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

Abstract

An improved, robust diesel emission control system employs a lightly diesel particulate filter (DPF), preferably with a platinum containing fuel borne catalyst (FBC) in the fuel. The DPF is preferably of wire mesh construction and 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 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 particulate filter 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 particulate filter 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 particulate filter has a catalyst metal loading of from about 3 to 5 grams per cubic foot.  
     
     
         5 . A system for reducing particulate emissions by over 30% while controlling the emissions of NO 2  to below 37% of exhaust nitrogen oxide species and minimizing the loading of precious metal catalyst, e.g., platinum group metal, to less than 15 grams per cubic foot of substrate installed in the exhaust of a diesel engine when used with an FBC comprising platinum and/or cerium and/or iron at a total metal concentration of less than 15 ppm in the fuel.  
     
     
         6 . An improved diesel emissions control system comprising: means for supplying diesel fuel containing a platinum, cerium or iron containing FBC and a lightly catalyzed exhaust treatment device.  
     
     
         7 . A diesel emissions control system according to  claim 1 , wherein the after treatment device is lightly catalyzed with platinum, having a metal loading of less than about 10 grams per cubic foot.  
     
     
         8 . A diesel emissions control system according to  claim 1 , wherein the FBC comprises platinum, iron, cerium or combinations of platinum, iron or platinum and cerium and/or cerium and iron.  
     
     
         9 . A diesel emissions control system according to  claim 1 , wherein the FBC comprises a fuel soluble platinum compound providing from about 0.01 to about 1.0 ppm of platinum in the fuel.  
     
     
         10 . A diesel emissions control system according to  claim 1 , wherein the after treatment device comprises an DPF and/or a DOC and has a metal loading of from about 3 to 5 grams per cubic foot.  
     
     
         11 . A diesel emissions control system according to  claim 1 , wherein the after treatment device comprises a catalyzed wire mesh filter and has a precious metal loading of 7-14 grams per cubic foot.  
     
     
         12 . A robust diesel particulate control system comprises providing a lightly catalyzed wire mesh filter on the exhaust system of a diesel engine and operating the diesel engine so equipped with a diesel fuel containing a low dose rate fuel borne catalyst comprising platinum in combination with cerium and/or iron at total fuel borne catalyst levels of under 15 ppm and preferably 4-8 ppm.  
     
     
         13 . A diesel particulate control system of  claim 12 , which provides particulate reduction of at least 60% without the substantial increase in NO 2  emissions.