【作者】 白鹏；

【导师】 阎子峰；

【作者基本信息】 中国石油大学 ， 化学工程与技术， 2007， 博士

【摘要】 氧化铝是一种重要的工业化学品,被广泛地应用于催化,吸附,陶瓷领域。但是传统的氧化铝材料由于孔结构不发达,大大限制了其在催化领域的应用。近年来,人们在制备具有优越孔结构的介孔氧化铝方面作了大量的工作,所采取的合成路线一般为模板导向法。本论文针对目前的一些合成方法所存在的合成路线复杂,价格昂贵等缺点,开发了介孔氧化铝合成新方法,并成功地将该方法扩展到新型功能材料的合成中。开创性地将阴阳离子双水解反应引入到介孔氧化铝的合成中,详细地阐述了该方法的理论基础,确定自调节和彻底性为该方法的两大主要特征。通过考察双水解反应中阴阳离子铝源对氧化铝结构的影响之后,确定了Al（NO₃）₃和NaAlO₂双水解体系为最佳合成体系,因为该体系合成的介孔氧化铝不仅具有较高的比表面和孔容,γ-Al₂O₃的晶型孔壁,很高的热稳定性,而且所得氧化铝中不会残留造成催化剂中毒的阴离子毒物。通过改变合成条件,如晶化温度,溶液pH值,P123含量等,详细考察了合成条件对氧化铝结构性质的影响。XRD和27Al MAS NMR结果表明双水解法合成的介孔γ-Al₂O₃不含无定形氧化铝微区,为纯的γ-Al₂O₃晶相。通过倒置铝源的加入顺序,可以合成具有双孔分布的介孔氧化铝,而且其比表面有所提高。将前人创造的“三步法”引入到双水解反应中,所得介孔氧化铝,其孔结构和晶型都大有改善。特别是在80oC下晶化的氧化铝,其比表面高达471m²/g,这是目前报道的最高比表面的纯γ-Al₂O₃材料。本论文还将阴阳离子双水解法扩展到介孔复合金属氧化物的合成中,所合成的复合金属氧化物催化材料具有比表面高,活性组分担载量高,分散好等优点,证明双水解法是一种有效合成介孔复合金属氧化物的通用方法。为了控制介孔氧化铝的微观形貌,开发了共聚物控制的均匀沉淀法,在水热条件下合成了具有规则形貌的介孔氧化铝微纤维,并且通过改变合成条件,可以实现介孔氧化铝孔结构和微观形貌的双重控制。并根据实验结果,提出了“层层自组装”的微纤维生长机理。除此之外,本论文还将该方法扩展到ZnO的合成中,合成了具有复杂三维形貌的线团状ZnO超结构,证明该方法是一种有效控制材料形貌的新方法。催化评价表明,双水解法合成的介孔氧化铝在羟醛反应中具有很高的催化活性,远远高于工业活性氧化铝材料。其优良的催化活性与其高比表面和较强的表面碱性有关。更多还原

【Abstract】 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.更多还原