Four-way conversion catalyst having improved filter properties

Patent metadata

Field	Value
Publication number	US-11376569-B2
Application number	US-201916966319-A
Country	US
Kind code	B2
Filing date	Feb 4, 2019
Priority date	Feb 5, 2018
Publication date	Jul 5, 2022
Grant date	Jul 5, 2022

Abstract

A four-way conversion catalyst for treating a gasoline engine exhaust gas has a porous wall flow filter substrate with an inlet end, outlet end, substrate axial length extending between the inlet and outlet end, and passages defined by porous internal walls of the substrate, the passages having inlet passages with an open inlet and closed outlet, and outlet passages having a closed inlet and open outlet. The internal wall pores have a three-way conversion catalytic in-wall coating with an oxygen storage compound and a platinum group metal supported on a refractory metal oxide. On at least a portion of the internal wall surface defining the interface between the internal walls and the passages, the catalyst has a porous on-wall coating from the internal wall surface to the passage. The coating has porous oxidic compound and platinum group metal content of 0 to 0.001 wt. %, of the total coating weight.

First claim

The invention claimed is:

1. A four-way conversion catalyst suitable for treating an exhaust gas stream of a gasoline engine, the catalyst comprising:
a porous wall flow filter substrate comprising an inlet end, an outlet end, a substrate axial length extending between the inlet end and the outlet end, and a plurality of passages defined by porous internal walls of the porous wall flow filter substrate,
wherein the plurality of 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 pores of the porous internal walls comprise a three-way conversion catalytic in-wall coating comprising an oxygen storage compound and a platinum group metal supported on a refractory metal oxide,
wherein, on at least a portion of a surface of the porous internal walls, the surface defining an interface between the porous internal walls and the passages, the catalyst comprises a porous on-wall coating extending from the surface of the internal walls to the passage, and
wherein the on-wall coating comprises a porous oxidic compound and has a platinum group metal content in a range of from 0 to 0.001 weight-%, based on total on-wall coating weight.

2. The catalyst of claim 1 , wherein the porous oxidic compound comprised in the on-wall coating comprises an oxygen storage compound and/or a refractory metal oxide.

3. The catalyst of claim 2 , wherein the oxygen storage compound in the on-wall coating comprises cerium, and/or
wherein the oxygen storage compound in the on-wall coating has a porosity in a range of from 0.1 to 1.2 mL/g, and/or has a BET specific surface area in a range of from 15 to 150 m 2 /g.

4. The catalyst of claim 2 , wherein the refractory metal oxide in the on-wall coating comprises an oxide comprising aluminum.

5. The catalyst of claim 2 , wherein the oxygen storage compound in the on-wall coating comprises cerium, and
wherein the oxygen storage compound in the on-wall coating has a porosity in a range of from 0.1 to 1.2 mL/g, and has a BET specific surface area in a range of from 15 to 150 m 2 /g.

6. The catalyst of claim 2 , wherein the oxygen storage compound in the on-wall coating comprises cerium oxide.

7. The catalyst of claim 2 , wherein the oxygen storage compound in the on-wall coating comprises a mixed oxide comprising cerium and zirconium and/or praseodymium.

8. The catalyst of claim 1 , wherein the on-wall coating further comprises a promotor.

9. The catalyst of claim 1 , wherein the on-wall coating further comprises a zeolitic compound.

10. The catalyst of claim 1 , wherein the on-wall coating comprises an inlet on-wall coating comprising a porous oxidic compound, or an outlet on-wall coating comprising porous oxidic compound, or an inlet on-wall coating comprising a porous oxidic compound and an outlet on-wall coating comprising porous oxidic compound,
wherein the internal walls defining the inlet passages comprise the inlet on-wall coating comprising a porous oxidic compound, wherein the inlet on-wall coating length is x % of the substrate axial length wherein 0≤x≤100;
wherein the internal walls defining the outlet passages comprise the outlet on-wall coating comprising a porous oxidic compound, wherein the outlet on-wall coating length is y % of the substrate axial length wherein 0≤y≤100;
wherein x+y>0.

11. The catalyst of claim 10 , wherein 0<x≤100, or
wherein 0<y≤100.

12. The catalyst of claim 1 , comprising the on-wall coating at a loading in a range of from 0.01 to 1.5 g/in 3 .

13. The catalyst of claim 1 , comprising the three-way conversion catalytic in-wall coating at a loading in a range of from 0.1 to 5 g/in 3 .

14. The catalyst of claim 1 , wherein the three-way conversion catalytic in-wall coating comprises a hydrocarbon oxidation component, a carbon monoxide oxidation component, and a nitrogen oxide reduction component.

15. The catalyst of claim 1 , wherein the platinum group metal of the three-way conversion catalytic in-wall coating comprises ruthenium, palladium, rhodium, platinum, and/or iridium,
wherein the oxygen storage compound of the three-way conversion catalytic in-wall coating comprises cerium,
wherein the refractory metal oxide support of the three-way conversion catalytic in-wall coating comprises aluminum,
wherein the three-way conversion catalytic in-wall coating comprises a promotor comprising zirconium.

16. A process for preparing the catalyst of claim 1 , comprising
(i) providing a washcoat slurry comprising a source for a three-way conversion catalytic in-wall coating, optionally comprising
(i.1) impregnating a source of a platinum group metal onto a refractory metal oxide support;
(i.2) admixing the platinum group metal supported on the refractory metal oxide with one or more of an adjuvant and a source for a promotor, preferably with an adjuvant and a source for a promotor; and preferably milling the obtained mixture;
(i.3) impregnating a source of a platinum group metal onto an oxygen storage compound;
(i.4) admixing the platinum group metal supported on the oxygen storage compound with one or more of an adjuvant and a source for a promotor, preferably with an adjuvant and a source for a promotor; and preferably milling the obtained mixture;
(i.5) admixing the mixture obtained from (i.2) and the mixture obtained from (i.4), obtaining the washcoat slurry comprising a source for the three-way conversion catalytic in-wall coating;
(ii) coating the washcoat of the washcoat slurry from the providing (i) onto the porous wall flow filter substrate, to obtain the wall flow filter substrate wherein the pores of the porous internal walls comprise a three-way conversion catalytic in-wall coating comprising the oxygen storage compound and the platinum group metal supported on the refractory metal oxide;
(iii) providing a washcoat slurry comprising a source for the on-wall coating comprising a porous oxidic compound, optionally comprising
(iii.1) preparing a suspension comprising admixing a porous oxidic compound with an adjuvant;
(iii 2) milling the suspension obtained from the preparing (iii 1); and
(iv) coating the washcoat of the washcoat slurry from the providing (iii) onto the coated porous wall flow filter substrate obtained in the coating (ii).

17. An exhaust gas treatment system downstream of a gasoline engine and in fluid communication with the gasoline engine, the system comprising:
the catalyst of claim 1 .

18. The system of claim 17 , wherein the gasoline engine is a gasoline direct injection engine.

Assignees

• Basf Corp

Inventors

• Schmitz Thomas
• Siani Attilio
• Siemund Stephan
• Cravillon Janosch

Classifications

• B01J35/56

  Foraminous structures having flow-through passages or channels, e.g. grids or three-dimensional [3D] monoliths · CPC title

• F01N2370/02

  used in catalytic reactors · CPC title

• B01J37/0228

  in several steps · CPC title

• B01D2255/2092

  Aluminium · CPC title

• B01D2255/9155

  Wall flow filters · CPC title