Study On Catalytic Oxidation Of Methane By Metal Doping And Hydrothermal Treament Of Perovskite-type Catalysts

The exhaust gas of industrial gas and natural automobile contains unused methane,and the amount of emissions daily increases.Methane is a greenhouse gas with a greenhouse effect of 21 times that of CO₂.Catalytic oxidation is an economically viable technology,without secondary pollution.Although the perovskite-type catalysts have high stability,but the activity of catalytic needs improving.In this paper,LaCoO₃ and LaMnO₃ perovskite-type?ABO₃?catalysts were prepared by sol-gel method,changed by different preparation conditions(different precursor ions concentration,calcination temperature and double complexing agent?citric acid and ethylenediaminetetraacetic acid?,different metal doping and hydrothermal treatment.The crystal structure,physical adsorption properties,pore size structure and microstructure of the catalysts were characterized by XRD,BET,TEM and SEM.The catalytic performance of the catalysts was evaluated by the on-line catalytic device.The main conclusions are as follows:LaCoO₃ and LaMnO₃ prepared by the precursor ion concentration 1 mol/L,calcination temperature 800?had the best activity.The effect of double complexing agent on low concentration precursor catalyst is higher than that of high concentration.The LaCoO₃ and LaMnO₃ activities can be improved by the strontium A site and the magnesium B sites droping.La_0.9Sr_0.1CoO₃,La_0.8Sr_0.2MnO₃,La Co_0.9Mg_0.1O₃ and La Mn_0.7Mg_0.3O₃ are the most effective in the respective doping ratios.The double-doped La CoO₃/La MnO₃ catalyst had not been significantly promoted or even inhibited by La CoO₃ catalyst activity.In different kinds of metal oxide chelated perovskite catalysts,alkaline earth metal Mg had the greatest effect on LaCoO₃,followed by transition metal Mn and transition metal Co.In addition,the metal Co and Ce had little effect on LaCoO₃,but the metal oxides Co₃O₄ and Ce₁₁O₂₀ had considerable activity.The hydrothermal treatment of LaCoO₃,La_0.9Sr_0.1CoO₃,La Co_0.9Mg_0.1O₃,La MnO₃ and LaMn_0.7Mg_0.3O₃ were the best for 4 h,8 h,8 h,4 h?or 8 h?and 12 h Heat treatment La_0.9Sr_0.1MnO₃ and La_0.8Sr_0.2Mn_0.7Mg_0.3O₃ catalyst,the activity is almost no change.