Study And Application Of Synergistic Removal Of Toluene By The Combination Of Microplasma And Catalyst At Atmosphric Pressure

In the last few years,volatile organic compounds(VOCs)released by industry in China have been increasing year by year,causing increasingly serious environmental pollution.The emerging low temperature plasma technology has received extensive attention from researchers,however,problems such as high energy consumption and toxic by-products have always plagued its development.In this study,according to the shortcomings of existing low temperature plasma technology,nano TiO2,Mn/TiO2,a-MnO2/TiO2 catalysts were introduced into the self-innovation microplasma,which was generated by Double Dielectric Barrier Discharge(DDBD).These experiments were carried out in the pilot scale under the condition of low-concentration toluene gas without high-volume.The interaction and synergy effects between the DDBD microplasma and the photocatalytic system were systematically investigated.(1)The discharge characteristics and electrode structure of the self designed DDBD microplasma were optimized,and the removal efficiency of VOCs was investigated under the condition of high volume and low concentration toluenin the pilot scale.By comparing its discharge state and emission spectrum using DDBD microplasma,the electrode gap distance of 2 mm was determined as optimal reactor structure parameter.Nano TiO2 and Mn/TiO2 catalysts with different masses of Mn were prepared by using sol-gel method.Different ratios of ?-MnO2/TiO2 composite catalysts were prepared by hydrothermal method,and compare the removal efficiency by using them with that by using P25 catalyst.The experimental results showed that the catalytic activity of the nano TiO2 catalyst was better than that of the P25 catalyst.Among the Mn doped TiO2 catalysts,it was found that the 1.0%Mn/TiO2 catalyst has the best catalytic activity.Among the nanowire type and nanotube type catalysts with a crystalline phase MnO2 and TiO2 composite catalysts(a-MnO2-W/TiO2 and a-MnO2-T/TiO2),it was found that the catalytic activity of 10.0%a-MnO2-W/TiO2 composite catalyst has the best catalytic activity and was better than that of 10.0%?-MnO2-T/TiO2 composite catalyst,and both of them were better than nano TiO2 catalyst and 1.0%Mn/TiO2 catalyst.Comparing the characterization analysis results of SEM,XRD and UV-vis,the results showed that the catalytic activity of 1.0%Mn/TiO2 is mainly attributed to the lower bond energy of Mn-O bond and the stronger stability.The 10.0%a-MnO2/TiO2 composite catalyst can further reduce the escape of O3 and reduce the type and quantity of by-products.The analysis of the characterization results showed that the 10.0%a-MnO2-W/TiO2 composite catalyst effectively improved the BET specific surface area of the catalyst,thereby effectively increased the active site of the catalyst and promoted the adsorption amount of toluene and organic by-products on the catalyst surface.It was contributed to the improvement of toluene removal efficiency.In addition,the TiO2 in the 10.0%?-MnO2-W/TiO2 composite catalyst can also be photocatalyzed by ultraviolet light generated by microplasma,which provides an effective optimization scheme for further enhancing the synergistic reaction performance of the plasma catalytic system.(2)The experimental results of removing toluene by separate microplasma showed that the removal efficiency of toluene,the generation efficiency of O3,and the selectivity of COx(CO,CO2)all increased with the increase of energy density,and decreased with the increase of air volume.At the same time,the experimental results of removing toluene by the combination of microplasma and catalyst showed that the introduction of photocatalyst can effectively increase the toluene removal efficiency and the selectivity of COx of toluene,reduce the escape amount of O3 and reduce the type and quantity of gas phase by-products.Appropriate relative humidity not only increased the removal efficiency of toluene,but also prolonged the deactivation time of the catalyst.Based on the analysis of by-products,we proposed the degradation mechanism and removal path way of toluene in the microplasma coordinated photocatalysis system:high energy electrons generated in the microplasma system,electron-hole pairs generated generated by TiO2,various active free radicals,and O3 all provided the main driving force for removing toluene.