초록 ▼

Catalysts and catalytic articles for treating exhaust gas streams are described. In one or more embodiments, a catalyst system includes a first zone to abate nitrogen oxides by selective catalytic reduction, a second zone to oxidize ammonia and a third zone to oxidize carbon monoxide and hydrocarbon

Catalysts and catalytic articles for treating exhaust gas streams are described. In one or more embodiments, a catalyst system includes a first zone to abate nitrogen oxides by selective catalytic reduction, a second zone to oxidize ammonia and a third zone to oxidize carbon monoxide and hydrocarbons. Methods for treating the exhaust gas stream are also provided. Methods of making and using such catalysts and catalytic articles are also described.

대표청구항 ▼

1. A catalytic article for treating an exhaust gas stream containing particulate matter, hydrocarbons, CO and ammonia, the article comprising: a substrate having an inlet end and an outlet end defining an axial length;a first catalyst coating including a platinum group metal, the first catalyst coat

1. A catalytic article for treating an exhaust gas stream containing particulate matter, hydrocarbons, CO and ammonia, the article comprising: a substrate having an inlet end and an outlet end defining an axial length;a first catalyst coating including a platinum group metal, the first catalyst coating extending from the outlet end toward the inlet end over less than the entire axial length of the substrate; anda second catalyst coating including a catalyst for selective catalytic reduction (SCR) of nitrogen oxides, the second catalyst coating extending from the inlet end toward the outlet end over less than the entire axial length of the substrate and overlapping a portion of the first catalyst coating. 2. The catalytic article of claim 1, wherein the substrate is a flow-through substrate having a plurality of longitudinally extending passages formed by longitudinally extending walls bounding and defining said passages, and the platinum group metal is directly supported on the substrate walls. 3. The catalytic article of claim 2, wherein at least a portion of the platinum group metal is on a particulate refractory oxide support. 4. The catalytic article of claim 1, wherein the substrate is a wall-flow filter having gas permeable walls formed into a plurality of axially extending channels, each channel having one end plugged with any pair of adjacent channels plugged at opposite ends thereof, and the platinum group metal is directly supported on the substrate walls. 5. The catalytic article of claim 1, wherein the platinum group metal is platinum. 6. The catalytic article of claim 1, wherein the first catalyst coating and second catalyst coating overlap to form three zones, a first zone to remove NOx by selective catalytic reduction, a second zone to oxidize ammonia and a third zone to oxidize carbon monoxide and hydrocarbons. 7. The catalytic article of claim 6, wherein each of the three zones individually occupies in the range of about 10 to about 80% of the axial length of the substrate. 8. An emissions treatment system comprising: a diesel engine emitting an exhaust stream including particulate matter, NOx and carbon monoxide;a first substrate selected from the group consisting of a wall-flow substrate and a flow-through substrate; andthe first substrate having an inlet end and an outlet end defining an axial length positioned downstream of and in flow communication with the diesel engine, the substrate having a first catalyst coating including a platinum group metal, the first catalyst coating extending from the outlet end toward the inlet end over less than the entire axial length of the substrate, and a second catalyst coating including a catalyst for selective catalytic reduction (SCR) of nitrogen oxides, the second catalyst coating extending from the inlet end toward the outlet end over less than the entire axial length of the substrate and overlapping a portion of the first catalyst coating layer. 9. The emissions treatment system of claim 8, wherein at least a portion of the platinum group metal is on refractory metal oxide support. 10. The emissions treatment system of claim 8, wherein the platinum group metal is platinum. 11. The emissions treatment system of claim 8, wherein there is an upstream substrate coated with a catalyst for selective catalytic reduction of nitrogen oxides disposed in flow communication with the exhaust stream and between the diesel engine and the first substrate. 12. The emissions treatment system of claim 11, wherein the upstream substrate comprises a wall flow filter substrate having gas permeable walls formed into a plurality of axially extending channels, each channel having one end plugged with any pair of adjacent channels plugged at opposite ends thereof, and the first substrate comprises a honeycomb flow through substrate and the first catalyst and second catalyst overlap to form three zones, a first zone to abate nitrogen oxides by selective catalytic reduction, a second zone to oxidize ammonia and a third zone to oxidize carbon monoxide and hydrocarbons, and at least a portion of the platinum group metal is on a particulate refractory oxide support. 13. The emissions treatment system of claim 11, the first catalyst and second catalyst overlap to form three zones, a first zone to abate nitrogen oxides by selective catalytic reduction, a second zone to oxidize ammonia and a third zone to oxidize carbon monoxide and hydrocarbons, and the platinum group metal is directly supported on the substrate walls in the first zone and the third zone. 14. The emissions treatment system of claim 11, wherein the first substrate is a wall flow filter substrate having gas permeable walls formed into a plurality of axially extending channels, each channel having one end plugged with any pair of adjacent channels plugged at opposite ends thereof. 15. The emissions treatment system of claim 8, wherein there is a wall flow filter substrate having gas permeable walls formed into a plurality of axially extending channels, each channel having one end plugged with any pair of adjacent channels plugged at opposite ends thereof coated with a hydrocarbon or CO oxidation catalyst disposed in flow communication with the exhaust stream and between the diesel engine and the porous substrate, and the first catalyst and second catalyst overlap to form three zones, a first zone to abate nitrogen oxides by selective catalytic reduction, a second zone to oxidize ammonia and a third zone to oxidize carbon monoxide and hydrocarbons and at least a portion of the platinum group metal is on a particulate refractory oxide support.