Preparation Of Metal Oxide Catalysts By Gliding Arc Plasma And Its Activity In Ozone Decomposition

Gliding arc plasma preparation of catalyst,because of its simple process,fast,efficient and good controllability,will become a new method of catalyst preparation with great industrial application prospects.In this paper,air plasma generated by gliding arc discharge was used to prepare MnO_x,FeO_x,CoO_x,NiO_x and CuO_x catalysts through the nitrate precursor aerosol flowing through the plasma zone.Its crystal structure,morphology,pore structure,reduction characteristics and valence state of surface elements were characterized,and its catalytic activity was evaluated by ozone decomposition reaction.1)The influence of the introduction of different precursor aerosols on the discharge characteristics was investigated,and the rotation temperature was estimated using emission spectra.Under the condition of single air discharge,the change of discharge voltage only appears in restrike mode.After the precursor aerosol is introduced into the plasma zone,the discharge voltage changes in two modes:restrike and take over;And for different precursors,the two discharge modes have different proportions.Under the conditions of input power of 100W and air flow of 3 L/min,the rotation temperature of N₂ is 2500 K,which is much higher than the thermal decomposition temperature of the precursor.2)The MnO_x,FeO_x,CoO_x,NiO_x,and CuO_x catalysts prepared by gliding arc plasma were characterized.The prepared catalysts had a crystal structure with average grain sizes of 39 nm,30 nm,26 nm,35 nm,and 26 nm,respectively;It has mesopores and microporous with a wide pore size distribution.The average pore size and specific surface area of NiO_x are higher than other catalysts,which are 5.3 nm and 25 m²/g,respectively;The morphology of the catalysts is mainly spherical particles;The adsorbed oxygen content on the surface of CoO_x and NiO_x accounts for 29%of the surface oxygen,and MnO_x is only 18%;The initial reduction temperature of CuO_x in hydrogen temperature-programmed reduction is lower than other catalysts.3)The ozone decomposition activity of the prepared catalyst was compared.The ozone conversion rates in dry gas atmosphere and wet gas atmosphere were investigated respectively.Under a dry gas atmosphere,NiO_x has the highest ozone conversion rate,reaching 94%.The reason may be that NiO_x has a large specific surface area and average pore diameter,as well as a higher surface oxygen content and a lower reduction temperature.After 1 h of reaction in a humid atmosphere,CuOx has the highest ozone conversion rate.The main reason may be that it has a lower reduction temperature than NiOx and the redox reaction rate is faster.The CuOx catalyst prepared by plasma method showed no deactivation in the stability experiment for 10h.In addition,the ozone conversion rate of CuOx prepared by plasma method is significantly higher than that of CuOx?C?prepared by calcination method under dry gas and wet gas atmospheres.