Plasma-catalytic destruction of xylene over Ag-Mn mixed oxides in a pulsed sliding discharge reactor

Highlights: • More reactive species can be generated from the sliding DBD than surface DBD. • Ag doping on Mn catalyst enhanced the content of surface-adsorbed oxygen. • Coupling of sliding DBD with Ag-Mn mixed catalysts improved plasma oxidation of VOC. • Ag-Mn oxide with Ag/Mn molar ratio of 1:2 presented the best catalytic activity. • Undesired byproducts were substantially reduced by using Ag-Mn mixed catalysts. -- Abstract: Plasma-assisted catalytic degradation of xylene was performed in a pulsed sliding dielectric barrier discharge (SLDBD) reactor based on three-electrode geometry over Ag-Mn bimetallic oxides catalysts at room temperature. Experimental results showed that more active species were distributed uniformly in the SLDBD plasma than traditional surface dielectric barrier discharge (SDBD), contributing to higher degradation and energy performance. The xylene degradation efficiency and energy yield in the SLDBD reactor driven by both +pulse (+18 kV) and –DC (–10 kV) were 40% and 2.3 g/kWh higher, respectively, than in the SDBD reactor energized by +pulse alone. The combination of SLDBD plasma with catalysts significantly improved the xylene degradation efficiency and CO₂ selectivity than the plasma-only system. The incorporation of Ag into Mn oxide further enhanced its catalytic activity for xylene degradation, and the catalytic activity of Ag-Mn oxides was closely correlated with the Ag/Mn molar ratio. Ag-Mn/γ-Al₂O₃ (1:2) presented the best performance in plasma-catalysis process, with 91.5% of degradation efficiency and 80.1% of CO₂ selectivity at 4.6 W. The higher proportion of surface O_ads and better reducibility through the interaction between Ag and Mn species can explain the excellent reactivity of Ag-Mn/γ-Al₂O₃ (1:2).