Mechanism And Experimental Study On Oxidation Removal Of NO By Heterogeneous Fenton Reaction

Nitrogen oxides（NOx）can endanger the health of human beings,animals and plants,and seriously damage the environment.Therefore,the treatment of NOx is particularly important.At present,SCR technology,which is widely used in industry,has some problems,such as expensive catalyst,easy deactivation and ammonia leakage,while SNCR technology has low denitrification efficiency and ammonia leakage.In view of these problems,it is necessary to develop a kind of low-cost and environmental protection denitrification technology with simple process and high denitrification efficiency.In this paper,the simulation and experimental research are combined.Firstly,NO is preoxidized by ozone by liquid redox method,and then NOx is removed by absorption with urea-H₂O₂ solution.Based on the relatively high power consumption cost and low utilization rate of ozonation,this paper further uses heterogeneous Fenton technology to simulate the reaction mechanism of several ZSM-5 catalysts for the decomposition of H₂O₂ to·OH radicals from the micro perspective by quantum chemical calculation.After that,NO can be oxidized to high valence nitrogen oxide which is easily soluble in water by·OH radical,and then absorbed by urea organic absorption solution,so NOx can be removed efficiently.Firstly,ozone was used to pre oxidize NO,and then urea-H₂O₂ solution was used to wash and remove NOx.The results indicate that 50%oxidation rate of NO is the most economical and efficient.Finally,the denitrification efficiency can reach more than 75%through the washing removal experiment.Based on the ozone oxidation technology,the power consumption cost is high,and the oxidation efficiency is still low.Furthermore,the heterogeneous Fenton reaction mechanism of ZSM-5 zeolite catalyst was simulated by B3LYP method in quantum chemistry.The specific reaction process and the relative energy of each step were obtained by calculation.It was found that the activation energy required for the catalytic decomposition of H₂O₂ was much lower than that for the direct decomposition of H₂O₂.It shows that the catalyst has a good catalytic effect,which can decompose H₂O₂ more quickly and efficiently to generate·OH radicals,thus improving the denitrification efficiency.The quantum chemical calculation can provide some guidance for the follow-up experiments.Finally,the catalyst was prepared and characterized,and then the heterogeneous Fenton technology was used to oxidize and remove NO.Results showed that the NO oxidation and removal can be achieved efficiently by heterogeneous Fenton reaction.The denitrification efficiency increased with the increase of H₂O₂ dosage and catalyst loading,while the oxygen concentration had little effect on the denitrification efficiency.The suitable atomization temperature of H₂O₂ is 125-175℃,and the catalytic reaction temperature should be lower than 100℃.The reduction of reaction residence time leads to the decrease of denitrification efficiency.The denitrification efficiency can be greatly improved by the doping of Ce.15%Fe₂O₃+15%Ce O₂/Al₂O₃ catalyst has the best performance.When the reaction residence time was only 3.0s,the denitrification efficiency was still up to about 80%.