Study On Synergistic Catalytic Degradation Of VOCs By Nanosecond Pulsed Sliding Discharge Plasma

As a new advanced oxidation technology,Non-thermal temperature plasma?NTP?purification technology has great application potential in the field of environmental VOCs treatment,it has been widely concerned by domestic and overseas researchers.Dielectric barrier discharge?DBD?has unique advantages in VOCs purification,because of its simple structure,discharge stability and large-scale plasma,In this paper,a new three-electrode DBD structure was designed by introducing a third electrode into the high voltage electrode side of the traditional surface dielectric barrier discharge structure,and the sliding surface discharge plasma was generated by nanosecond pulse and negative DC power supply at the same time.The experiment setup and diagnosing system were built for measuring the photoelectric characteristics of nanosecond pulse sliding discharge along the surface.The photoelectric characteristics of traditional surface discharge and sliding surface discharge were compared.The effects of pulse voltage amplitude and DC voltage amplitude on the photoelectric characteristics of sliding discharge were studied.By measuring the voltage and current characteristics of the second electrode and the third electrode under different conditions,the power energy of the second electrode and the third electrode was calculated and analyzed.The emission spectrum intensity of sliding discharge along the surface under different conditions was compared by using space-time resolved emission spectrum and iCCD device,and the development of streamer and the relative distribution of active species were observed by discharge image.The results show that the pulse power was the main energy supply of the reactor input,the active species produced by sliding discharge are more evenly distributed in the horizontal direction.The negative DC voltage applied to the third electrode can effectively prolong the length of the plasma,which theoretically proves that the sliding discharge has the advantage of purifying VOCs compared with the traditional surface discharge.The effect of carrier gas composition,oxygen content and humidity on toluene degradation by sliding discharge plasma was studied.The degradation performance was analyzed by calculating the degradation rate,energy yield and mineralization rate.The significant relationship between the degradation rate of target response and independent variables was investigated by using the response surface Methodology BBD model with the appropriate variables range selected by the single factor experiment.The experimental results show that the sliding surface discharge plasma can significantly improve the degradation performance of toluene,and according to the response surface Methodology BBD model,the pulse voltage amplitude has a significant effect on the degradation rate comparing with the amplitude of negative DC voltage,oxygen content and humidity.Finally,combined with FTIR and GC-MS analysis,the main degradation path was proposed and the results showed that benzaldehyde,benzoic acid,formaldehyde and formic acid are the key intermediates in the degradation of toluene.In addition,sliding discharge plasma combined with Ag-Mn/?-Al₂O₃ catalyst can further improve the degradation of toluene.Compared with the plasma system,the plasma catalytic system has better performance in mineralization.The combination of silver and manganese oxide improved the content of adsorbed oxygen on the catalyst surface and the redox performance of the catalyst,which were beneficial to the deep oxidation of VOCs and organic intermediates.Under the discharge power of 4.6 W,the Ag-Mn/?-Al₂O₃?1:2?catalyst achieved91.5%degradation efficiency and 80.1%mineralization rate,and effectively inhibited the formation of ozone and nitrogen oxides.