Perovskite-type Oxides Catalytic Elimination Of No By

Nitrogen oxides (NO_x) are serious pollutants in earth's atmosphere, they are harmful gases both to environment and human body. As one catalyst for NO_x removal, special attention has been paid to the use of perovskite mixed oxides due to their remarkable stability, and perovskite-type oxides can accommodate a large number of metal, which result in the obtained samples possessing special character.In this dissertation, a series of perovskite-type oxides via substituting the A or B site of LaFeO₃ and LaMnO₃ were successfully synthesized through citric acid complexing sol-gel method. The influence of doping elements in A site and B site and the doping ratio on the catalytic activity of perovskite-type oxides was also discussed in this thesis. It was found that the activity in NO direct decomposition could be improved by substituting alkaline-earth metals for La, in which the samples of substituting Ba for La performed best activity. XRD results demonstrated that perovskite phase is retained at low 20% Ba doping content, H₂ temperature programmed reduction (H₂-TPR) indicate that low substituting Ba for La performed their activity for NO removal through enhancing the oxidability of B site metal. The conversion of 1.0% NO to nitrogen over La_0.75Ba_0.25FeO₃ can attain 72% at 850℃. The influence of doping elements in B site was also discussed in this thesis. It was found that doping Fe and Mn series catalysts performed special catalytic activity. H₂-TPR and O₂ temperature programmed desorption (O₂-TPD) indicate that B site doping different transition metal can enhance the oxidability of B site metal, increase the amount of oxygen vacancy and promote the mobility of crystal lattice oxygen. The conversion of 1.0% NO to nitrogen is 88% and 90% at 850℃over La_0.85Ba_0.15Fe_0.7Ni_0.3O₃, La_0.8Ba_0.2Mn_0.6Cu_0.4O₃ catalysts, respectively.