# US 6,296,822 B1 · Process for manufacturing nox traps with improved sulfur tolerance

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- Number: US 6,296,822 B1
- Document ID: US6296822B1
- Status: Granted
- Kind: B1
- Application number: 09/537,649
- Filed: 2000-03-29
- Granted: 2001-10-02
- Earliest claimed: 2000-03-29
- Assignees: Ford Global Technologies, LLC
- Inventors: Jeffrey Scott Hepburn; John Denari; William Lewis Henderson Watkins
- Web page: https://patentgrep.com/patent/US6296822B1

## CPC

- F01N 3/0842: {Nitrogen oxides}
- B01D 53/9422: {for removing nitrogen oxides by NOx storage or reduction by cyclic switching between lean and rich exhaust gases (LNT, NSC, NSR)}
- B01J 23/58: with alkali- or alkaline earth metals
- B01J 23/63: with rare earths or actinides
- B01J 37/0244: {Coatings comprising several layers}
- F01N 3/0807: {by using absorbents or adsorbents}
- B01D 2255/1021: Platinum
- B01D 2255/2025: Lithium
- B01D 2255/2042: Barium
- Y02T 10/12: Improving ICE efficiencies
- 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)
- 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)
- B01J: CHEMICAL OR PHYSICAL PROCESSES, e.g. CATALYSIS OR COLLOID CHEMISTRY; THEIR RELEVANT APPARATUS
- Y02T: CLIMATE CHANGE MITIGATION TECHNOLOGIES RELATED TO TRANSPORTATION

## Abstract

A method for manufacturing a NOx absorbent useful to purge exhaust gases during lean-burn internal combustion engine operation. The material is resistant to sulfur poisoning hence improving the long term NOx absorption efficiency. The method comprises providing an alumina/ceria support with barium and precious metal of at least platinum and then overcoating with a layer of lithium. The absorbent can be used in the exhaust gas system and subjected to lean operation when the nitrogen oxides are absorbed and then to stoichiometric or rich A/F operation which causes the nitrogen oxide to desorb and then they are reduced over the precious metal.

## Claims

### Claim 1

A method for treating exhaust gases from an internal combustion engine using a nitrogen oxide absorbent, said method comprising the steps of:
exposing a nitrogen oxide absorbent material located in the exhaust gas passage of an internal combustion engine to engine exhaust gases having a lean of stoichiometric air/fuel ratio whereby said absorbent absorbs nitrogen oxides from said exhaust gas, said absorbent made by a method which comprises the steps of:
providing a support material of alumina/ceria including at least 0.5 wt. % ceria;
providing the material with barium and precious metal including at least platinum so as to provide at least 1.0 wt. % barium and 0.2 wt. % platinum on the material; and
overcoating the material containing barium and precious metal with a layer of 0.5-5 wt. % lithium based on the total weight of the material;
purging said absorbed nitrogen oxides from said absorbent by subjecting said absorbent to engine exhaust gases whose air/fuel ratio is stoichiometric or rich of stoichiometry.

### Claim 2 (depends on 1)

The method according to claim 1 wherein the amount of ceria in the alumina/ceria material is 0.5 to 50 wt. %.

### Claim 3 (depends on 1)

The method according to claim 1 wherein the amount of barium in the material is at least 1.0 wt. %.

### Claim 4 (depends on 1)

The method according to claim 1 wherein the amount of platinum in the material is at least 5 wt. %.

### Claim 5 (depends on 1)

The method according to claim 1 wherein the barium and precious metal are impregnated on the material from a solution containing a mixture of their soluble salts.

### Claim 6 (depends on 1)

The method according to claim 1 wherein the barium and precious metal are impregnated on the material from separate solutions thereof.

### Claim 7 (depends on 1)

The method according to claim 1 wherein the layer of lithium is provided by contacting the material with a solution of lithium nitrate.

### Claim 8 (depends on 1)

The method according to claim 1 wherein the precious metal further includes rhodium in an amount of 0.1 to 5 wt. % based on the weight of the support material.