AFTERTREATMENT SYSTEM WITH LEAN NOx TRAP FILTER

Abstract

An aftertreatment system includes a first pipe section in fluid communication with an exhaust manifold on an internal combustion engine. A first aftertreatment device includes a housing and a porous substrate having substrate walls defining a plurality of flow channels including first channels obstructed at a first end of the substrate and second channels obstructed at a second end of the substrate opposite the first end. The first and second channels are interleaved and internal pore surfaces in the porous substrate form a plurality of internal pores. A passive NOx adsorption catalyst is deposited on the substrate walls and internal pore surfaces such that the mean porosity of the porous substrate is not greater than a particulate matter secondary grain size. A second aftertreatment device having an inlet is in fluid communication with the outlet of the first aftertreatment device.

1 . An exhaust gas aftertreatment device for exhaust gases from an internal combustion engine comprising:
 a housing having an inlet and an outlet;   a porous substrate having substrate walls defining a plurality of flow channels formed therein including first channels obstructed at a first end of the substrate and second channels obstructed at a second end of the substrate opposite the first end, wherein the first and second channels are interleaved and internal pore surfaces in the porous substrate form a plurality of internal pores that define tortuous passageways between the substrate walls; and   a passive NOx adsorption catalyst deposited on the substrate walls and internal pore surfaces such that the mean porosity of the porous substrate is not greater than a particulate matter secondary grain size.   
     
     
         2 . The exhaust gas aftertreatment device according to  claim 1 , wherein the mean porosity of the substrate is not less than 10 μm and not greater than 20 μm. 
     
     
         3 . The exhaust gas aftertreatment device according to  claim 1 , wherein the porous substrate is uniformly coated with the catalyst such that the concentration of the catalyst on the substrate in the exhaust gas flow direction remains substantially constant over the length of the substrate. 
     
     
         4 . The exhaust gas aftertreatment device according to  claim 1 , the porous substrate is zoned coated with the catalyst such that the concentration of the catalyst varies over the length of the substrate to define distinct zones based on the catalyst concentration in a given region of the substrate. 
     
     
         5 . The exhaust gas aftertreatment device according to  claim 1 , further comprising a Diesel oxidation catalyst section disposed in the housing between the inlet and the porous substrate. 
     
     
         6 . The exhaust gas aftertreatment device according to  claim 1 , further comprising a fuel injector configured to inject a hydrocarbon fuel into the exhaust gas stream downstream of the internal combustion engine and upstream of the porous substrate. 
     
     
         7 . An aftertreatment system for exhaust gas from an internal combustion engine having an exhaust manifold, the aftertreatment system comprising:
 a first pipe section configured to be in fluid communication with the exhaust manifold;   a first aftertreatment device including a housing having an inlet and an outlet, a porous substrate having substrate walls defining a plurality of flow channels formed therein including first channels obstructed at a first end of the substrate and second channels obstructed at a second end of the substrate opposite the first end, wherein the first and second channels are interleaved and internal pore surfaces in the porous substrate form a plurality of internal pores that define tortuous passageways between the substrate walls, and a passive NOx adsorption catalyst deposited on the substrate walls and internal pore surfaces such that the mean porosity of the porous substrate is not greater than a particulate matter secondary grain size;   a second aftertreatment device having an inlet in fluid communication with the outlet of the first aftertreatment device.   
     
     
         8 . The aftertreatment system according to  claim 7 , wherein the porous substrate in the first aftertreatment device has a mean porosity not less than 10 μm and not greater than 20 μm. 
     
     
         9 . The aftertreatment system according to  claim 7 , wherein the porous substrate in the first aftertreatment device is uniformly coated with the catalyst such that the concentration of the catalyst on the substrate in the exhaust gas flow direction remains substantially constant over the length of the substrate. 
     
     
         10 . The aftertreatment system according to  claim 7 , wherein the porous substrate in the first aftertreatment device is zoned coated with the catalyst such that the concentration of the catalyst varies over the length of the substrate to define distinct zones based on the catalyst concentration in a given region of the substrate. 
     
     
         11 . The aftertreatment system according to  claim 7 , further comprising a Diesel oxidation catalyst section disposed in the housing between the inlet and the porous substrate. 
     
     
         12 . The aftertreatment system according to  claim 7  further comprising a fuel injector configured to inject a hydrocarbon fuel into the aftertreatment system downstream of the exhaust manifold and upstream of the first aftertreatment device. 
     
     
         13 . The aftertreatment system according to  claim 7 , wherein the second aftertreatment device comprises a selective catalytic reduction (SCR) unit. 
     
     
         14 . The aftertreatment system according to  claim 13 , further comprising a fluid injector configured to inject a diesel exhaust fluid into the aftertreatment system downstream of the first aftertreatment device and upstream of the SCR unit. 
     
     
         15 . The aftertreatment system according to  claim 7  wherein the first aftertreatment device has a NOx conversion efficiency greater than 40% in a first temperature range between about 100° C. and 300° C. and the second aftertreatment device has a NOx conversion efficiency greater that 55% in a second temperature range between about 200° C. and 450° C. 
     
     
         16 . The aftertreatment system according to  claim 7 , further comprising a second pipe section having a first end in fluid communication with the outlet of the first aftertreatment device and a second end in fluid communication with the second aftertreatment device such that second pipe section separates the first and second aftertreatment devices. 
     
     
         17 . The aftertreatment system according to  claim 16 , further comprising a low-pressure exhaust gas recirculation circuit in fluid communication with the second pipe section.