Selective catalytic reduction catalyst system with expanded temperature window

• US 8,506,893 B2
• Filed: 04/23/2008
• Issued: 08/13/2013
• Est. Priority Date: 04/23/2008
• Status: Active Grant

• Current Assignee: Ford Global Technologies, LLC (Ford Motor Company)
• Original Assignee: Ford Global Technologies, LLC (Ford Motor Company)
• Inventors: Gandhi, Harendra S, Theis, Joseph Robert
• Primary Examiner(s): Duong, Tom
• Application Number:
  US12/108,175
• Publication Number:
  US 20090266063A1
• Time in Patent Office: 1,938 Days
• Field of Search: 422/171, 422/177, 422/180
• US Class Current: 422/171
• CPC Class Codes: B01D 2251/2062 Ammonia
• CPC Class Codes: B01D 2255/20738 Iron
• CPC Class Codes: B01D 2255/20761 Copper
• CPC Class Codes: B01D 53/9418 for removing nitrogen oxides by selective catalytic reduction [SCR] using a reducing agent in a lean exhaust gas
• CPC Class Codes: B01D 53/9477 with catalysts positioned on separate bricks, e.g. exhaust systems
• CPC Class Codes: Y02T 10/12 Improving ICE efficiencies

Abstract

According to one embodiment of the present invention a selective reduction catalyst system with a broad temperature window for lean-burn gasoline and diesel engines is disclosed. The system includes a first and second zone, wherein the first zone is composed of an iron SCR catalyst and a second zone is composed of a copper SCR catalyst, and wherein the second zone is positioned downstream of the first zone. In another embodiment, a small copper SCR catalyst is placed in front of a second zone composed of an iron SCR catalyst and a third zone composed of a copper SCR catalyst, wherein the volume of the first copper SCR catalyst is a fraction of the volume of the second copper SCR catalyst. In yet another embodiment, a diverter valve would be included in the system to eliminate any NO_x penalty produced by the front Cu SCR catalyst.

Claims

1. A selective catalytic reduction system for lean-burn gasoline and diesel engine emissions that expands the operating temperature range of the system, comprising a first and second zone, wherein the first zone is composed of an iron SCR catalyst and a second zone is composed of a copper SCR catalyst, and wherein the second zone is positioned adjacent and downstream of the first zone.

2. The selective catalytic reduction system of claim 1, wherein the first zone comprises 60% to 85% of the total SCR catalyst volume and the second zone comprises 15 to 40% of the total SCR catalyst volume and the maximum space velocity ranges from 5,000 to 20,000 hr⁻

1.

3. The selective catalytic reduction system of claim 1, wherein the first zone comprises 65% to 80% of the total SCR volume and the second zone comprises 20% to 35% of the total SCR catalyst volume and the maximum space velocity ranges from 7,500 to 15,000 hr⁻

1.

4. The selective catalytic reduction system of claim 1, wherein the first zone comprises 65% to 75% of the total SCR catalyst volume and the second zone comprises 25% to 35% of the total SCR catalyst volume and the maximum space velocity ranges from 7,500 to 12,500 hr⁻

1.

5. The selective catalytic reduction system of claim 1, wherein the first zone comprises 75% to 90% of the total SCR catalyst volume and the second zone comprises 10% to 25% of the total SCR catalyst volume and the maximum space velocity ranges from 5,000 to 10,000 hr⁻

1.

6. A selective catalytic reduction system for lean-burn gasoline and diesel engines, comprising a first, second and third zone, wherein the first zone is composed of a copper SCR catalyst, the second zone is composed of an iron SCR catalyst, and the third zone is composed of a copper SCR catalyst, wherein the third zone is adjacent and positioned downstream of the second zone and wherein the second zone is adjacent and positioned downstream of the first zone.

7. The selective catalyst reduction system of claim 6, wherein the total SCR catalyst volume of the first copper zone is between 25%-75% of the total SCR catalyst volume of the third copper zone.

8. The selective catalytic reduction system of claim 6, wherein the front copper zone is between 23 and 4% of the total SCR catalyst volume, the second iron zone is between 46 and 82% of the total SCR catalyst volume, and the third copper zone is between 31 and 14% of the total SCR catalyst volume, and the maximum space velocity ranges from 4,000 to 19,000 hr⁻

1.

9. The selective catalytic reduction system of claim 6, wherein the front copper zone is between 21 and 5% of the total SCR catalyst volume, the second iron zone is between 51 and 76% of the total SCR catalyst volume, and the third copper zone is between 28 and 19% of the total SCR catalyst volume, and the maximum space velocity ranges from 6,000 to 14,000 hr⁻

1.

10. The selective catalytic reduction system of claim 6, wherein the front copper zone is between 21 and 6% of the total SCR catalyst volume, the second iron zone is between 51 and 71% of the total SCR catalyst volume, and the third copper zone is between 28 and 24% of the total SCR catalyst volume, and the maximum space velocity ranges from 6,000 to 12,000 hr⁻

1.

11. The selective catalytic reduction system of claim 6, wherein the front copper zone is between 16 and 2% of the total SCR catalyst volume, the second iron zone is between 63 and 88% of the total SCR catalyst volume, and the third copper zone is between 21 and 10% of the total SCR catalyst volume, and the maximum space velocity ranges from 4,000 to 10,000 hr⁻

1.

12. A durable catalyst system for the reduction of emissions from an engine exhaust stream, comprising:

a light-off catalyst closely coupled to the engine;

a first copper selective catalytic reduction catalyst positioned downstream of the light-off catalyst;

a reductant injection system positioned between the light-off catalyst and the first copper selective catalytic reduction catalyst;

a diverter valve positioned downstream of the location for reductant injection and upstream of the first copper selective catalytic reduction catalyst, the diverter valve being connected to a bypass arm that can be utilized to bypass the first copper selective reduction catalyst and improve NOx conversion under high temperature conditions; and

a second catalytic reduction catalyst that includes a first Fe SCR catalyst and a second Cu SCR catalyst, wherein the second Cu SCR catalyst is positioned downstream of the Fe SCR catalyst.