Catalyst blends

Abstract

Provided is a catalyst for the selective reduction of NOx comprising a two molecular sieve materials having a CHA structure, wherein the first molecular sieve has a mean crystal size of about 0.01 to 1 μm and the second molecular sieve has a mean crystal size of about 1-5 μm, and wherein the first molecular sieve contains a first extra-framework metal, the second molecular sieve contains a second extra-framework metal, and wherein said first and second extra-framework metals are independently selected from the group consisting of cesium, copper, nickel, zinc, iron, tin, tungsten, molybdenum, cobalt, bismuth, titanium, zirconium, antimony, manganese, chromium, vanadium, niobium, and combinations thereof.

What is claimed is: 
     
         1 . A catalyst composition comprising a blend of two molecular sieve materials each having a CHA structure, wherein the first molecular sieve has a first silica-to-alumina ratio (SAR) of about 10-25 and contains a first extra-framework metal, the second molecular sieve has second SAR of about 20-35 and contains a second extra-framework metal, and wherein said first and second SAR are different and said first and second extra-framework metals are independently selected from the group consisting of cesium, copper, nickel, zinc, iron, tin, tungsten, molybdenum, cobalt, bismuth, titanium, zirconium, antimony, manganese, chromium, vanadium, niobium, and combinations thereof,
 and wherein at least one of the first and second extra-framework metals comprises manganese.   
     
     
         2 . The catalyst of  claim 1 , wherein the two molecular sieve materials are aluminosilicates. 
     
     
         3 . The catalyst of  claim 1 , wherein said first and second extra-framework metals are independently selected from the group consisting of copper, iron, and manganese, and wherein at least one of the first and second extra-framework metals comprises manganese. 
     
     
         4 . The catalyst of  claim 1 , wherein at least one of the first molecular sieve and the second molecular sieve is an extrudate. 
     
     
         5 . The catalyst of  claim 1 , wherein the first extra-framework metal is present in an amount of about 1 to about 5 wt % based on the total weight of the molecular sieve, and the second extra-framework metal is present in amount sufficient to achieve a weight ratio of the first extra-framework metal and the second extra-framework metal of about 0.4:1.0 to about 1.5:1.0. 
     
     
         6 . The catalyst of  claim 1 , wherein the first molecular sieve and the second molecular sieve are present in a mole ratio of about 0.5:1:0 to about 1.5:1.0. 
     
     
         7 . The catalyst of  claim 1 , wherein the catalyst composition is washcoated on a wall-flow filter. 
     
     
         8 . The catalyst of  claim 7 , wherein the filter contains inlet and outlet channels and the washcoat is on outlet channels. 
     
     
         9 . The catalyst of  claim 1 , wherein the catalyst composition is washcoated on a flow-through honeycomb monolith. 
     
     
         10 . The catalyst of  claim 9 , wherein the flow-through honeycomb monolith further comprises an oxidative underlayer. 
     
     
         11 . The catalyst of  claim 10 , wherein said underlayer comprises a platinum group metal. 
     
     
         12 . The catalyst of  claim 7 , further comprising an ammonia oxidation catalyst disposed downstream of the wall-flow filter. 
     
     
         13 . The catalyst of  claim 9 , further comprising an ammonia oxidation catalyst disposed downstream of the flow-through honeycomb monolith. 
     
     
         14 . The catalyst of  claim 7 , further comprising a NO x  adsorber catalyst (NAC), a lean NO x  trap (LNT), or a NO x  storage/reduction catalyst (NSRC) located upstream of the wall-flow filter. 
     
     
         15 . The catalyst of  claim 7 , further comprising an oxidation zone comprising a platinum group metal. 
     
     
         16 . The catalyst of  claim 15 , wherein the platinum group metal comprises Pd and/or Pt. 
     
     
         17 . A catalyst composition comprising a blend of two molecular sieve materials having a CHA structure, wherein the first molecular sieve has a mean crystal size of about 0.01 to 1 μm and the second molecular sieve has a mean crystal size of about 1-5 μm, and wherein the first molecular sieve contains a first extra-framework metal, the second molecular sieve contains a second extra-framework metal, and wherein said first and second extra-framework metals are independently selected from the group consisting of cesium, copper, nickel, zinc, iron, tin, tungsten, molybdenum, cobalt, bismuth, titanium, zirconium, antimony, manganese, chromium, vanadium, niobium, and combinations thereof, and wherein at least one of the first and second extra-framework metals comprises manganese. 
     
     
         18 . The catalyst of  claim 17 , wherein said first and second extra-framework metals are independently selected from the group consisting of copper, iron, and manganese, and wherein at least one of the first and second extra-framework metals comprises manganese. 
     
     
         19 . A catalyst composition comprising a blend of an aluminosilicate molecular sieve having a CHA framework and a silicoaluminophosphate molecular sieve having a CHA framework, wherein
 a. the aluminosilicate molecular sieve and the silicoaluminophosphate molecular sieve are present an aluminosilicate:silicoaluminophosphate mole ratio of about 0.8:1.0 to about 1.2:1.0; and   b. said aluminosilicate molecular sieve contains a first extra-framework metal, said silicoaluminophosphate molecular sieve contains a second extra-framework metal, wherein said first and second extra-framework metals are independently selected from the group consisting of cesium, copper, nickel, zinc, iron, tin, tungsten, molybdenum, cobalt, bismuth, titanium, zirconium, antimony, manganese, chromium, vanadium, niobium, and combinations thereof, wherein said first extra-framework metal is present in about 2 to about 4 weight percent, based on the weight of the aluminosilicate, and wherein the weight ratio of said first extra-framework metal and said second extra-framework metal is about 0.4:1.0 to about 1.5:1.0,   and wherein at least one of the first and second extra-framework metals comprises manganese.   
     
     
         20 . The catalyst of  claim 19 , wherein said first and second extra-framework metals are independently selected from the group consisting of copper, iron, and manganese, and wherein at least one of the first and second extra-framework metals comprises manganese.