Experimental investigation on photochemical NOx gas treatment for diesel engine combustion exhaust by a dielectric barrier discharge type Xe excimer lamp

In this work, a NOx gas treatment using photochemical reactions with a VUV irradiation was investigated. From the theoretical considerations, an effective photon energy (165 kcal/mol) higher than the binding energies of NO (150 kcal/mol) and NO₂ (74 kcal/mol) was applied to the photochemical reaction. The experimental evaluation was conducted by using a photochemical reactor with a diesel engine combustion exhaust tube attached on a Xe excimer lamp operated on dielectric barrier discharges. It was confirmed that the discharge lamp radiated the excimer light of 172 nm in wavelength as the effective photon energy. The experimental results indicated that the concentration of NO and NO₂ gas molecules in the combustion exhaust were decreased with increasing the excimer light irradiation time. The photochemical effect on the NO removal was improved due to increasing NO₂ molecules as a secondary product with NO molecules and photochemically dissociated O atoms from residual O₂ molecules. This fact suggested that the NO and NO₂ removal rates were depended on residual O₂ concentration. This paper presents the application of the VUV irradiation from the Xe excimer lamp to the effective NOx treatment for diesel engine combustion exhaust gas. The fundamental characteristics is quantitatively discussed as functions of the experimental parameter such as the Xe excimer operation and the combustion exhaust gas condition.