Study On Catalytic Oxidation Of Toluene Over Cu-Ce Binary Oxides

In this study,four kinds of Cu-Ce binary oxides were prepared via a facile co-precipitation method.Their toluene catalytic oxidation activity was investigated.The physicochemical properties of the samples were characterized by XRD,SEM,TEM,adsorption-desorption isotherms,H₂-TPR,O₂-TPD,and XPS.The results showed that the oxidation activity of toluene over the Cu₁Ce₃ catalyst was superior,with the T₉₀ being 178°C.The catalytic activity of the four samples ranking as:Cu₁Ce₃>Cu₁Ce₂>Cu₁Ce₄>Cu₁Ce₅.The catalytic activity of Cu-Ce binary oxides is mainly related to the specific surface area,reducibility,and surface oxygen vacancy of the catalyst.The results of XRD and TEM showed that the Cu-Ce synergistic effect is mainly represented by the distortion of lattice fringes at the Cu-Ce interface and the formation of amorphous Cu-Ce solid solution,which greatly promotes the generation of oxygen vacancy on the surface.Then,the effects of flue gas components（O₂,H₂O,and NO）and space velocity on toluene oxidation efficiency were investigated over the Cu₁Ce₃ catalyst.O₂ plays a key role in promoting lattice oxygen regeneration during the catalytic oxidation of toluene by Cu₁Ce₃.H₂O inhibited the oxidation of toluene over Cu₁Ce₃,but the inhibition was reversible.When water vapor was withdrawn from the reaction system,the catalytic activity could be restored to the original level.The catalytic efficiency of Cu₁Ce₃ can exceed 99%at 210℃and last for more than 120 h.The catalytic activity of Cu₁Ce₃ was slightly promoted by NO.The catalytic oxidation activity of Cu₁Ce₃ decreased with the increase of space velocity,but when the space velocity reached 180000 h^-1,the toluene conversion rate of Cu₁Ce₃ was still more than 90%at a lower temperature.It can be seen that Cu₁Ce₃ is an ideal catalyst for removing toluene.In this paper,the oxidation pathways of toluene were concluded by in-situ DRIFTs.It was determined that the primary step of catalytic oxidation of toluene by Cu₁Ce₃was the abstraction of H atom,the primary intermediate was benzyl alcohol,and the rate control step was the oxidation of benzyl alcohol to benzoic acid.In addition,interface lattice oxygen plays a key role in catalytic reactions.Finally,it is proved that the catalytic oxidation of toluene by Cu₁Ce₃ conforms to the MVK mechanism.