# US 8,784,759 B2 · NOx storage catalyst with reduced Rh loading

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- Number: US 8,784,759 B2
- Document ID: US8784759B2
- Status: Granted
- Kind: B2
- Application number: 13/156,886
- Filed: 2011-06-09
- Published: 2011-12-15
- Granted: 2014-07-22
- Earliest claimed: 2010-06-10
- Assignees: BASF SE
- Applicants: Marcus Hilgendorff
- Inventors: Marcus Hilgendorff
- Web page: https://patentgrep.com/patent/US8784759B2

## CPC

- F01N 3/0814: {combined with catalytic converters, e.g. NOx absorption/storage reduction catalysts}
- B01J 23/58: with alkali- or alkaline earth metals
- B01J 23/63: with rare earths or actinides
- B01J 35/56: Foraminous structures having flow-through passages or channels, e.g. grids or three-dimensional [3D] monoliths
- B01J 37/0036: {Grinding}
- B01J 37/0244: {Coatings comprising several layers}
- B01J 37/0248: {Coatings comprising impregnated particles}
- B01D 53/9422: {for removing nitrogen oxides by NOx storage or reduction by cyclic switching between lean and rich exhaust gases (LNT, NSC, NSR)}
- B01D 2255/1021: Platinum
- B01D 2255/1023: Palladium
- B01D 2255/1025: Rhodium
- B01D 2255/1028: Iridium
- B01D 2255/2022: Potassium
- B01D 2255/2025: Lithium
- B01D 2255/2027: Sodium
- B01D 2255/2042: Barium
- B01D 2255/2045: Calcium
- B01D 2255/2047: Magnesium
- B01D 2255/2063: Lanthanum
- B01D 2255/2065: Cerium
- B01D 2255/2066: Praseodymium
- B01D 2255/2068: Neodymium
- B01D 2255/9022: Two layers
- B01D 2255/91: NOx-storage component incorporated in the catalyst
- B01J 35/396: {Distribution of the active metal ingredient}
- F01N 3/0842: {Nitrogen oxides}
- F01N 2510/0682: having a discontinuous, uneven or partially overlapping coating of catalytic material, e.g. higher amount of material upstream than downstream or vice versa
- F01N 2510/0684: having more than one coating layer, e.g. multi-layered coatings
- F01N: GAS-FLOW SILENCERS OR EXHAUST APPARATUS FOR MACHINES OR ENGINES IN GENERAL; GAS-FLOW SILENCERS OR EXHAUST APPARATUS FOR INTERNAL-COMBUSTION ENGINES (arrangements in connection with gas exhaust of propulsion units in vehicles B60K13/00; combustion-air intake silencers specially adapted for, or arranged on, internal-combustion engines F02M35/00; protecting against, or damping, noise in general G10K11/16)
- B01J: CHEMICAL OR PHYSICAL PROCESSES, e.g. CATALYSIS OR COLLOID CHEMISTRY; THEIR RELEVANT APPARATUS
- B01D: SEPARATION (separating solids from solids by wet methods B03B, B03D; by pneumatic jigs or tables B03B; by other dry methods B07; magnetic or electrostatic separation of solid materials from solid materials or fluids, separation by high-voltage electric fields B03C; centrifuges, vortex apparatus B04; presses per se for squeezing-out liquid from liquid-containing material B30B9/02; treatment of water C02F, e.g. softening by ion-exchange C02F1/42; {arrangements of air intake cleaners in gas turbine plants F02C7/05} ; arrangements or mounting of filters in air-conditioning, air-humidification or ventilation F24F13/28)

## Abstract

The present invention relates to a nitrogen oxide storage catalyst comprising: a substrate; a first washcoat layer disposed on the substrate, the first washcoat layer comprising metal oxide support particles and a nitrogen oxide storage material comprising at least one metal compound selected from the group consisting of alkaline earth metal compounds, alkali metal compounds, rare earth metal compounds, and mixtures thereof, at least a portion of said at least one metal compound being supported on the metal oxide support particles; and a second washcoat layer disposed over the first washcoat layer, said second washcoat layer comprising Rh, wherein the first washcoat layer contains substantially no Rh, and wherein the second washcoat layer is disposed on 100-x % of the surface of the first washcoat layer, x ranging from 20 to 80.

## Claims

### Claim 1

A nitrogen oxide storage catalyst comprising:
a substrate;
a first washcoat layer disposed on the substrate, the first washcoat layer comprising metal oxide support particles and a nitrogen oxide storage material comprising at least one metal compound selected from the group consisting of alkaline earth metal compounds, alkali metal compounds, rare earth metal compounds, and mixtures thereof, at least a portion of said at least one metal compound being supported on the metal oxide support particles; and
a second washcoat layer disposed over the first washcoat layer, said second washcoat layer comprising Rh,
wherein the first washcoat layer contains substantially no Rh, and
wherein the second washcoat layer is disposed on 100- x % of the surface of the first washcoat layer, x ranging from 20 to 80.

### Claim 2 (depends on 1)

The nitrogen oxide storage catalyst according to claim 1, wherein the first and second washcoat layers are both disposed on the substrate starting from one end and/or side of the substrate body.

### Claim 3 (depends on 1)

The nitrogen oxide storage catalyst according to claim 1, wherein the second washcoat layer further comprises metal oxide support particles on which Rh is at least partially supported.

### Claim 4 (depends on 1)

The nitrogen oxide storage catalyst according to claim 1, wherein the metal oxide support particles comprise at least one metal oxide selected from the group consisting of alumina, zirconia, zirconia-alumina, baria-alumina, lanthana-alumina, lanthana-zirconia-alumina, and mixtures thereof.

### Claim 5 (depends on 1)

The nitrogen oxide storage catalyst according to claim 1, wherein the nitrogen oxide storage material comprises at least one element selected from the group consisting of Li, Na, K, Rb, Cs, Mg, Ca, Sr, Ba, Ce, La, Pr, Nd, and mixtures thereof.

### Claim 6 (depends on 1)

The nitrogen oxide storage catalyst according to claim 1, wherein the nitrogen oxide storage material comprises a cerium compound and a barium compound.

### Claim 7 (depends on 1)

The nitrogen oxide storage catalyst according to claim 1, wherein the first washcoat layer further comprises at least one platinum group metal selected from the group consisting of platinum, palladium, iridium, and mixtures thereof.

### Claim 8 (depends on 7)

The nitrogen oxide storage catalyst according to claim 7, wherein the first washcoat layer comprises Pd and/or Pt.

### Claim 9 (depends on 1)

The nitrogen oxide storage catalyst according to claim 1, wherein the nitrogen oxide storage catalyst further comprises a third washcoat layer which comprises Pd and which is disposed onto at least a portion of the first washcoat layer, onto which the second washcoat layer is not disposed.

### Claim 10 (depends on 9)

The nitrogen oxide storage catalyst according to claim 9, wherein Pd comprised in the third washcoat layer is at least partially supported on metal oxide support particles.

### Claim 11 (depends on 1)

The nitrogen oxide storage catalyst according to claim 1, wherein the substrate comprises a honeycomb substrate comprising a plurality of longitudinally extending passages formed by longitudinally extending walls bounding and defining said passages.

### Claim 12 (depends on 11)

The nitrogen oxide catalyst according to claim 11, wherein the first washcoat layer onto 100-x % of the surface of which the second washcoat layer is disposed is the first washcoat layer disposed on the walls of the inlet passages of the honeycomb substrate.

### Claim 13 (depends on 11)

The nitrogen oxide catalyst according to claim 11, wherein the nitrogen oxide storage catalyst comprises a third washcoat layer which comprises Pd and which is disposed onto at least a portion of the first washcoat layer, onto which the second washcoat layer is not disposed, and
wherein the first washcoat layer onto the surface of which the third washcoat layer is disposed is the first washcoat layer disposed on the outlet passages of the honeycomb substrate, said third washcoat layer being disposed on at least a portion of said first washcoat layer of the outlet passages of the honeycomb substrate.

### Claim 14 (depends on 1)

A treatment system for an automobile exhaust gas stream, comprising:
a combustion engine which operates periodically between lean and rich conditions;
an exhaust gas conduit in communication with the engine; and
a nitrogen oxide storage catalyst according to claim 1 provided within the exhaust gas conduit.

### Claim 15 (depends on 14)

The treatment system according to claim 14, wherein the nitrogen storage catalyst comprises separate substrates with respect to the portions or sections of the catalyst which comprise the second washcoat layer, and those which do not comprise the second washcoat layer.

### Claim 16 (depends on 1)

A method for the treatment of automobile engine exhaust gas comprising:
(i) providing a nitrogen oxide storage catalyst according to claim 1, and
(ii) conducting an automobile engine exhaust gas stream over and/or through the nitrogen oxide storage catalyst.

### Claim 17 (depends on 16)

The method according to claim 16, wherein the automobile engine operates periodically between lean and rich conditions.

### Claim 18

A method of producing a nitrogen oxide storage catalyst comprising the steps of:
(i) providing a substrate, preferably a honeycomb substrate;
(ii) providing a first washcoat layer on said substrate, said first washcoat layer comprising metal oxide support particles and at least one metal compound selected from the group consisting of alkaline earth metal compounds, alkali metal compounds, rare earth metal compounds, and mixtures thereof, at least a portion of said at least one metal compound being supported on the metal oxide support particles;
(iii) drying and/or calcining the coated substrate;
(iv) providing a second washcoat layer comprising Rh on 100-x % of the surface of the first washcoat layer, wherein x ranges from 20 to 80;
(v) drying and/or calcining the coated substrate.

### Claim 19 (depends on 18)

The method of claim 18, further comprising the steps of:
(vi) providing a third washcoat layer onto at least a portion of the surface of the first washcoat layer, onto which the second washcoat layer has not been provided;
(vii) drying and/or calcining the coated substrate;
wherein alternatively, steps (vi) and (vii) are conducted after step (iii) and prior to step (iv).

### Claim 20 (depends on 19)

The method according to claim 19, wherein step (ii) comprises the steps of:
(a) mixing a solution of the at least one metal compound with particles of at least one metal compound;
(b) drying and/or calcining the mixture to obtain a composite material;
(c) impregnating metal oxide support particles with a solution comprising Pt;
(d) impregnating metal oxide support particles with a solution comprising Pd;
(e) providing and milling a slurry of the particles obtained in steps (c) and (d);
(f) providing a slurry comprising the milled particles obtained in step (e) and the composite material obtained in step (b) and milling the resulting mixture;
(g) coating the substrate with the slurry obtained in step (f).

### Claim 21 (depends on 20)

The method according to claim 20, wherein step (iv) comprises the steps of:
(aa) impregnating metal oxide support particles with a solution comprising Rh;
(bb) providing and milling a slurry of the impregnated particles;
(cc) coating the substrate with the slurry obtained in step (bb).

### Claim 22 (depends on 21)

The method according to claim 21, wherein step (vi) comprises the steps of:
(dd) impregnating metal oxide support particles with a solution comprising Pd;
(ee) providing and milling a slurry of the impregnated particles;
(ff) coating the substrate with the slurry obtained in step (ee).

### Claim 23 (depends on 22)

The method according to claim 22, wherein in steps (e), (f), (bb) and/or (ee) the slurry is milled to a particle size (d90) ranging from 5 to 20 μm, preferably from 8 to 14 μm, more preferably from 9 to 13 μm, and even more preferably from 10 to 12 μm.

### Claim 24 (depends on 22)

The method according to claim 22, wherein in steps (c), (d), (aa) and/or (dd) the metal oxide support particles are impregnated by an incipient wetness procedure.

### Claim 25 (depends on 22)

The method according to claim 22, wherein in steps (g), (cc) and/or (ff) the coating is performed by dip coating.

### Claim 26 (depends on 20)

The method according to claim 20, wherein the slurry in step (f) contains substantially no Rh.

### Claim 27 (depends on 19)

The method according to claim 19, wherein the substrate is a honeycomb substrate, and wherein the method preferably comprises a further step of:
(viii) alternatively closing the inlet our outlet ends of the honeycomb substrate to form 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.

### Claim 28 (depends on 18)

A nitrogen oxide storage catalyst obtainable by a method according to claim 18.