The Desulfation Characteristics of Lean NOx Traps

Theis, Joseph R.; Li, John J.; Ura, Justin; Hurley, R. G.

doi:10.4271/2002-01-0733

Cited by 16 publications

(5 citation statements)

References 13 publications

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“…Evidence of WGS reaction over NSR catalysts has been reported previously and used mainly to explain catalyst desulfation behavior [22][23][24]. However, it is still not clear if and how H 2 produced by WGS reaction impacts NSR catalyst regeneration.…”

Section: Impact Of Wgs Reaction On Nsr Catalyst Regenerationmentioning

confidence: 90%

Intra-channel evolution of carbon monoxide and its implication on the regeneration of a monolithic Pt/K/Al2O3 NOx storage-reduction catalyst

et al. 2006

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Section: Impact Of Wgs Reaction On Nsr Catalyst Regenerationmentioning

confidence: 90%

Intra-channel evolution of carbon monoxide and its implication on the regeneration of a monolithic Pt/K/Al2O3 NOx storage-reduction catalyst

et al. 2006

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“…Previous testing on lean NO x traps indicated that 10 to 15 minutes of rich operation at 675 to 750°C are required to recover the NO x storage capacity of a poisoned LNT [22]. Therefore, after the TWC was desulfated, the LNT was desulfated by heating the second oven to achieve a bed temperature of 700°C under rich conditions.…”

Section: Desulfations On the Reactormentioning

confidence: 99%

TWC+LNT/SCR Systems for Satisfying Tier 2, Bin 2 Emission Standards on Lean-Burn Gasoline Engines

Theis¹,

Kim²,

Cavataio³

2015

SAE Int. J. Fuels Lubr.

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A laboratory study was performed to assess the potential capability of TWC+LNT/SCR systems to satisfy the Tier 2, Bin 2 emission standards for lean-burn gasoline applications. It was assumed that the exhaust system would need a close-coupled (CC) TWC, an underbody (U/B) TWC, and a third U/B LNT/SCR converter to satisfy the emission standards on the FTP and US06 tests while allowing lean operation for improved fuel economy during select driving conditions. Target levels for HC, CO, and NO x during lean/ rich cycling were established. Sizing studies were performed to determine the minimum LNT/SCR volume needed to satisfy the NO x target. The ability of the TWC to oxidize the HC during rich operation through steam reforming was crucial for satisfying the HC target. Temperature studies indicated that the CC TWC needed to operate at a minimum of 500°C to provide good steam reforming activity, while the LNT/SCR needed to operate between 300 and 350°C to satisfy the NO x slip target while minimizing the slip of NH 3 , N 2 O, and HC during the purges. Sulfur poisoning increased the HC slip by degrading the steam reforming reaction, and the sulfur increased the NO x slip by decreasing the NO x storage capacity of the LNT. Both the TWC and LNT/SCR could be desulfated with rich exhaust at 700°C. However, it was projected that the ability to obtain 700°C at the underbody LNT/SCR location would be difficult without additional exhaust hardware, such as fuel injectors or air pumps. Consequently, development of the LNT/SCR system was terminated in favor of a passive TWC+SCR approach because of its superior sulfur tolerance. Investigations into the passive TWC+SCR approach are discussed in a companion SAE paper.

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“…The above discussion summarizes an overall mechanism for NSR. Although numerous studies have been carried out with the standard catalyst formulation (Pt−Ba/Al 2 O 3 ) to evaluate the mechanistic aspect, a practical problem remains, sulfur poisoning. − Sulfur poisoning of NSR catalysts can generally originate from two different pathways. SO 2 in the exhaust gas can be oxidized on precious metals and reacts with the support, forming aluminum sulfate, or SO x reacts with the NO x storage component to form barium sulfate.…”

Section: Mechanistic Viewsmentioning

confidence: 99%

NO_x Storage−Reduction Catalysis: From Mechanism and Materials Properties to Storage−Reduction Performance

2009

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The Desulfation Characteristics of Lean NOx Traps

Cited by 16 publications

References 13 publications

Intra-channel evolution of carbon monoxide and its implication on the regeneration of a monolithic Pt/K/Al2O3 NOx storage-reduction catalyst

Intra-channel evolution of carbon monoxide and its implication on the regeneration of a monolithic Pt/K/Al2O3 NOx storage-reduction catalyst

TWC+LNT/SCR Systems for Satisfying Tier 2, Bin 2 Emission Standards on Lean-Burn Gasoline Engines

NO_x Storage−Reduction Catalysis: From Mechanism and Materials Properties to Storage−Reduction Performance

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The Desulfation Characteristics of Lean NOx Traps

Cited by 16 publications

References 13 publications

Intra-channel evolution of carbon monoxide and its implication on the regeneration of a monolithic Pt/K/Al2O3 NOx storage-reduction catalyst

Intra-channel evolution of carbon monoxide and its implication on the regeneration of a monolithic Pt/K/Al2O3 NOx storage-reduction catalyst

TWC+LNT/SCR Systems for Satisfying Tier 2, Bin 2 Emission Standards on Lean-Burn Gasoline Engines

NOx Storage−Reduction Catalysis: From Mechanism and Materials Properties to Storage−Reduction Performance

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NO_x Storage−Reduction Catalysis: From Mechanism and Materials Properties to Storage−Reduction Performance