Copper Containing Levyne Molecular Sieve For Selective Reduction Of NOx

Abstract

Aspects of the present invention relates to a copper containing Levyne molecular sieve having a silica to alumina mole ratio less than 30 and a Cu:Al atomic ratio less than 0.45, wherein the Levyne molecular sieve retains at least 60% of its surface area after exposure to a temperature of from about 750° C. to about 950° C. in the present of up to 10 volume percent water vapor for a time ranging from about 1 to about 48 hours.

1 .- 20 . (canceled) 
     
     
         21 . A process for the preparation of a copper-containing Levyne molecular sieve having a silica to alumina mole ratio of from about 15 to about 26 and a Cu:Al atomic ratio of from about 0.20 to about 0.45, wherein copper acetate and/or an ammoniacal solution of copper ions is used as a copper source. 
     
     
         22 . The process of  claim 21 , wherein the silica to alumina mole ratio of the copper-containing Levyne molecular sieve is less than 23. 
     
     
         23 . The process of  claim 21 , wherein Cu content of the copper containing Levyne molecular sieve, calculated as CuO, is from about 2 to about 4 wt.-% based on the total weight of the calcined Levyne molecular sieve. 
     
     
         24 . The process of  claim 21 , wherein the Cu:Al atomic ratio of the copper containing Levyne molecular sieve is from about 0.2 to about 0.4. 
     
     
         25 . The process of  claim 21 , wherein the Levyne molecular sieve is ZSM-45. 
     
     
         26 . The process of  claim 21 , wherein the Levyne molecular sieve is a Nu-3. 
     
     
         27 . An exhaust gas treatment system comprising:
 an exhaust gas stream containing ammonia;   a catalyst comprising a copper-containing Levyne molecular sieve having a silica to alumina mole ratio of from about 15 to about 26 and a Cu:Al atomic ratio of from about 0.20 to about 0.45;   a catalyzed soot filter; and   a diesel oxidation catalyst.   
     
     
         28 . The system of  claim 27 , wherein the silica to alumina mole ratio of the copper-containing Levyne molecular sieve is less than 23. 
     
     
         29 . The system of  claim 27 , wherein Cu content of the copper containing Levyne molecular sieve, calculated as CuO, is from about 2 to about 4 wt.-% based on the total weight of the calcined Levyne molecular sieve. 
     
     
         30 . The system of  claim 27 , wherein the Cu:Al atomic ratio of the copper containing Levyne molecular sieve is from about 0.2 to about 0.4. 
     
     
         31 . The system of  claim 27 , wherein the Levyne molecular sieve is ZSM-45. 
     
     
         32 . The system of  claim 27 , wherein the Levyne molecular sieve is a Nu-3. 
     
     
         33 . The system of  claim 27 , wherein the catalyst is disposed on a substrate. 
     
     
         34 . A method of selectively reducing nitrogen oxides NOx, the method comprising contacting a gaseous stream containing nitrogen oxides NOx with a copper containing Levyne molecular sieve having a silica to alumina mole ratio of from about 15 to about 26 and a Cu:Al atomic ratio of from about 0.20 to about 0.45. 
     
     
         35 . The method of  claim 34 , wherein the silica to alumina mole ratio of the copper-containing Levyne molecular sieve is less than 23. 
     
     
         36 . The method of  claim 34 , wherein Cu content of the copper containing Levyne molecular sieve, calculated as CuO, is from about 2 to about 4 wt.-% based on the total weight of the calcined Levyne molecular sieve. 
     
     
         37 . The method of  claim 34 , wherein the Cu:Al atomic ratio of the copper containing Levyne molecular sieve is from about 0.2 to about 0.4. 
     
     
         38 . The method of  claim 34 , wherein the Levyne molecular sieve is ZSM-45. 
     
     
         39 . The method of  claim 34 , wherein the Levyne molecular sieve is a Nu-3. 
     
     
         40 . The method of  claim 34 , wherein the copper containing Levyne molecular is disposed on a substrate.