Aftertreatment System Using LNT and SCR

Abstract

A multiple catalyst system for the treatment of exhaust gases generated by a combustion engine in an after treatment system. The system includes a substrate and a plurality of catalysts. The plurality of catalysts may provide a plurality of catalyst sections. A variety of different catalysts, as well as a variety of different combinations of catalysts, may be employed. Catalysts may include both catalysts that assist in the removal of nitrogen oxides from the exhaust gas during cold start operation of the engine, as well as catalysts that are generally more effective in removing nitrogen oxides after the temperature of the after treatment system and/or exhaust gas is elevated to normal operating temperatures.

1 . A multiple catalyst system for the treatment of exhaust gas in an after treatment system, the multiple catalyst system comprising:
 a common substrate; and   a plurality of catalysts applied to at least a portion of the common substrate to provide a plurality of catalyst sections.   
     
     
         2 . The multiple catalyst system of  claim 1 , wherein the multiple catalyst system includes a plurality of common substrates joined together, each of the plurality of common substrates having a plurality of catalysts. 
     
     
         3 . The multiple catalyst system of  claim 1 , wherein the plurality of catalysts include a first catalyst, a second catalyst, and a third catalyst. 
     
     
         4 . The multiple catalyst system of  claim 3 , wherein the first catalyst is a lean nitrogen oxide trap catalyst, the second catalyst is a selective catalytic reduction catalyst, and the third catalyst is an ammonia oxidizing catalyst. 
     
     
         5 . The multiple catalyst system of  claim 4 , wherein the lean nitrogen oxide trap catalyst is positioned upstream of the selective catalytic reduction catalyst on the substrate, and the selective catalytic reduction catalyst is positioned upstream of the ammonia oxidizing catalyst on the substrate so that exhaust gas in the after treatment system first encounters the lean nitrogen oxide trap catalyst before encountering the selective catalytic reduction catalyst. 
     
     
         6 . The multiple catalyst system of  claim 4 , wherein at least at least two of the plurality of catalyst sections abut each other. 
     
     
         7 . The multiple catalyst system of  claim 1 , wherein the substrate includes a first substrate portion and a second substrate portion, a portion of the plurality of catalysts being applied to at least a portion of the first substrate portion, and the remaining plurality of catalysts applied to at least a portion of the second substrate portion. 
     
     
         8 . A multiple catalyst system for the treatment of exhaust gas in an after treatment system, the multiple catalyst system comprising:
 a substrate;   a first catalyst applied to a portion of the substrate, the first catalyst having a lean nitrogen oxide trap catalyst; and   a second catalyst applied to a portion of the substrate, the second catalyst having a selective catalytic reduction catalyst.   
     
     
         9 . The multiple catalyst system of  claim 8 , wherein the first catalyst is positioned upstream of the second catalyst so that exhaust gas passes the first catalyst before reaching the second catalyst. 
     
     
         10 . The multiple catalyst system of  claim 9 , further including a third catalyst applied to a portion of the substrate and a fourth catalyst applied to another portion of the substrate, the third catalyst being a selective catalytic reduction catalyst, the fourth catalyst being an ammonia oxidizing catalyst. 
     
     
         11 . The multiple catalyst system of  claim 10 , wherein the substrate includes a first substrate portion and a second substrate portion, wherein the first and second catalysts are applied at least a portion of the first substrate portion, and the third and fourth catalysts are applied to at least a portion of the second substrate portion. 
     
     
         12 . A multiple catalyst system for an exhaust gas after treatment system comprising:
 a common substrate having a plurality of catalyst sections, each of the plurality of catalyst sections having at least one catalyst formulated to treat exhaust gas generated by a combustion engine.   
     
     
         13 . The multiple catalyst system of  claim 14 , wherein the plurality of catalysts sections include a first catalyst section having a first catalyst and a second catalyst section having a second catalyst, the first and second catalysts formulated for the removal of nitrogen oxides from exhaust gas, wherein the first catalyst is more effective than the second catalyst in removing nitrogen oxides from exhaust gas generated during cold start engine conditions, and wherein the second catalyst is more effective than the first catalyst in removing nitrogen oxides from exhaust gas during normal engine operating temperatures. 
     
     
         14 . The multiple catalyst system of  claim 13 , further including a third catalyst, and wherein the first catalyst is a lean nitrogen oxide trap catalyst, the second catalyst is a selective catalytic reduction catalyst, and the third catalyst is an ammonia oxidizing catalyst. 
     
     
         15 . The multiple catalyst system of  claim 14 , wherein the lean nitrogen oxide trap catalyst is positioned upstream of the selective catalytic reduction catalyst on the substrate, and the selective catalytic reduction catalyst is positioned upstream of the ammonia oxidizing catalyst on the substrate so that exhaust gas in the after treatment system first encounters the lean nitrogen oxide trap catalyst before encountering the selective catalytic reduction catalyst.