LNT+SCR Catalyst Systems Optimized for NOx Conversion on Diesel Applications Ford Motor Company

Format:

Conference/Event

Author/Creator:

Theis, Theis, author.

Contributor:

Dearth, Mark

McCabe, Robert

Conference Name:

SAE 2011 World Congress & Exhibition (2011-04-12 : Detroit, Michigan, United States)

Language:

English

Physical Description:

1 online resource

Place of Publication:

Warrendale, PA SAE International 2011

Summary:

A laboratory study was performed to assess the effectiveness ofLNT+SCR systems for NOx control in lean exhaust. Theeffects of the catalyst system length and the spatial configurationof the LNT and SCR catalysts were evaluated for their effects onthe NOx conversion, NH₃ yield, N₂O yield, and HCconversion. It was found that multi-zone catalyst architectureswith four or eight alternating LNT and SCR catalyst zones hadequivalent gross NOx conversion, lower NH₃ and N₂Oyield, and significantly higher net conversion of NOx toN₂ than an all-LNT design or a standard LNT+SCR configuration,where all of the SCR volume is placed downstream of the LNT. Thelower NH₃ emissions of the two multi-zone designs relative to thestandard LNT+SCR design were attributed to the improved balance ofNOx and NH₃ in the SCR zones. The lower N₂O emissionswith the multi-zone designs were attributed to the fact that asignificant portion of the NOx conversion occurred inthe SCR zones in the front of the catalyst system, as thecopper/zeolite SCR catalyst is less prone for generating N₂O thanthe platinum-containing LNT. The two multi-zone designs also hadimproved HC conversion relative to the standard LNT+SCR design.This was due to the adsorption of some of the HC on thezeolite-containing SCR zones during a rich purge; some of thisadsorbed HC was released during the subsequent lean period andoxidized by the downstream LNT. For the same overall length, afour-zone LNT+SCR design was nearly as beneficial as an eight-zonedesign. This has important implications for manufacturability, as afour-zone design would be considerably simpler to produce than aneight-zone design

Notes:

Vendor supplied data

Publisher Number:

2011-01-0305

Access Restriction:

Restricted for use by site license