Structural Optimization And Doping Modification Of Perovskite Catalysts And Their Catalytic Oxidation Performance For Methane-containing Exhaust Gas

Methane emissions from fossil fuel combustion,gas-fueled vehicles exhaust and numerous industrial exhausts had caused serious environmental problems.For methane-containing waste gas,catalytic oxidation is an effective and feasible degradation treatment technology,while the research on various catalysts with low cost,high catalytic activity and stability is the key to achieve high-efficiency catalytic oxidation of methane.In this paper,the perovskite catalysts synthesized with different conditions（e.g.,synthetic method,calcination temperature and gas space velocity）and B-site doping（e.g.,doping element,doping level）were used to study the catalytic oxidation of methane by means of structural control.The physicochemical properties of the catalyst,such as the structure,morphologies and surface element valence state,were analyzed with a variety of characterization methods,and the relationship between the structural characteristics and the catalytic performance was built.The main research contents and conclusions are as follows:（1）Three-dimensional ordered macroporous structure（3DOM）LaFeO₃ catalyst was prepared by PMMA template method,and the effects of calcination temperature and preparation method on the microscopic morphology,pore structure parameters and methane catalytic activity were studied.The results showed that the calcination temperature of catalyst affected the crystallite size of the catalyst.LaFeO₃-700 catalyst possessed better pore structure,redox performance,and higher Fe⁴⁺/Fe³⁺value,thus showing better methane catalytic performance.T₅₀ and T₉₀ were 55 and 37℃,lower than those of bulk LaFeO₃ catalyst.24 h stability test showed that LaFeO₃-700 catalyst had good stability at high temperature.（2）3DOM LaFe_1-xCo_xO₃ perovskite catalysts doped with transition metal Co were prepared by PMMA template method,and the effects of Co doping and doping amount on the catalytic oxidation activity of methane were studied.The results showed that the Fe⁴⁺/Fe³⁺,O_ads/O_lat value and surface adsorption water content of 3DOM LaFe_1-xCo_xO₃catalyst increased with the increase of Co doping amount.The increase of Fe⁴⁺/Fe³⁺and O_ads/O_lat value was conducive to the improvement of catalytic activity.However,the increase of adsorbed water content on the surface inhibited the catalytic activity of the catalyst.Therefore,if the adsorbed water content is controlled by the surface technology of catalyst,the catalytic activity of Co doped perovskite catalyst to methane could be effectively improved.（3）3DOM LaFe_1-xNi_xO₃ catalysts doped with transition metal Ni were prepared by PMMA template method,and the effects of Ni doping and doping amount on the catalytic oxidation activity of methane were studied.The results showed that the Ni-Fe bimetallic synergy was more conducive to the improvement of the catalyst performance,and the reasonable doping level had an impact on the catalytic effect of the catalyst.Among them,the 3DOM LaFe_0.9Ni_0.1O₃ catalyst possessed the best methane catalytic performance,thermal stability and anti-carbon deposition,with T₁₀,T₅₀ and T₉₀ being397,511 and 598°C,respectively,realizing the efficient catalytic oxidation of methane,and has the application potential to replace precious metal catalyst because of its low price and high quality.