Preparation And Characterization Of La_1-xCe_xMn_1-yCo_yO₃for Catalytic Combustion Of Soot

In this paper, a series of La-Mn-O perovskite-type oxides were prepared using thenew sol-gel method. A site and B site ions on the basis of LaMnO₃are partiallyion-doped to make the comparative study of the structure, catalytic performance andeffects of automobile exhaust purification. The physical and chemical properties ofthe material were characterized by means of XRD, BET, FT-IR, H2-TPR and O₂-TPD.The activity for removing soot was investigated in an atmosphere of differentproportions of O₂, N2, and NOxby TPO. The factors of catalytic activity for the ABO₃catalyst involved in the catalytic oxidation of soot combustion reaction wereinvestigated.Compared with different preparation method for perovskite-type catalyst,optimize conditions continually and finally synthesize a series of perovskite-typecomposite oxide of La-Mn-O. A bits and B bits of LaMnO₃catalyst were doped by Ceand Co in different proportions, generating the La_1-xCe_xMnO₃（x=0,0.1,0.2,0.3,0.4,0.5,0.6,0.7and0.8） and La_1-xCe_xMn_1-yCo_yO₃（x=0,0.2; y=0,0.1,0.2,0.3,0.4,0.5and0.6）sample and consider the factors to the physical and chemical properties of the catalyst.The study found that a smaller proportion substitution of the doping ions could enterinto the crystal lattice of the perovskite structure.The results of H2-TPR indicated that Ce partially doped into the A-site ion ofLaMnO₃perovskite oxides, not only increase the content of active oxygen species, butalso improves the activity of that; however, Co doped in the B-site have a oppositeeffect, so that metal cations in ABO₃are more difficult to restore, and Co-substitutingalso reduces the fluidity of the lattice oxygen.In O₂-TPD spectrum, the area of α-O₂desorption peak of the catalyst sampleshowed that the partial substitution of Co reduce the ability of containing excessoxygen for a catalytic system, resulting in an increase in oxygen vacancies.The TPO results show that La-Mn-O prepared by the new sol-gel couldeffectively reduce the combustion temperature (T₁₀, T_p, T₉₀) of soot in differentatmosphere. Appropriate proportion of Ce, Co replacing the A or B site of the ABO₃could greatly improve the activity of the catalyst samples, but overdoping will inhibitthe effect of catalyst activity. La_0.8Ce_0.3MnO₃samples showed the best activity in TPO test, and the combustion temperature T₁₀, Tp, and T90were reduced respectivelyby116°C,87°C, and44°C. La_1-xCe_xMn_1-yCo_yO₃samples showed a high activity insoot combustion experiments, but a less the reaction temperature span for sootcombustion. It is likely to be caused by a lower number of active sites onCo-substituted samples, so that the average rate of the burning reaction decreases alittle.