【作者】 甘志宏；

【导师】 宁桂玲；

【作者基本信息】 大连理工大学 ， 化学工艺， 2008， 博士

【摘要】 介孔氧化铝具有机械强度高、比表面积大、独特的孔结构、易于装载不同金属物种等优良特性,在多相催化、大分子吸附与分离、陶瓷、功能材料等诸多领域展现出诱人的应用前景。但是由于铝的电负性比硅低,更易进行亲核反应,导致铝盐水解、缩聚速率快,形成无定形的骨架,从而表现出较差的热稳定性和水热稳定性,制约了介孔材料的实际应用。此外,目前介孔氧化铝的合成路线多是基于表面活性剂模板法开发的,合成成本较高,而且合成的产物结构和形貌有待进一步改善。本文通过吸收纳米技术及介孔材料的最新研究结果,致力于探索经济、简便、快速的合成方法,制备高热稳定性和形貌可控的介孔氧化铝。论文中详细研究了介孔氧化铝在模板及无模板存在条件下的形成过程,开发了模板及无模板存在条件下高热稳定性介孔氧化铝的合成路线,探索溶剂、合成方法、产物形貌及焙烧方法等因素与介孔氧化铝热稳定性的关系,并采用X-射线衍射（XRD）、傅立叶变换红外光谱（FT-IR）、氮气吸附、透射电镜（TEM）、热重-差热分析（TG-DTG）等表征手段对产物的结构和性质进行了分析,同时初步考察了典型材料在催化和先进陶瓷材料方面的应用。主要研究结果如下:有机溶剂对无机物种的溶解度和表面张力对介孔氧化铝的形成和热稳定性有很大的影响。在辛醇/乙腈二元体系中,异丙醇铝溶解于亲油性溶剂辛醇中,水溶解于亲水性溶剂乙腈中,使得反应在两相界面上进行,从而降低了醇盐水解和缩聚反应速率合成得到高热稳定性介孔氧化铝。在溶胶-凝胶法中,Triton X-100的超分子模板作用诱导蠕虫孔洞介孔氧化铝的生成,产物孔道结构的调控可通过陈化温度的调变实现。超声合成热稳定性更为优异的产物,超声产生的高温促使薄水铝石晶粒的生成,表面活性剂通过和薄水铝石晶粒间的氢键作用诱导“刚性”晶粒的堆积,导向具有晶化γ-Al₂O₃骨架的介孔氧化铝生成;且合成时间从数天缩短到3-6h,显著提高了合成效率。廉价、环境友好的小分子尿素通过-NH₂与薄水铝石胶粒表面形成氢键导向介孔氧化铝的形成。氨水控制水解条件下,产物的晶态骨架以及特殊的脚手架状形貌使其具有高比表面积、大孔容和高热稳定性,600℃焙烧3h后比表面积高达372m²/g,孔容为0.84cm³/g。表面活性剂模板法和尿素模板法两种合成路线均利用选定的组装模板与无机纳米颗粒之间的识别作用,使得模板指导纳米颗粒组装形成介孔结构,但介孔孔道的形成不一定需要模板的参与。介孔氧化铝可在无模板存在的条件下通过均匀球形胶粒有序堆积成功合成。乙酰乙酸乙酯+醋酸复合螯合剂与铝醇盐形成配位结构,控制生成形状均匀、粒度分布均一的球形胶粒;而快速焙烧的方法抑制了相转变导致的颗粒异常长大获得高热稳定性产物。基于薄水铝石层状结构特点,在无模板条件下,通过调控溶剂热反应温度和溶剂组分,实现了层状结构卷曲形成一维纳米结构介孔氧化铝的设想,实验现象初步揭示了薄水铝石晶体结构与一维纳米介孔结构生长的内在关联,为一维纳米结构液相生长的相关理论与机理研究提供了实验依据。适宜的溶剂体系是合成高热稳定性介孔氧化铝的关键因素之一;辛醇/乙腈二元体系可以合成并提高介孔氧化铝的热稳定性。合成方法的改变导致孔壁的结构和组成的变化;与常规方法相比,超声合成获得了具有晶化孔壁的介孔氧化铝,而且增加了孔壁厚度,因而显著改善了产物的热稳定性,产物经900℃焙烧3h后介孔结构不坍塌,且比表面积高达258 m²/g。颗粒的生长与产物的晶体结构性质密切相关;产物形貌控制的同时无机相缩聚形成薄水铝石晶化孔壁;另一方面纤维状产物相互接触面积小、耐烧结,最终改善了介孔氧化铝的热稳定性。焙烧升温速率的不同影响介孔氧化铝的热稳定性。以介孔氧化铝为载体,负载Ni-Mo双组分的催化剂具有比商品催化剂更优异的二苯并噻吩（DBT）加氢脱硫活性和稳定性:低温260℃时,DBT转化率高达98.8%,比同类商业催化剂同温度下的DBT转化率（67.3%）高出31.5个百分点,有望实现柴油加氢脱硫生产的大幅度节能降耗。基于多孔及纳米α-Al₂O₃的表面性质,利用高速剪切乳化分散技术开发出陶瓷墨水制备新工艺,使球形α-Al₂O₃纳米粉体在乙醇/异丙醇陶瓷墨水体系中稳定分散的固相含量高达10 Vol%以上。墨水满足打印成型要求,成功实现了在基底上的单层和多层打印;同时制备时间从数天（球磨工艺）缩短至4h,大大降低了能耗。该工艺与喷墨打印技术的成功结合有望实现复杂结构薄膜材料、多层显微电路和小体积、高复杂的整体陶瓷元件的制造。更多还原

【Abstract】 Mesoporous alumina is superior to silica due to resistance toward oxidation and corrosion, high mechanical strength, favorable combination of surface and textural properties, and convenience to be loaded with different metal species. These features make it highly desirable in catalysis and adsorption, especially in bulk molecule processes. However, the applications going beyond laboratory tests are at present out of reach. Aluminum alkoxides are susceptible to hydrolysis and phase transitions accompanied by thermal breakdown of the structural integrity, which make them difficult to create mesoporous alumina. Moreover, the structure in mesopore scale and morphology control need further improve. In the dissertation, with the recently development in nanotechnology and mesoporous materials formation mechanism, we hope to overcome the above motioned question, develop cost effective mesoporous alumina synthesis method, and improve the thermal stability and morphology control of mesoporous alumina. XRD, FT-IR, TG-DTG, TEM, and N₂ adsorption were used to characterize the mesoporous alumina. The results are listed below:A combination of octanol and acetonitrile is optimal for the synthesis of mesoporous alumina with high thermal stability. In the mixed solution, the aluminum alkoxide dissolved into octanol and not into acetonitrile, but water dissolved into acetonitrile. Hence, alkoxide hydrolysis is inhibited by the two phase interface. Mesoporous alumina with wormhole like mesopore channel can be synthesized with surfactant as template in sol-gel method. And mesopore diameters can be easily modified by the aging temperature. The nonionic PEO surfactant acts as a structure-directing agent to direct the formation of alumina mesostructure with excellent thermal stability through hydrogen bond inducing the arrangement of rigid boehmite particulates in the sonochemical method. Another advantage in the application of ultrasound radiation is the drastic reduction in the fabrication time from days to 3-6 h.Mesoporousγ-Al₂O₃ has been successfully synthesized by using the cheap and environmental-friendly urea. It has demonstrated that urea not only acts as a structure-directing agent via the hydrogen bonds, but also effectively preserves the sintering behavior of nanocrystals during calcination. The structural properties and thermal stability of the products can be effectively controlled through adjusting the morphologies and crystalline phases. The mesoporousγ-Al₂O₃ obtained 372 m²/g surface area and 0.84 cm³/g pore volume after calcination at 600℃. Mesoporous aluminas with high thermal stability have been prepared by hydrolysis of Al（OC₃H₇）₃ using sol-gel technique combining instant calcination without the aid of template. The results show that the organic compounds of acetoacetic ester （EAA） and acetic acid （AcOH） not only control the rate of hydrolysis and condensation but also determine the particle size and the morphology of alumina. And the instant calcination can inhibit the formation ofα-Al₂O₃ "dendrites" and improve the thermal stability.Based on the layer-structured A100H, a rolling mechanism has been introduced to explain the formation of the mesopores and the growth of one-dimensional nanostructures under solvothermal conditions at 190℃. The structural properties and morphologies of the products can be effectively controlled by manipulating the composition of the solvent and the reaction temperature.Solvent is a key factor for the formation of mesostructured alumina with high thermal stability. The thermal stability of the mesoporous alumina can be enhanced by the combination of octanol and acetonitrile. The structure and composition of pore wall can be modified by synthesis through different methods. Mesoporous aluminas prepared by ultrasound radiation obtain high specific surface areas, large porosities, and excellent thermal stabilities, which should be attributed to their crystalline and thicker framework walls. The obtained mesoporous alumina had still mesoporous structure after calcination at 900℃for 3 h and obtained 258 m²/g surface area. The growth of particle is related to the crystalline structure. The mesoporous framework is composed of fibrous nanoparticles of boehmite. The thermal stability of mesoporous alumina was affected by the heating rate.The dibenzothiophene conversions and durability superior to that of a commercial catalyst have been achieved over the mesoporous alumina catalysts. Compared with the commercial catalyst, the dibenzothiophene conversion reached 98.8% and increased 31.5% at 260℃. Inks in the form of alumina suspension have been prepared by high-shear dispersing emulsifier firstly. Compared with ball milling methodology,α-Al₂O₃ ceramic inks have shown excellent dispersiveness, stability, and high solid content （10 vol%） obtained by high-shear dispersing emulsifier which satisfy the requirements of ink-jet printer based on the print test. Another advantage of high-shear dispersing emulsifier is the drastic reduction in the fabrication time from days to 4 h.更多还原