Experimental Study On Non-Thermal Plasma Coupled With MOFs And Their Derivatives For Toluene Degradation

In rencent years,the situation of air pollution caused by the massive emission of VOCs from industrial sources is grim.Non-thermal plasma coupled with catalyst can not only fully utilize the high reactivity of plasma and the adsorption and catalytic performance of catalyst,but also produce synergistic effects between them,hereby promoting the oxidative decomposition of VOCs,improving energy utilization,and effectively controlling by-products concentration.As a new pattern of porous materials,MOFs have large specific surface area,ordered pore structure,and abundant active sites,which has become research hotspots in the domain of VOCs degradation.Owing to the interaction between different active species,MOFs derived bimetallic oxides are conducive to improve the performance of catalysts,and have also been widely studied.In this paper,toluene is degraded by non-thermal plasma(NTP)produced by dielectric barrier discharge reactor,and the effects of different parameters on the degradation performance are studied.MOFs and their derivatives are introduced into the plasma system,the catalyst types(MnyCe1-MOF and MnOx-CeO2)and filling position(in-plasma catalysis and post-plasma catalysis)on the degradation performance of toluene are compared and analyzed.The specific contents and relevant conclusions are as below:(1)The effects of input power,gas flow rate,initial concentration and discharge length on the degradation of toluene in NTP are investigated.The experimental results show that with the increase of input power,the discharge intensity increase,and the degradation efficiency and CO2 selectivity increase,and the energy efficiency first increases and then decreases.Reducing the gas flow rate and initial concentration is beneficial to improve the degradation efficiency and CO2 selectivity,but it will decrease the energy efficiency.With the increase of copper mesh length,the degradation efficiency,energy efficiency and CO2 selectivity increase first and then decrease.(2)MnyCe1-MOF materials are synthesized via a hydrothermal method.The degradation of toluene by post-plasma catalysis(PPC)combined with MOFs is studied.The results show that the effects of input power,gas flow rate and initial concentration on toluene degradation were independent of whether the catalyst is filled or not.The introduction of MOFs significantly improves the degradation efficiency and energy efficiency,deeply oxidizes the intermediate products,improves the CO2 selectivity and carbon balance,and effectively reduces the concentration of O3.The order of toluene degradation performance of each system is Mn6Ce1MOF>Mn4Cei-MOF>Mn2Ce1-MOF>Mn1Ce1-MOF>Mn-MOF>NTP.(3)Using MOFs as precursor,the derived bimetallic oxide MnOx-CeO2 materials are prepared by pyrolysis method.The degradation performance of toluene by in-plasma catalysis(IPC)and PPC combined with MnOx-CeO2 is studied.The results show that whether IPC or PPC,the filling of MnOx-CeO2 can improve the degradation performance.The difference is that the degradation efficiency,energy efficiency,CO2 selectivity and carbon balance of IPC are higher than PPC,but the utilization rate of O3 is lower than PPC.Mn6Ce1Ox achieves the best degradation performance.In IPC,the maximum degradation efficiency and energy efficiency are 90.4%and 5.65 g/kWh,the highest CO2 selectivity and carbon balance are 83.4%and 98.2%.But in PPC,the maximum values of these parameters are 81.6%,5.08 g/kWh,73.9%and 87%,respectively.(4)The decomposition ability and performance of MnOx-CeO2 for O3 and toluene are lower than MOFs.But through IPC,the performance of MnOx-CeO2 is greatly improved and close to MOFs,indicating that it can improve the catalytic performance of materials.The order of toluene degradation performance of each system is PPC:Mn6Ce1-MOF)IPC:Mn6Ce1Ox>PPC:Mn6Ce1Ox>>NTP.