【作者】 刘恒；

【导师】 阚秋斌；

【作者基本信息】 吉林大学 ， 物理化学， 2014， 博士

【摘要】 现如今，已经探测到的天然气储量是非常巨大的，并且新发现储量的增长速度要远远大于液化石油等的增长速度。专家预测，这种趋势在21世纪将会体现的更加明显。甲烷在无氧条件下催化转化芳烃是一个十分重要的催化反应，他将为天然气的有效利用开辟新的途径。自从第一个高效的催化剂Mo/ZSM-5在1993年被发现以来，甲烷无氧芳构化反应就成为了工业上和学术上研究的一个热点方向。无机多孔材料在石油化工领域有着广泛的应用。多级孔复合材料作为一种新兴的材料，比如微孔-介孔复合材料，由于其具有微孔和介孔的双重特性，使其在一些催化反应中表现出了很好的活性。微孔为反应物提供孔道和择形效应，介孔的存在使反应物更容易接触到活性中心，促进产物的分离。IM-5是一种新型分子筛，它具有与众不同的二维十元环孔道系统。它的大体结构在2000年被Corma教授的小组报道，但直到2007年，它的具体的晶体结构参数才被发现。作为已知的最复杂的沸石分子筛之一，IM-5展现出了独特的骨架结构。它的骨架包括了24种不同类型的Si并且具有比ZSM-5大三倍的晶胞单元。它的孔道结构系统是由不同的二维孔道互相交联产生的。中间的二维孔道和旁边的孔道通过沿着[010]晶面的十元环相连，并且由此产生一个约为2.5nm大小的空穴。因此，IM-5分子筛的结构可以被定义为是由二维十元环孔道系统和一些三维特征的空穴构成。这些三维的空穴使它具有与之前的ZSM-5,ZSM-11等分子筛不同的结构特征，IM-5不但具有普通微孔材料的长程有序的二维孔道，同时空穴的存在能对反应物与活性中心的接触，生成物的扩散以及减少积碳的生成起到积极的作用。由于IM-5具有比ZSM-5更好的水热稳定性，使它在烃类催化裂化和NO吸附实验中表现出了较高的活性。IM-5优异的物理化学性质，使它在石油化工领域可以得到更广泛的应用。TNU-9是由Hong等人在2007年合成出了一种新型的十元环交叉结构的分子筛。TNU-9包含24个拓扑硅原子，其晶胞体积要大于ZSM-5。TNU-9有两套10元环的孔道。在两套10元环孔道相距较窄的地方，通过另一套10元环孔道互相连通，此外在TNU-9的孔道内部还包含一个较大的笼结构。作为已知的最复杂的沸石分子筛之一，TNU-9展现出了独特的骨架结构。同时，TNU-9作为高硅的沸石分子筛，具有非常好的水热稳定性。TNU-9已经在某些反应中表现出了较好的活性和择形性，TNU-9是一种新型分子筛，它具有独特的二维十元环孔道系统。本文主要从以下三个方面入手，围绕多级孔材料的合成及其应用展开工作。1.新型IM-5和TNU-9载体的合成条件考察及在甲烷无氧芳构化反应中的应用在本小组的对甲烷无氧芳构化反应载体的考察中，IM-5和TNU-9分子筛被证实是甲烷无氧芳构化的新型优良载体，IM-5和TNU-9比传统的ZSM-5载体具有更好的催化活性和稳定性。在本文中，动态和静态条件下合成了IM-5和TNU-9分子筛，并检验了不同晶化条件，不同晶化时间对两种载体合成的影响。与此同时，我们检验了不同合成状况下制成的材料的催化表现，并且对比了在不同的催化剂制备方法下，催化活性与以往有哪些不同。合成的IM-5和TNU-9材料的表征采用多种方法，如X射线衍射，红外FT-IR，SEM，TEM，N2吸附脱附，在催化剂性能测试中，动态条件下合成的IM-5和TNU-9样品的甲烷转化率比静态条件下合成样品的高，与此同时，苯的产率也较高。我们认为催化剂反应活性的差异是由于动态和静态条件下合成的分子筛具有不同的结构性质和酸性。在此之外，我们还检验了催化剂在不同的制备方法下，催化剂活性与以往有哪些不同，结果显示浸渍法制备的催化剂具有高的初始活性，但是稳定性欠佳，固态交换法制备的催化剂初始活性低。我们认为固态交换法和浸渍法制备的样品催化性质的差异，是由于不同催化剂制备方法下活性成分Mo物种在催化剂上的落位不同所致。2.模板法合成新型IM-5和TNU-9多级孔材料及其催化应用首先，我们以介孔材料SBA-15和MCM-48为硅源合成了多级孔IM-5和TNU-9材料，多级孔载体制成的催化剂展示了比传统催化剂更好的稳定性。其次，我们在IM-5和TNU-9的合成体系中添加葡萄糖作硬模板，合成出了带有一定量介孔的多级孔IM-5和TNU-9分子筛，含有介孔的IM-5和TNU-9分子筛催化剂表现出比常规IM-5和TNU-9分子筛催化剂更好的性能。再次，我们在IM-5和TNU-9的合成体系中添加不同量的介孔碳作硬模板，带有一定量介孔的IM-5和TNU-9复合材料被合成出来，我们考察了添加不同量介孔碳对催化活性的影响。微孔-介孔复合材料中介孔的存在有利于Mo物种迁移进入到催化剂的孔道中并且与酸位相互作用形成活性位，有利于芳烃产物的生成，提高催化剂的活性。同时，介孔的存在有利于产物的分离，减少生成物对孔道的堵塞作用，可以提高催化剂的稳定性。同时，微孔-介孔复合材料中介孔含量的多少对甲烷转化芳烃反应的结果有很大的影响，适当的添加介孔有利于提高催化剂的活性，过多的介孔存在对材料的微孔结构有较强的破坏，抑制催化剂的择形效应，不利于芳烃产物的生成。3．非模板法合成新型多级孔IM-5和TNU-9材料及其催化应用我们通过陈化法以及调整水硅比后陈化的方法合成出了带有介孔的IM-5和TNU-9复合分子筛，我们将多级孔IM-5和TNU-9分子筛制备成钼基催化剂，同时应用到甲烷无氧芳构化反应中，检验其活性。合成的IM-5和TNU-9材料的表征采用多种方法，如X射线衍射，红外FT-IR，SEM，TEM，N2吸附脱附，在催化测试中，陈化法和调整水硅比陈化法合成的IM-5和TNU-9催化剂展示了较高的芳烃产率和稳定性。我们认为不同条件下合成的分子筛具有不同的结构性质，这是导致催化剂反应活性差异的主要原因。多级孔IM-5和TNU-9分子筛合成的催化剂在甲烷无氧芳构化反应中的表现更加出色。更多还原

【Abstract】 The known reserves of natural gas (mostly methane) are enormous and thereserves are increasing more rapidly than those of liquid petroleum. It is anticipatedthat this trend will extend well into the21st century and the effective utilization ofmethane is becoming more important than ever before. Since the first active catalystMo/ZSM-5was found in1993, methane non-oxidative aromatization has been avaluable and challengeable research subject in both academy and industry.Moreover, it has been found that materials with both micropores and mesoporescan remarkably enhance their activities in the catalytic reactions. Micropores inzeolite provide size and shape-selectivity for guest molecules, while mesopores leadto easier access to the active sites for reactants and better diffuse of the products.High-silica zeolite IM-5with an unusual2D10-MR channel system has beenreported by Benazzi et al. in1998. Due to its excellent physico-chemical properties,the zeolite IM-5could be applied in the petrochemical and refining industry ascommercial catalyst. For instance, IM-5is very active in hydrocarbon cracking andNO reduction due to its high thermal and hydrothermal stabilities which are evenbetter than those of ZSM-5. Although the general features of its pore system werededuced from a variety of catalytic reactions in2000, its detailed crystal structureinformation was not fully elucidated until2007. As one of the most complicatedzeolites hitherto solved, IM-5shows a special framework structure containing24topologically distinct Si atoms and an unusually large unit cell (C-centeredorthorhombic with a=14.2088, b=57.2368, c=19.9940) with nearly triplevolume than ZSM-5. IM-5consists of different2D channels with complex channelintersections connected by10-MR apertures. The central2D channel systemconnects to another2D channel system through10-MR along [010] and forms anapproximate2.5nm thick cavity. The structure of IM-5can be described asconsisting in a2D10-MR channel system with the presence of3D cavity, which isdifferent from the early zeolites, ZSM-5, ZSM-11, and MCM-22etc. The3D channel system with complex channel intersections gives IM-5a distinctive porestructure which can accommodate bulky intermediates in a catalytic reaction andIM-5also retains the long-range diffusion property of2D channel system.TNU-9, a new high-silica zeolite with an3D10-ring channel system, haspreviously been synthesized by Suk Bong Hong et al. Recently, the frameworkstructure of this zeolite has been solved through the combined use of powderdiffraction and electron microscopy. More recently, a complete account of thesynthesis, characterization and catalytic properties of TNU-9has been given in thework. As one of the most complex zeolites hitherto solved, the framework structureof TNU-9is that it contains24crystallographically and topologically distinct Siatoms in its large monoclinic unit cell (almost double that of ZSM-5) and possessesan unique3D10-ring channel system. Similar with MCM-22, TNU-9also ownslarge12-ring cavities around7.2that are accessible only through10-ring windows.Moreover, due to the unique pore structure and excellent hydrothermal stability,TNU-9exhibits superior shape selectivity for catalytic reaction such as theisomerization of m-xylene.1. Synthesis of zeolite IM-5and TNU-9under rotating and static conditions and thecatalytic performance in methane non-oxidative aromatizationThe hydrothermal crystallization of zeolite IM-5and TNU-9were investigatedunder rotating and static synthesis conditions. Mo-modified catalysts were preparedfor the methane non-oxidative aromatization. The physical properties and acidities ofthe samples were characterized by XRD, SEM, BET and IR spectroscopy. Comparedwith catalysts synthesized by static condition, catalyst synthesized by rotatingcondition showed both a higher conversion of methane and higher selectivity tobenzene in methane aromatization. We supposed that the higher catalytic activity maybe attributed to the preferable textural properties and acidities of zeolite. Moreover,the catalyst prepared by the physical mixing method exhibited lower initial activity,but better stability for methane aromatization than that prepared by the impregnationmethod. 2. Synthesis of mesoporous IM-5and TNU-9materials using three different methodsand the catalytic performance in methane non-oxidative aromatizationFirstly, the mesoporous IM-5and TNU-9samples were synthesized by usingSBA-15and MCM-48as the silica source.Secondly, the mesoporous IM-5and TNU-9samples were synthesized by usingglucose as the hard template.The third, the mesoporous IM-5and TNU-9samples were synthesized by addingordered mesoporous carbon into the synthesise system.Mesoporous IM-5and TNU-9exhibited larger geometrical shape as conventionalmaterials. Moreover, Mo-modified catalysts were prepared for non-oxidativearomatization of methane. For comparison, conventional catalysts (without addition ofcarbon template) were synthesized for the same reaction. The physical property andacidity of the samples were characterized by XRD, SEM, TEM, BET and IRspectroscopy. Compared with conventional catalysts, mesoporous Mo-modified IM-5and TNU-9catalysts showed higher yields of aromatics. In addition, the stabilities ofmesoporous Mo-modified IM-5and TNU-9catalysts were better than that ofconventional catalysts. It is considered that the catalytic behavior of Mo-modifiedmesoporous IM-5and TNU-9catalysts may be attributed to the generation ofsecondary mesoporous systems within zeolite crystal, which could improve theaccessibility of reactants to the active sites and promote the diffusion of productsformed in the microporous channels.3. Synthesis of new mesoporous IM-5and TNU-9materials using aging method andthe catalytic performance in methane non-oxidative aromatizationThe new mesoporous IM-5and TNU-9materials were prepared by agingmethod. The physical property and acidity of the samples were characterized byXRD, SEM, TEM, BET and IR spectroscopy. Compared with conventional catalysts,mesoporous Mo-modified IM-5and TNU-9catalysts showed higher yields ofaromatics. In addition, the stabilities of mesoporous Mo-modified IM-5and TNU-9catalysts synthesized by aging method were better than that of conventional catalysts. We supposed that the higher catalytic activity may be attributed to the preferabletextural properties. Mesoporous catalysts showed better performance than that ofconventional catalysts.更多还原