초록 ▼

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

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.

대표청구항 ▼

[ The invention claimed is:] [1.] A method for reducing nitrogen oxides (NO.sub.x) in exhausts from high-temperature combustion, the method comprising the steps of:converting substantially all NO in an engine exhaust with a non-thermal plasma to an intermediate gas flow including NO.sub.2 ;convertin

[ The invention claimed is:] [1.] A method for reducing nitrogen oxides (NO.sub.x) in exhausts from high-temperature combustion, the method comprising the steps of:converting substantially all NO in an engine exhaust with a non-thermal plasma to an intermediate gas flow including NO.sub.2 ;converting, in the presence of hydrocarbons, substantially all of said intermediate gas flow including NO.sub.2 and essentially no SO.sub.3 to an output gas flow comprising NO.sub.2 conversion products of N.sub.2, CO.sub.2 and H.sub.2 O and substantially little NO and NO.sub.2 (NO.sub.x); andwherein, a storage reduction catalyst is used to convert said NO.sub.2 in the presence of said hydrocarbons, to N.sub.2, CO.sub.2, and H.sub.2 O.