Optimized Design And Methane Catalytic Oxidation Study Of Composite Metal Oxides

As the second largest greenhouse gas in the world,methane（CH₄）was highly explosive and flammable,which posed a serious threat to human production,life and the ecological environment.Catalytic oxidation technology was widely used as an efficient and low-cost option for methane treatment.However,methane had a relatively stable structure,the low-temperature catalytic breaking of the first C-H bond became the key rate-controlling step in catalytic oxidation.This technology required the catalyst with not only high activation performance,but also hydrothermal stability and certain resistance to poisoning.The composite metal oxides with Co₃O₄ as the main active phase had the properties of easy valence regulation and easy defect construction,which could produce unique catalytic properties and gradually became prominent in catalytic materials.This paper mainly focused on the preparation of novel composite oxides using organic carbon hydrothermal coupling and acid etching on precursor oxides,and optimized parameters to achieve complete degradation of methane in low temperature window period.1)Co₃O₄ as the active body was loaded with La₂O₂CO₃ to investigate the effect of different process parameters and loading amount on the complex.The combination between the two phases of Co₃O₄ and La₂O₂CO₃ reached the best loading effect when the Co₃O₄ loading amount reached 100%.The catalytic performance of methane was significantly enhanced after loading with La₂O₂CO₃.Characterization data analysis yielded that the two-phase loading effectively optimized the physical properties and thermal stability of the catalysts.2)The physical morphology of Co₃O₄ was changed by external morphology optimization to enhance the catalytic performance of x D Co₃O₄/La₂O₂CO₃-loaded catalysts.In the process of morphology optimization,the Co₃O₄ catalyst with two-dimensional morphology was obtained by modulating the preparation process,which greatly optimized the surface physical and chemical acid-base properties of the catalyst.The structural stability of the catalyst was further enhanced by the loading of the oxygen supply additive La₂O₂CO₃.3)The optimization of the internal environment with Co₃O₄ was achieved by component modulation,which enhanced the methane catalytic performance of the composite catalysts.Carbon doping for the Co₃O₄ component enriched and improved the surface oxygen species and acid-base properties of the catalysts,which enhanced the adsorption activation of methane molecules.Activity tests showed that the 6C-Co₃O₄catalyst had the best catalytic performance with T₅₀（temperature at which 50%methane conversion was achieved）of 300°C and T₉₀（temperature at which 90%methane conversion was achieved）of 340°C.After coupled loading with La₂O₂CO₃,the thermal stability of the catalyst was further improved,although the activity of the catalyst was reduced.4)Based on the effects of surface acidity and alkalinity on the performance of catalytic materials,we conducted an exploratory experiment on the effect of acid etching on catalysts.The as-prepared catalysts were applied to the catalytic degradation reaction of methane.The catalytic evaluation revealed that OALSM-0.01M was the best catalytic performance catalyst,with T₅₀ of 340°C and T₉₀ of 420°C.Characterization analysis showed that oxalic acid etching of the La Sr Mn-based catalyst structure could generate abundant unsaturated Mn³⁺coordination bonds and increase the concentration of adsorbed oxygen on the surface,which effectively improved the catalytic performance of the catalyst.However,high acid etching concentration could damage the catalyst structure and affect the catalytic oxidation reaction process.