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A NO x adsorber catalyst and its use in an emission treatment system for internal combustion engines, is disclosed. The NO x adsorber catalyst composition comprises a support material, one or more platinum group metals disposed on the support material, and a NO x storage material.
1. An emissions treatment system for treating a flow of a combustion exhaust gas that comprises a NO x adsorber catalyst in fluid communication with a lean burn engine, wherein the lean-burn engine is a diesel engine, and wherein the NO x adsorber catalyst has a first layer comprising:
a mixture or alloy of platinum and palladium on a support containing alumina or a composite or mixed oxide containing alumina; and
a NO x storage material consisting of neodymium-doped ceria; and
wherein the NO x adsorber catalyst is deposited directly on a metal or ceramic substrate.
2. The emissions treatment system as claimed in claim 1 , wherein the neodymium-doped ceria comprises about 0.5-18 mol % neodymium.
3. The emissions treatment system as claimed in claim 1 , wherein the support material is alumina, or a magnesia/alumina composite oxide or mixed oxide.
4. The emissions treatment system of claim 1 , wherein the first layer is substantially free of rhodium.
5. The emissions treatment system of claim 1 , wherein the first layer is substantially free of alkali metals.
6. The emissions treatment system of claim 1 , wherein the substrate is a flow-through monolith or a filter monolith.
7. The emissions treatment system of claim 4 , wherein the first layer contains no rhodium.
8. The emissions treatment system of claim 1 , further comprising an emissions control device downstream of the NO x adsorber catalyst.
9. The emissions treatment system of claim 8 , wherein the emissions control device is selected from a diesel particulate filter (DPF), a lean NOx trap (LNT), a lean NOx catalyst (LNC), a selective catalytic reduction (SCR) catalyst, a diesel oxidation catalyst (DOC), a catalysed soot filter (CSF), a selective catalytic reduction filter (SCRF™) catalyst, or an ammonia slip catalyst (ASC).
10. The emissions treatment system of claim 8 , wherein the emissions control device is a selective catalytic reduction (SCR) catalyst or a selective catalytic reduction filter (SCRF™) catalyst.
11. The emissions treatment system of claim 10 , further comprising an injector for injecting a nitrogenous reductant into exhaust gas downstream of the NOx adsorber catalyst and upstream of the SCR catalyst or the selective catalytic reduction filter (SCRF™) catalyst.