Plasma-assisted catalytic storage reduction system
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.
- Sponsoring Organization:
- USDOE
- OSTI ID:
- 20015730
- Resource Relation:
- Other Information: PBD: 21 Mar 2000
- Country of Publication:
- United States
- Language:
- English
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