System and method for inhibiting uncontrolled regeneration of a particulate filter for an internal combustion engine

Abstract

A NOx adsorber catalyst may comprise a housing defining an inlet configured to receive exhaust gas produced by an internal combustion engine, an outlet and a chamber between the inlet and the outlet. A NOx adsorber element may be positioned in the chamber adjacent to the inlet. The NOx adsorber element may be configured to trap NOx in the exhaust gas during lean fuel operation of the engine, and to release the trapped NOx and reduce the released NOx to nitrogen during rich fuel operation of the engine. A hydrocarbon trap may be positioned in the chamber between the NOx adsorber element and the outlet. The hydrocarbon trap may be configured to trap hydrocarbons that travel through the NOx adsorber element during the rich fuel operation of the engine. The trapped hydrocarbons may be oxidized by oxygen present in the exhaust gas during lean fuel operation following rich fuel operation.

1 . A NOx adsorber catalyst comprising:
 a housing defining an inlet at one end configured to receive exhaust gas produced by an internal combustion engine, an outlet at an opposite end and a chamber between the inlet and the outlet,   a NOx adsorber element positioned in the chamber adjacent to the inlet of the housing, the NOx adsorber element configured to trap NOx in the exhaust gas during lean fuel operation of the engine, and to release the trapped NOx and reduce the released NOx to nitrogen during rich fuel operation of the engine, and   a hydrocarbon trap positioned in the chamber between the NOx adsorber element and the outlet of the housing, the hydrocarbon trap configured to trap hydrocarbons that travel through the NOx adsorber element during the rich fuel operation of the engine,   wherein the trapped hydrocarbons are oxidized by oxygen present in the exhaust gas during lean fuel operation of the engine following rich fuel operation.   
   
   
       2 . The NOx adsorber catalyst of  claim 1  wherein the hydrocarbon trap is integral with the NOx adsorber element. 
   
   
       3 . The NOx adsorber catalyst of  claim 1  wherein the hydrocarbon trap is attached to the NOx adsorber element. 
   
   
       4 . The NOx adsorber catalyst of  claim 1  wherein the hydrocarbon trap is spaced apart from the NOx adsorber element within the chamber of the housing. 
   
   
       5 . The NOx adsorber catalyst of  claim 1  wherein the hydrocarbon trap comprises a substrate wash-coated with a zeolite-containing material. 
   
   
       6 . A NOx adsorber catalyst comprising:
 a housing defining an inlet at one end configured to receive exhaust gas produced by an internal combustion engine, an outlet at an opposite end and a chamber between the inlet and the outlet,   a NOx adsorber element positioned in the chamber, the NOx adsorber element including a first portion adjacent to the inlet of the housing and configured to trap NOx in the exhaust gas during lean fuel operation of the engine, and to release the trapped NOx and reduce the released NOx to nitrogen during rich fuel operation of the engine, and a second portion integral with the first portion with the first portion positioned between the inlet of the housing and the second portion, the second portion configured to trap hydrocarbons that travel through the first portion during the rich fuel operation of the engine,   wherein the trapped hydrocarbons are oxidized by oxygen present in the exhaust gas during lean fuel operation of the engine following rich fuel operation.   
   
   
       7 . A NOx adsorber catalyst comprising:
 a housing defining an inlet at one end configured to receive exhaust gas produced by an internal combustion engine, an outlet at an opposite end and a chamber between the inlet and the outlet,   a NOx adsorber element positioned in the chamber adjacent to the inlet of the housing, the NOx adsorber element configured to trap NOx in the exhaust gas during lean fuel operation of the engine, and to release the trapped NOx and reduce the released NOx to nitrogen during rich fuel operation of the engine, and a hydrocarbon trap separate from the NOx adsorber element and positioned in the chamber between the NOx adsorber element and the outlet of the housing, the hydrocarbon trap configured to trap hydrocarbons that travel through the NOx adsorber element during the rich fuel operation of the engine,   wherein the trapped hydrocarbons are oxidized by oxygen present in the exhaust gas during lean fuel operation of the engine following rich fuel operation.   
   
   
       8 . The NOx adsorber catalyst of  claim 7  wherein the hydrocarbon trap is attached to the NOx adsorber element. 
   
   
       9 . The NOx adsorber catalyst of  claim 7  wherein the hydrocarbon trap is spaced apart from the NOx adsorber element within the chamber of the housing. 
   
   
       10 . A system for processing NOx present in exhaust gas produced by an internal combustion engine, comprising:
 a NOx adsorber catalyst having housing defining an inlet at one end that is configured to receive the exhaust gas, an outlet at an opposite end and a chamber between the inlet and the outlet, a NOx adsorber element positioned in the chamber adjacent to the inlet of the housing, the NOx adsorber element configured to trap NOx in the exhaust gas during lean fuel operation of the engine, and to release the trapped NOx and reduce the released NOx to nitrogen during rich fuel operation of the engine, and a hydrocarbon trap positioned in the chamber between the NOx adsorber element and the outlet of the housing, the hydrocarbon trap configured to trap hydrocarbons that travel through the NOx adsorber element during the rich fuel operation of the engine,   a fuel system configured to supply fuel to the engine, and   a control circuit including a memory having stored therein a set of instructions that are executable by the control circuit to control the fuel system to normally supply fuel for lean fuel operation of the engine, and to control the fuel system to supply fuel for alternate rich fuel operation of the engine and lean fuel operation of the engine to regenerate the NOx adsorber,   wherein the hydrocarbons trapped in the hydrocarbon trap are oxidized by oxygen present in the exhaust gas during lean fuel operation of the engine following rich fuel operation.   
   
   
       11 . The system of  claim 10  further comprising an oxidation catalyst positioned between the engine and the NOx adsorber,
 wherein the instructions stored in the memory include instructions that are executable by the control circuit to control the fuel system to introduce hydrocarbons in the form of unburned or partially burned fuel into the exhaust gas during regeneration of the NOx adsorber, the oxidation catalyst reacting with the introduced hydrocarbons to heat the exhaust gas supplied to the NOx adsorber to an elevated temperature suitable for regeneration of the NOx adsorber.   
   
   
       12 . The system of  claim 10  wherein the hydrocarbon trap is integral with the NOx adsorber element. 
   
   
       13 . The system of  claim 10  wherein the hydrocarbon trap is attached to the NOx adsorber element. 
   
   
       14 . The system of  claim 1  wherein the hydrocarbon trap is spaced apart from the NOx adsorber element within the chamber of the housing. 
   
   
       15 . The system of  claim 10  wherein the hydrocarbon trap comprises a substrate wash-coated with a zeolite-containing material. 
   
   
       16 . The system of  claim 10  further comprising an oxygen sensor configured to produce an oxygen signal corresponding to an oxygen concentration of exhaust gas exiting the NOx adsorber catalyst,
 wherein the instructions stored in the memory include instructions that are executable by the control circuit to control the fuel system to supply fuel for alternate rich fuel operation of the engine and lean fuel operation of the engine to regenerate the NOx adsorber according to a closed-loop control strategy as a function of the oxygen concentration of exhaust gas exiting the NOx adsorber catalyst.   
   
   
       17 . The system of  claim 16  further comprising means for determining an oxygen concentration of exhaust gas entering the NOx adsorber catalyst,
 wherein the instructions stored in the memory include instructions that are executable by the control circuit to control the fuel system to supply fuel for alternate rich fuel operation of the engine and lean fuel operation of the engine to regenerate the NOx adsorber according to the closed-loop control strategy further as a function of the oxygen concentration of exhaust gas entering the NOx adsorber catalyst.