| In this paper, perovskite lanthanum manganese complex oxides were fabricated by solid-solid state synthesis with the metal element acetate and oxalic acid as raw materials. The influencing facters during the course of preparation and optimal technic-condition of preparation were also researched. Lanthanum manganese composite oxide was modified by partially doped in A site and B site. The influence of substituted element ion and dopping content on the crystal structure and CO oxidation of lanthanum-manganese perovskite composite were also investigated.At the system of fabricating lanthanum manganese composite oxide by solid-solid state synthesis, lanthanum acetate, manganese acetate and oxalate were used. Also, the influence of milling time, raw material ratio of acetate and oxalate, decomposing temperature and decomposing time on particle size were investigated. The preparation conditions was optimized by orthogonal experiment and the orthogonal experiment analysis results showed that primary order of four factors on the influence of the particle size from high to low was decomposition time, decomposition temperature, raw material raw material ratio of acetate and oxalate, milling time. The optimum conditions for preparation were milling time=60 min, raw material ratio of acetate and oxalate=1:1.2, decomposing temperature=900℃ and decomposing time=6h. Under these conditions, the size of product obtained was 22.1nm, the major product phase was LaMnO3+δ. LaMnO3+δ synthesized by this method belongs to Rhombohedral, R-3C space group, with the following cell parameters:a=b=5.52245A, c=14.34254A, α=β=90零, γ=120°. LaMnO3+δ had four active center of CO adsorption, including the strong adsorption center 422.2℃, and three weak adsorption centers 201.50℃, 255.32℃,622.58℃. CO was oxidized to CO2 on the adsorption center. There were three times reduction of LaMnO3+δ happened at 484.98℃,683.23℃,798.23℃,which resulted from the reduction process of Mn4+â†'Mn3+, Mn3+â†'Mn2+, and the oxidization of CO to CO2.La1-xA’xMnO3+δ was modified by doping in A site. The influence of substituted element ion and substituted content on the crystal structure of lanthanum-manganese perovskite-type composite, CO adsorption and oxidation were also explored. With fraction content of Sr2+ from 0.1 to 0.4, the crystal structure of La1-xSrxMnO3+δ changed from Rhombohedral to Cubic. Having three adsorption centers,CO adsorption properties of La1-xSrxMnO3+δ from high to low was La0.6Sr0.4MnO3+δ, La0.7Sr0.3MnO3+δ, La0.8Sr0.2MnO3+δ; then CO oxidation capacity from high to low was La0.6Sr0.4MnO3+δ, La0.7Sr0.3MnO3+δ, La0.8Sr0.2MnO3+δ.In the system of La1-xCexMnO3+δ(x=0.2-0.4), CeO2 could not be completely embeded into the lattice of perovskite composite oxides. And high dispersion of CeO2 did exist among product. The production referred to as La1-xCexMnO3+δ/CeO2. CO adsorption properties from high to low was La0.6Ce0.4MnO3+s/CeO2, La0.7Ce0.3MnO+δ CeO2,La0.8Ce0.2MnO3+δ CeO2; redox capacity from high to low was La0.7Ce0.3MnO+δ CeO2 La0.8Ce0.2MnO3+δ CeO2, La0.8Ce0.2MnO3+δ/CeO2.LaB’1-xMnO3+δ (B’=Co,Ni,Fe,Cu) was modified by doping in B site.The influence of substituted element ion and substituted content on the crystal structure of lanthanum-manganese perovskite-type composite, CO adsorption and desorption properties, redox capacity were also studied. When x= 0.2～0.4, Co2+,Cu2+ could be completely embedded into the lattice of perovskite composite oxides. With fraction content of Co2+, Cu 2+ increased, the crystal structure of LaB’1-xMnO3+δ (B’=Co,Cu) changed from Rhombohedral to Cubic. Ni2+,Fe3+could also be completely embedded into the lattice of perovskite composite oxides, but the crystal structure was not changed.Adsorption properties depended on desorption temperature, redox capacity depended on low reduction temperature and consumption of CO. In the system of LaCoxMn1-xO3+δ, CO adsorption and desorption properties from high to low was LaCoo.3Mno.703+5, LaCo0.4Mn0.6O3+δ, LaCo0.2Mn0.8O3+δ; redox capacity from high to low was LaCo0.3Mn0.7O3+δ, LaCo0.4Mn0.6O3+δ, LaCo0.2Mn0.8O3+δ. In the system of LaNixMn1-xO3+δ, CO adsorption from high to low was LaNi0.2Mn0.8O3+δ, LaNi0.3Mn0.7O3+δ, LaNi0.4Mn0.6O3+δ; redox capacity from high to low was LaNi0.4Mn0.6O3+δ,LaNi0.2Mn0.8O3+δ, LaNi0.2Mn0.8O3+δ.In the system of LaFexMn1-xO3+δ, CO adsorption properties from high to low was LaFe0.2Mn0.803+δ, LaFe0.4Mn0.6O3+δ,LaFe0.3Mn0.7O3+δ; redox capacity from high to low was LaFe0.4Mn0.6O3+δ, LaFe0.3Mn0.7O3+δ, LaFe0.2Mn0.8O3+δ. In the system of LaCuxMn1-xO3+δ, CO adsorption properties from high to low was LaCuo.4Mn0.6O3+δ, LaCu0.3Mn0.7O3+δ, LaCu0.2Mn0.8O3+δ; redox capacity from high to low was LaCu0.4Mn0.6O3+δ, LaCu0.3Mn0.7O3+δ, LaCu0.2Mn0.8O3+δ. |
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