Photocatalytic Oxidation Of Toluene With Photothermal Assisted Catalyst With Microwave And UV Lamp

With the rapid development of industrialization,the total amount of VOCs emitted by in-dustrial sources is also increasing,which is set as one of the improvement indicators in the"fourteenth five-year plan".The operation of VOCs by microwave and UV treatment is simple and free of new pollutants,but the ozone problem has attracted great attention.In this paper,HFSS,CFD and other numerical simulation software are used to simulate the distribution of electric field and ultraviolet radiation intensity in the microwave nonpolar UV generator,which provides theoretical basis for its design and designs and transforms the microwave nonpolar UV generator based on the simulation results.The temperature rise and ozone generation law of the device were explored.The Mn O_x was loaded on the surface of silicon carbide by precip-itation method.The toluene in VOCs was used as the target.The optimal conditions and mech-anism were explored by adjusting the humidity,residence time,the ratio of Mn O_x to Si C,and Degradation of toluene at low temperature.Microwave（MW）,electrodeless ultraviolet light irradiation（UV）,microwave heating single manganese oxide catalyst（MW+Mn）,microwave heating and electrodeless ultraviolet light irradiation single manganese oxide catalyst（MW+UV+Mn）,microwave heating silicon carbide supported manganese oxide catalyst（MW+Mn/Si C）Manganese oxide catalyst（MW+UV+Mn/Si C）supported on silicon carbide was prepared by microwave heating and electrodeless ultraviolet light irradiation.In this project,the HFSS and CFD numerical simulation of microwave electrodeless ultra-violet cavity is carried out,and the electric field intensity inside the cavity is simulated by changing different waveguide positions,different placement positions of the electrodeless ul-traviolet lamp and the position of the electrodeless ultraviolet lamp from the center,so as to determine the placement positions of the waveguide and cylindrical resonant cavity.Simulate the intensity distribution of ultraviolet radiation,observe whether the intensity distribution of ultraviolet radiation in the resonant cavity meets the requirements,simulate the flow of waste gas in the quartz tube,and simulate the velocity distribution of waste gas in the quartz tube.According to the simulation,the visual distribution of microwave field,UV radiation intensity and flow velocity in the basin can be obtained,which can be used in the device design and provide the relevant theoretical basis for the design of microwave electrodeless ultraviolet heat-ing device system.In this project,the temperature rise curve of Mn O_x/Si C catalyst,ozone concentration curve under different power,the degradation performance of toluene in different working condition was tested,and the performance of microwave electrodeless ultraviolet system was discussed.It was found that the temperature rising effect of the catalyst was stable when the height of the catalyst bed was 30 mm under the microwave input power of 595.30 W.the ozone concentration in the quartz tube was relatively stable after a period of time.By comparing six working con-ditions,other conditions are the same,MW+UV+Mn/Si C has the best degradation effect on toluene.It was found that when the relative humidity of waste gas was 50%,the residence time was 1.50 s,the space velocity was 6336.93 h^-1,the ratio of catalyst to silicon carbide was 1:0.5,and the initial concentration of toluene was 235.23 mg/m³,the treatment efficiency was 94%.The residence time of microwave electrodeless UV oxidation and Mn O_x/Si C catalyst for tolu-ene degradation was in accordance with the first-order kinetics within 2.50 s.In this project,the Mn O_x/Si C catalyst before and after the use of a comprehensive charac-terization analysis.The results show that the main components of the catalyst are Si C,Mn₂O₃and Mn₃O₄.The manganese oxide catalyst is granular and has obvious flocculent irregular ac-cumulation on the surface of Si C.The specific surface area of the catalyst increases after load-ing,and the pore size is mainly concentrated in the mesoporous range of 2-50 nm.The results of EDS and XPS show that the main valence forms of manganese are Mn²⁺and Mn⁴⁺,among which Mn⁴⁺accounts for a large proportion.The results show that the catalyst has good UV effect,and it has good photoresponsiveness even though it is reduced after use.After use,the catalyst has good stability,less surface oxygen,constant lattice oxygen concentration and less activity.Through the analysis of the experimental results and characterization results,it is specu-lated that there are four main degradation paths of toluene by microwave electrodeless ultravi-olet combined with Mn O_x/Si C catalyst.The first path is to use high-energy photons to break the chemical bond according to the energy of the chemical bond.The second route is based on the interaction of high energy photons and H₂O to form·OH,which is used to oxidize toluene.The third route is based on the formation of O₃by the interaction of high energy photons with O₂ in the air,and·O formed by ozone catalyzed by Mn O_x/Si C catalyst.Toluene is degraded by strong oxidation.Finally,Si C in Mn O_x/Si C catalyst absorbs microwave energy to heat up and catalyzes the oxidation of toluene with Mn O_x at low temperature.