Synthesis And Catalytic Behaviors Of Muitiply Optimized Manganese-based Perovskites

This research concentrates on investigating the impact of preparation technology,structural parameter,redox property,long-term catalytic resistance and catalytic behavior of multiply optimized Mn-based perovskites.Some experiments are adopted to evaluate the structure-activity relationship of catalysts,such as XRD(X-ray diffraction),N2-physisorption,HRTEM(High Resolution Transmission Electron Microscope),H2-TPR(H2-TPR,Hydrogen Temperature Programmed Reduction),O2-TPD(Oxygen Temperature Programmed Desorption),ICP-AES(Inductively Coupled Plasma Atomic Emission Spectrometer),XPS(X-ray Photoelectron Spectroscopy)and In situ DRIFTS(In Situ Diffusion Reflectance Infrared Fourier Transform Spectroscopy).The results are shown below.A series of LaM0.5Mn0.5O3(M = Cu,Co,Fe)perovskite catalysts are achieved by sol-gel method to investigate the impact of partial substitution on B site for the physico-chemical properties and the catalytic behavior in catalytic reduction NO by CO.The partial substitution on B site of LaMnO3 perovskite obviously promotes the catalytic behavior in the following order:LaCu0.5Mn0.5O3>LaCo0.5Mn0.5O3 ? LaFe0.5Mn0.5O3>LaMnO3.The greatest catalytic behavior is obtained in LaCu0.5Mn0.5O3 sample at 300 ?,with completely selective conversion for NO and CO,respectively.Meanwhile,LaCu0.5Mn0.5O3 sample displays the hopeful long-term catalytic stability in comparison to LaMnO3 perovskite.The reducing property and percentage composition for oxygen defect sites of decorated perovskites are deemed to be the important factors for the enhancement of catalytic behavior.The variation of calcination temperature on LaCu0.5Mn0.5O3 perovskite has some impacts on its phase composition,phase crystalline and content of phases.The intergrowth and coexistence effect of phases apparently influences the structural property,redox ability and the catalytic performance of LaCu0.5Mn0.5O3 catalyst in catalytic reduction NO by CO.With suitable enhancement of calcination temperature,the occurrence of the intergrowth and coexistence effect of LaMnO3 and La2CuO4 is conductive to the catalytic behavior.However,excessive calcination temperature results in the inappropriate proportion of LaMnO3 to La2CuO4,which partially breaks the intergrowth and coexistence connection of LaMnO3 and La2CuO4,inducing the declining catalytic behavior.Meanwhile,the content of Cu+/(Cu++Cu2+)and Mn3+/(Mn3+ + Mn4+),the reduction ability and the amount of surface oxygen deficiencies are the decisive points for the improvement of catalytic property.The influence for changed ratio of Cu to Mn in LaCuxMn1-xO3 mixed oxides are presented to analyze the variation on catalytic behavior in CO oxidation and NO reduction by CO.With appropriate content of copper,the existence of the intergrowth and coexistence effect between LaMnO3 and La2CuO4 is beneficial to the catalytic performance.However,excessive content of copper leads to the occurrence of crystalline CuO,which destroys the intergrowth and coexistence system between LaMnO3 and La2CuO4,causing the decreasing catalytic performance.Simultaneously,the percentage of Cu+/(Cu++Cu2+)and Mn3+/(Mn3+ + Mn4+),the reducing capacity and the content of surface oxygen species are deemed to be the determining factors for the increasing catalytic performance.In addition,giving LaCu0.5Mn0.5O3 catalyst as an example,the total catalytic process is tentatively provided to completely investigate the reaction essence for CO oxidation and NO+CO reaction.