SCR Catalyst

Abstract

The present invention relates to a catalyst comprising at least one oxide of vanadium, at least one oxide of tungsten, at least one oxide of cerium, at least one oxide of titanium and at least one oxide of niobium, and an exhaust system containing said oxides.

1 - 10 . (canceled) 
     
     
         11 . A method of making a catalyst comprising
 at least one oxide of vanadium in an amount of 2 to 6 wt.-%,   at least one oxide of cerium in an amount of 2 to 4 wt.-%,   at least one oxide of niobium in an amount of 1 to 7 wt.-%,   up to 2 wt.-% of at least one oxide of tungsten,   
       and
 at least one oxide of titanium as a carrier material in an amount measured so as to result in a total of 100 wt.-%, 
 
       in each case based on the total weight of the catalyst and calculated as V 2 O 5 , CeO 2 , Nb 2 O 5 , TiO 2 , or, if at least one oxide of tungsten is present, WO 3 , said method comprising:
 obtaining oxides of vanadium, cerium, niobium, titanium, and, if present, tungsten, said method comprising: 
 forming a mixture of the oxides, and 
 calcining the mixture. 
 
     
     
         12 . The method of  claim 11 , wherein the mixture contains at least one oxide of silicon. 
     
     
         13 . The method of  claim 12 , wherein the at least one oxide of silicon is present in amounts of 2 to 7 wt.-%, relative to the weight of the catalyst and calculated as SiO 2 . 
     
     
         14 . The method of  claim 11 , wherein the mixture contains at least one oxide of tungsten in an amount of 0.001 to 2 wt.-%, relative to the weight of the catalyst and calculated as WO 3 . 
     
     
         15 . The method of  claim 11 , wherein the mixture further comprises at least one oxide of molybdenum, antimony, zirconium, tantalum, and/or hafnium. 
     
     
         16 . The method of  claim 11 , wherein the mixture further comprises at least one oxide of molybdenum, antimony, zirconium, tantalum, and/or hafnium in a total amount of said oxides of 0.5 to 20 wt.-%, relative to the total weight of the catalyst and calculated as MoO 3 , Sb 2 O 5 , ZrO 2 , Ta 2 O 5 , of HfO 2 . 
     
     
         17 . The method of  claim 11 , wherein the oxides are provided in powder form. 
     
     
         18 . The method of  claim 11 , wherein the mixture is a slurry of the oxides in water, and the method further comprises drying the slurry before calcining. 
     
     
         19 . The method of  claim 11 , wherein a portion of the oxides are provided in the mixture in the form of an aqueous solution. 
     
     
         20 . The method of  claim 11 , wherein the mixture comprises oxides of tungsten, cerium, niobium, and titanium that have been impregnated with a vanadium oxide. 
     
     
         21 . The method of  claim 11 , wherein the mixture comprises oxides of vanadium, cerium, niobium, and titanium that have been impregnated with a tungsten oxide. 
     
     
         22 . The method of  claim 11 , wherein at least two oxides in the mixtures are provided as one oxide doped with the other oxide. 
     
     
         23 . The method of  claim 11 , wherein the two or more oxides are provided in the mixture as mixed oxide. 
     
     
         24 . The method of  claim 11 , which comprises forming the mixture by dispersing titanium dioxide doped with 5 wt.-% silicon dioxide in water, and adding vanadium dioxide, tungsten trioxide, cerium dioxide, and niobium dioxide thereto. 
     
     
         25 . The method of  claim 24 , wherein the added amounts of vanadium dioxide, tungsten trioxide, cerium dioxide, and niobium pentoxide result in a catalyst composition comprising 85.98 wt.-% TiO 2 , 4.53 wt.-% SiO 2 , 3.75 wt.-% V 2 O 5 , 1.00 wt.-% WO 3 , 2.00 wt.-% CeO 2 , and 2.75 wt.-% Nb 2 O 5 . 
     
     
         26 . The method of  claim 24 , wherein the added amounts of vanadium dioxide, tungsten trioxide, cerium dioxide, and niobium pentoxide result in a catalyst composition comprising 86.93.-wt % TiO 2 , 4.58 wt,-% SiO 2 , 3.75 wt.-% V 2 O 5 , 2.00 wt.-% CeO 2 , and 2.75 wt.-% Nb 2 O 5 .