Exhaust aftertreatment system

Abstract

In one exemplary embodiment of an exhaust aftertreatment system, the system includes an oxidation catalyst configured to receive an exhaust gas flow from an internal combustion engine and a particulate filter positioned downstream of the oxidation catalyst, the particulate filter comprising a substrate. The system also includes a nitrogen oxide adsorbing catalyst applied to a downstream portion of the substrate and a selective catalytic reduction device positioned downstream of the nitrogen oxide adsorbing catalyst, wherein the selective catalytic reduction device is configured to remove nitrogen oxides from the exhaust gas flow.

What is claimed is: 
     
         1 . An exhaust aftertreatment system, comprising:
 an oxidation catalyst configured to receive an exhaust gas flow from an internal combustion engine;   a particulate filter positioned downstream of the oxidation catalyst, the particulate filter comprising a substrate;   a nitrogen oxide adsorbing catalyst applied to a downstream portion of the substrate; and   a selective catalytic reduction device positioned downstream of the nitrogen oxide adsorbing catalyst, wherein the selective catalytic reduction device is configured to remove nitrogen oxides from the exhaust gas flow.   
     
     
         2 . The exhaust aftertreatment system of  claim 1 , wherein the nitrogen oxide adsorbing catalyst adsorbs nitrogen oxides below a threshold temperature during a start up period for the internal combustion engine and releases the nitrogen oxides above the threshold temperature, wherein the second temperature is greater than the first temperature. 
     
     
         3 . The exhaust aftertreatment system of  claim 1 , wherein the selective catalytic reduction device removes nitrogen oxides at an operating temperature that is greater than its temperature following a start up period for the internal combustion engine. 
     
     
         4 . The exhaust aftertreatment system of  claim 1 , wherein a temperature of the exhaust gas flow is substantially matched between the nitrogen oxide adsorbing catalyst and the selective catalytic reduction device. 
     
     
         5 . The exhaust aftertreatment system of  claim 1 , wherein the configuration of the nitrogen oxide adsorbing catalyst and the selective catalytic reduction device enable adsorption of nitrogen oxides by the nitrogen oxide adsorbing catalyst during a start up period, release of the nitrogen oxides after the start up period and removal of the nitrogen oxides simultaneously by the selective catalytic reduction device from the exhaust gas flow as the nitrogen oxides are released by the nitrogen oxide adsorbing catalyst. 
     
     
         6 . The exhaust aftertreatment system of  claim 1 , comprising an emission fluid injector positioned in a flow path between the nitrogen oxide adsorbing catalyst and the selective catalytic reduction device. 
     
     
         7 . The exhaust aftertreatment system of  claim 1 , wherein the oxidation catalyst and the particulate filter are closely coupled to the internal combustion engine. 
     
     
         8 . An internal combustion engine comprising:
 an oxidation catalyst in fluid communication with an exhaust manifold;   a particulate filter configured to receive an exhaust gas flow from the oxidation catalyst;   a nitrogen oxide adsorbing catalyst configured to receive the exhaust flow from the particulate filter; and   a selective catalytic reduction device configured to receive the exhaust flow from the nitrogen oxide adsorbing catalyst, wherein the configuration of the nitrogen oxides catalyst and the selective catalytic reduction catalyst enable adsorption of nitrogen oxides by the nitrogen oxide adsorbing catalyst during a start up period, release of the nitrogen oxides after the start up period and removal the nitrogen oxides from the exhaust flow by the selective catalytic reduction catalyst as the nitrogen oxides are released by the nitrogen oxide adsorbing catalyst.   
     
     
         9 . The internal combustion engine of  claim 8 , wherein the nitrogen oxide adsorbing catalyst adsorbs nitrogen oxides below a threshold temperature during a start up period for the internal combustion engine and releases the nitrogen oxides after the start up period above the threshold temperature. 
     
     
         10 . The internal combustion engine of  claim 8 , wherein the selective catalytic reduction device removes nitrogen oxides at an operating temperature that is greater than its temperature during the start up period. 
     
     
         11 . The internal combustion engine of  claim 8 , wherein a temperature of the exhaust gas flow is substantially matched between the nitrogen oxide adsorbing catalyst and the selective catalytic reduction device. 
     
     
         12 . The internal combustion engine of  claim 8 , comprising an emission fluid injector positioned in a flow path between the nitrogen oxide adsorbing catalyst and the selective catalytic reduction device. 
     
     
         13 . The internal combustion engine of  claim 8 , wherein the oxidation catalyst, the particulate filter and the nitrogen oxide adsorbing catalyst are closely coupled to the internal combustion engine. 
     
     
         14 . An exhaust aftertreatment system, comprising:
 an oxidation catalyst configured to receive an exhaust gas flow from an internal combustion engine;   a particulate filter configured to receive an exhaust gas flow from the oxidation catalyst;   a nitrogen oxide adsorbing catalyst configured to receive the exhaust flow from the particulate filter; and   a selective catalytic reduction device configured to remove nitrogen oxides from the exhaust gas flow received from the nitrogen oxide adsorbing catalyst, wherein a temperature of the exhaust gas flow is substantially matched between the nitrogen oxide adsorbing catalyst and the selective catalytic reduction device.   
     
     
         15 . The exhaust aftertreatment system of  claim 14 , wherein the nitrogen oxide adsorbing catalyst adsorbs nitrogen oxides below a threshold temperature during a start up period for the internal combustion engine and releases the nitrogen oxides above the threshold temperature. 
     
     
         16 . The exhaust aftertreatment system of  claim 15 , wherein the selective catalytic reduction device removes nitrogen oxides at about the second temperature. 
     
     
         17 . The exhaust aftertreatment system of  claim 14 , wherein the configuration of the nitrogen oxide adsorbing catalyst and the selective catalytic reduction device enable adsorption of nitrogen oxides by the nitrogen oxide adsorbing catalyst during a start up period of the internal combustion engine, release of the nitrogen oxides after the start up period and removal of the nitrogen oxides from the exhaust flow as the nitrogen oxides are released by the nitrogen oxide adsorbing catalyst. 
     
     
         18 . The exhaust aftertreatment system of  claim 14 , comprising an emission fluid injector positioned in a flow path between the nitrogen oxide adsorbing catalyst and the selective catalytic reduction device. 
     
     
         19 . The exhaust aftertreatment system of  claim 14 , wherein the nitrogen oxide adsorbing catalyst is applied to a downstream portion of a substrate of the particulate filter. 
     
     
         20 . The exhaust aftertreatment system of  claim 19 , wherein the oxidation catalyst and the particulate filter are closely coupled to the internal combustion engine.