Method for increasing internal combustion engine exhaust gas catalyst durability

Abstract

Durability of emissions catalysts in vehicular and other emissions control systems is significantly increased by positioning, prior to the catalyst-laden catalytic converter, at least one poison trap consisting of a low back pressure structure having a coating which reacts with non-metal or amphoteric oxides to form non-volatile reaction products.

What is claimed is:  
     
         1 . A method of increasing the durability of an emissions control exhaust catalyst, said method comprising: 
 positioning a low back pressure flow through element between the exhaust valve or port of an internal combustion engine and a catalytic converter element, said pass through element having deposited thereon a catalyst durability enhancing coating comprising a metal oxide, metal compound, a precursor thereof, said metal oxide or metal compound reactive with acidic gases contained in an exhaust stream emanating from said internal combustion engine such that he durability of catalytic elements downstream from said pass through element is enhanced.    
     
     
         2 . The method of  claim 1 , wherein said pass through element is a tubular poison trap, conical poison trap, grid, or honeycomb structure having deposited thereon a washcoat comprising said metal oxide, metal compound, or precursor thereof.  
     
     
         3 . The method of  claim 1 , wherein said pass through element comprises a hollow metal cylinder, the walls of said cylinder being perforated with a plurality of holes.  
     
     
         4 . The method of  claim 1 , wherein said metal oxide or metal compound is at least one of an oxide or silicate of one of Li, Na, K, Rb, Mg, Ca, Ba, Sr, Ti, Zr, Mn, Fe, Co, Ni, Zn, Ga, Al, Si, Sn, Bi, Y, La, Ce, or Pr.  
     
     
         5 . The method of  claim 4 , wherein said metal oxide or compound is produced in situ by passing exhaust gas through a pass through element having a coating comprising a metal oxide or metal compound precursor.  
     
     
         6 . The method of  claim 1 , wherein said catalyst durability enhancing coating is coated onto at least one of an engine exhaust manifold, an exhaust pipe, engine exhaust ports, or surfaces of the driven side of a turbocharger.  
     
     
         7 . The method of  claim 1 , wherein said catalyst durability enhancing coating is coated onto a first portion of a monolith located in a catalytic converter, with a second portion of said monolith being coated with an emissions reducing catalyst.  
     
     
         8 . The method of  claim 7 , wherein there is no overlap between the catalyst durability enhancing coating on said first portion of said monolith and said emissions reducing catalyst on said second portion of said monolith.  
     
     
         9 . The method of  claim 1 , wherein said catalyst durability enhancing coating comprises a slurry of aluminum oxide containing a compound of barium, titanium, or magnesium, which is subsequently calcined.  
     
     
         10 . The method of  claim 1 , wherein said pass through element comprising a monolith having at least a first portion coated with a catalyst durability enhancing coating with a portion of said first portion being coated with an emissions reducing catalyst, with said monolith being located in a catalytic converter.  
     
     
         11 . An emissions control exhaust system for an internal combustion engine in which hot exhaust gases exit said engine from an exhaust valve or port, said exhaust system comprising 
 a) at least one catalytic converter containing an exhaust catalyst which lowers at least one of CO, NO x , particulate matter or HC;    b) positioned in the exhaust stream of said engine prior to said exhaust catalyst, a discrete low back pressure flow through element having a catalyst durability enhancing coating thereon,    said durability enhancing coating capable of removing at least a portion of acidic oxides contained in said exhaust stream.    
     
     
         12 . The exhaust system of  claim 11 , wherein said catalyst durability enhancing coating is coated onto at least one of a) the engine exhaust passage located between the exhaust valve or port and the engine exhaust manifold; b) the exhaust manifold; c) an exhaust pipe; d) a separate canister containing a substrate on which said durability enhancing coating is deposited; e) a tubular or conical poison trap, or f) the blades of a turbo charger fan.  
     
     
         13 . The exhaust system of  claim 12 , wherein said poison trap is welded to the interior of the leading end of said catalytic converter.  
     
     
         14 . The exhaust system of  claim 11 , wherein said catalyst durability enhancing coating comprises a slurry of aluminum oxide containing a compound of barium, titanium, or magnesium, which is subsequently calcined.  
     
     
         15 . An emissions control exhaust system for an internal combustion engine in which hot exhaust gases exit said engine from an exhaust valve or port, said exhaust system comprising 
 a) at least one catalytic converter containing an exhaust catalyst which lowers at least one of CO, NO x , particulate matter, or HC;    b) positioned in the exhaust stream of said engine prior to said exhaust catalyst, a low back pressure flow through element having a catalyst durability enhancing coating thereon, said element comprising an essentially exhaust emissions catalyst-free portion of a monolith, said monolith having an exhaust emissions catalyst located on a rear-most portion thereof,    said durability enhancing coating capable of removing at least a portion of acidic oxides contained in said exhaust stream.    
     
     
         16 . The exhaust system of  claim 15 , wherein there is no overlap between the catalyst durability enhancing coating on said first portion of said monolith and said emissions reducing catalyst on said second portion of said monolith.  
     
     
         17 . The exhaust system of  claim 15 , wherein said catalyst durability enhancing coating comprises a slurry of aluminum oxide containing a compound of barium, titanium, or magnesium, which is subsequently calcined.  
     
     
         18 . The exhaust system of  claim 15 , wherein said catalyst durability enhancing coating comprises lanthanium-stabilized y-aluminum oxide.  
     
     
         19 . The method of  claim 10  wherein said first portion comprises the entire surface of said monolith.