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Emissions treatment system with ammonia-generating and SCR catalysts

A technology of SCR catalyst and exhaust gas treatment, which is applied in the direction of gas treatment, exhaust equipment, chemical instruments and methods, etc., and can solve problems such as limiting the range of operating conditions

Active Publication Date: 2012-03-21
BASF CORP
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  • Summary
  • Abstract
  • Description
  • Claims
  • Application Information

AI Technical Summary

Problems solved by technology

This deficiency may limit the range of operating conditions in which NOx can be effectively treated by other exhaust gas treatment systems

Method used

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  • Emissions treatment system with ammonia-generating and SCR catalysts
  • Emissions treatment system with ammonia-generating and SCR catalysts
  • Emissions treatment system with ammonia-generating and SCR catalysts

Examples

Experimental program
Comparison scheme
Effect test

Embodiment 1

[0116] The oxidation catalyst was placed on a flow-through monolithic substrate having a 50in 3 capacity (0.83 L), a cell density of 300 cells per square inch, and a wall thickness of approximately 125 μm. Catalyst contains 2.5g / in 3 activated alumina, which has 40g / ft 3 Pt and 8g / ft 3 Pd's and 8g / ft 3Pd H-beta zeolite.

[0117] The coated LNT catalyst was placed on a flow-through monolithic substrate having a 152 in 3 (2.5L) capacity, a cell density of 400 cells per square inch and a wall thickness of approximately 100 μm. Primer contains 3.84g / in 3 Washcoat of activated alumina containing 10% ceria and 18% BaO, 1.1 g / in 3 Cerium oxide (87% of cerium oxide is in the form of particles), 0.24g / in 3 MgO and 0.096g / in 3 ZrO 2 . This base coat washcoat contains 34.3g / ft 3 Pt and 4.3g / ft 3 Pd. The top coat contains activated alumina which has 21.7 g / ft 3 Pt and 2.7g / ft 3 0.7g / in Pd 3 and with 7.0g / ft 3 Rh 0.5g / in 3 A washcoat of cerium oxide, substantially free o...

Embodiment 3

[0124] test

[0125] Pore ​​samples were taken from each of the flow-through catalysts in Example 1 above. The individual well sample dimensions are 0.75"(D) x 0.42"(L) for DOC, 0.75"(D) x 1.25"(L) for LNT and 0.75"(D) x 0.75"(L) for SCR. Three sets of system samples were installed in a single experimental reactor. The distance between each catalyst component in the experimental reactor was 0.25 ". The exhaust system of Example 1 of the present invention (i.e. DOC+LNT+Cu-CHA and DOC+LNT+Cu-SAPO) and Comparative Example 2 (i.e. only DOC +LNT) aging alone. The aging process consists of two steps. First, the catalyst system is aged at 800° C. for 5 hours in flowing air with 10% water vapor. Then, the catalyst system is subjected to cyclic aging records, which Consists of a sulfation mode (loading 1 g S / L) at 300 °C and a desulfation mode (10 sec lean and 15 sec rich (λ = 0.9) cycle for 5 min) at 700 °C (LNT bed temperature). Cyclic aging was performed for 40 cycles. After agin...

Embodiment 4

[0128] According to the method described herein, an exhaust system was formed by preparing an LNT catalyst with a 2-layer structure and an SCR catalyst comprising copper-SSZ-13 (CuCHA) on a diesel particulate filter (DPF).

[0129] The LNT catalyst was placed on a flow-through monolithic substrate having a 152in 3 (2.5L) capacity, a cell density of 400 cells per square inch, and a wall thickness of approximately 100 μm. The preparation of the LNT was substantially the same as described in Example 1 except for the PGM loading. The primer contains 63g / ft 3 Pt and 6.5g / ft 3 Pd, and the top coat has 40g / ft on activated alumina 3 Pt and 4g / ft 3 Pd and has 6.5g / ft on ceria 3 . The resulting coated LNT catalyst contains a total of 103 g / ft 3 Pt, 10.5g / ft 3 Pd and 6.5g / ft 3 Rh.

[0130] The CuCHA SCR catalyst was placed on a wall flow filter substrate with a 152in 3 (2.5L) capacity, a cell density of 300 cells per square inch, and a wall thickness of approximately 300 μm. ...

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Abstract

Provided are emissions treatment systems for an exhaust stream having an ammonia- generating component, such as a NOx storage reduction (NSR) catalyst or a lean NOx trap (LNT) catalyst, and an SCR catalyst disposed downstream of the ammonia-generating catalyst. The SCR catalyst can be a molecular sieve having the CHA crystal structure, for example SSZ- 13 or SAPO-34, which can be ion-exchanged with copper.; The LNT can be layered, having an undercoat washcoat layer comprising a support material, at least one precious metal, and at least one NOx sorbent selected from the group consisting of alkaline earth elements, rare earth elements, and combinations thereof and a top washcoat layer comprising a support material at least one precious metal, and ceria in particulate form, the top washcoat layer being substantially free of alkaline earth components, The emissions treatment system is advantageously used for the treatment of exhaust streams from diesel engines and lean burn gasoline engines.

Description

technical field [0001] The present invention relates to exhaust gas treatment systems with ammonia generating and SCR catalysts, and methods for reducing pollutants in exhaust gas streams, particularly those containing nitrogen oxides (NOx). More specifically, the present invention is concerned with exhaust treatment systems containing ammonia generating catalysts such as NOx storage reduction (NSR) catalysts or lean NOx trap (LNT) catalysts in combination with selective catalytic reduction (SCR) catalysts, and Their method is used in a lean-burn engine of a lean-burn gasoline engine. technical background [0002] Operating lean burn engines such as diesel and lean burn gasoline engines provides the user with good fuel burn efficiency and emits very low amounts of gaseous hydrocarbons and carbon monoxide due to their operation at high air / fuel ratios under fuel-scarce conditions. In particular, diesel engines are also significantly superior to gasoline engines in terms of d...

Claims

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Application Information

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IPC IPC(8): B01D53/94B01D53/58F01N3/035
CPCB01D2255/9155F01N3/033B01D2255/2063B01D2255/20761B01D53/9477B01D2255/20753B01D2255/206F01N2510/063B01D53/9472F01N3/10B01D2255/50B01D53/9431B01D2251/2062F01N3/0807B01D53/9418B01D2255/2045F01N3/0842F01N3/0814B01D2258/012B01D2255/9205F01N3/2066F01N3/035F01N3/2073B01D2255/2042B01D2255/2066F01N13/02B01D2255/9022B01D2255/2068B01D2255/102B01D53/9422Y02T10/24F01N2510/0682B01D2255/91B01D2255/2092Y02T10/12B01D53/58B01D53/92F01N3/02F01N3/021F01N3/0821F01N3/103F01N3/206
Inventor C-Z·万X·郑S·斯蒂贝尔斯C·文特S·R·布尔斯
Owner BASF CORP
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