Fundamental Research On Degradation Of VOCs Such As Toluene Using Gas-solid Phase Fenton Reaction

Fenton reaction is a pollutant removal technology with very promising applications.A lot of valuable work has been done on the study of VOCs removal by Fenton reaction.However,little literature has been reported on VOCs removal from low-temperature flue gases by gas-solid phase Fenton.To address this core problem,this paper presents a detailed study of the reaction mechanism of VOCs（toluene,phenol,naphthalene）removal by gas-solid phase Fenton reaction based on quantum chemical calculations and related experiments,which provides a strong theoretical basis for the further development of gas-solid phase Fenton removal technology in the future.Firstly,a reasonable Fenton catalyst model was constructed and a four-step reaction mechanism was obtained using quantum chemical calculations.It was found that the catalyst activity not only depends on the loaded transition metal Fe,but also highly correlated with the active T-center of the catalyst.In addition,the fluffiness of the molecular structure had a large influence on the energy barrier of catalytic reaction.Based on this,the Fe-Ce-Al₂O₃catalyst was screened to have a better catalytic activity.Then,based on density functional theory,toluene,phenol and naphthalene were selected as degradation targets.And the reaction mechanisms of OH radicals and O₃to destroy toluene,phenol and naphthalene were explored in detail.Theoretical results showed that for phenol and toluene,due to the activation of methyl and hydroxyl groups,OH radicals preferentially attack the vicinal C atom,while ozone preferentially destroys the 1,2-position C=C bond.But for naphthalene,due to its inherent benzo structure,the OH radical preferentially attacks the para-position C atom,while ozone preferentially destroys the C=C bond at the 3,4-position.In addition,based on the mechanistic studies,the reaction rate constants were fitted,and the results were in good agreement with the experimental data in the literature.The calculated results showed that the rate constant for the destruction of naphthalene by OH radicals was greater than that for toluene,but lower than that for phenol also:phenol>naphthalene>toluene.And the degradation order of ozone on VOCs components is naphthalene>phenol>toluene.Subsequently,the catalysts with different active substance loading ratios were prepared by impregnation method,and the sample characterization revealed that Fe-Ce（1:1）-Al₂O₃had a large specific surface area,more homogeneous pore size structure and higher active substance crystallinity,which had a better catalytic potential.Finally,in the flue gas toluene removal experiments under different reaction conditions,the better reaction conditions for toluene removal were obtained,and Fe-Ce（1:1）-Al₂O₃showed excellent toluene removal efficiency in the experimental study of catalyst performance comparison,which was more than 10%higher than other catalysts.In addition,the rapid cooling of hydrogen peroxide after flash evaporation not only avoided its own decomposition,but also promoted its surface contact reaction with the catalyst,which was the key to improve the toluene removal efficiency.