Study On The Mechanism Of Non-thermal Plasma Coupling Metal Oxide/Zeolite Toward Catalytic Degradation Of Toluene

VOCs are important atmospheric pollutants，which are key precursors that causingregional ozone exceed the standard, PM2.5heavily pollution. With the social development andeconomic development, VOCs emissions of china increased year after year, air pollution issuecaused by the VOCs further highlight, control the pollution of VOCs pollution is imminent.Scholars have tried lots of studies to combine non-thermal plasma and catalytic form thenon-thermal plasma catalytic technology, which can degrade VOCs in ambient temperatureand pressure, improve the energy utilization efficiency, reducing secondary pollution. Due tothe complexity of the plasma-catalytic system, the reaction process of oxidative VOCs is notclear, thus impede application of this technology.Prepared a series of5%Mn/SBA-15by impregnation using different calcinationtemperature, Mn/SBA-15(400oC) has the best catalytic degradation activity is due to thecalcination temperature of the catalyst maintain the best redox properties.Continuous discharge and adsorptive storage-intermittent discharge combined withSBA-15for toluene decomposition was investigated under ambient pressure and temperature.The results showed that adsorptive storage-intermittent discharge method exhibited highertoluene conversion, CO2selectivity and better carbon balance compared to the former. Bypre-adsorption of toluene greatly enhance the utilization efficiency of the active speciesgenerated in the plasma, intermittent discharge mode maintain the active sites of the catalystexposed, thereby promoting the complete oxidation of toluene to CO2.Then, the activities of four different catalysts, SBA-15, Mn/SBA-15, Ag/SBA-15andAgMn/SBA-15were tested with dsorptive storage-intermittent discharge mode. TheAgMn/SBA-15catalyst exhibited the highest CO2selectivity and carbon balance, which maybe due to2-heptene alcohol oxidation catalyzed by the addition of Ag and Mn.Tolueneadsorption capacity effect on the degradation rate of toluene, loading of Ag can enhance theadsorption capacity of the catalyst due to form Ï€-Complexing bond. Loading of Ag, Mnenhance the capacity of the ozone degradation of the catalyst, thereby strengthen the activityof degrade toluene。 Meanwhile, loading of Mn hoist the redox properties of catalyst, loadingof Ag can promote the deep decomposition of intermediate products to CO2.The evolution of the intermediate products on the catalyst surfaces with time werealso analysed by GC-MS and in situ infrared spectroscopic. Main intermediates of plasmacatalytic degradation of toluene are benzyl alcohol, benzaldehyde, benzoic acid andnitrophenol. The reaction process of plasma catalytic degrade toluene is speculated by the results, tolueneâ†'benzylalcoholâ†'benzaldehydeâ†'benzoic acidâ†'small moleculesâ†'CO2and H2O is the main path.The results indicated that formaldehyde oxidation is therate-determining step for toluene decomposition.