Exhaust Aftertreatment System with Pre-Catalysis

Abstract

An exhaust aftertreatment system includes an exhaust tube or housing having a catalyzed inner wall catalytically reacting with engine exhaust prior to reaching an aftertreatment element.

1 - 11 . (canceled) 
   
   
       12 . An SCR, selective catalytic reduction, system for engine exhaust, comprising:
 a housing having an upstream inlet for receiving said exhaust, and a downstream outlet for discharging said exhaust;   an injector injecting urea into said housing to hydrolyze to ammonia to react with and reduce NO x  in said exhaust;   an SCR catalyst in said housing catalytically treating said exhaust;   said housing having a catalyzed inner wall catalytically reacting with said exhaust prior to reaching said SCR catalyst and accelerating the rate of urea hydrolysis to ammonia and reducing urea crystalline formation on said inner wall.   
   
   
       13 . A method for reducing housing length in an SCR, selective catalytic reduction, system for engine exhaust having a housing having an upstream inlet for receiving said exhaust, and a downstream outlet for discharging said exhaust, an injector injecting urea into said housing to hydrolyze to ammonia to react with and reduce NO x  in said exhaust, and an SCR catalyst in said housing catalytically treating said exhaust, said method comprising providing said housing with a catalyzed inner wall catalytically reacting with said exhaust prior to reaching said SCR catalyst and accelerating the rate of urea hydrolysis to ammonia and reducing the length of said inner wall otherwise required between said injector and said SCR catalyst.