Layered diesel oxidation catalyst composites

1. A layered diesel oxidation catalyst composite comprising:

a diesel oxidation catalytic material on a carrier, the catalytic material comprising a palladium component in an amount in the range of 5 to 75 g/ft 3 (0.18 to 2.65 kg/m 3 ) and at least two layers:

a hydrocarbon trap layer comprising at least one molecular sieve, the hydrocarbon trap layer being substantially free of palladium; and

a palladium-containing layer that comprises the palladium component, and is substantially free of a molecular sieve, wherein the palladium component is located on a high surface area, porous refractory metal oxide support, wherein the high surface area, porous refractory metal oxide support comprises alumina having a pore volume in the range of 0.5 to 1.5 cm 3 /g and an average pore diameter of at least 75 Å.

2. The layered catalyst composite of claim 1 , wherein the catalytic material further comprises a platinum component, in the range of 10 g/ft 3 to 150 g/ft 3 (0.35 to 5.30 kg/m 3 ), an amount of up to 20% by weight of the platinum component being incorporated into the at least one molecular sieve, and an amount of at least 80% by weight of the platinum component being on the high surface area, porous refractory metal oxide support of the palladium-containing layer.

3. The layered catalyst composite of claim 1 , wherein the high surface area, porous refractory metal oxide support 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 catalyst composite of claim 1 , wherein the average pore diameter in the range of 75 Å to 150 Å.

5. The layered catalyst composite of claim 1 , wherein the molecular sieve comprises a zeolite that comprises a beta-zeolite, ZSM-5, zeolite-Y or combinations thereof.

6. The layered catalyst composite of claim 5 , wherein the zeolite comprises a silica to alumina ratio in the range of 20:1 to 1000:1.

7. The layered catalyst composite of claim 5 , wherein the high surface area, porous refractory metal oxide support comprises alumina having a surface area in the range of 80 to 200 m 2 /g, a pore volume in the range of 0.6 to 1.0 cm 3 /g, and an average pore diameter in the range of 70 Å to 150 Å, and wherein the zeolite comprises a beta zeolite into which the amount of at least 10% by weight of the platinum component is incorporated.

8. The layered catalyst composite of claim 1 having a total precious metal component loading in an amount in the range of 15 to 225 g/ft 3 (0.53 to 7.95 kg/m 3 ).

9. 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 diesel oxidation catalyst composites of claim 1 .

10. The method of claim 9 , wherein the catalytic material further comprises a platinum component, in the range from 10 g/ft 3 to 150 g/ft 3 (0.35 to 5.30 kg/m 3 ), 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, porous refractory metal oxide support of the palladium-containing layer.

11. The method of claim 10 , wherein the high surface area, porous refractory metal oxide support comprises alumina having a surface area in the range of 60 to 200 m 2 /g, a pore volume in the range of 0.6 to 1.0 cm 3 /g, and an average pore diameter is in the range of 70 Å to 150 Å, and wherein the molecular sieve comprises a zeolite that comprises a beta zeolite into which the amount of at least 10% by weight of the platinum component is incorporated.

12. The method of claim 10 , 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).

13. 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; and

one 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.

14. A layered diesel oxidation catalyst composite comprising:

a diesel oxidation catalytic material on a carrier, the catalytic material comprising a palladium component in an amount in the range of 5 to 75 g/ft 3 (0.18 to 2.65 kg/m 3 ) and at least two layers:

a hydrocarbon trap layer comprising at least one molecular sieve, the hydrocarbon trap layer being substantially free of palladium; and

an undercoat layer located on the carrier and below the at least two layers, the undercoat layer comprising a high surface area refractory metal oxide.

15. A layered diesel oxidation catalyst composite comprising:

a diesel oxidation catalytic material on a carrier, the catalytic material comprising a palladium component in an amount in the range of 5 to 75 g/ft 3 (0.18 to 2.65 kg/m 3 ) and at least two layers:

a hydrocarbon trap layer comprising at least one molecular sieve, the hydrocarbon trap layer being substantially free of palladium; and

a palladium-containing layer that comprises the palladium component, and is substantially free of a molecular sieve, wherein the palladium-containing layer is located on the carrier and the hydrocarbon trap layer is located on the palladium-containing layer.

16. The layered catalyst of claim 15 , further comprising an undercoat layer wherein the palladium component in the catalytic material is present in the amount of about 40 g/ft 3 , the palladium-containing layer comprises 100% of the palladium component in the catalytic material and gamma alumina having a single point adsorption total pore volume about 0.85 cm 3 /g and an average BET pore diameter of about 100 Å, wherein the palladium-containing layer further comprises platinum, and the hydrocarbon trap layer comprises beta-zeolite, gamma alumina, and platinum.

17. A layered diesel oxidation catalyst composite comprising:

a diesel oxidation catalytic material on a carrier, the catalytic material comprising a palladium component in an amount in the range of 5 to 75 g/ft 3 (0.18 to 2.65 kg/m 3 ) and at least two layers:

a hydrocarbon trap layer comprising at least one molecular sieve, the hydrocarbon trap layer being substantially free of palladium; and

a palladium-containing layer that comprises the palladium component, and is substantially free of a molecular sieve, wherein the palladium component is located on a high surface area, porous refractory metal oxide support, wherein the high surface area, porous refractory metal oxide support comprises alumina having a surface area in the range of 80 to 200 m 2 /g, a pore volume in the range of 0.5 to 1.0 cm 3 /g, and an average pore diameter of at least 75 Å, wherein the molecular sieve comprises a zeolite and a platinum component, and wherein the zeolite comprises a beta zeolite into which the amount of at least 10% by weight of the platinum component is incorporated.

18. The layered catalyst of claim 17 , wherein the average pore diameter is in the range of 75 Å to 150 Å.