An Experimental Study On The Removal Of Toluene By Perovskite Catalysts Combined With Non-thermal Plasma

With In recent years,most areas in China have suffered from severe haze weather.Air pollution,especially volatile organic pollutants?VOCs?,has drawn lots of attention.It is urgent to develop efficient techniques to utilize or mitigate VOCs.Plasma technique plays a significant role in the utilization of VOCs,especially at low concentrations,due to its advantages of short process,high efficiency and low price.However,the low-temperature plasma technique could yield toxic by-products and consume extensive energy.Currently,the plasma-catalyst coordination technique?PCCT?paved a way for the effective utilization of VOCs,which has attracted more and more attention.In the present work,removal of toluene by the perovskite catalyst was studied.Five perovskite catalysts,LaMnO₃,LaCoO₃,LaCeO₃,LaNiO₃,La_0.8Ce_0.2MnO₃,were synthesized by the sol-gel method.The catalysts were characterized by SEM,BET and XRD.The catalytic combustion performance of the catalysts for the conversion of toluene was investigated as well.The results showed that La_0.8Ce_0.2MnO₃ has the highest activity with the conversion of toluene close to 100%at around 300?,indicating that the efficiency could be significantly enhanced with the trace amount of Ce.It shows that a small amount of Ce in LaMnO₃ can further enhance the catalytic activity without affecting the stability of its catalytic performance.Removal of toluene by the plasma technique was also investigated in terms of initial concentration of toluene,air velocity,length of the discharge zone of the plasma reactor,peak voltage of the discharge and energy density.The results showed that the removal efficiency of toluene decreased with increasing the initial toluene concentration and the air velocity,while increased with increasing the length of the discharge region,the peak voltage and the energy density.In the end,removal of toluene by PCCT was investigated in the aspects of peak voltage,energy density and perovskite catalysts.The results indicated that the removal efficiency and the removal amount of toluene increased with the increase of the discharge voltage and the energy density.The addition of appropriate perovskite catalyst in plasma could improve the removal efficiency of toluene.Under the same conversion of toluene,the addition of catalyst could effectively reduce the discharge voltage and the energy consumption of the reactor.By comparison of the experimental results of the thermo-catalysis with those of the PCCT,it was found that the specific surface area of LaMnO₃ was higher than that of LaCoO₃,whereas the removal of toluene was more efficient on LaCoO₃.Therefore,during the process of thermo-catalysis,oxidation of the catalyst element,besides the specific surface area,also played a role in the removal efficiency of toluene.In the process of PCCT,the removal efficiency of toluene on the five perovskite catalysts generally followed the same trend as that in the specific surface areas.This indicated that the specific surface area is more dominant in the removal of toluene due to the synergistic effect of plasma and catalyst.