COATED ARTICLES HAVING HIGH KNOx/KSOx RATIOS FOR SELECTIVE CATALYTIC REDUCTION

Abstract

Articles comprising a catalyst film comprising VOx, MoO 3 or WO 3 , and TiO 2 deposited on a substrate are disclosed. The articles are useful for selective catalytic reduction (SCR) of NOx in exhaust gases. Methods for producing such articles deposit a catalyst film on the substrate to form a coated substrate, which is then calcined. When used in an SCR process, the coated articles have enhanced activity for NOx conversion, reduced activity for SOx conversion, or both. Light-weight, coated articles having high catalyst loads can be fabricated at the same or reduced dimensions when compared with laminated articles, and increased kNOx/kSOx ratios are available even from coated articles having relatively thin catalyst films. The articles should have particular value for power plant operations, where coal and high-sulfur fuels are commonly used and controlling sulfur trioxide generation is critical.

1 . An article comprising:
 (a) a substrate; and   (b) a film deposited on the substrate;   wherein the film comprises VOx, MoO 3  or WO 3 , and TiO 2 , and the article catalyzes the conversion of nitrogen oxides in a gas containing nitrogen oxides.   
     
     
         2 . The article of  claim 1 , wherein the film comprises 0.1 to 5 wt. % of VOx, 0.5 to 20 wt. % of MoO 3  or WO 3 , and 75 to 99.4 wt. % of TiO 2 . 
     
     
         3 . The article of  claim 1 , wherein the film comprises 0.5 to 2 wt. % of VOx, 1 to 10 wt. % of MoO 3  or WO 3 , and 88 to 98.5 wt. % of TiO 2 . 
     
     
         4 . The article of  claim 1 , wherein the film has a thickness of from about 20 μm to about 500 μm. 
     
     
         5 . The article of  claim 1 , wherein the film has a thickness of from about 50 μm to about 150 μm. 
     
     
         6 . The article of  claim 1 , wherein the substrate is a monolith or a plate. 
     
     
         7 - 9 . (canceled) 
     
     
         10 . The article of  claim 1 , the article having less mass and at least one of: (a) enhanced activity for NOx conversion at a temperature between 350° C. and 400° C.; and (b) reduced activity for SOx conversion at a temperature between 380° C. and 430° C., compared with an article of similar dimensions and composition. 
     
     
         11 . The article of  claim 1 , wherein the article also catalyzes the conversion of SOx in a gas containing SOx and the conversions of NOx and SOx occur at rates kNOx and kSOx, respectively, and the ratio of kNOx/kSOx is from 0.22 to 0.30. 
     
     
         12 . An article comprising:
 (a) a substrate;   (b) a used catalyst on the surface of a substrate; and   (c) a film deposited over the used catalyst,   wherein the film deposited over the used catalyst comprises VOx, MoO 3  or WO 3 , and TiO 2  and the article catalyzes the conversion of nitrogen oxides in a gas containing nitrogen oxides.   
     
     
         13 - 22 . (canceled) 
     
     
         23 . An article comprising:
 (a) a substrate; and   (b) a film deposited on the substrate;
 wherein the film comprises: (i) VOx or a VOx precursor, (ii) MoO 3 , a MoO 3  precursor, WO 3 , a WO 3  precursor or a mixture thereof, and (iii) TiO 2  or a TiO 2  precursor, and the article, upon calcination, catalyzes the conversion of nitrogen oxides in a gas containing nitrogen oxides. 
   
     
     
         24 . The article of  claim 23 , wherein the film comprises 0.1 to 5 wt. % of VOx or a VOx precursor, 0.5 to 20 wt. % of MoO 3 , a MoO 3  precursor, WO 3 , a WO 3  precursor or a mixture thereof, and 75 to 99.4 wt. % of TiO 2  or a TiO 2  precursor. 
     
     
         25 . The article of  claim 23 , wherein the film comprises 0.5 to 2 wt. % of VOx or a VOx precursor, 1 to 10 wt. % of MoO 3 , a MoO 3  precursor, WO 3 , a WO 3  precursor or a mixture thereof; and 88 to 98.5 wt. % of TiO 2  or a TiO 2  precursor. 
     
     
         26 . The article of  claim 23 , wherein the film has a thickness of from about 20 μm to about 500 μm. 
     
     
         27 . The article of  claim 23 , wherein the film has a thickness of from about 50 μm to about 150 μm. 
     
     
         28 . The article of  claim 23 , wherein the substrate is a monolith or a plate. 
     
     
         29 - 31 . (canceled) 
     
     
         32 . An article comprising:
 (a) a substrate; and   (b) a used catalyst on the surface of a substrate; and   (c) a film deposited over the used catalyst,
 wherein the film comprises: (i) VOx or a VOx precursor, (ii) MoO 3 , a MoO 3  precursor, WO 3 , a WO 3  precursor or a mixture thereof, and (iii) TiO 2  or a TiO 2  precursor. 
   
     
     
         33 . The article of  claim 32 , wherein the film comprises 0.1 to 5 wt. % of VOx or a VOx precursor, 0.5 to 20 wt. % of MoO 3 , a MoO 3  precursor, WO 3 , a WO 3  precursor or a mixture thereof, and 75 to 99.4 wt. % of TiO 2  or a TiO 2  precursor. 
     
     
         34 . The article of  claim 32 , wherein the film comprises 0.5 to 2 wt. % of VOx, 1 to 10 wt. % of MoO 3  or WO 3 , and 88 to 98.5 wt. % of TiO 2 . 
     
     
         35 . The article of  claim 32 , wherein the film has a thickness of from about 20 μm to about 500 μm. 
     
     
         36 . The article of  claim 32 , wherein the film has a thickness of from about 50 min to about 150 μm. 
     
     
         37 . The article of  claim 32 , wherein the substrate is a monolith or a plate. 
     
     
         38 - 40 . (canceled) 
     
     
         41 . A method for producing an article having selective catalytic reduction activity, the method comprising:
 (a) forming a coated substrate by depositing a catalyst film comprising: (i) VOx or a VOx precursor, (ii) MoO 3 , a MoO 3  precursor, WO 3 , a WO 3  precursor or a mixture thereof, and (iii) TiO 2  or a TiO 2  precursor, onto a substrate, and   (b) calcining the coated substrate.   
     
     
         42 - 51 . (canceled) 
     
     
         52 . A method for producing a selective catalytic reduction catalyst from a used SCR article, the method comprising:
 (a) removing particulates from a used article comprising a substrate and a used catalyst on the substrate;   (b) forming a coated substrate by depositing a catalyst film comprising: (i) VOx or a V 2 Ox precursor, (ii) MOO 3 , a MoO 3  precursor, WO 3 , a WO 3  precursor or a mixture thereof, and (iii) TiO 2  or a TiO 2  precursor onto a substrate, and   (c) calcining the coated substrate.   
     
     
         53 - 61 . (canceled) 
     
     
         62 . A process for selectively reducing nitrogen oxides in a gaseous mixture, the method comprising contacting a gaseous mixture comprising nitrogen oxides with a reductant in the presence of an article of  claim 1 . 
     
     
         63 . (canceled) 
     
     
         64 . (canceled) 
     
     
         65 . The process of  claim 62 , wherein the process provides at least one of: (a) enhanced activity for NOx conversion at a temperature between 350° C. and 400° C.; and (b) reduced activity for SOx conversion at a temperature between 380° C. and 430° C.