Catalytic article with segregated washcoat and methods of making same

Abstract

Provided herein are catalytic articles and methods of making same using a single coat process. The catalytic article comprises an elongated substrate monolith having a plurality of longitudinally extending passages, each passage having at least a first surface and a second surface opposite the first surface, the first and second surfaces coated with at least a first coating and a second coating, wherein the first coating comprises a first catalyst composition and overlies the second coating on the first surface, the second coating comprises a second catalyst composition and overlies the first coating on the second surface, and wherein the first catalyst composition and second catalyst composition have a difference in surface charge. The washcoat may be applied as one slurry, which then self-segregates into two coatings.

1 - 10 . (canceled) 
     
     
         11 . A method of making a catalytic article, the method comprising providing a first support having a first surface charge and a first platinum group metal thermally or chemically fixed to the first support;
 providing a second support having a second surface charge less than the first surface charge and a second platinum group metal thermally or chemically fixed to the second support;   suspending the first and second supports in a single slurry comprising a liquid medium and the first and second supports; and   applying the single slurry to a substrate.   
     
     
         12 . The method of  claim 11 , wherein the single slurry provides two compositionally distinct coatings, a first coating and a second coating. 
     
     
         13 . The method of  claim 11 , wherein the substrate comprises an elongated substrate monolith having a plurality of longitudinally extending passages, each passage having at least a first surface and a second surface opposite the first surface, and wherein the first coating overlies the second coating on the first surface, and the second coating overlies the first coating on the second surface. 
     
     
         14 . The method of  claim 11 , wherein the difference in surface charge is equal to or greater than about 10 Coulombs/m 2 . 
     
     
         15 . The method of  claim 11 , wherein the first support comprises high density ceria and the second support comprises low density zirconia doped with Pr. 
     
     
         16 . The method of  claim 11 , wherein thermally fixing the platinum group metal to the first support and second support comprises impregnating the platinum group metal onto the first and second support to provide an impregnated support and calcining impregnated support. 
     
     
         17 . The method of  claim 11 , wherein the pH of the slurry is maintained in the range of about 3 to about 9. 
     
     
         18 . The method of  claim 11 , wherein the platinum group metal thermally or chemically fixed to the first support comprises Rh in an amount of about 0.5-10% by weight of the total catalyst. 
     
     
         19 . The method of  claim 11 , wherein the platinum group metal thermally fixed to the second support comprises Pd or Pt in an amount of about 0.05-5% by weight of the total catalyst. 
     
     
         20 . The method of  claim 11 , wherein the first support comprises alumina or zirconia, and the second support comprises ceria.