Catalytic plasma reduction of nox

Abstract

The present invention is based upon the discovery that microporous catalysts, especially zeolites in the class of metallic Faujasites, Linde Type A (LTA) and combinations thereof having a pore size greater than 3 angstroms in combination with a plasma are capable of catalyzing conversion of NO x to N 2 in a real or actual exhaust stream without any gas phase additive.

We claim:  
     
         1 . A method of catalytic plasma conversion of at least one nitrogen oxide from an exhaust gas stream containing said at least one nitrogen oxide to a nitrogen gas, comprising the steps of: 
 (a) providing a vessel with an inlet and an outlet, the vessel having a zeolite catalyst selected from the group of metallic Faujasite, Linde Type A and combinations thereof therein together with electrodes for creating a plasma, said zeolite catalyst containing a metal in an exchange site;    (b) passing said exhaust gas stream into the inlet through said vessel and contacting said exhaust gas stream with said catalyst and said plasma thereby converting said at least one nitrogen oxide to said nitrogen gas, forming a nitrogen oxide reduced exhaust gas stream; and    (c) flowing said nitrogen oxide reduced exhaust stream through the outlet.    
     
     
         2 . The method as recited in  claim 1 , wherein said metallic Faujasite has a structure selected from the group of zeolite X, zeolite Y and combinations thereof.  
     
     
         3 . The method as recited in  claim 2 , wherein said metal is selected from the group of alkali, alkali earth, transition metal and combinations thereof.  
     
     
         4 . The method as recited in  claim 1 , wherein said zeolite catalyst contains metal atoms from about 5% to about 100% of available sites.  
     
     
         5 . The method as recited in  claim 1 , wherein said zeolite catalyst has a pore size of greater than 3 angstrom units.  
     
     
         6 . The method as recited in  claim 5 , wherein said metallic Faujasite has a pore size of at least 6 angstrom units.  
     
     
         7 . The method as recited in  claim 1 , wherein said metal in said Linde Type A is a cation selected from the group consisting of Li, Na, Ca and combinations thereof.  
     
     
         8 . The method as recited in  claim 1 , wherein said exhaust gas is at a temperature of at least 100° C.  
     
     
         9 . The method as recited in  claim 1 , wherein said zeolite catalyst has a metal selected from the group consisting of Na, Cs, Ca, Co, Ag, Ni, and K.  
     
     
         10 . The method as recited in  claim 1 , wherein said electrodes are arranged in a tube array.  
     
     
         11 . An apparatus for catalytic plasma conversion of at least one nitrogen oxide from an exhaust gas stream containing said at least one nitrogen oxide to a nitrogen gas, comprising: 
 (a) a vessel with an inlet and an outlet;    (b) the vessel having therein a zeolite microporous catalyst selected from the group of metallic Faujasite, Linde Type A and combinations thereof; together with    (c) electrodes for creating a plasma; wherein    (d) said exhaust gas stream passes into the inlet through said vessel and contacts said exhaust gas stream with said catalyst and said plasma, thereby converting said at least one nitrogen oxide to said nitrogen gas, forming a nitrogen oxide reduced exhaust gas stream, and said nitrogen oxide reduced exhaust stream passing through the outlet.    
     
     
         12 . The apparatus as recited in  claim 11 , wherein said metallic Faujasite has a structure selected from the group of zeolite X, zeolite Y and combinations thereof.  
     
     
         13 . The apparatus as recited in  claim 12 , wherein said metallic Faujasite has a metal selected from the group of alkali, alkali earth, transition metal and combinations thereof.  
     
     
         14 . The apparatus as recited in  claim 11 , wherein said zeolite catalyst contains metal atoms from about 5% to about 100% of available sites.  
     
     
         15 . The apparatus as recited in  claim 11 , wherein said zeolite catalyst has a pore size greater than 3 angstrom units.  
     
     
         16 . The apparatus as recited in  claim 15 , wherein said metallic Faujasite has a pore size of at least 6 angstrom units.  
     
     
         17 . The apparatus as recited in  claim 11 , wherein said electrodes are arranged in a tube array.  
     
     
         18 . The apparatus as recited in  claim 11 , wherein said zeolite microporous catalyst has a metal selected from the group consisting of Na, Cs, Ca, Co, Ag, Ni, and K.  
     
     
         19 . A method of converting at least one nitrogen oxide to nitrogen gas, comprising the steps of: 
 (a) providing a vessel with an inlet and an outlet, the vessel having a microporous catalyst of a titanosilicate with a free aperture of at least 3.5 angstroms, said free aperture defined by a base porous material impregnated with a cation selected from the group consisting of alkaline earth, alkali, transition, and combinations thereof therein together with electrodes for creating a plasma;    (b) passing said exhaust gas stream into the inlet through said vessel and contacting said exhaust gas stream with said catalyst and said plasma thereby converting said at least one nitrogen oxide to a nitrogen gas, forming a nitrogen oxide reduced exhaust gas stream; and    (c) flowing said nitrogen oxide reduced exhaust stream through the outlet.    
     
     
         20 . The method as recited in  claim 19 , wherein said cation is selected from the group consisting of Li, Na, K, Cs and combinations thereof.  
     
     
         21 . The method as recited in  claim 19 , wherein said electrodes are arranged in a tube array.  
     
     
         22 . A method of catalytic plasma conversion of at least one nitrogen oxide from an exhaust gas stream containing said at least one nitrogen oxide to a nitrogen gas, wherein at an optimum temperature from about 150° C. to about 180° C., NO x  reduction is greater than 52%, comprising the steps of: 
 (a) providing a vessel with an inlet and an outlet, the vessel having a zeolite catalyst selected from the group of metallic Faujasite, Linde Type A and combinations thereof therein together with electrodes for creating a plasma, said zeolite catalyst containing a metal in an exchange site;  
 (b) passing said exhaust gas stream into the inlet through said vessel and contacting said exhaust gas stream with said catalyst and said plasma thereby converting said at least one nitrogen oxide to said nitrogen gas, forming a nitrogen oxide reduced exhaust gas stream; and  
 (c) flowing said nitrogen oxide reduced exhaust stream through the outlet.  
 
     
     
         23 . The method as recited in  claim 22  wherein said zeolite has a free aperture from 3 angstroms to 7 angstroms.  
     
     
         24 . The method as recited in  claim 22 , wherein said zeolite catalyst has a metal selected from the group consisting of Na, Cs, Ca, Co, Ag, Ni, and K.  
     
     
         25 . The method as recited in  claim 24  wherein said zeolite has a free aperture from 3 angstroms to 7 angstroms.  
     
     
         26 . The method as recited in  claim 22 , wherein said electrodes are arranged in a tube array.