Experimental Study On The Purification Of Trichloroethylene By Low Temperature Plasma Coupled With Co-Mn Bimetallic Catalyst

Volatile organic compounds（VOCs）come from a wide range of sources,have complex composition and are widely used in production and life.Since VOCs inevitably enter the air through volatilization and combustion in the process of production,transportation,storage and use,polluting the environment and endangering human health,VOCs treatment is particularly important.Low-temperature plasma technology has the advantages of simple equipment,convenient start/stop and rapid response in degrading VOCs.Coupling low-temperature plasma technology and catalytic oxidation technology can further improve the removal rate and energy efficiency of VOCs.Therefore,the performance of catalysts is the key to the degradation of VOCs by Non-thermal Plasma（NTP）coupled with catalytic technology.It has been shown that bimetallic catalysts have higher catalytic activity compared to monometallic catalysts.Therefore,in this study,Co-Mn bimetallic catalysts with different cobalt-manganese ratios and different carriers were prepared to investigate the performance of coupled low-temperature plasma degradation of trichloroethylene.Firstly,different ratios of Co-Mn bimetallic catalysts were prepared by equal volume impregnation method usingγ-Al₂O₃as the carrier to investigate the effect of Co:Mn ratio on the degradation performance of trichloroethylene when low temperature plasma coupled Co-Mn bimetallic catalysts were used for the degradation of trichloroethylene.Compared with single NTP,the NTP-coupled catalysts significantly improved the removal rate,CO_xyield,CO₂selectivity,HCl and Cl₂yield,and decreased the yield of O₃and N₂O of trichloroethylene.Among them,Co₃Mn₁/γ-Al₂O₃had the highest catalytic activity,with 39.7%-96.94%and 33.04%-87.36%of trichloroethylene removal and CO_xyield for Co₃Mn₁/γ-Al₂O₃coupled NTP at voltages of 6-10 k V,respectively.The physicochemical properties of the catalysts were characterized by BET,XRD,XPS,H₂-TPR,and NH₃-TPD to elucidate the reasons for the differences in the effectiveness of different catalysts coupled with NTP for trichloroethylene degradation.The results showed that the Co₃Mn₁/γ-Al₂O₃catalyst had the smallest Co₃O₄grain size,the largest specific surface area,the strongest reduction,and higher content of Mn⁴⁺,Co³⁺and O_adson the catalyst surface,which were favorable for the degradation of trichloroethylene.Secondly,the effect of catalyst carriers on the degradation performance of trichloroethylene was investigated.For different carriers,Co₃Mn₁/ZSM-5 had the highest trichloroethylene removal,CO_xyield,CO₂selectivity,HCl and Cl₂yield,which could reach 97.1%,94.4%,49.3%and 94.3%at 10 k V,respectively,and the Co₃Mn₁/ZSM-5 catalyst had the lowest O₃and N₂O yields.The characterization by BET,XRD,Raman,XPS,H₂-TPR,NH₃-TPD showed that the Co₃Mn₁/ZSM-5 catalyst had a high specific surface area,strong reduction and the highest Co³⁺,Mn⁴⁺,and O_adscontents,indicating that the catalytic activity of Co₃Mn₁/ZSM-5 was better.And the stability test of Co₃Mn₁/ZSM-5 catalyst was carried out for 50 h.The reduction of trichloroethylene removal and CO_xyield were less than 5%,indicating that Co₃Mn₁/ZSM-5 catalyst has good stability.Finally,in this paper,the reaction kinetics of low-temperature plasma-catalyzed degradation of trichloroethylene was studied by varying the gas residence time.The reaction kinetics model of low-temperature plasma coupled Co₃Mn₁/ZSM-5 degradation of trichloroethylene is:-ln(1-η_TCE)=kt.The reaction rate constant has a good linear relationship with the input power,and the regression equation is:k=0.2501P-0.045,R²=0.9919.and the model is/was verified,and the model The calculated values basically matched with the experimental values,indicating that the model equation was reliable.