Process for Elimination of Hexavalent Chromium Compounds on Metallic Substrates within Zero-PGM Catalyst Systems

Abstract

Process for manufacturing ZPGM catalysts systems that may allow the prevention of formation or the conversion of corrosion causing compounds, such as hexavalent chromium compounds, within ZPGM catalyst systems is disclosed. In one embodiment, disclosed ZPGM catalysts systems, may include metallic substrate, which may include alloys of iron and chromium, a washcoat and an overcoat. Disclosed manufacturing process may include a thermal decomposition of hexavalent chromium compounds which may allow the decomposition of such compounds into trivalent chromium compounds, and may also produce metallic catalyst, such as silver. Such conversion may prevent corrosion formation, such as red color corrosion within ZPGM catalyst system. An embodiment of the disclosed process may include a reducing agent, which may be present in exhaust conditions, which may convert hexavalent chromium compounds into trivalent chromium compounds as well as produce metallic catalyst, such as silver. Employing the disclosed manufacturing process may allow the production of ZPGM catalyst systems that may exhibit high activity and enhanced performance.

What is claimed is: 
     
         1 . A method for reducing corrosion of a catalytic system, comprising:
 providing a catalyst system, comprising:
 a substrate; and 
 a washcoat suitable for deposition on the substrate, comprising at least one first oxide solid selected from the group consisting of a first carrier material oxide, at least one first catalyst, and a mixture thereof; 
 wherein the washcoat is aged; and 
   providing an exhaust stream having one selected from the group consisting of hydrogen, carbon monoxide, ammonia and combinations thereof.   
     
     
         2 . The method according to  claim 1 , wherein aging is by heating to about 1100° C. 
     
     
         3 . The method according to  claim 2 , wherein the heating may continue for about 3 hours to about 6 hours. 
     
     
         4 . The method according to  claim 2 , wherein the heating occurs in the presence of one selected from the group consisting of hydrogen, carbon monoxide, ammonia, and combinations thereof. 
     
     
         5 . The method according to  claim 1 , wherein at least one hexavalent chromium compound is reduced. 
     
     
         6 . The method according to  claim 1 , wherein aging is by heating to about 900° C. 
     
     
         7 . The method according to  claim 6 , wherein the heating may continue for about  3  hours to about  6  hours. 
     
     
         8 . The method according to  claim 6 , wherein the heating occurs in the presence of one selected from the group consisting of hydrogen, carbon monoxide, ammonia, and combinations thereof. 
     
     
         9 . The method according to  claim 1 , wherein the washcoat is at least partially prepared by co-milling. 
     
     
         10 . The method according to  claim 1 , wherein the washcoat is heated to about 550° C. for about 4 hours. 
     
     
         11 . The method according to  claim 1 , wherein the substrate about 100 cells per square inch. 
     
     
         12 . The method according to  claim 1 , wherein the substrate comprises metal. 
     
     
         13 . The method according to  claim 1 , wherein at least one first catalyst is substantially free of platinum group metals. 
     
     
         14 . The method according to  claim 1 , wherein at least one first catalyst comprises at least one selected from the group consisting of copper, cerium, silver, and combinations thereof. 
     
     
         15 . The method according to  claim 1 , wherein the substrate comprises one selected from the group consisting of iron, chromium, and combinations thereof.