【作者】 蔡晓慧；

【导师】 王策； 朱广山；

【作者基本信息】 吉林大学 ， 高分子化学与物理， 2006， 博士

【摘要】 本论文致力于介孔和多级孔材料的合成和表征,研究了介孔材料模板剂的脱除、介孔硅铝材料的合成和介孔硅材料的组装以及介孔/大孔复合孔材料的合成。第一章为绪论,介绍了多孔材料的分类和介孔材料的形成机理、合成路线、空间结构等以及多级复合孔材料的概况;在第二章中,在酸性条件下以沸石导向剂为原料合成出一系列介孔硅铝材料,结合实验现象参照核磁结果和凝胶的相关理论讨论了其形成机理以及合成条件对产物的影响;在第三章中,以高锰酸钾和浓硝酸的混合溶液为氧化剂,脱除一系列具有六方和立方结构的介孔硅材料中的模板剂,并研究了该方法对不同结构和不同模板剂的脱除效果;第四章中,利于银镜反应的原理在介孔硅SBA-15的孔道内控制合成出银纳米粒子和纳米棒,并检测了Ag/ SBA-15复合材料的抑菌作用;在第五章中,利用碳复制技术将硅藻的大孔结构特征进行复制,再以其碳复制品和表面活性剂为双模板制备出多级有序介孔/大孔复合材料。更多还原

【Abstract】 Microporous zeolites with uniform and molecular-size pores have been widelyused in many fields such as ion-exchange, adsorption, separation, and industrialcatalysts. However, they cannot effectively deal with large molecules due to thelimitation of the micropore size. Mesoporous materials attract considerable attentiondue to larger mesopores, narrow pore size distributions, adjustable pore size andordered structures.Compared with zeolite, mesoporous materials have weaker hydrothermalstability and catalytic activity due to the amorphous nature of their pore wall. Inorder to improve their hydrothermal stability and catalytic activity, it is a goodmethod to introduce prozeolitic nanoclusters (zeolite seeds) into the amorphous wallof mesoporous materials. In this process, zeolite precursor including zeolite primaryand secondary structure units is used to instead of conventional silicon source andself-assemblies with surfactant to prepare ordered mesoporous materials. Althoughthese structure units are not the real zeolite crystal and cannot be detected by X-rayor TEM, they possess the property similar to zeolite, such as acidity. The study aboutthe synthesizing mechanism is limited by the measurement of zeolite precursor. Herewe prepared a series of aluminosilicates with different acidities by FAU-Y and LTLzeolite precursor in acidic condition. XRD patterns of the samples indicate that whenTEOS and zeolite precursor were used as silica source at the same time, highlyordered aluminosilicates can be obtained, and due to the decrease of zeolite structureunits in the wall, the acidity becomes weaker. The formation procedure ischaracterized by in-situ 27Al NMR and 29Si NMR techniques. Considering the NMRspectra, the literatures of gel and experiment phenomenon, the formation of theinorganic framework in a strong acidic media is mostly due to the condensation ofthe silica species. During the process of the preparation of MAS-Y, pH value iscontrolled to descend slowly. The formation of Si-O-Si bond protects the4-coordinated Al, reduces the loss of aluminum species under strong acidiccondition and prevents zeolite bulding units from destroying. Owing the propertiesof the mesoporous solid such as acidity are relative to the composition of the wall ofthe mesoporous materials, MAS-Y prepared by slowly adjusting pH value canpreserve more zeolite units consisting more 4-coordinated Al in the wall, so theacidity and aluminum content of MAS-Y are higher than that of MAS-Y1.Choosing right method to remove the templates from as-synthesizedmesoporous materials is in great importance in the preparation process, and haseffect on their further application. Acidic potassium permanganate solution preparedby using nitric acidic and potassium permanganate was used as oxidant to removethe template from mesoporous materials. When as-synthesized materials encounterwith high oxidated solution of acidic potassium permanganate, the organic templatecan be oxidated to small moleculues and leave off the mesoprous system. Comparedwith conventional thermal calcinations method, this oxidation method provides moremerits such as richer silanol groups and lower structural shrinkage, which is in favorof the channels of mesoporous materials modified with organic functional groupsand encapsulated of guest molecules. The mesoporous materials with differentstructure prepared by the same template have different removing ratio of templates.P6mm is the highest, secondly is Ia3d, and Im3m is the lowest. The mesoporousmaterials with similar structure prepared by different template also have differentremoving ratio of templates, and block-copolymer is higher than quaternaryammonium surfactant. Ordered 2D hexagonal mesoporous silica SBA-15 preparedby block-copolymer P123 has the highest removing ratio of templates, which ishigher than 98%. This method needs neither special instrument nor especialexperimental condition, and the whole experimental operation is easy to control,which is convenient for popularizing.Based on their ordered nano-sized channel or cages, mesoporous materials canbe incorporate or modified by functional groups for improving their properties.Metal nanostructure can be prepared in the channels or cages of mesoporousmaterials, which are used as mini-reactor. Metal nanostructure/silica composites areobtained if the structure is retained. Here the channel of ordered 2D hexagonalmesoporous silica SBA-15 is used as a mini-reactor. Spherelike and rodlike Agnanostructures were prepared in the channels of mesoporous silica through Tollenreaction. SBA-15 is immerged in glucose solution first, which is used as reducingagent, and then Tollens’ reagent is added to prepare Ag/SBA-15. The X-raydiffraction (XRD) and transmission electron microscopy (TEM) revealed that Agnanoparticles with uniform size about 2 ~ 3 nm were dispersed inside the channelsof mesoporous SBA-15 when Tollens’ reagent is insufficient. UV-Vis absorptionspectra indicated the quantum size effect of the Ag nanoparticles. It was found thatthe shape of Ag nanoparticles was changed from sphere to rod-shape by adding theamount of Tollens’ reagent. This Ag nanostructure/SBA-15 nanocomposite wasshown to be an effective bactericide against E. coli and Staphylococcus.Microporous, mesoporous and macroporous materials owing their respectiveunique structure characteristics can be applied in corresponding application areas. Inrecent years hierarchical porous materials with two or more levels of porosities haveattracted much attention owing to their potential applications in catalysis, separationand ion-exchange. Such materials improve the diffusion of the guest moleculesthrough the inorganic network of pores and channels, because larger pores allow forbetter molecular accessibility while the smaller pores provide higher surface areasand larger pore volumes. The hierarchical porous silica materials with the structureconsisted of ordered hexagonal mesopores and macropores have been preparedusing block copolymer P123 (EO20PO70EO20) and inverse carbon replica of diatomas dual templates. The silica wall of the diatom was replaced by ordered mesoporoussilica, while the micron-sized diatom architecture was replicated by using an inversecarbon replication technique. The mesoporous silica was found to have macroporousstructures with both columnar and discoid diatom templates. The presence ofhierarchical meso/macroporous systems was confirmed by the results from scanningand transmission electron microscopy, powder X-ray diffraction, and nitrogenadsorption-desorption studies.更多还原