High temperature ammonia SCR catalyst and method of using the catalyst
First Claim
1. A catalyst for selective catalytic reduction of nitrogen oxides with ammonia at exhaust temperatures greater than about 300°
- C., the catalyst comprising;
a first component comprising a zeolite selected from the group consisting of ZSM-5, zeolite beta, and mixtures thereof, wherein the catalyst comprises about 40 to about 80 weight percent zeolite;
a second component comprising at least one member selected from the group consisting of cerium, iron, manganese, and mixtures thereof;
and about 30 to about 60 weight percent of an oxygen storage material, based on the entire catalyst composition, wherein the oxygen storage material composition comprises Ce1-c-dZrcLandO2, where Lan is one or more of Y, La, Pr, Nd, Sm, Eu, Gd, Ho, Yb, the weight percent of the oxygen storage material is on the basis of the oxides in the oxygen storage material;
optionally, an inorganic oxide component;
wherein the catalyst comprises about 5 to about 20 weight percent of the second component, where the weight percentage of the second component is calculated based on the total metal content relative to the total weight of the zeolite, oxygen storage material and any inorganic oxide.
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Abstract
A catalyst and a method for selectively reducing nitrogen oxides (“NOx”) with ammonia are provided. The catalyst includes a first component comprising a zeolite or mixture of zeolites selected from the group consisting of ZSM-5, ZSM-11, ZSM-12, ZSM-18, ZSM-23, MCM-zeolites, mordenite, faujasite, ferrierite, zeolite beta, and mixtures thereof; a second component comprising at least one member selected from the group consisting of cerium, iron, copper, gallium, manganese, chromium, cobalt, molybdenum, tin, rhenium, tantalum, osmium, barium, boron, calcium, strontium, potassium, vanadium, nickel, tungsten, an actinide, mixtures of actinides, a lanthanide, mixtures of lanthanides, and mixtures thereof; optionally an oxygen storage material and optionally an inorganic oxide. The catalyst selectively reduces nitrogen oxides to nitrogen with ammonia at high temperatures. The catalyst has high hydrothermal stability. The catalyst has high activity for conversion of low levels of nitrogen oxides in exhaust streams. The catalyst and the method may have special application to selective reduction of nitrogen oxides in exhaust gas from gas turbines and gas engines, although the catalyst and the method have broad application to a wide range of gas streams that have excess oxygen and high temperatures. The temperature of exhaust gas from gas turbines and gas engines is high. Both the high temperature and the low levels of inlet NOx are challenging for selective catalytic reduction (SCR) catalysts.
65 Citations
19 Claims
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1. A catalyst for selective catalytic reduction of nitrogen oxides with ammonia at exhaust temperatures greater than about 300°
- C., the catalyst comprising;
a first component comprising a zeolite selected from the group consisting of ZSM-5, zeolite beta, and mixtures thereof, wherein the catalyst comprises about 40 to about 80 weight percent zeolite; a second component comprising at least one member selected from the group consisting of cerium, iron, manganese, and mixtures thereof; and about 30 to about 60 weight percent of an oxygen storage material, based on the entire catalyst composition, wherein the oxygen storage material composition comprises Ce1-c-dZrcLandO2, where Lan is one or more of Y, La, Pr, Nd, Sm, Eu, Gd, Ho, Yb, the weight percent of the oxygen storage material is on the basis of the oxides in the oxygen storage material; optionally, an inorganic oxide component; wherein the catalyst comprises about 5 to about 20 weight percent of the second component, where the weight percentage of the second component is calculated based on the total metal content relative to the total weight of the zeolite, oxygen storage material and any inorganic oxide. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19)
- C., the catalyst comprising;
Specification