Exhaust gas purification system for the treatment of engine exhaust gases by means of SCR catalyst
원문보기
IPC분류정보
국가/구분
United States(US) Patent
등록
국제특허분류(IPC7판)
F01N-003/10
B01J-023/00
B01J-029/76
F01N-003/20
B01J-035/00
F01N-013/00
B01J-023/30
B01D-053/94
F01N-003/035
B01J-037/02
B01J-029/072
출원번호
US-0937089
(2009-03-18)
등록번호
US-8863507
(2014-10-21)
우선권정보
EP-08007163 (2008-04-11)
국제출원번호
PCT/EP2009/001997
(2009-03-18)
§371/§102 date
20110307
(20110307)
국제공개번호
WO2009/124643
(2009-10-15)
발명자
/ 주소
Adelmann, Katja
Soeger, Nicola
Pfeifer, Marcus
Schneider, Wolfgang
Jeske, Gerald
Kreuzer, Thomas
출원인 / 주소
Umicore AG & Co. KG
대리인 / 주소
Smith, Gambrell & Russell, LLP
인용정보
피인용 횟수 :
2인용 특허 :
4
초록▼
An exhaust gas purification system (method and device) for the treatment of diesel exhaust gases containing nitrogen oxides and hydrocarbons is disclosed, which comprises the addition of ammonia or of a compound decomposable to ammonia into the exhaust gas stream and the subsequent leading of the ex
An exhaust gas purification system (method and device) for the treatment of diesel exhaust gases containing nitrogen oxides and hydrocarbons is disclosed, which comprises the addition of ammonia or of a compound decomposable to ammonia into the exhaust gas stream and the subsequent leading of the exhaust gas stream over two successively arranged SCR catalysts with different properties and compositions. Both SCR catalysts are free of vanadium compounds and only the downstream SCR catalyst contains zeolite compounds. The exhaust gas purification system according to the invention is characterized by good “kick-off” behavior at low temperatures and a simultaneously high conversion performance over a wide temperature range.
대표청구항▼
1. A method of treatment of diesel engine exhaust gases in an exhaust system containing nitrogen oxides and hydrocarbons comprising: (a) addition of ammonia or of a compound decomposable to ammonia from a source that does not form part of the exhaust system into the exhaust gas stream containing nit
1. A method of treatment of diesel engine exhaust gases in an exhaust system containing nitrogen oxides and hydrocarbons comprising: (a) addition of ammonia or of a compound decomposable to ammonia from a source that does not form part of the exhaust system into the exhaust gas stream containing nitrogen oxides and hydrocarbons;(b) passing the exhaust gas stream containing nitrogen oxides, hydrocarbons and ammonia or a compound decomposable to ammonia over a first, upstream SCR catalyst, which catalyzes the comproportionation of nitrogen oxides with ammonia in a temperature range between 300° C. and 500° C., while at least partially oxidizing the hydrocarbons contained in the exhaust gas; and(c) passing the exhaust gas resulting from (b) over a second, downstream SCR catalyst, which catalyzes the comproportionation of nitrogen oxides with ammonia in a temperature range between 150° C. and 400° C. and at the same time stores excess ammonia. 2. The method as claimed in claim 1, wherein the exhaust gas stream containing nitrogen oxides and hydrocarbons is led, before the addition of ammonia or of a compound decomposable to ammonia in (a), over an oxidation catalyst that oxidizes at least a portion of the NO contained in the nitrogen oxides to NO2. 3. The method as claimed in claim 2, wherein the NO2/NOx ratio in the exhaust gas is altered so that the exhaust gas stream, before being led over the first, upstream SCR catalyst in (b), has an NO2/NOx ratio from 0.3 to 0.7. 4. The method as claimed in claim 1, wherein the amount of ammonia or of a compound decomposable to ammonia to be added to the exhaust gas stream in (a) is selected so that the exhaust gas stream, before being led over the first, upstream SCR catalyst in (b), has an NH3/NOx ratio from 0.8 to 1.2. 5. The method as claimed in claim 4, wherein the exhaust gas stream, after being passed through the second, downstream SCR catalyst in (c), is led over an oxidation catalyst, which selectively catalyzes the oxidation of ammonia to nitrogen. 6. The method as claimed in claim 5, wherein the oxidation catalyst is arranged on a soot particle-filtering support. 7. The method as claimed in claim 1, wherein the first, upstream SCR catalyst, which the exhaust gas stream is passed over in (b), does not contain zeolite compounds. 8. The method as claimed in claim 7, wherein the first, upstream SCR catalyst, which the exhaust gas stream is passed over in (b), contains neither vanadium compounds nor zeolite compounds. 9. The method as claimed in claim 1, wherein the first, upstream SCR catalyst, which the exhaust gas stream is passed over in (b), contains tungsten oxide WO3 and a homogeneous cerium-zirconium mixed oxide (Ce,Zr)O2. 10. An exhaust gas purification system for lowering the content of nitrogen oxides in the lean exhaust gas of an internal combustion engine containing, in combination and in this order: (1) a feeding device that feeds ammonia or a compound decomposable to ammonia into the exhaust gas stream containing nitrogen oxides from a source that does not form part of the exhaust system;(2) a first, upstream SCR catalyst, which catalyzes the comproportionation of nitrogen oxides with ammonia in a temperature range between 300° C. and 500° C. and contains neither vanadium compounds nor zeolite compounds; and(3) a second, downstream and vanadium-free SCR catalyst, which catalyzes the comproportionation of nitrogen oxides with ammonia in a temperature range between 150° C. and 400° C. and contains a copper- (Cu-)exchanged zeolite compound. 11. The exhaust gas purification system as claimed in claim 10, wherein each of the two SCR catalysts is in form of a coating on an inert support. 12. The exhaust gas purification system as claimed in claim 10, wherein the first and the second SCR catalyst are arranged as coatings on the same support. 13. The exhaust gas purification system as claimed in claim 12, wherein the first, upstream SCR catalyst is in the form of a coating zone arranged on the inlet side on the support and the second, downstream SCR catalyst forms the coating zone on the outlet side on the support. 14. The exhaust gas purification system as claimed in claim 13, wherein the ratio of the lengths of coating zone arranged on the inlet side to coating zone on the outlet side is between 0.1 and 3. 15. The exhaust gas purification system as claimed in claim 10, wherein the first SCR catalyst contains tungsten oxide WO3 and a homogeneous cerium-zirconium mixed oxide (Ce,Zr)O2. 16. The exhaust gas purification system as claimed in claim 15, wherein the content of tungsten oxide WO3 in the first SCR catalyst is between 5 and 25 wt. %, relative to the total amount of the first SCR catalyst without consideration of the mass of the inert support. 17. The exhaust gas purification system as claimed in claim 15, wherein the content of homogeneous cerium-zirconium mixed oxide (Ce,Zr)O2 in the first SCR catalyst is between 50 and 95 wt. %, relative to the total amount of the first SCR catalyst without consideration of the mass of the inert support. 18. The exhaust gas purification system as claimed in claim 17, wherein the weight ratio of cerium oxide CeO2 and zirconium oxide ZrO2 in the homogeneous cerium-zirconium mixed oxide (Ce,Zr)O2 is between 0.43 and 2.33. 19. The exhaust gas purification system as claimed in claim 10, wherein the second SCR catalyst contains a copper- (Cu-)exchanged zeolite compound with a content of 2 to 10 wt. % Cu relative to the total weight of the zeolite compound. 20. The exhaust gas purification system as claimed in claim 18, wherein the zeolite compound is selected from the group consisting of beta-(β-)zeolite, Y-zeolite, ZSM-5, ZSM-20, ferrierite and mordenite.
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이 특허에 인용된 특허 (4)
Tran, Pascaline H.; Liu, Xinsheng; Chen, James M., Hydrothermally stable metal promoted zeolite beta for NOx reduction.
Speronello Barry K. (Belle Mead NJ) Byrne John W. (Edison NJ) Chen James M. (Edison NJ), Staged metal-promoted zeolite catalysts and method for catalytic reduction of nitrogen oxides using the same.
Castagnola, Mario Jaime; Chiffey, Andrew Francis; Phillips, Paul Richard; Rajaram, Raj Rao; Walker, Andrew Peter, Substrate monolith comprising SCR catalyst.
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