Lean NOx trap diesel oxidation catalyst with hydrocarbon storage function

Patent metadata

Field	Value
Publication number	US-9498775-B2
Application number	US-201214389605-A
Country	US
Kind code	B2
Filing date	Apr 6, 2012
Priority date	Apr 6, 2012
Publication date	Nov 22, 2016
Grant date	Nov 22, 2016

Abstract

The present invention is directed to a lean NOx trap diesel oxidation catalyst for the treatment of exhaust gas emissions, such as the oxidation of unburned hydrocarbons (HC), and carbon monoxide (CO) and the trapping and reduction of nitrogen oxides (NOx). Catalytic composites can comprise a catalytic material on a carrier, the catalytic material comprising a first NOx trap layer that comprises a NOx sorbent and one or more precious metal components located on the carrier and a second NOx trap layer containing hydrocarbon trapping functionality located over the first NOx trap layer that comprises a NOx sorbent, one or more precious metal components, and a zeolite, for example a beta zeolite, wherein the zeolite is substantially free of framework aluminum. Such zeolites are characterized by high crystallinity and/or by being substantially free of framework aluminum to minimize surface acidity.

First claim

What is claimed is:

1. A catalyst composite for abatement of exhaust gas emissions from an engine comprising: a catalytic material on a carrier, the catalytic material comprising a first NOx trap layer that comprises a first NOx sorbent and one or more precious metal components located on the carrier and a second NOx trap layer that comprises a second NOx sorbent, one or more precious metal components, and a zeolite, wherein the zeolite is substantially free of framework aluminum; wherein the catalytic material is effective to oxidize hydrocarbons and carbon monoxide and to trap and reduce NOx.

2. The catalyst composite of claim 1 , wherein the zeolite comprises a beta zeolite.

3. The catalyst composite of claim 1 , wherein the Si structure in a solid state 29 Si NMR spectrum of the zeolite is essentially for tetrahedron Si (OSi) 4 centers.

4. The catalyst composite of claim 1 , wherein the zeolite comprises essentially no acid sites as measured by pyridine-adsorption diffuse reflectance infrared Fourier transform (DRIFT) spectroscopy.

5. The catalyst composite of claim 1 , wherein the Al structure in a solid state 27 Al NMR spectrum of the zeolite is essentially free of signals of tetra- and hexa-coordinated aluminum centers.

6. A catalyst composite for abatement of exhaust gas emissions from an engine comprising: a catalytic material on a carrier, the catalytic material comprising a first NOx trap layer located on the carrier and a second NOx trap layer located on the first NOx trap layer, wherein:
the first NOx trap layer comprises an alkaline earth component; a rare earth oxide component; a precious metal component; a first high surface area refractory metal oxide support;
the second NOx trap layer comprises a precious metal component; a second high surface area refractory metal oxide support; a rare earth oxide component, and a zeolite that is substantially free of framework aluminum; and
wherein the catalytic material is effective to oxidize hydrocarbons and carbon monoxide and to trap and reduce NOx.

7. The catalyst composite of claim 6 , wherein the alkaline earth component of the first NOx trap layer is selected from the group consisting of oxides of Mg, Ca, Sr, Ba, and combinations thereof.

8. The catalyst composite of claim 6 , wherein the zeolite comprises a beta zeolite.

9. The catalyst composite of claim 8 , wherein the zeolite comprises a beta zeolite that comprises less than 2000 ppm aluminum concentration.

10. A method for treating a diesel exhaust gas stream comprising contacting the exhaust gas stream with the catalyst composite of claim 1 that is effective to oxidize hydrocarbons and carbon monoxide and to trap and reduce NOx.

11. The method of claim 10 , further comprising directing the diesel exhaust gas stream to a soot filter downstream of the catalyst composite.

12. A method of making a catalyst composite, the method comprising:
forming a first NOx trap layer that comprises a first NOx sorbent and one or more precious metal components on a carrier; and
forming a second NOx trap layer on the first NOx trap layer, wherein the second NOx trap layer comprises a second NOx sorbent, one or more precious metal components, and a zeolite that is substantially free of framework aluminum.

13. The method of claim 12 , wherein the zeolite comprises a beta zeolite.

14. The catalyst composite of claim 12 , wherein the Si structure in a solid state 29 Si NMR spectra of the zeolite is essentially for tetrahedron Si (OSi) 4 center.

15. The method of claim 12 , wherein the zeolite exhibits essentially no acid sites as measured by pyridine-adsorption diffuse reflectance infrared Fourier transform (DRIFT) spectroscopy.

Assignees

• Zheng Xiaolai
• Wan Chung-Zong
• Burk Patrick
• Basf Corp

Inventors

• Zheng Xiaolai
• Wan Chung-Zong
• Burk Patrick

Classifications

• B01D53/944

  Simultaneously removing carbon monoxide, hydrocarbons or carbon making use of oxidation catalysts (three-way-catalysts [TWC] B01D53/9445) · CPC title

• B01D2258/012

  Diesel engines and lean burn gasoline engines · CPC title

• B01D53/9477

  with catalysts positioned on separate bricks, e.g. exhaust systems · CPC title

• B01D2255/9022

  Two layers · CPC title

• B01J20/08

  comprising aluminium oxide or hydroxide; comprising bauxite · CPC title