IN-EXHAUST ELECTRICAL ELEMENT FOR NOx STORAGE CATALYST AND SCR SYSTEMS

Abstract

An exhaust system comprising: a NOx storage catalyst; an electric heating element; and a NOx reduction catalyst wherein the heating element is located downstream of the NOx storage catalyst.

We claim: 
     
         1 . An exhaust system comprising:
 a. a NOx storage catalyst;   b. an electric heating element; and   c. a NOx reduction catalyst
 wherein the heating element is located downstream of the NOx storage catalyst. 
   
     
     
         2 . The exhaust system of  claim 1 , wherein the electric heating element is located directly behind the NOx storage catalyst. 
     
     
         3 . The exhaust system of  claim 1 , wherein the electric heating element is coupled with a mixer. 
     
     
         4 . The exhaust system of  claim 1 , wherein the electric heating element is coupled with a hydrolysis catalyst. 
     
     
         5 . The exhaust system of  claim 1 , wherein the electric heating element is located upstream of the NOx reduction catalyst. 
     
     
         6 . The exhaust system of  claim 1 , wherein the electric heating element is coupled with the NOx reduction catalyst. 
     
     
         7 . The exhaust system of  claim 1 , wherein the electric heating element and the NOx reduction catalyst are combined in a single substrate. 
     
     
         8 . The exhaust system of  claim 1 , wherein the exhaust system is associated with a vehicle powered by a hybrid electric motor and internal combustion engine. 
     
     
         9 . A method for treating an exhaust gas stream from an internal combustion engine, comprising:
 a. adsorbing NO x  onto a NOx storage catalyst at temperatures at or below a low temperature;   b. thermally desorbing NO x  from the NOx storage catalyst at a temperature above the low temperature;   c. heating a downstream NOx reduction catalyst with an electrical heating element; and   d. catalytically removing the desorbed NO x  on the NOx reduction catalyst.   
     
     
         10 . The method of  claim 9 , wherein the low temperature is between about 200° C. and about 250° C. 
     
     
         11 . The method of  claim 9 , wherein the heating element heats the NOx reduction catalyst on an intermittent pattern, while for a remainder of time the NOx is stored on the NOx storage catalyst. 
     
     
         12 . The method of  claim 9 , wherein the NOx reduction catalyst is heated to a temperature sufficient to activate the catalyst. 
     
     
         13 . The method of  claim 9 , wherein the electric heating element is located directly behind the NOx storage catalyst. 
     
     
         14 . The method of  claim 9 , wherein the electric heating element is located upstream of the NOx reduction catalyst 
     
     
         15 . The method of  claim 9 , wherein the electric heating element and the NOx reduction catalyst are combined in a single substrate. 
     
     
         16 . The method of  claim 9 , wherein the electric heating element is coupled with the NOx reduction catalyst. 
     
     
         17 . The method of  claim 9 , wherein the exhaust system is associated with a vehicle powered by a hybrid electric motor and internal combustion engine. 
     
     
         18 . The method of  claim 9 , wherein step b comprises creating a thermal purge. 
     
     
         19 . The method of  claim 18 , wherein the thermal purge lasts less than 30 seconds. 
     
     
         20 . The method of  claim 18 , wherein a duration and timing of the thermal purge is selected to coordinate with step c, such that NOx is released from the NOx storage catalyst when the NOx reduction catalyst is heated to a temperature sufficient to be active.