Multi-stage selective catalytic reduction of NOx in lean burn engine exhaust

Conference · Wed Dec 31 04:00:00 EST 1997

OSTI ID:334043

Penetrante, B M; Hsaio, M C; Merritt, B T; Vogtlin, G E ^[1]

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1. Lawrence Livermore National Lab., CA (United States)

Many studies suggest that the conversion of NO to NO{sub 2} is an important intermediate step in the selective catalytic reduction (SCR) of NO{sub x} to N{sub 2}. Some effort has been devoted to separating the oxidative and reductive functions of the catalyst in a multi-stage system. This method works fine for systems that require hydrocarbon addition. The hydrocarbon has to be injected between the NO oxidation catalyst and the NO{sub 2} reduction catalyst; otherwise, the first-stage oxidation catalyst will also oxidize the hydrocarbon and decrease its effectiveness as a reductant. The multi-stage catalytic scheme is appropriate for diesel engine exhausts since they contain insufficient hydrocarbons for SCR, and the hydrocarbons can be added at the desired location. For lean-burn gasoline engine exhausts, the hydrocarbons already present in the exhausts will make it necessary to find an oxidation catalyst that can oxidize NO to NO{sub 2} but not oxidize the hydrocarbon. A plasma can also be used to oxidize NO to NO{sub 2}. Plasma oxidation has several advantages over catalytic oxidation. Plasma-assisted catalysis can work well for both diesel engine and lean-burn gasoline engine exhausts. This is because the plasma can oxidize NO in the presence of hydrocarbons without degrading the effectiveness of the hydrocarbon as a reductant for SCR. In the plasma, the hydrocarbon enhances the oxidation of NO, minimizes the electrical energy requirement, and prevents the oxidation of SO{sub 2}. This paper discusses the use of multi-stage systems for selective catalytic reduction of NO{sub x}. The multi-stage catalytic scheme is compared to the plasma-assisted catalytic scheme.

• Research Organization: Dept. of Energy Assistant Secretary for Energy Efficiency and Renewable Energy, Office of Transportation Technologies, Washington, DC (United States)
• Sponsoring Organization: USDOE, Washington, DC (United States)
• DOE Contract Number: W-7405-ENG-48
• OSTI ID: 334043
• Report Number(s): CONF-970799--PROC.; ON: DE99000798
• Country of Publication: United States
• Language: English

Related Subjects

02 PETROLEUM
33 ADVANCED PROPULSION SYSTEMS
54 ENVIRONMENTAL SCIENCES
AIR POLLUTION CONTROL
COLD PLASMA
EXHAUST GASES
NITRIC OXIDE
NITROGEN OXIDES
OXIDATION
POLLUTION CONTROL EQUIPMENT
SELECTIVE CATALYTIC REDUCTION