Plasma-catalytic Decomposition Of Adsorbed Benzene, Toluene, Styrene, Benzene/Toluene And Benzene/Styrene With Gas Circulation

With the rapid development of China's economy, the problem of air pollution isbecoming more and more serious. Volatile organic compounds (VOCs) is an importantpart of air pollution, their damage to human body and the environment cannot beignored. Among the technologies in the processing of VOCs, technology with highprocessing efficiency, short process and wide scope of application in the treatment oflow concentration VOCs gradually shows advantages on the technical and economic.Choosing the single-component such as benzene, toluene, styrene and mixedcomponents such as benzene/toluene, benzene/styrene as the research object, this studyinvestigated the degradation of gaseous VOCs with Nonthermal plasma technologyalone. The degradation characteristics of absorbed benzene, toluene, styrene,benzene/toluene and benzene/styrene in the system of adsorption storage-gascirculation Nonthermal plasma catalytic oxidation are also studied, which can providethe basic theory and design basis for the industrial application. Nonthermal plasmaalone was used to degrade of gaseous VOCs and adsorption storage-gas circulationNonthermal plasma catalytic oxidation experiment system was used to degrade ofabsorbed benzene, toluene, styrene, benzene/toluene and benzene/styrene. Thedegradation effect of the single-component VOC and two-component of VOCs weretested; The effect of Initial concentration, and the input voltage, the amounts ofadsorption, oxidation background gas and the type of catalyst on the degration ofsingle-component VOC and two-component VOCs were studied. The regularity impactof catalyst on by-products O3, N2O was also analyzed. With ?-Al2O3as the carrier,MnOx-AgOx, CoOx-CeOxcomposite metal oxide catalyst were prepared using impregnation method. BET, SEM and XRD were used to characterize the catalyst.Main conclusions are as follows:(1) Degradation of gaseous benzene, toluene, styrene, benzene/toluene andbenzene/styrene with nonthermal plasma alone, the lower the initial concentration ofpollutants, the higher removal rate is under the same conditions; The higher the inputvoltage, the higher removal rate is; the main gas phase products were CO2, H2O and asmall amount of CO, the by-products were N2O and O3, and some contaminantresidues. There were no NO or NO2detected by FT-IR. Nonthermal plasma alone hadlittle effect on removal of benzene, toluene, styrene, benzene/toluene andbenzene/styrene.(2) Under gas cycle operation with ?-Al2O3as adsorbent, the yield of COxand theselectivity of CO2of the adsorbed benzene, toluene, styrene, benzene/toluene andbenzene/styrene decrease with the increase amount of adsorption. The yield of COxandthe selectivity of CO2increased when the background gas changed from air to oxygen.(3) Under the gas cycle operation, COxyield and selectivity of CO2increasedwhen ?-Al2O3loaded with MnOx-AgOx, CoOx-CeOxduring the degradation ofabsorbed VOCs, while the concentrations of O3was obviously lower than the absenceof catalyst. The yield of COx, the selectivity of CO2and the decomposition capabilityof O3are in the order of MnOx-AgOx/?-Al2O3> CoOx-CeOx/?-Al2O3> ?-Al2O3.(4) FT-IR analysis results showed that under the gas circulation operation mode,the main gas phase products in plasma oxidation absorbed benzene, toluene, styrene,benzene/toluene and benzene/styrene were CO2, H2O and small amounts of CO,mainly by-products are O3. When the circulation gas changed from oxygen to air, therewas a small amount of N2O.(5) N2O concentration increases with the extension of time during the Nonthermalplasma degradation of absorbed benzene, toluene, styrene, benzene/toluene andbenzene/styrene with air circulation. All of the studied composite metal oxidesCoOx-CeOx, MnOx-AgOxhave certain inhibitory effect on N2O. The inhibition abilityof N2O followed by CoOx-CeOx/?-Al2O3> MnOx-AgOx/?-Al2O3> ?-Al2O3.(6) The results of Nonthermal plasma catalytic oxidation of absorbed VOCsshowed that, the absorbed state of benzene, toluene, styrene, benzene/toluene andbenzene/styrene can realize the depth of catalytic oxidation with circulation conditions, which effectively avoided VOCs pollution caused by plasma desorption. After gascycled90min, the CO2selectivity were greater than94%, degradation rate from highto low was in turn as follows: toluene> benzene/toluene> benzene>benzene/styrene> styrene.