Study On Stability And Durability Of Modified Perovskite Catalyst For Styrene Catalytic Combustion

In order to screen out a high-efficient,cheap and stable catalyst in the filed of styrene catalytic combustion,which is still less studied in the VOCs pollution control,four perovskite catalysts,such as La Mn O₃,La_0.9Ce_0.1Mn O₃,La Mn_0.6Cu_0.4O₃ and La_0.9Ce_0.1Mn_0.6Cu_0.4O₃,were prepared by sol-gel method in this paper.The effects of doping at A or/and B site on the catalytic activity,stability and durability of perovskite catalysts were investigated by means of XRD,BET,SEM,XPS,H₂-TPR,O₂-TPR,TGA,TG-GC-MS and carbon balance analysis.The catalytic activity,stability and durability of La_0.9Ce_0.1Mn O₃ were further enhanced after doping Ce in A site,where T₁₀ decreased from 299℃to 285℃,T₉₀decreased from 356℃to 328℃,and the conversion of CO₂ increased from 84.68%to88.03%.Although there were still trace styrene residued or polymerized on the catalyst surface,no carbon was deposited.Meanwhile,the physical and chemical properties of La_0.9Ce_0.1Mn O₃,such as crystal structure,surface morphology,specific surface area,ratio of Mn⁴⁺/Mn³⁺,content of O_βand O_α,low temperature oxidation-reduction property,etc.,were relatively stable in the multi round catalytic experiments.The activity of La Mn_0.6Cu_0.4O₃ was greatly enhanced by doping Cu in B site,where T₁₀ decreased to 259℃,T₉₀ decreased to 307℃,and the conversion of CO₂ increased to94.36%.There was neither carbon deposition nor styrene residue or polymerization on the catalyst surface.How e Ver,the specific surface area and content of Oβof the catalyst decreased,and the perovskite phase changed from orthorhombic to rhombohedral.In addition,after s e Veral rounds of experiments,the crystal phase of the catalyst changes back to orthorhombic crystal,and the Cu O impurity on the surface is reduced to elemental Cu.The hydrogen consumption peak at low temperature was obviously weakened and moves towards high temperature,which means the oxidation-reduction capacity at low temperature is relatively reduced.Therefore,doping in B site can greatly enhance the catalytic activity of perovskite type catalyst,but its effect on the stability is relatively limited.The catalytic activity,stability and durability of La_0.9Ce_0.1Mn_0.6Cu_0.4O₃ was most greatly improved after doping in A and B sites at the same time,.T₁₀ decreased by 47℃to 252℃,T₉₀ decreased by 52℃to 304℃,and the CO₂ conversion rate reached 97.93%.In addition,the physical and chemical properties of La_0.9Ce_0.1Mn_0.6Cu_0.4O₃ are the most stable in the multi round catalytic process,and the Ce O₂ and Cu O impurities on the surface of the catalyst are also basically unchanged.Therefore,La_0.9Ce_0.1Mn_0.6Cu_0.4O₃ is the best catalyst of La_1-xCe_xMn_1-yCu_yO₃（x=0,0.1;y=0,0.4）catalysts with the best catalytic activity,the strongest deep oxidation ability and the best catalytic stability and durability.