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Plasma-assisted catalytic storage reduction system

Patent ·
OSTI ID:874355
 [1];  [2];  [3];  [3]
  1. San Ramon, CA
  2. Fremont, CA
  3. Livermore, CA
+ Show Author Affiliations

A two-stage method for NO.sub.x reduction in an oxygen-rich engine exhaust comprises a plasma oxidative stage and a storage reduction stage. The first stage employs a non-thermal plasma treatment of NO.sub.x gases in an oxygen-rich exhaust and is intended to convert NO to NO.sub.2 in the presence of O.sub.2 and hydrocarbons. The second stage employs a lean NO.sub.x trap to convert such NO.sub.2 to environmentally benign gases that include N.sub.2, CO.sub.2, and H.sub.2 O. By preconverting NO to NO.sub.2 in the first stage with a plasma, the efficiency of the second stage for NO.sub.x reduction is enhanced. For example, an internal combustion engine exhaust is connected by a pipe to a first chamber in which a non-thermal plasma converts NO to NO.sub.2 in the presence of O.sub.2 and hydrocarbons, such as propene. A flow of such hydrocarbons (C.sub.x H.sub.y) is input from usually a second pipe into at least a portion of the first chamber. The NO.sub.2 from the plasma treatment proceeds to a storage reduction catalyst (lean NO.sub.x trap) that converts NO.sub.2 to N.sub.2, CO.sub.2, and H.sub.2 O, and includes a nitrate-forming catalytic site. The hydrocarbons and NO.sub.x are simultaneously reduced while passing through the lean-NO.sub.x trap catalyst. The method allows for enhanced NO.sub.x reduction in vehicular engine exhausts, particularly those having relatively high sulfur contents.

Research Organization:
Lawrence Livermore National Laboratory (LLNL), Livermore, CA
DOE Contract Number:
W-7405-ENG-48
Assignee:
The Regents of the University of California (Oakland, CA)
Patent Number(s):
US 6374595
OSTI ID:
874355
Country of Publication:
United States
Language:
English

References (5)

Recent Progress in NOx Trap Technology conference February 1998
Non-Thermal Plasma Techniques for Pollution Control book
Reduction of Nitric Oxide in Flue Gases by Point to Plane Corona Discharge with Catalytical Coatings on the Plane Electrode journal July 1990
The new concept 3-way catalyst for automotive lean-burn engine: NOx storage and reduction catalyst journal January 1996
Highly Durable NOx Reduction System and Catalysts for NOx Storage Reduction System conference February 1998

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