Study On Catalytic Ozonation Of Ethyl Acetate By Nano-MnO₂

Volatile organic compounds(VOCs)come from a wide range of sources,including oxygen-containing volatile organic compounds(OVOCs),the second largest type of VOCs emitted by the industry,which not only pollute the environment but also threaten human health.In this paper,ethyl acetate as the typical representative of OVOCs is the target pollutant,which is degraded into CO2 and H2O by catalytic ozonation technology.Catalytic ozonation treatment of low concentration,low boiling VOCs has the characteristics of low cost and no secondary pollution,which the key is the choice of catalyst.Transition metal catalysts are low in cost but low in efficiency and have a short life.This paper aims to prepare transition metal oxide catalysts with good catalytic performance and long life.The Mn(NO3)2 and KMn04 were used as reactant to prepare nano-MnO2 catalyst by chemical precipitation method.The calcination temperature played an important role in the preparation process.It was found by XPS and XRD,when the calcination temperature was 200℃,300℃ and 400℃,that the three catalysts were all y-MnO2.The HRTEM and BET characterization of the threeγ-MnO2 showed that the three catalysts have similar structures and all have ordered pore structure.The specific surface area is 120 m1/g,the pore volume is 0.35 cm3/g,and the pore diameter is distributed between 2～50 nm,which belongs to a mesoporous material.It was found that the catalytic activity of nano-MnO2 prepared at 400℃ was better than the other two.Therefore,the catalyst was selected for subsequent experimental research.The results show that the nano-MnO2 prepared in this experiment is suitable for the degradation of low-concentration ethyl acetate(60 mg/m3).The removal rate of ethyl acetate was 100%at an gas hourly space velocity of 10000 h-1,the decomposition efficiency of O3(1000 ppm)was 100%,and the selectivity of CO2 was 70%.The presence of water vapor had a great negative effect on the catalyst,and the space velocity was 10000 h-1,the relative humidity is operated from 0-85%for 56 days,and the nano-MnO2 is deactivated.The nano-MnO2 is regenerated by calcined at 400℃ for 4h.The removal rate of ethyl acetate is recovered to 100%,and CO2 selectivity recovered to 67.9%,and O3 decomposition efficiency returned to 96.11%.Preparation of loaded nano-MnO2 treatment concentration of 60mg/m3 ethyl acetate,and gas hourly space velocity was 10000 h-1.When nano-Mn02 mass fraction should not below 50%,the effect is similar to that of nano-MnO2,which the ethyl acetate removal rate is 100%,and the O3 decomposition efficiency is 100%,and the CO2 selectivity is 69.4%.By analyzing the infrared spectrum,it was found that ethylene and acetic acid were in the degradation products of ethyl acetate.Through the analysis of the intermediate products,it was speculated that the degradation of ethyl acetate was mainly divided into two stages to produce CO2 and H2O.