Study On The Effect Of Film Forming Temperature On Surface Catalytic Ozone Generation And The Catalytic Decomposition Of Ozone

The development of society makes green environmental protection deeply rooted in people’s hearts.As a green oxidant,ozone is widely used in many fields such as drinking water purification,medical treatment,sewage treatment and coal-burning flue gas purification.In commercial ozone generators,Dielectric Barrier Discharge（DBD）is well used.In recent decades,a large number of studies have been conducted on the generation mechanism of ozone,electrode materials,discharge chamber structure,gas source,power supply and its optimization.For commercial ozone generators,however,improvements in ozone production efficiency have long been stagnant.In recent years,a large number of studies have shown that surface reaction is also an effective way to improve ozone concentration and yield.However,there are few studies on the effect of the surface properties of the same material on the surface reaction.The mechanism of catalytic ozone generation can be well studied by loading catalytic material film on the surface of dielectric plate and changing the characteristics of the surface of catalytic material by changing the film forming temperature.At the same time,the production of high concentration ozone is bound to bring the problem of subsequent high concentration ozone treatment.In this paper,two technical difficulties of high concentration ozone generation and high concentration ozone decomposition were experimentally studied.Ozone concentration and ozone yield are two important indexes to evaluate ozone generator.In this paper,the effects of Si O₂ film on DBD ozone concentration and ozone yield under different film forming temperatures were studied experimentally.At the same time,thermal constant analyzer,surface area tester and XPS were used to analyze the heat transfer coefficient,specific surface area and surface hydroxyl of the supported silica dielectric plate at different film forming temperatures,so as to quantitatively study the influence of specific surface area and hydroxyl content on the reaction surface.The experimental results show that the specific surface area and hydroxyl content of the films are changed by the film forming temperature,which affects the enhancement of DBD ozone generation by the Si O₂ films.The main conclusions are as follows:（1）The surface area of the Si O₂ film first increases and then decreases with the increase of film forming temperature.At 550℃,the specific surface area is the largest,which increases by about 4 times compared with that of the unsupported film.The amount of hydroxyl group on the surface of Si O₂ film decreases continuously with the increase of film forming temperature.（2）The silica film loaded on the dielectric plate can effectively promote the generation of ozone under DBD oxygen source to a certain extent,and the film forming temperature will affect the promotion effect.When the discharge voltage is 5.5 k V～8 k V and the film forming temperature is 550℃,the film has the best performance because it has the highest specific surface area.At the optimum discharge voltage of 7 k V,it has the highest ozone concentration and ozone yield,which are 83.3 g/m³ and 41.7 g/k Wh,respectively.Compared with unloaded,it increases by 9.3%and 32.9%,respectively.Under the condition of insufficient discharge（discharge voltage 5 k V）and film forming temperature 450℃,the film has better performance because it has the highest hydroxyl content.This also indicates that increasing the specific surface area and hydroxyl content of the reaction surface are effective ways to increase the ozone concentration and ozone yield of DBD ozone generator.Under sufficient discharge conditions,ozone concentration and yield can be improved by increasing specific surface area.However,in the case of insufficient discharge,it is more effective to increase the surface hydroxyl content.Ozone decomposition is another difficult problem that affects the application of ozone technology.While high concentration ozone generation technology has achieved good application results,this problem is particularly important,and the development of high activity catalyst is the key to solve this problem.In this paper,activated carbon supported manganese oxide was used as catalyst to investigate the effects of initial ozone concentration,reaction flow rate and catalyst amount on the ozone removal efficiency of Mn-XC catalyst.At the same time,coupled with surface characterization technology,the catalyst was characterized to explore the influence of different loading amount on the morphology and valence state of the catalyst.The main conclusions are as follows:（1）Because the ozone decomposition reaction is exothermic reaction,the ozone decomposition will make the reaction system temperature rise.Under the condition of high concentration,the rate of ozone decomposition is high,and the temperature of the reaction system rises obviously,which in turn leads to the further acceleration of the rate of ozone decomposition,and the further acceleration of the rate of ozone decomposition will promote the rise of temperature again,thus causing a chain reaction.As a result,high concentrations of ozone always break down at a faster rate.（2）Under the experimental conditions,the catalytic activity of the catalysts from large to small is Mn-2C>Mn-3C>Mn-4C>Mn-1C.The ozone removal rate and decomposition rate of the four catalysts were affected by the initial concentration of ozone gas flow and the amount of catalyst.At the same time,the catalytic material Mn-2C produced can achieve a good decomposition effect.20 g catalytic material Mn-3C can completely decompose ozone in ozone-containing gases with flow rate of 2 L/min and ozone concentration of 55 g/min,basically meeting the national ozone emission standard.