Photocatalytic Oxidation Of Gaseous Benzene Based On Circulation Reactor

The benzene waste gas,a carcinogenic substance,greatly hurts people in the production and living,which is representative of benzene series matter and an important component of volatile organic pollutants.At present,national and local governments have introduced the VOCs emission charges and VOCs emission industry standards have been promulgated,the efficient governance of VOCs is imminent.In this thesis the research of photocatalytic removal of gaseous benzene by TiO₂ was carried out.Based on the previous experimental study and reference to the relevant literature,and the test of economic and operational considerations,the sol-gel method was chosen as a method for preparing TiO₂.At the same time,the photocatalytic removal of benzene off-gas from TiO₂ was carried out using a homemade photocatalytic reactor.This study mainly includes the following two parts:The main research content of this dissertation is the preparation of TiO₂ catalysts.The butyl titanate?TBOT?raw material used in this experiment was used as a source of titanium,anhydrous ethanol as a solvent,HNO3 as a catalyst,and acetylacetone as an inhibitor for the sol ratio.Combined with the actual conditions of this experiment,the factors that mainly consider the impact on benzene removal efficiency include: amount of water added,amount of ethanol,pH,amount of acetylacetone,gelation time,calcining temperature increase rate,and calcining temperature.The research conclusions are as follows:?1?In a single-factor test study,the optimal proportion of sol-gel was: 30 ml of butyl titanate,3% of water,80% of anhydrous ethanol,and 1.6% of acetylacetone,pH=3.The molar ratio thereof is TBOT: water: absolute ethanol: acetylacetone=1:2.94:24.16:0.27.The best heating rate is 5.2°C/min and the calcination temperature is 450°C.?2?If the amount of water added is too high or too low,the removal efficiency of the catalyst to benzene is reduced,and it is found that the sol absorbs the moisture in the air during the sol-gel process.This in turn leads to an optimum water addition of butyl titanate water=1:2.94?molar ratio?,not a theoretical molar ratio of 1:4.?3?When the addition amount of ethanol is between 50% and 80%,the removal efficiency of benzene on the catalyst increases linearly with the amount of ethanol added.When the amount of ethanol added is greater than 80%,the efficiency of benzene removal by the catalyst is basically independent of the amount of ethanol added.?4?When the pH is less than 3,the removal efficiency of benzene on the catalyst increases with the increase of pH,while when the pH is greater than 5,the removal efficiency of benzene on the catalyst decreases with the increase of pH.When the pH was between 3 and 5,the removal efficiency of benzene on the catalyst changed little with increasing pH.?5?When the amount of acetylacetone is more than 1.6%,the removal efficiency of benzene decreases with the increase of the amount of acetylacetone added,while the addition of acetylacetone is between 1.2% and 1.6%.The removal efficiency varies little with the amount of acetylacetone added.?6?When the calcination temperature is lower than 450 °C,the catalytic effect of the catalyst increases with the increase of the calcination temperature.When the calcination temperature is higher than 500 °C,the catalytic effect of the catalyst decreases with the increase of calcination temperature.At 450 °C to 500 °C,the catalytic effect of the catalyst showed a slight decrease.This article also studied the influencing factors and optimization conditions.Combining the actual conditions of this experiment,the main external influence factors include: intensity of ultraviolet light,initial concentration of benzene waste gas,flow rate of air circulation pump,number of catalyst layers,and comparison with commercial P25.?1?The TiO₂ self-made by sol-gel method has a much higher catalytic effect than P25,and the efficiency of the homemade catalyst for benzene removal is about 15%³0% higher than that of P25.This shows that the homemade catalyst has good catalytic performance and has further research value.?2?The removal efficiency of benzene with catalysts showed a logarithmic growth trend with time at different concentrations.At the same time as the initial concentration of benzene increased,the removal efficiency of benzene on the catalysts began to decrease at 0-100 mg/m3.The removal efficiency of benzene is the highest.When the initial concentration of benzene is between 100-200 mg/m3 and 200-300 mg/m3,the removal efficiency of benzene on the catalyst is not much different.When the initial concentration of benzene was between 300-400 mg/m3 and 400-500 mg/m3,the efficiency of removal of benzene by the catalyst was similar.?3?The light intensity of UV lamp has a great influence on the removal efficiency of benzene.When the UV lamp power is 10 W,the benzene removal is 89.32% at 54 min.When the UV lamp power is 38 W,the removal efficiency of the catalyst to benzene is as high as 79.1% at 9 minutes,and it reaches 100% at 36 minutes.