(95i) Measurement of OH Radical in DBD Reactor with/without Catalyst by HPLC for Toluene Removal

In this paper, a new kind of way was used to detect the concentration of OH radical in DBD reaction. A film which was impregnated with salicylic acid was used to catch OH radical in plasma reaction at room temperature and atmospheric pressure. Salicylic acid would react with OH radical and a product of 2,5-DHBA was produced. Then, a high performance liquid chromatography (HPLC) was associated to detect the concentration of 2,5-DHBA. Therefore, OH radical in non-thermal plasma reaction could be calculated. Manganese oxide was used as a catalyst and it was placed in the discharge area of a wire-plate dielectric barrier discharge reactor. The combination effect of plasma and manganese oxide catalyst was studied on the toluene removal efficiency, byproducts inhibition and hydroxyl radical formation. In addition, in order to investigate the performance of MnOX catalyst and the formation of other radicals, a characterization of the catalyst was performed by BET, XPS, TPR, and FT-IR. It was found that the amount of OH radical increases with the increase of SED, and the concentration of HO* in gas stream with catalyst is much lower than that without catalyst. The concentrations of HO* without catalyst were in the range of (5.9~23.6) ×1013 radicals/cm3. But with catalyst, they just varied with (0.67~4.12) ×1013 radicals/cm3. In addition, OH radical concentration was detected under different relative humidity including 0, 20%, 40%, 60% and 80%. The results showed that the highest OH yield was obtained at a RH of 20%. The results of XPS and FT-IR suggested that various oxygen species and some compounds containing N element deposited on the catalyst after plasma reaction. And the spectra of FT-IR also verified the formation of OH on the surface of catalyst.