Novel Approaches To The Preparation Of Mesoporous Alumina And Emerging Functional Materials

Alumina is an important industrial chemical, widely applied in catalysis, adsorption and ceramics. However the poor textural properties of the traditional alumina have strictly limited its application in catalysis. Recently, a considerable amount of efforts have been devoted to the preparation of mesoporous alumina with superior structural properties. And the adopted strategies are commonly template approaches. This dissertation is intended for the development of novel approaches to mesoporous alumina by avoiding the shortcomings haunting in the previous approaches, such as complicated synthesis route, high cost and so on.The cation-anion double hydrolysis reaction was innovatively introduced in the synthesis of mesoporous alumina. By elaborating the theoretical basis of double hydrolysis, self-adjusted and complete are the two unique characteristics of this novel approach. By investigating the effect of cationic and anionic aluminum sources on the structural properties of alumina, Al(NO3)3+NaAlO2 was established as the optimum system, for the prepared alumina in this system has high surface, high pore volume,γ-Al₂O₃ crystalline pore wall, high thermal stability and also no poisonous anion remnants. By changing the synthesis parameters, such as crystallization temperature, solution pH, P123 content, the effect of synthesis conditions on the alumina structure were thoroughly studied. XRD and 27Al MAS NMR results show the double hydrolysis derived mesoporous alumina has a pureγ-Al₂O₃ crystalline phase without amorphous domains. By inversely adding aluminum sources, mesoporous alumina with bimodal pore distribution and higher surface area was prepared. By introducing a"three-step procedure"reported by previous researchers into the double hydrolysis reaction, mesoporous alumina with greatly improved structural properties was synthesized. Especially, the sample crystallized at 80oC exhibited very high surface area of up to 471m²/g, which is the highest one reported so far for the pureγ-Al₂O₃. The double hydrolysis approach was further extended into the preparation of mesoporous mixed metal oxides, and the obtained mixed oxide catalytic materials have high surface area, high loading and high dispersion of active components, which demonstrates the double hydrolysis approach is a versatile method to the synthesis of mesoporous mixed metal oxides.To control the morphology of mesoporous alumina, a copolymer controlled homogeneous precipitation approach was developed. A uniform mesoporous microfiber was synthesized under the hydrothermal condition. By varying the synthesis conditions, both the morphology and mesoporous structure of alumina can be controlled. And a"layer-by-layer self-assembly"mechanism was proposed to interpret the growth of alumina microfibers. Besides, this approach was extended into the synthesis of ZnO material, and a complex 3D clewlike ZnO superstructure was assembled, which proves that the copolymer controlled homogeneous precipitation approach is an effective morphology-controlling method.Catalytic evaluation results show the double hydrolysis derived mesoporous alumina exhibits very high activity in the aldol reaction, far higher than the commercial activated alumina. The excellent catalytic performance of mesoporous alumina is attributed to its high surface area and basic surface.