Preparation, Characterization And Application Of LaMnO₃ Perovskite-type Oxides

In this paper, ABO3 perovskite-type oxides were synthesized by solid state reaction method and sol-gel method, and the effects of modification by A-site and B-site ion-doping for the structure and catalytic performance were also investigated. Structure and reduction ability of the material were characterized by X-ray diffraction(XRD), BET, temperature programmed reduction(H₂-TPR). The activity for removing soot in the O2 atmosphere was investigated by temperature programmed oxidation(TPO). The catalytic performance for decomposing N₂O and simultaneously removing soot and NOx was studied by self-made experimental device.The LaMnO₃ perovskite-type oxides were prepared by solid state reaction method and sol-gel method and the conditions were optimized. Other metal ions were tentatively substituted into the A/B sites of perovskite-type oxides and it was found that the doping ions could enter the lattice sites while in low loading.The results of TPO showed that the perovskite-type oxides could obviously decrease the combustion temperature of soot. The appropriate metal ions were doped into the A-site and B-site lattice of the perovskite-type oxides and the catalytic performance was improved. H2-TPR results showed that the content and the activity of active oxygen in the modified perovskite-type oxides were improved.The evaluation results of decomposing N₂O showed that for the catalysts synthesized by the solid state reaction method, the catalytic performance for decomposing N₂O were improved slightly by doping in A-site only and the initial N₂O decomposition temperature were raised by doping in B-site and A/B-site of the catalysts; for the catalysts synthesized by the sol-gel method, the catalytic performance for decomposing N₂O directly were improved by doping K and Ce in the A-site of LaMnO₃ separately or simultaneously. At the same time, the evaluation results of simultaneously removing soot and NOx in the diesel exhaust showed that the LaMnO₃ prepared by solid state reaction method and sol-gel method could greatly lower the combustion temperature of soot, and they had high activity in reducing NOx to N₂. The catalytic activity of doped perovskite-type oxides were greatly improved by both methods. The La0.7Ag0.3Mn0.9Co0.1O3 prepared by solid state reaction method had best activity in simultaneously removing soot and NOx of diesel exhaust, and the T10, T50 and T90 of soot was lowered by 111℃, 172℃and 219℃respectively. The yield of N2 could reach up to 77.6%.