NOx Adsorber Catalyst with Superior Low Temperature Performance
First Claim
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1. A combined lean NOx trap/catalyst system for treatment of exhaust gas emissions, comprising:
- a. a carrier substrate;
b. an undercoat washcoat layer comprising a support material, one or more precious metals and one or more NOx trapping components, wherein said undercoat layer is coated on said carrier substrate; and
c. a top washcoat layer comprising a support material, one or more precious metals, and ceria, said top washcoat layer being devoid of alkali or alkaline earth components, and wherein said top washcoat layer is coated on said carrier substrate.
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Abstract
The lean NOx trap catalyst composition of the present invention comprises distinct layers, or zone configuration or multi-brick arrangement. The top layer, front zone or front brick is free of any alkali or alkaline earth NOx trapping components. The under layer, rear zone or rear brick may contain any desirable NOx trapping component in contact with a precious metals group catalyst (e.g., Pt). Catalysts of this invention show wide temperature operation window with superior low temperature performance.
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Citations
20 Claims
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1. A combined lean NOx trap/catalyst system for treatment of exhaust gas emissions, comprising:
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a. a carrier substrate; b. an undercoat washcoat layer comprising a support material, one or more precious metals and one or more NOx trapping components, wherein said undercoat layer is coated on said carrier substrate; and c. a top washcoat layer comprising a support material, one or more precious metals, and ceria, said top washcoat layer being devoid of alkali or alkaline earth components, and wherein said top washcoat layer is coated on said carrier substrate. - View Dependent Claims (2, 3, 4, 5, 6, 7)
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8. An exhaust gas treatment system for treating exhaust gas emissions from a lean burn engine comprising:
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a. a multiple-brick arrangement comprising at least two bricks; b. wherein said first brick contains a washcoat layer comprising a support material, one or more precious metals, ceria and is devoid of any alkali or alkaline earth components; and c. wherein said second brick contains a support material, one or more precious metals and one or more NOx trapping components. - View Dependent Claims (9, 10, 12, 13, 14)
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11. The exhaust gas treatment system of claim 11, wherein one of said first brick or said second brick further comprises a particulate filter.
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15. A method for treating exhaust gas emissions from lean burn engine, said method comprising the steps of:
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a. providing a combined NOx trap/catalyst component, comprising; i. a carrier substrate; ii. an undercoat washcoat layer comprising a support material, one or more precious metals and one or more NOx trapping components, wherein said undercoat washcoat layer is coated on said carrier substrate; and iii. a top washcoat layer comprising a support material, one or more precious metals, and ceria, said top washcoat layer being devoid of alkali or alkaline earth components, and wherein said top washcoat layer is coated on said carrier substrate. b. passing an exhaust gas stream comprising unburned hydrocarbons, carbon monoxides and nitrogen oxides, from a lean burn engine across said carrier substrate; c. wherein under lean burn conditions said undercoat washcoat layer is capable of simultaneously storing nitrogen oxides (NOx) and catalyzing the conversion of hydrocarbons (HC) and carbon monoxides (CO), and said top washcoat layer is capable of oxidizing nitrogen oxides (NOx) and catalyzing the conversion of hydrocarbons and carbon monoxides (CO); and d. wherein under rich burn conditions both of said top and undercoat washcoat layers are capable of releasing and oxidizing nitrogen oxides (NOx) and catalyzing the conversion of hydrocarbons and carbon monoxide. - View Dependent Claims (16, 17, 18, 19, 20)
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Specification