Zeolite promoted V/TiW catalysts
Provided is a catalyst composition for treating exhaust gas comprising a blend of a first component and second component, wherein the first component is an aluminosilicate or ferrosilicate molecular sieve component wherein the molecular sieve is either in H+ form or is ion exchanged with one or more transition metals, and the second component is a vanadium oxide supported on a metal oxide support selected from alumina, titania, zirconia, cella, silica, and combinations thereof. Also provided are methods, systems, and catalytic articles incorporating or utilizing such catalyst blends.
1. An SCR catalyst composition for treating exhaust gas, the SCR catalyst composition comprising a blend of a first component and second component,
wherein the first component is an Fe ion-exchanged aluminosilicate molecular sieve component having the MFI framework, and the second component is tungsten oxide supported on a titanium oxide support and mixed with vanadium oxide;
wherein the catalyst composition comprises about 15 to about 25 weight percent of the first component and about 75 to about 85 weight percent of the second component based on the total weight of catalytically active components in the blend.
2. The catalyst of claim 1 , wherein molecular sieve contains in a range of from about 1 to about 10 weight percent ion exchanged Fe.
3. The catalyst composition of claim 1 , wherein the second component further comprises iron vanadate.
4. The catalyst composition of claim 1 , wherein the blend comprises from about 0.5 to about 5 weight percent of the vanadium oxide based on the weight of the first and second components.
5. A catalytic washcoat comprising the catalyst composition of claim 1 , further comprising one or more filler, binder, processing aide, water, or dopant.
6. A catalytic article comprising a substrate coated with or incorporating the catalyst composition of claim 1 , wherein the substrate is a metal flow-through substrate, a ceramic flow-through substrate, a wall-flow filter, a sintered metal filter, a partial filter, or an extruded catalyst honeycomb.
7. A system for treating exhaust gas comprising a selective catalytic reduction (SCR) catalyst upstream of an ammonia slip catalyst (ASC), wherein said SCR catalyst comprises the catalyst composition of claim 1 .
8. The system of claim 7 , further comprising a diesel oxidation catalyst having a platinum group metal disposed upstream of said selective catalytic reduction catalyst.
9. A method for treating an exhaust gas comprising the steps of:
contacting an exhaust gas stream containing NOx and NH 3 in the presence of the catalyst of claim 1 ; and
converting at least a portion of said NOx to N 2 .
10. The method of claim 9 , wherein said exhaust gas comprises NO to NO 2 present in a ratio of NO to NO 2 ranging from about 4:1 to about 1:3 by volume.