Partial coating of platinum group metals on filter for increased soot mass limit and reduced costs

Abstract

A diesel particulate filter has a thin band of washcoated filter material either on the inlet of the upstream side or the outlet of the downstream side. The washcoating is with platinum group metals (PGM), e.g., Pt and Pd added to the surface and pore structure of a DPF. The PDF should provide comparable or improved distance between active regeneration and/or should prevent HC/CO slip during active DPF regeneration.

The invention claimed is: 
     
         1 . A diesel particulate filter, comprising:
 a housing having an inlet and an outlet and containing a diesel particulate filter material therein wherein a band of said filter material includes a washcoat with platinum group metals added to the surface and pore structure of the filter material.   
     
     
         2 . The diesel particulate filter according to  claim 1 , wherein said band is located adjacent to said inlet. 
     
     
         3 . The diesel particulate filter according to  claim 1 , wherein said band is located adjacent to said outlet. 
     
     
         4 . The diesel particulate filter according to  claim 1 , wherein said platinum group metals comprises at least one metal selected from Pt and Pd. 
     
     
         5 . An exhaust gas after treatment system for a diesel engine, comprising:
 a containment defining a flow path for exhaust gas;   a diesel oxidation catalyst unit arranged in the flow path;   a diesel particulate filter unit arranged in the flow path downstream of the diesel oxidation unit, wherein the diesel particulate filter comprises a housing having an inlet and an outlet and containing a diesel particulate filter material therein wherein a band of said filter material includes a washcoat with platinum group metals added to the surface and pore structure of the filter.   
     
     
         6 . The diesel particulate filter according to  claim 5 , wherein said band is located adjacent to said inlet. 
     
     
         7 . The diesel particulate filter according to  claim 6 , wherein said platinum group metals comprises at least one metal selected from Pt and Pd. 
     
     
         8 . The diesel particulate filter according to  claim 5 , wherein said band is located adjacent to said outlet. 
     
     
         9 . The diesel particulate filter according to  claim 8 , wherein said platinum group metals comprises at least one metal selected from Pt and Pd. 
     
     
         10 . The diesel particulate filter according to  claim 5 , wherein said platinum group metals comprises at least one metal selected from Pt and Pd.