CATALYST FOR REMOVING NITROGEN OXIDES FROM THE EXHAUST GAS OF DIESEL ENGINES

• US 20130156668A1
• Filed: 09/08/2011
• Published: 06/20/2013
• Est. Priority Date: 09/13/2010
• Status: Active Grant

• Current Assignee: Umicore AG & Company KG (Umicore S.A.)
• Original Assignee: Umicore AG & Company KG (Umicore S.A.)
• Inventors: Spurk, Paul, Soeger, Nicola, Mueller, Elena, Malmberg, Stephan
• Granted Patent: US 8,753,596 B2
• Time in Patent Office: Days
• US Class Current: 423/213.2
• CPC Class Codes: B01D 2251/2067 Urea
• CPC Class Codes: B01D 2255/1023 Palladium
• CPC Class Codes: B01D 2255/2042 Barium
• CPC Class Codes: B01D 2255/2047 Magnesium
• CPC Class Codes: B01D 2255/2063 Lanthanum
• CPC Class Codes: B01D 2255/2065 Cerium
• CPC Class Codes: B01D 2255/20715 Zirconium
• CPC Class Codes: B01D 2255/20761 Copper
• CPC Class Codes: B01D 2255/2092 Aluminium
• CPC Class Codes: B01D 2255/407 Zr-Ce mixed oxides
• CPC Class Codes: B01D 2255/50 Zeolites
• CPC Class Codes: B01D 2255/9022 Two layers
• CPC Class Codes: B01D 2255/9032 Two zones
• CPC Class Codes: B01D 2258/012 Diesel engines and lean burn gasoline engines
• 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 53/9422 for removing nitrogen oxides by NOx storage or reduction by cyclic switching between lean and rich exhaust gases (LNT, NSC, NSR)
• CPC Class Codes: B01D 53/9477 with catalysts positioned on separate bricks, e.g. exhaust systems
• CPC Class Codes: B01J 21/04 Alumina
• CPC Class Codes: B01J 21/066 Zirconium or hafnium; Oxides or hydroxides thereof
• CPC Class Codes: B01J 23/10 of rare earths
• CPC Class Codes: B01J 23/63 : with rare earths or actinides
• CPC Class Codes: B01J 23/66 : Silver or gold
• CPC Class Codes: B01J 23/72 : Copper
• CPC Class Codes: B01J 23/8926 : Copper and noble metals
• CPC Class Codes: B01J 23/894 : with rare earths or actinides
• CPC Class Codes: B01J 23/8946 : with alkali or alkaline earth metals
• CPC Class Codes: B01J 29/072 : Iron group metals or copper
• CPC Class Codes: B01J 29/7215 : Zeolite Beta
• CPC Class Codes: B01J 29/723 : CHA-type, e.g. Chabazite, LZ-218
• CPC Class Codes: B01J 29/83 : Aluminophosphates [APO compounds]
• CPC Class Codes: B01J 29/85 : Silicoaluminophosphates [SAPO compounds]
• CPC Class Codes: B01J 35/19 : Catalysts containing parts with different compositions
• CPC Class Codes: B01J 37/0215 : Coating
• CPC Class Codes: B01J 37/0244 : Coatings comprising several layers
• CPC Class Codes: B01J 37/0246 : Coatings comprising a zeolite
• CPC Class Codes: B01J 37/0248 : Coatings comprising impregnated particles
• CPC Class Codes: B01J 37/038 : to form slurries or suspensions, e.g. a washcoat
• CPC Class Codes: F01N 2370/04 : Zeolitic material
• CPC Class Codes: F01N 2510/063 : zeolites
• CPC Class Codes: 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
• CPC Class Codes: F01N 2510/0684 : having more than one coating layer, e.g. multi-layered coatings
• CPC Class Codes: F01N 2610/02 : the substance being ammonia or urea
• CPC Class Codes: F01N 3/0814 : combined with catalytic converters, e.g. NOx absorption/storage reduction catalysts
• CPC Class Codes: F01N 3/0842 : Nitrogen oxides
• CPC Class Codes: F01N 3/2066 : Selective catalytic reduction [SCR]
• CPC Class Codes: Y02T 10/12 : Improving ICE efficiencies

Abstract

The invention relates to a catalyst for removal of nitrogen oxides from the exhaust gas of diesel engines, and to a process for reducing the level of nitrogen oxides in the exhaust gas of diesel engines. The catalyst consists of a support body of length L and of a catalytically active coating which in turn may be formed from one or more material zones. The material zones comprise a copper-containing zeolite or a zeolite-like compound. The materials used include chabazite, SAPO-34, ALPO-34 and zeolite β. In addition, the material zones comprise at least one compound selected from the group consisting of barium oxide, barium hydroxide, barium carbonate, strontium oxide, strontium hydroxide, strontium carbonate, praseodymium oxide, lanthanum oxide, magnesium oxide, magnesium/aluminum mixed oxide, alkali metal oxide, alkali metal hydroxide, alkali metal carbonate and mixtures thereof. Noble metal may optionally also be present in the catalyst.

Claims

1. A catalyst for removal of nitrogen oxides from the exhaust gas of diesel engines, comprised of a support body of length L and of a catalytically active coating composed of one or more material zones comprising:

a zeolite or a zeolite-like compound containing 1-10% by weight of copper, based on the total weight of the zeolite or of the zeolite-like compound, the zeolite or the zeolite-like compound being selected from the group consisting of chabazite, SAPO-34, ALPO-34 and zeolite β

; and

at least one compound selected from the group consisting of barium oxide, barium hydroxide, barium carbonate, strontium oxide, strontium hydroxide, strontium carbonate, praseodymium oxide, lanthanum oxide, magnesium oxide, magnesium/aluminum mixed oxide, alkali metal oxide, alkali metal hydroxide, alkali metal carbonate and mixtures thereof.

2. The catalyst as claimed in claim 1,

wherein

the zeolite or the zeolite-like compound has an average mean pore size less than 4 Angstrom and is selected from the group consisting of chabazite, SAPO-34 and ALPO-34.

3. The catalyst as claimed in claim 1,

wherein

the catalytically active coating additionally comprises cerium oxide and/or cerium/zirconium mixed oxide.

4. The catalyst as claimed in claim 3,

wherein

the cerium oxide and/or cerium/zirconium mixed oxide is a support oxide for the compound selected from the group consisting of barium oxide, barium hydroxide, barium carbonate, strontium oxide, strontium hydroxide, strontium carbonate, praseodymium oxide, lanthanum oxide, magnesium oxide, magnesium/aluminum mixed oxide, alkali metal oxide, alkali metal hydroxide, alkali metal carbonate and mixtures thereof.

5. The catalyst as claimed in claim 1,

wherein

the catalytically active coating additionally comprises one or more noble metals selected from the group consisting of platinum, palladium, rhodium, iridium, ruthenium, gold, silver and mixtures and/or alloys thereof.

6. The catalyst as claimed in claim 1,

wherein

the catalytically active coating comprises two material zones, the first material zone comprising the zeolite or the zeolite-like compound, while the compound selected from the group consisting of barium oxide, barium hydroxide, barium carbonate, strontium oxide, strontium hydroxide, strontium carbonate, praseodymium oxide, lanthanum oxide, magnesium oxide, magnesium/aluminum mixed oxide, alkali metal oxide, alkali metal hydroxide, alkali metal carbonate and mixtures thereof is present in the second material zone.

7. The catalyst as claimed in claim 5,

wherein

the catalytically active coating comprises two material zones, the first material zone comprising the zeolite or the zeolite-like compound, while the noble metal selected from the group consisting of platinum, palladium, rhodium, iridium, ruthenium, gold, silver and mixtures and/or alloys thereof is present in the second material zone.

8. The catalyst as claimed in claim 6,

wherein

the second material zone has been applied directly to the support body and covers it over the entire length L thereof, while the first material zone has been applied to the second material zone and covers it completely on the exhaust gas side.

9. The catalyst as claimed in claim 6,

wherein

the two material zones are arranged successively on the support body in flow direction of the exhaust gas, with the second material zone arranged on the inflow side and the first material zone on the outflow side.

10. The catalyst as claimed in claim 6,

wherein

the two material zones are arranged successively on the support body in flow direction of the exhaust gas, with the first material zone arranged on the inflow side and the second material zone on the outflow side.

11. A process for removing nitrogen oxides from the exhaust gas of diesel engines,

wherein

the exhaust gas to be cleaned has an air ratio λ

greater than 1 and is passed over a catalyst as claimed in claim 1.

12. The process as claimed in claim 11,

wherein

ammonia or a compound decomposable to ammonia is supplied as a reducing agent to the exhaust gas to be cleaned from a source independent of the engine prior to entry into the catalyst.

13. The process as claimed in claim 11,

wherein

the exhaust gas to be cleaned is additionally passed over a catalyst which predominantly accelerates the selective catalytic reduction of nitrogen oxides with ammonia.

14. An apparatus comprising a catalyst as claimed in claim 1 and an SCR catalyst arranged on the outflow side with respect thereto.

15. A process for removing nitrogen oxides from the exhaust gas of diesel engines,

wherein the exhaust gas to be cleaned has an air ratio λ

greater than 1 and is passed through the apparatus of claim 14.