Manganese-containing diesel oxidation catalyst
An oxidation catalyst composite, methods, and systems for the treatment of exhaust gas emissions from a diesel engine are described. More particularly, an oxidation catalyst composite including a first washcoat comprising a zeolite, Pt, and first refractory metal oxide support containing manganese, a second washcoat comprising a second refractory metal oxide support, a Pt component and a Pd component, and a third washcoat comprising palladium and a rare earth oxide component is described.
1. An oxidation catalyst composite for an abatement of exhaust gas emissions from a lean burn engine comprising:
a carrier substrate having a length, an inlet end and an outlet end, an oxidation catalyst catalytic material on the carrier, the oxidation catalyst catalytic material comprising:
a first washcoat including a zeolite, platinum (Pt), and a first refractory metal oxide support containing a manganese (Mn), wherein the Mn is present either in a form of surface dispersed Mn on the first refractory metal oxide or in a form of discrete manganese oxide particles on the first refractory metal oxide support, wherein the Mn content of the first washcoat is in a range of 0.1% to 20% by weight and wherein the manganese is doped with Fe, Ni, Co, Cu, Ce, Sn, Ir, In, or a combination thereof;
a second washcoat including a second refractory metal oxide support, a platinum (Pt) component and a palladium (Pd) component in a ratio of Pt:Pd in a range of about 10:1 to 1:10; and
a third washcoat comprising palladium and a rare earth oxide component, the third washcoat being substantially free of a platinum;
wherein the oxidation catalyst composite is effective to abate hydrocarbon and carbon monoxide, and to oxidize nitrogen monoxide (NO) to nitrogen dioxide (NO 2 ) in the lean burn engine exhaust.
2. The oxidation catalyst composite of claim 1 , wherein the first washcoat further optionally comprises a palladium component, and the Pt:Pd ratio of the first washcoat is in a range of 1:0 to 10:1.
3. The oxidation catalyst composite of claim 2 , wherein the palladium component is present in an amount in a range of about 0.1 g/ft 3 to about 10 g/ft 3 .
4. The oxidation catalyst composite of claim 1 , wherein the first washcoat is substantially free of a palladium.
5. The oxidation catalyst composite of claim 1 , wherein the Mn is derived from a soluble Mn species or from bulk Mn oxides.
6. The oxidation catalyst composite of claim 1 , wherein the first washcoat comprises the Pt component in an amount in a range of about 10 g/ft 3 to 100 g/ft 3 .
7. The oxidation catalyst composite of claim 1 , wherein the first washcoat comprises a hydrothermally stable zeolite in the form of 6 to 12 member ring structures selected from ZSM-5, beta, mordenite, Y zeolite, chabazite, ferrierite, or combinations thereof.
8. The oxidation catalyst composite of claim 1 , wherein the second refractory metal oxide support comprises an oxide of alumina, silica, zirconia, titania, ceria, or combinations thereof.
9. The oxidation catalyst composite of claim 1 , wherein the first washcoat is substantially free of barium, and the second washcoat is substantially free of zeolite.
10. The oxidation catalyst composite of claim 1 , wherein the third washcoat comprises the rare earth oxide component selected from Ce, Nd, Y, Pr, Zr, La, or combinations thereof.
11. The oxidation catalyst composite of claim 1 , wherein the first, second and third washcoats of the oxidation catalyst can be layered or zoned on a flow-through monolith substrate in any combination.
12. The oxidation catalyst composite of claim 1 , wherein the carrier substrate comprises a flow-through monolith.
13. A method for treating a diesel engine exhaust gas stream, the method comprising contacting the diesel exhaust gas stream with the oxidation catalyst composite of claim 1 .
14. The method of claim 13 , further comprising passing the diesel exhaust gas stream to a selective catalyst reduction (SCR) catalyst composition immediately downstream from the oxidation catalyst.
15. A system for treatment of a lean burn engine exhaust gas stream including hydrocarbons, carbon monoxide, and other exhaust components, the system comprising:
an exhaust conduit in fluid communication with the lean burn engine via an exhaust manifold;
the oxidation catalyst composite of claim 1 , wherein the carrier substrate is a flow through substrate; and
a catalyzed soot filter and a selective catalytic reduction (SCR) catalyst located downstream from the oxidation catalyst.
16. The system of claim 15 , wherein the SCR catalyst is coated onto the catalyzed soot filter.
17. The system of claim 15 , wherein the SCR catalyst is on the flow through substrate immediately downstream from the oxidation catalyst composite and the catalyzed soot filter is downstream from the SCR catalyst.