NOx ADSORBER CATALYST

Abstract

A NOx adsorber catalyst and its use in an emission treatment system for internal combustion engines, is disclosed. The NOx adsorber catalyst comprises a first layer consisting essentially of a support material, one or more platinum group metals disposed on the support material, and a NOx storage material.

1 . A catalyst for treating emissions from a lean burn engine comprising a first layer having:
 a support material containing alumina or a mixed oxide containing alumina;   a mixture or alloy of platinum and palladium, and optionally one or more platinum group metals, disposed on the support material;   and a NOx storage material containing lanthanum-doped ceria.   
     
     
         2 . The catalyst of  claim 1 , wherein the NOx storage material comprises about 0.5-18 mol % lanthanum. 
     
     
         3 . The catalyst of  claim 1 , wherein the NOx storage material comprises about 1.0-15 mol % lanthanum. 
     
     
         4 . The catalyst of  claim 1 , wherein the NOx storage material comprises about 2.0-14 mol % lanthanum. 
     
     
         5 . The catalyst of  claim 1 , wherein the NOx storage material is substantially free of barium. 
     
     
         6 . The catalyst of  claim 1 , wherein the first layer is substantially free of rhodium. 
     
     
         7 . The catalyst of  claim 1 , wherein the first layer is substantially free of alkali metals. 
     
     
         8 . The catalyst of  claim 1 , wherein the first layer is substantially free of molecular sieves. 
     
     
         9 . The catalyst of  claim 1 , wherein the first layer is substantially free of dysprosium (Dy), erbium (Er), europium (Eu), gadolinium (Gd), holmium (Ho), lutetium (Lu), neodymium (Nd), praseodymium (Pr), promethium (Pm), samarium (Sm), scandium (Sc), terbium (Tb), thulium (Tm), ytterbium (Yb) and yttrium (Y). 
     
     
         10 . A catalyst article for absorbing NOx comprising a metal or ceramic substrate and a catalyst according to  claim 1 , wherein said catalyst is disposed on said substrate or is extruded to form said substrate. 
     
     
         11 . A catalyst article of  claim 10 , wherein the substrate is a flow-through monolith or a filter monolith. 
     
     
         12 - 17 . (canceled) 
     
     
         18 . An emission treatment system for treating a flow of a combustion exhaust gas comprising a lean-burn diesel engine and the catalyst of  claim 1 ;
 wherein the lean-burn engine is in fluid communication with the catalyst.   
     
     
         19 . The emission treatment system of  claim 18 , further comprising one or more of a selective catalytic reduction catalyst system, a particulate filter, a selective catalytic reduction filter system, a passive NOx adsorber, and a three-way catalyst system. 
     
     
         20 . A method of treating an exhaust gas from an internal combustion engine comprising contacting the exhaust gas with a catalyst according to  claim 1 , wherein the exhaust gas is at a temperature of about 180 to 300° C.