Catalyst for decomposition of nitrogen oxides

Abstract

This invention relates generally to a platinized tin oxide-based catalyst. It relates particularly to an improved platinized tin oxide-based catalyst able to decompose nitric oxide to nitrogen and oxygen without the necessity of a reducing gas.

1 . A catalyst composition for the decomposition of nitrogen oxides to nitrogen and oxygen without the need for a reducing gas, comprising: 
 at least one noble metal and at least one metal oxide wherein the catalyst is prepared by heating said catalyst to a temperature from about 650° C. to about 800° C. in the presence of a noble gas.    
   
   
       2 . The catalyst of  claim 1  wherein said temperature is from about 700° C. to about 750° C.  
   
   
       3 . The catalyst of  claim 1  wherein said noble gas is selected from the group consisting of: helium, neon, argon, krypton, xenon and radon.  
   
   
       4 . The catalyst of  claim 3  wherein said noble gas is helium.  
   
   
       5 . The catalyst of  claim 1  wherein said at least one noble metal is a selected from the group consisting of platinum, palladium, gold, silver, ruthenium and rhodium.  
   
   
       6 . The catalyst of  claim 5  wherein said at least one noble metal is platinum.  
   
   
       7 . The catalyst of  claim 1  wherein said at least one metal oxide is selected from the group consisting of tin oxide, manganese oxide and copper oxide.  
   
   
       8 . The catalyst of  claim 7  wherein said at least one metal oxide is tin oxide.  
   
   
       9 . A method for making a catalyst composition for the decomposition of nitrogen oxides to nitrogen and oxygen comprising: 
 (a) preparing a catalyst comprising at least one noble metal and at least one metal oxide;    (b) heating said catalyst to a temperature between about 650° C. and 800° C. in the presence of a noble gas.    
   
   
       10 . The method of  claim 9  wherein said at least one noble metal is selected from the group consisting of platinum, palladium, gold, silver, ruthenium and rhodium.  
   
   
       11 . The method of  claim 10  wherein said at least one noble metal is platinum.  
   
   
       12 . The method of  claim 9  wherein said at least one metal oxide is selected from the group consisting of tin oxide, manganese oxide and copper oxide.  
   
   
       13 . The method of  claim 12  wherein said at least one metal oxide is tin oxide.  
   
   
       14 . The method of  claim 9  wherein the temperature is from about 700° C. to about 750° C.  
   
   
       15 . The method of  claim 9  wherein said noble gas is selected from the group consisting of: helium, neon, argon, krypton, xenon and radon.  
   
   
       16 . The method of  claim 15  wherein said noble gas is helium.  
   
   
       17 . A catalyst composition for the decomposition of nitrogen oxides to nitrogen and oxygen comprising at least one noble metal and at least one metal oxide wherein the catalyst is prepared by heating said catalyst in the presence of a noble gas to a temperature sufficient to effectively reduce the concentration of water absorbed/adsorbed to the catalytic active surface to thereby lower the concentration of surface hydroxyl moieties.  
   
   
       18 . The catalyst of  claim 17  wherein said temperature is from about 650° C. to about 800° C.  
   
   
       19 . A catalyst composition for the decomposition of nitrogen oxides to nitrogen and oxygen comprising: 
 at least one noble metal and at least one metal oxide wherein the catalyst is prepared by heating said catalyst to a temperature from about 650° C. to about 800° C. in the presence of a noble gas.    
   
   
       20 . The catalyst of  claim 19  wherein said temperature is from about 650° C. to about 800° C.