Low Temperature Plasma Treatment Of Toluene Waste Gas And Its Mechanism

In this paper,the degradation of toluene exhaust gas is carried out in the form of dielectric barrier discharge plasma catalytic oxidation.The concentrations of toluene and ozone in the gas products of the reaction were measured by gas chromatography and sodium indigo disulfonate spectrophotometry.The effects of discharge power,gas flow rate,plasma energy density and catalyst loading on toluene degradation were investigated.The Langmuir probe method and plasma emission spectrometry were used to diagnose plasma parameters during discharge.Experimental results show:?1?Increasing the discharge power and reducing the reaction gas flow can increase the plasma energy density of the reaction,thereby increasing the removal rate of toluene in the reaction process.Under the same discharge conditions,the catalyst filling can effectively promote the toluene degradation reaction,increase the toluene removal rate and the energy efficiency of the reaction,and at the same time reduce the concentration of by-product ozone.The promotion of the reaction was in the following order:MnO_X-AgO_X/?-Al₂O₃>MnO_X/?-Al₂O₃>?-Al₂O₃>Empty tube discharge.Increasing the gas flow rate of the reaction,the energy efficiency of the reaction increases first and then decreases,which indicates the presence of an optimal gas flow rate,and the addition of the catalyst can increase the optimal gas flow rate for the reaction.The MnO_X-AgO_X/?-Al₂O₃ catalyst was packed into the reactor.The initial concentration of toluene waste gas was 342.5 mg·m^-3.When the plasma energy density was 73.85 kJ·L^-1,the highest toluene removal rate was 94%.?3?Langmuir probe was used to diagnose plasma ion current density and ion density under the condition of ATC discharge.When the discharge power was increased from 120 W to 200 W,the plasma ion current density during the reaction was 0.997 A·m^-33 gradually decreased to 0.361 A·m^-3,while the plasma ion density gradually decreased from 8.76 e+15 m^-33 to 4.24 e+15 m^-3.The results show that the increase of discharge power can promote the reaction of high energy electrons and active particles generated by discharge with toluene molecules.?4?The results of plasma emission spectroscopy showed that the oxygen plasma characteristics were different from those filled in the reaction chamber,but the oxygen plasma characteristic lines were composed of O_II,O_IIIII and O_IVV lines radiation composition.Under the same conditions,the O_IIIII plasma electron temperature is much higher than the O_III plasma electron temperature.With the increase of discharge power,the electron temperature of O_III plasma shows an upward trend,while the electron temperature of O_IIIII plasma shows a gradual downward trend.