Multi-Component Filters For Emissions Control
AssigneeBASF SE
InventorR. Samuel Boorse
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Abstract
Catalytic articles, systems and methods for treating exhaust gas streams are described. A catalytic article comprising a wall flow filter having gas permeable walls, a hydrolysis catalyst, an optional soot oxidation catalyst, a selective catalytic reduction catalyst permeating the walls, an ammonia oxidation catalyst and an oxidation catalyst to oxidize CO and hydrocarbons is described. Methods of treating exhaust gas streams comprising soot, an ammonia precursor such as urea, ammonia, NOx, CO and hydrocarbons are also provided.
Claims26
A catalytic article to remove emissions from a gas stream containing soot, ammonia, an ammonia precursor NOx, CO and hydrocarbons, the article comprising:
- a wall-flow filter for trapping soot in the gas stream, the filter having an inlet end and an outlet end defining an overall length, gas permeable walls having a thickness formed into a plurality of axially extending inlet channels and outlet channels, each inlet channel having inlet walls, an open inlet end and a plugged outlet end, each outlet channel having outlet walls, a plugged inlet end and an open outlet end, with each inlet channel having adjacent outlet channels;
- an optional hydrolysis catalyst that promotes the hydrolysis of the ammonia precursor, the hydrolysis catalyst coated on a portion of the inlet walls of the inlet channels extending from the inlet end;
- a selective catalytic reduction catalyst permeating the gas permeable walls, the selective catalytic reduction catalyst promoting the conversion of NOx in the gas stream to N2 in the presence of excess oxygen;
- an ammonia oxidation catalyst coating a length of the outlet walls of the outlet channels that promotes the selective oxidation of ammonia to N2 in the gas stream;
- and
- an oxidation catalyst coated on a portion of the outlet walls of the outlet channels extending from the outlet end toward the inlet end that promotes the oxidation of CO and hydrocarbons to CO2.
A method of treating an exhaust gas stream comprising soot, urea, ammonia, NOx, CO and hydrocarbons, the method comprising:
- promoting the hydrolysis of urea with a hydrolysis catalyst located at an inlet end of inlet channels of a catalytic article;
- filtering the soot from the gas stream after the hydrolysis catalyst by passing the gas stream through a gas permeable wall in the catalytic article and forming a filter cake on the wall of the inlet channels;
- promoting the reaction of the ammonia and NOx to form N2 with a selective catalytic reduction catalyst permeating the gas permeable wall of the catalytic article;
- promoting the oxidation of the ammonia in the gas stream exiting the gas permeable walls of the catalytic article with an ammonia oxidation catalyst coated on outlet walls of the catalytic article;
- and
- promoting the oxidation of CO and hydrocarbons to form carbon dioxide and water with an oxidation catalyst coated on the outlet walls at an outlet end of the catalytic article.
Dependencies are inferred from the claim text.