Study On Treatment Of Benzene By UV Photolysis-ozone Catalytic Oxidation Process

In recent years,with the rapid development of the industry,the energy required has continued to increase,leading to the continuous increase of volatile organic compounds（VOCs）emissions,which is related to the rapid development of the chemical industry.UV photolysis technology has unique advantages in processing low-concentration,poorly soluble,and difficult to decompose VOCs.However,there are problems such as low removal rate and excessive ozone concentration in the exhaust gas.In this paper,the pollutant benzene emitted from the chemical industry is taken as the research object.First,the photolysis reactor is optimized,and then the ozone catalytic oxidation process is used to further process the optimized reactor tail gas.First,the effects of 3 factors（intake gas concentration,residence time,and relative humidity）on the treatment of benzene in an unfilled UV photolysis reactor were investigated,and then 4 factors（intake gas concentration,residence time,relative humidity,and filler filling amount）on the treatment of benzene in a filled UV photolysis reactor（honeycomb activated carbon filler）were investigated.The results show that when the intake gas concentration,residence time,and relative humidity range are the same,compared with the unfilled reactor,the removal rate of benzene in the filled reactor is significantly improved,with a maximum increase of 21%,O₃is relatively small.The benzene intake gas concentration was maintained at 500mg/m³,and three factors for benzene treatment in the filled UV photolysis reactor were optimized.The results show that the effect of three factors on the removal rate is as follows:filler filling amount>residence time>relative humidity,When the intake gas concentration is 500mg/m³,the filler filling amount is 12 groups,the residence time is 29s,and the relative humidity is 75%,the removal rate is 77.02%,the removal effect is the best.It was determined that under the above optimal reaction conditions,benzene,ethanol,acetic acid,lactic acid,2,3-butanediol,and palmitic acid existed in the photolysis tail gas,and the main component was benzene.The effects of UV photolysis and UV photolysis-ozone catalytic oxidation combined process（catalyst MnO_x/γ-Al₂O₃,Mn loading 3%）were compared to remove benzene.The results show that When the intake air concentration is 500mg/m³,the filler filling amount is12 groups,the intake air flow is 5.6L/min,and the relative humidity is 75%,compared with the UV photolysis process,the removal rate of benzene by the combined process was increased by 7.5%,and the tail gas O₃ concentration was reduced by 82 mg/m³.Aiming at the problem that the combined process emissions cannot meet the standards,two methods are used to optimize the combined process.First,increase the loading of the catalyst（MnO_x/γ-Al₂O₃,Mn loading 3%）in the combined process;second,the ozone catalytic oxidation process is used to improve the performance of the catalyst（MnO_x/γ-Al₂O,Mn loading 3%）from the support type and Mn loading,and the improved catalyst is used in the combined process for benzene degradation.The results show that the effect is not improved when the catalyst loading is increased,so this method is not used to optimize the combined process.Among activated carbon,alumina and molecular sieve carriers,with activated carbon as the carrier and 5%loading of Mn,the removal rate and O₃ utilization rate were the best,78%and 71%,respectively.The removal rate of benzene is basically 96.5%in combined process（catalyst MnO_x/AC,Mn loading 5%）,which is 12%higher than before catalyst optimization.In the discharged VOCs,the concentration of benzene is 15mg/m³,and the concentration of tail gas O₃ is zero.