Methods Utilizing Non-Zeolitic Metal-Containing Molecular Sieves Having The CHA Crystal Structure

Abstract

Catalysts comprising metal-loaded non-zeolitic molecular sieves having the CHA crystal structure, including Cu-SAPO-34, and methods for treating exhaust gas incorporating such catalysts are disclosed. The catalysts can be used to remove nitrogen oxides from a gaseous medium across a broad temperature range and exhibit hydrothermal stability at high reaction temperatures.

1 - 19 . (canceled) 
     
     
         20 . A catalyst comprising:
 an ion-exchanged Cu-SAPO-34 non-zeolitic molecular sieve having a CHA crystal structure; wherein the Cu content of the Cu-SAPO-34 non-zeolitic molecular sieve on a CuO basis is in the range of about 1% to about 5% by weight;   wherein the Cu-SAPO-34 non-zeolitic molecular sieve has a BET surface area greater than 350 m 2 /g;   wherein the catalyst is effective to promote the reaction of ammonia with nitrogen oxides (NOx) to form nitrogen and H 2 O selectively in an exhaust gas stream at 200° C. when the catalyst has been deposited on a honeycomb substrate having a cell density of 400 cpsi at a loading between 2 and 2.5 g/in 3  and tested at a space velocity of 80,000 hr −1  where the feed stream comprises a mixture of 10% O 2 , 5% H 2 O, 500 ppm NO and 500 ppm NH 3  to provide at least 80% NOx conversion; and   wherein the catalyst is effective to make less than 5 ppm N 2 O over a temperature range of 200° C. to 450° C.   
     
     
         21 . The catalyst of  claim 20 , wherein the Cu-SAPO-34 non-zeolitic molecular sieve has a BET surface area in the range of 375 m 2 /g to 600 m 2 /g. 
     
     
         22 . The catalyst of  claim 20 , wherein the Cu-SAPO-34 non-zeolitic molecular sieve contains a secondary metal. 
     
     
         23 . The catalyst of  claim 22 , wherein the secondary metal comprises zirconium. 
     
     
         24 . The catalyst of  claim 20 , wherein the Cu content of the Cu-SAPO-34 non-zeolitic molecular sieve on a CuO basis is in the range of about 2% to 4 by weight. 
     
     
         25 . The catalyst of  claim 20 , wherein the catalyst is effective to provide at least about 85% NOx conversion in the exhaust gas stream at 200° C. 
     
     
         26 . The catalyst of  claim 20 , wherein the catalyst is effective to provide at least about 90% NOx conversion in the exhaust gas stream at 200° C. 
     
     
         27 . The catalyst of  claim 20 , wherein the Cu-SAPO-34 non-zeolitic molecular sieve, upon hydrothermal aging in 10% steam at 850° C. for 6 hours, retains at least 85% on a percentage basis of the NOx conversion at 200° C. 
     
     
         28 . The catalyst of  claim 20 , wherein the Cu-SAPO-34 non-zeolitic molecular sieve, upon hydrothermal aging in 10% steam at 900° C. and 1 hour, retains at least 90% of the NOx conversion on a percentage basis at 200° C. 
     
     
         29 . The catalyst of  claim 20 , wherein the Cu-SAPO-34 non-zeolitic molecular sieve, upon hydrothermal aging in 10% steam at 900° C. and 1 hour, retains at least 95% of the NOx conversion on a percentage basis at 200° C. 
     
     
         30 . The catalyst of  claim 20 , wherein the catalyst is effective to reduce NOx so that the exhaust gas stream contains a ratio of NOx to N 2 O after passing through the catalyst of greater than 2.5 
     
     
         31 . The catalyst of  claim 20 , wherein the catalyst is effective to reduce NOx so that the exhaust gas stream contains a ratio of NOx to N 2 O after passing through the catalyst of greater than 5. 
     
     
         32 . The catalyst of  claim 20 , wherein the Cu-SAPO-34 non-zeolitic molecular sieve is combined with a metal-containing zeolitic SCR catalyst. 
     
     
         33 . The catalyst of  claim 32 , wherein the metal-containing zeolitic SCR catalyst comprises a zeolite selected from beta zeolite, zeolite Y, and ZSM-5. 
     
     
         34 . The catalyst of  claim 32 , wherein the metal-containing zeolitic SCR catalyst comprises FeBeta. 
     
     
         35 . The catalyst of  claim 32 , wherein the Cu-SAPO-34 non-zeolitic molecular sieve is physically mixed with the metal-containing zeolitic SCR catalyst. 
     
     
         36 . A catalyst composite comprising the catalyst of  claim 20  deposited on a honeycomb substrate as a washcoat at a loading in the range of about 0.5 g/in 3  to 3.5 g/in 3 . 
     
     
         37 . The catalyst composite of  claim 36 , wherein the Cu-SAPO-34 non-zeolitic molecular sieve is in a separate washcoat from the metal-containing zeolitic SCR catalyst. 
     
     
         38 . The catalyst composite of  claim 36 , wherein the honeycomb substrate comprises a wall-flow substrate. 
     
     
         39 . The catalyst composite of  claim 36 , wherein the honeycomb substrate comprises a flow-through substrate. 
     
     
         40 . The catalyst composite of  claim 38 , wherein at least a portion of the wall-flow substrate is coated with a washcoat containing Pt and a metal-loaded non-zeolitic molecular sieve to oxidize ammonia in the exhaust gas stream. 
     
     
         41 . The catalyst composite of  claim 39 , wherein at least a portion of the flow-through substrate is coated with a washcoat containing Pt and a metal-loaded non-zeolitic molecular sieve to oxidize ammonia in the exhaust gas stream. 
     
     
         42 . An exhaust gas treatment system comprising an oxidation catalyst and the catalyst composite of  claim 36 .