current to said electrically conductive substrate.  
     
     
         7 . A method of desulfation of NOx-adsorbers in a diesel exhaust system as in  claim 1 , said NOx-adsorbing compound comprising BaO.  
     
     
         8 . A method of desulfation of NOx-adsorbers in a diesel exhaust system as in  claim 1 , said electrically conductive substrate is a sintered metal fiber fleece.  
     
     
         9 . A method of desulfation of NOx-adsorbers in a diesel exhaust system as in  claim 1 , said metal fibers comprising Fe, Al and Cr.  
     
     
         10 . An NOx-adsorbing element, comprising a substrate, an oxidizing catalyst, a reducing catalyst and a NOx-adsorbing compound, characterized in that said substrate being electrically conductive, said electrically conductive substrate comprising metal fibers.  
     
     
         11 . An NOx-adsorbing element as in  claim 10 , said metal fibers metal fibers of said electrically conductive substrate comprising Fe, Al and Cr.  
     
     
         12 . An NOx-adsorbing element as in  claim 10 , said electrically conductive substrate being a sintered metal fiber fleece.  
     
     
         13 . An NOx-adsorbing element as in  claim 10 , said NOx-adsorbing compound comprising BaO.  
     
     
         14 . An NOx-adsorbing element as in  claim 10 , said metal fibers having an equivalent diameter in the range of 1 to 100 μm.  
     
     
         15 . An NOx-adsorbing element as in  claim 10 , said metal fiber fleece being pleated.  
     
     
         16 . An NOx-adsorbing element as in  claim 10 , said NOx-adsorbing element further comprising an electrically regeneratable metal fiber soot filter located upstream of said electrically conductive substrate.  
     
     
         17 . An NOx-adsorbing element as in  claim 16 , said metal fibers of said electrically conductive substrate and metal fibers of said electrically regeneratable metal fiber soot filter being identical.  
     
     
         18 . An NOx-adsorbing unit, comprising at least one NOx-adsorbing element as in  claim 10 .  
     
     
         19 . An NOx-adsorbing unit, comprising at least one NOx-adsorbing element as in  claim 16 .  
     
     
         20 . An NOx-adsorbing unit as in  claim 18 , said NOx-adsorbing unit comprising an integrated circuit, being connected to said electrically conductive substrates of said NOx-adsorbing elements.  
     
     
         21 . An NOx-adsorbing unit as in  claim 19 , said NOx-adsorbing unit comprising an integrated circuit, being connected to said electrically conductive substrates of said NOx-adsorbing elements.  
     
     
         22 . An NOx-adsorbing unit as in  claim 20 , said NOx-adsorbing unit comprising a valve system.