Reduced-emissions combustion utilizing multiple-component metallic combustion catalyst and lightly catalyzed diesel oxidation catalyst

Abstract

An improved diesel operation system employs a lightly diesel oxidation catalyst (DOC), preferably with a platinum containing fuel borne catalyst (FBC) in the fuel. The DOC is at least partially lightly catalyzed with precious metal catalyst, e.g., platinum group metal, having a metal loading of from about 3 to 15 grams per cubic foot to minimize formation of NO 2 in the exhaust gas. Preferred fuel borne catalyst levels will be low, e.g., from 0.05 to 0.5 ppm for platinum and 3 to 8 ppm for cerium and/or iron, thereby providing effective engine out emissions reductions without discharging excessive amounts of metal catalysts or NO 2 to the atmosphere.

1 . A method for reducing particulate emissions from a diesel engine while also controlling emissions of NO 2  as a percent of exhaust total nitrogen oxides, comprising: adding a fuel borne catalyst comprising platinum and cerium and/or iron at a total metal concentration of from 2 to 15 ppm in the fuel to a diesel fuel; and passing exhaust produced by the combustion through a diesel oxidation catalyst having substrate with a precious metal catalyst thereon, the catalyst be present on the substrate in an amount of less than 15 grams per cubic foot of substrate.  
     
     
         2 . A diesel emissions control system according to  claim 1 , wherein the diesel oxidation catalyst has a catalyst metal loading of less than about 10 grams per cubic foot.  
     
     
         3 . A diesel emissions control system according to  claim 1 , wherein the fuel comprises a fuel soluble platinum compound providing from about 0.05 to about 0.5 ppm of platinum in the fuel.  
     
     
         4 . A diesel emissions control system according to  claim 1 , wherein the diesel oxidation catalyst has a catalyst metal loading of from about 3 to 5 grams per cubic foot.