NOx reduction behavior on alumina with discharging nonthermal plasma in simulated oxidizing exhaust gas

The NO_x reduction activity on γ‐alumina was significantly improved by discharging nonthermal plasma in a simulated oxidizing exhaust gas under conditions of a high space velocity. On the other hand, those on a Pt‐loaded catalyst and Cu‐ZSM‐5 could not be improved. The discharging nonthermal plasma converted NO to NO₂ and hydrocarbons to partial‐oxidized hydrocarbons, such as aldehydes, under the oxidizing conditions. From the relationship between the NO_x reduction activities and the properties of several alumina catalysts, it was found that the NO_x reduction activity was correlated with the number of acid sites on the alumina based on the NH₃ adsorption measurement. Therefore, it is concluded that the NO_x reduction occurred at the acid sites of the alumina, and the discharging nonthermal plasma improves the NO_x reduction activity by NO₂ formation and partial‐oxidation of hydrocarbons. These results suggest that a catalytic reaction assisted by the discharging nonthermal plasma could be a promising technology for NO_x reduction in lean‐burn and diesel exhaust gases even under the conditions of high space velocity. Copyright © 2006 Society of Chemical Industry