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Provided is a diesel oxidation catalyst for the treatment of exhaust gas emissions from a diesel engine and a method for treating a diesel exhaust gas stream, the method comprising providing a diesel oxidation catalyst and contacting said diesel exhaust gas stream with said diesel oxidation catalyst

Provided is a diesel oxidation catalyst for the treatment of exhaust gas emissions from a diesel engine and a method for treating a diesel exhaust gas stream, the method comprising providing a diesel oxidation catalyst and contacting said diesel exhaust gas stream with said diesel oxidation catalyst for the treatment of exhaust gas emissions. More particularly, the present invention is directed to a catalyst structure comprising three distinct layers; in which layer comprises a precious metal component such as palladium is located between two hydrocarbon storage layers comprising a molecular sieve such as a zeolite.

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1. A layered diesel oxidation catalyst composite for the treatment of exhaust gas emissions from a diesel engine comprising: (a) a carrier substrate;(b) a bottom layer coated on said carrier substrate comprising at least one first molecular sieve;(c) a middle layer coated over said bottom layer comp

1. A layered diesel oxidation catalyst composite for the treatment of exhaust gas emissions from a diesel engine comprising: (a) a carrier substrate;(b) a bottom layer coated on said carrier substrate comprising at least one first molecular sieve;(c) a middle layer coated over said bottom layer comprising at least one precious metal component on a refractory metal oxide support and being substantially free of a molecular sieve; and(d) a top layer coated over said middle layer comprising at least one second molecular sieve. 2. The layered diesel oxidation catalyst composite of claim 1, wherein the precious metal component comprises Pt, Pd, or both. 3. The layered diesel oxidation catalyst composite of claim 1, wherein the refractory metal oxide support of the middle layer comprises a compound that is activated, stabilized, or both selected from the group consisting of alumina, zirconia, silica, titania, silica-alumina, zirconia-alumina, titania-alumina, lanthana-alumina, lanthana-zirconia-alumina, baria-alumina, baria-lanthana-alumina, baria-lanthana-neodymia-alumina, zirconia-silica, titania-silica, and zirconia-titania. 4. The layered diesel oxidation catalyst composite of claim 1, wherein the first molecular sieve, the second molecular sieve, or both each independently has a pore size from 0.3 to 1.0 nm. 5. The layered diesel oxidation catalyst composite of claim 1, wherein the first molecular sieve, the second molecular sieve, or both each independently comprises a zeolite. 6. The layered diesel oxidation catalyst composite of claim 1, wherein the bottom layer, the top layer, or both each independently further comprises a refractory metal oxide support. 7. The layered diesel oxidation catalyst composite of claim 1, wherein the bottom layer, the top layer, or both additionally comprises a precious metal component. 8. The layered diesel oxidation catalyst composite of claim 1, wherein: the bottom layer comprises a first zeolite, activated gamma-alumina, and a platinum component;the middle layer comprises activated gamma alumina, a platinum component, and a palladium component, and is substantially free of a zeolite; andthe top layer comprises a second zeolite, activated gamma-alumina, and a platinum component. 9. The layered diesel oxidation catalyst composite of claim 8, wherein the bottom layer and the top layer are both substantially free of palladium. 10. The layered diesel oxidation catalyst composite of claim 8, wherein the activated gamma alumina of the middle layer has a surface area in the range of 80 to 200 m2/g, a pore volume in the range of 0.6 to 1.0 cm3/g, and an average pore diameter in the range of 70 Å to 150 Å, and wherein the first zeolite and the second zeolite both comprise a beta zeolite. 11. The layered diesel oxidation catalyst composite of claim 1 having a total precious metal component loading in an amount in the range of 15 to 225 g/ft3 (0.53 to 7.95 kg/m3). 12. A method of treating a gaseous exhaust stream of a diesel engine, the exhaust stream including hydrocarbons, carbon monoxide, and other exhaust gas components, the method comprising: contacting the exhaust stream with the layered diesel oxidation catalyst composites of claim 1. 13. The method of claim 12, wherein the catalytic material further comprises the palladium component in an amount in the range of 5 to 75 g/ft3 (0.18 to 2.65 kg/m3) and a platinum component, in the range from 10 g/ft3 to 150 g/ft3 (0.35 to 5.30 kg/m3), an amount of up to 10% by weight of the platinum component being incorporated into the at least one molecular sieve, and an amount of at least 90% by weight of the platinum component being on the high surface area, refractory metal oxide support of the palladium-containing layer. 14. The method of claim 13, further comprising directing the diesel exhaust gas stream one or more to a soot filter located downstream of the diesel oxidation catalyst composite and a selective catalytic reduction (SCR) catalytic article located upstream or downstream of the catalyzed soot filter (CSF). 15. A system for treatment of a diesel engine exhaust stream including hydrocarbons, carbon monoxide, and other exhaust gas components, the emission treatment system comprising: an exhaust conduit in fluid communication with the diesel engine via an exhaust manifold;the diesel oxidation catalyst composite of claim 1 wherein the carrier is a flow through substrate or a wall-flow substrate; andone or more of the following in fluid communication with the composite: a soot filter, a selective catalytic reduction (SCR) catalytic article and a NOx storage and reduction (NSR) catalytic article.