METHOD AND APPARATUS TO MINIMIZE DEACTIVATION OF A LOW TEMPERATURE NOx ADSORBER IN AN EXHAUST AFTERTREATMENT SYSTEM

Abstract

An exhaust aftertreatment system for purifying an exhaust gas feedstream from an internal combustion engine disposed to operate at a lean air/fuel ratio is described, and includes an oxidation catalyst disposed upstream of a low-temperature NOx adsorber. The oxidation catalyst includes a zeolite catalyst including a base metal, a noble metal, and a zeolite disposed on a substrate, and the low-temperature NOx adsorber includes a zeolite catalyst and a supported platinum group metal catalyst.

1 . An exhaust aftertreatment system for purifying an exhaust gas feedstream from an internal combustion engine configured to operate at a lean air/fuel ratio, the exhaust aftertreatment system comprising:
 an oxidation catalyst and a low-temperature NOx adsorber;   wherein the oxidation catalyst is disposed upstream of the low-temperature NOx adsorber;   wherein the oxidation catalyst comprises a zeolite catalyst including a base metal, a noble metal, and a zeolite disposed on a substrate; and   wherein the low-temperature NOx adsorber comprises a zeolite catalyst and a supported platinum group metal catalyst.   
     
     
         2 . The exhaust aftertreatment system of  claim 1 , wherein the oxidation catalyst and the low-temperature NOx adsorber are disposed on a common substrate. 
     
     
         3 . The exhaust aftertreatment system of  claim 2 , wherein the oxidation catalyst and the low-temperature NOx adsorber are disposed on the common substrate in a zoned arrangement. 
     
     
         4 . The exhaust aftertreatment system of  claim 3 , wherein the common substrate comprises a wall-flow filter element. 
     
     
         5 . The exhaust aftertreatment system of  claim 3 , wherein the common substrate comprises a flow-through filter element. 
     
     
         6 . The exhaust aftertreatment system of  claim 1 , wherein the oxidation catalyst and the low-temperature NOx adsorber are configured to be disposed in a close-coupled arrangement in relation to the internal combustion engine. 
     
     
         7 . The exhaust aftertreatment system of  claim 1 , wherein the oxidation catalyst further comprises an oxygen storage capacity material disposed on the substrate. 
     
     
         8 . The exhaust aftertreatment system of  claim 1 , wherein the oxygen storage capacity material comprises ceria. 
     
     
         9 . The exhaust aftertreatment system of  claim 1 , wherein the base metal is selected from the group consisting of iron, copper, manganese, chromium, cobalt, nickel, tin, and mixtures thereof. 
     
     
         10 . The exhaust aftertreatment system of  claim 1 , wherein the noble metal is selected from the group consisting of platinum, palladium, rhodium, and mixtures thereof. 
     
     
         11 . The exhaust aftertreatment system of  claim 1 , wherein the zeolite is selected from the group consisting of a beta zeolite, a faujasite, an L-zeolite, a ZSM zeolite, an SSZ-zeolite, a mordenite, a chabazite, an offretite, an erionite, a clinoptilolite, a silicalite, an aluminum phosphate zeolite, a mesoporous zeolite, a metal-incorporated zeolite, and mixtures thereof. 
     
     
         12 . The exhaust aftertreatment system of  claim 1 , wherein the supported platinum group metal catalyst of the low-temperature NOx adsorber comprises one or more platinum group metals and one or more inorganic oxide carriers. 
     
     
         13 . The exhaust aftertreatment system of  claim 12 , wherein the one or more platinum group metals is selected from the group consisting of platinum, palladium, rhodium, iridium, and mixtures thereof. 
     
     
         14 . The exhaust aftertreatment system of  claim 12 , wherein the one or more inorganic oxide carriers is selected from the group consisting of alumina, silica, titania, zirconia, ceria, niobia, tantalum oxides, molybdenum oxides, tungsten oxides, and mixed oxides or composite oxides thereof. 
     
     
         15 . An exhaust aftertreatment system configured to purify an exhaust gas feedstream from an internal combustion engine disposed to operate at a lean air/fuel ratio, wherein the internal combustion engine includes a forced air induction device, the exhaust aftertreatment system comprising:
 an oxidation catalyst, a low-temperature NOx adsorber, and a selective catalytic reduction device;   wherein the oxidation catalyst is configured to be disposed in a close-coupled configuration in relation to the internal combustion engine;   wherein the forced air induction device is disposed downstream of the oxidation catalyst;   wherein the low-temperature NOx adsorber is disposed downstream of the forced air induction device;   wherein the selective catalytic reduction device is disposed downstream of the low-temperature NOx adsorber;   wherein the oxidation catalyst comprises a zeolite catalyst including a base metal, a noble metal, and a zeolite disposed on a substrate; and   wherein the low-temperature NOx adsorber comprises a zeolite catalyst and a supported platinum group metal catalyst.   
     
     
         16 . A method for purifying an exhaust gas feedstream from a compression-ignition internal combustion engine, comprising:
 installing, in a close-coupled configuration in relation to the internal combustion engine, an oxidation catalyst upstream of a low-temperature NOx adsorber;   wherein the oxidation catalyst comprises a zeolite catalyst including a base metal, a noble metal, and a zeolite disposed on a substrate; and   wherein the low-temperature NOx adsorber comprises a zeolite catalyst and a supported platinum group metal catalyst.   
     
     
         17 . The method of  claim 16 , wherein the oxidation catalyst further comprises an oxygen storage capacity material disposed on the substrate. 
     
     
         18 . The method of  claim 17 , wherein the oxygen storage capacity material comprises ceria.