Study On Alumina Preparation By AACH Thermal Decomposition And Its Application In Propane Dehydrogenation Catalyst

As a traditional material,alumina is widely used in many fields such as catalysis,adsorption,and medical materials.Its morphology,pore structure,and crystal structure determine its properties and application fields.Therefore,in this paper,we mainly focus on the preparation of ammonium aluminum carbonate hydroxide with good crystal structure and excellent morphology andγ-Al₂O₃ with controlled channel structure.Precipitation method,solid-phase reaction method and hydrothermal synthesis method were used to synthesize the precursor ammonium aluminum carbonate hydroxide,and the corresponding macroporous structure ofγ-Al₂O₃ was prepared.XRD,N₂ adsorption-desorption,SEM,FT-IR,TGA-DSC and other means were used to characterize the ammonium aluminum carbonate hydroxide andγ-Al₂O₃.The experimental results show that all three methods can successfully prepareγ-Al₂O₃ with excellent performance.The optimal conditions for preparingγ-Al₂O₃ in the precipitation method are:the molar ratio of NH₄HCO₃ to Al（NO₃）₃ is 6:1,the concentration of NH₄HCO₃ is 1.6 mol/L,and the concentration of Al（NO₃）₃ is 0.4mol/L,the dropping speed of aluminum nitrate was 4 ml/min.The specific surface area and pore structure ofγ-Al₂O₃ prepared under the optimal conditions were 299.10 m²/g and 0.83 cm³/g,respectively.In the solid-phase reaction method with PEG400 as a surfactant,the optimal conditions for preparingγ-Al₂O₃ are:NH₄HCO₃ and Al（NO₃）₃=8:1,and the aging temperature is 100°C.The specific surface area and pore structure ofγ-Al₂O₃ prepared under the optimal conditions were 300.54 m²/g and 1.13 cm³/g,respectively.The smooth rod-shaped ammonium aluminum carbonate hydroxide was prepared by hydrothermal synthesis.The optimal conditions for synthesizingγ-Al₂O₃are:the molar ratio of CO（NH₂）₂ toρ-Al₂O₃ is 3:1,and the hydrothermal temperature is 140°C,hydrothermal time is 20h.The specific surface area and pore structure ofγ-Al₂O₃ prepared under the optimal conditions can reach 358.1 m²/g and 0.96 cm³/g,respectively.Comparing the three methods,the solid-phase reaction method for the preparation ofγ-Al₂O₃ is simply and easy to achieve industrialization.Therefore,Pt/γ-Al₂O₃,Pt-Sn/γ-Al₂O₃ and Pt-Sn-K/γ-Al₂O₃ catalysts were prepared by usingγ-Al₂O₃ prepared by the solid-phase reaction method as a support and continuous equal volume impregnation method.The morphology of the catalyst was analyzed using TEM technology,and the reactivity of the catalyst was evaluated on a propane dehydrogenation fixed-bed microreactor.The Pt-Sn-K/γ-Al₂O₃ catalyst showed more excellent performance.The conversion of propane and the selectivity of propylene can reach 33.2%and 91.0%,respectively.