Catalyzed SCR filter and emission treatment system
First Claim
1. An emission treatment system for treatment of an exhaust stream comprising NOx and particulate matter, the emission treatment system comprising:
- a) an oxidation catalyst;
b) an injector in fluid communication with and downstream of the oxidation catalyst, wherein the injector periodically meters ammonia or an ammonia precursor into the exhaust stream; and
, c) a wall flow monolith in fluid communication with and downstream of the injector, wherein the wall flow monolith has a plurality of longitudinally extending passages formed by longitudinally extending walls bounding and defining said passages, wherein the passages comprise inlet passages having an open inlet end and a closed outlet end, and outlet passages having a closed inlet end and an open outlet end, wherein the wall flow monolith comprises an SCR catalyst composition that permeates the walls at a concentration of at least 1.3 g/in3;
wherein the wall flow monolith has a wall porosity of at least 50% with an average pore size of at least 5 microns.
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Accused Products
Abstract
Provided is an emission treatment system and method for simultaneously remediating the nitrogen oxides (NOx), particulate matter, and gaseous hydrocarbons present in diesel engine exhaust streams. The emission treatment system has an oxidation catalyst upstream of a soot filter coated with a material effective in the Selective Catalytic Reduction (SCR) of NOx by a reductant, e.g., ammonia. Also provided is a method for disposing an SCR catalyst composition on a wall flow monolith that provides adequate catalyst loading, but does not result in unsuitable back pressures in the exhaust.
185 Citations
24 Claims
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1. An emission treatment system for treatment of an exhaust stream comprising NOx and particulate matter, the emission treatment system comprising:
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a) an oxidation catalyst;
b) an injector in fluid communication with and downstream of the oxidation catalyst, wherein the injector periodically meters ammonia or an ammonia precursor into the exhaust stream; and
,c) a wall flow monolith in fluid communication with and downstream of the injector, wherein the wall flow monolith has a plurality of longitudinally extending passages formed by longitudinally extending walls bounding and defining said passages, wherein the passages comprise inlet passages having an open inlet end and a closed outlet end, and outlet passages having a closed inlet end and an open outlet end, wherein the wall flow monolith comprises an SCR catalyst composition that permeates the walls at a concentration of at least 1.3 g/in3;
wherein the wall flow monolith has a wall porosity of at least 50% with an average pore size of at least 5 microns. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11)
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12. A method for treating emissions produced in an exhaust stream comprising NOx and particulate matter, the method comprising:
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(a) passing the exhaust stream through an oxidation catalyst wherein a substantial portion of NO is oxidized to NO2 to provide an NO2-enriched exhaust stream;
(b) metering at periodic intervals, ammonia or an ammonia precursor into the NO2-enriched exhaust stream; and
,(c) subsequently passing the exhaust stream through a wall flow monolith wherein particulate matter is filtered and a substantial portion of NOx is reduced to N2;
wherein the wall flow monolith has a plurality of longitudinally extending passages formed by longitudinally extending walls bounding and defining said passages, wherein the passages comprise inlet passages having an open inlet end and a closed outlet end, and outlet passages having a closed inlet end and an open outlet end, wherein the wall flow monolith comprises an SCR catalyst composition that permeates the walls at a concentration of at least 1.3 g/in3;
wherein the wall flow monolith has a wall porosity of at least 50% with an average pore size of at least 5 microns. - View Dependent Claims (13, 14, 15, 16, 17, 18, 19, 20, 21)
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22. A method for disposing an SCR catalyst composition on a wall flow monolith, wherein the wall flow monolith has a plurality of longitudinally extending passages formed by longitudinally extending walls bounding and defining said passages, wherein the passages comprise inlet passages having an open inlet end and a closed outlet end, and outlet passages having a closed inlet end and an open outlet end, the method comprising:
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(a) immersing the wall flow monolith in an aqueous slurry comprising the SCR catalyst composition from a first direction to deposit the SCR catalyst composition on the inlet passages;
(b) removing excess slurry from the inlet passages by forcing a compressed gas stream through the outlet passages and applying a vacuum to the inlet passages;
(c) immersing the wall flow monolith in the aqueous slurry from a second direction, opposite the first direction, to deposit the SCR catalyst composition on the outlet passages;
(d) removing excess slurry from the outlet passages by forcing a compressed gas stream through the inlet passages and applying a vacuum to the outlet passages; and
(e) drying and calcining the coated wall flow monolith. - View Dependent Claims (23, 24)
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Specification