| 摘要 |
A two-stage method for NOx 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 NOx gases in an oxygen-rich exhaust and is intended to convert NO to NO2 in the presence of O2 and hydrocarbons. The second stage employs a lean NOx trap to convert such NO2 to environmentally benign gases that include N2, CO2, and H2O. By preconverting NO to NO2 in the first stage with a plasma, the efficiency of the second stage for NOx 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 NO2 in the presence of O2 and hydrocarbons, such as propene. A flow of such hydrocarbons (CxHy) is input from usually a second pipe into at least a portion of the first chamber. The NO2 from the plasma treatment proceeds to a storage reduction catalyst (lean NOx trap) that converts NO2 to N2, CO2, and H2O, and includes a nitrate-forming catalytic site. The hydrocarbons and NOx are simultaneously reduced while passing through the lean-NOx trap catalyst. The method allows for enhanced NOx reduction in vehicular engine exhausts, particularly those having relatively high sulfur contents.
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