【作者】 程晓维；

【导师】 龙英才；

【作者基本信息】 复旦大学 ， 物理化学， 2008， 博士

【摘要】 沸石分子筛是一类具有骨架结构的无机硅铝酸盐。规则的孔径分布,高比表面积和孔容积,优良的热稳定性和水热稳定性,以及易于调变组成、结构和性质等,使其得以广泛应用于工业催化、吸附分离以及离子交换等领域。沸石合成是研究其性质和应用的基础。采用低成本工业原料、以最优化路线实现低污染绿色合成沸石分子筛一直是该领域专家所探索的热点之一。基于这一出发点,本论文选择几种具有广泛应用前景的沸石分子筛,在不同胶态原料体系中研究其结晶,以新合成方法实现其低成本制备或改性,使之有可能作为吸附剂和催化剂应用于工业过程。本论文共六章,主要内容分别如下:第一章概述沸石分子筛合成、改性及应用研究。简介了水热合成、溶剂热合成、干胶转化等主要合成方法,以及在原料中有机模板剂或矿化剂(F^-1)的应用,微波加热合成等。沸石的改性又称为二次合成,是对分子筛结构的修饰与进一步加工。通过阳离子交换改性、骨架脱铝、骨架杂原子同晶置换以及对沸石孔道与外表面的修饰等调变其表面酸性、热稳定性与水热稳定性,优化催化性能,使其适应于吸附、催化及离子交换,或满足近年来在高新技术先进材料等不同领域应用的要求。第二章介绍一种在四氢呋喃（THF）/水体系中以蒸气相传输（VPT）制备高硅FER沸石的新颖方法、结晶动力学和结晶机理。本章分两节详细介绍在THF/H₂O混合蒸气相中,含沸石晶种的Na₂O-SiO₂-Al₂O₃干胶（SDG）的结晶行为。第一节以XRD,SEM,低温氮吸附,¹³C CP MAS NMR等观察反应温度、反应时间、蒸气相组成等合成条件对结晶的影响,研究THF、H₂O及晶种的作用。第二节首先以XRD,FT-IR,SEM,TEM,HRTEM及SAED等来观察干胶宏观状态下的结晶过程,发现干胶的块状颗粒在THF/H₂O蒸气作用下,逐渐分离成为粒度均匀、具有较高反应活性的粒子。反应至10.5 h时,FER沸石晶体开始出现,至35.5 h晶体不断生长,36 h时反应迅速完成,至72 h产物结晶度保持不变,为再生长过程。本节最后部分则以²⁷Al,²⁹Si,¹³C CP MAS NMR,NH₃-TPD,低温氮吸附等方法,从分子水平上研究干胶中铝硅原子配位状态的改变,THF模板剂分子与[SiO₄]四面体、(AlO₄]四面体及沸石骨架的相互作用,以THF分子为中心形成前驱体,及其在胶体和孔道中位置的变化等,对该沸石从干胶中成核与生长过程以及机理有了清晰、完整地认识。在之前报道THF-Na₂O-SiO₂-Al₂O₃-H₂O反应物体系中FER沸石水热合成基础上,第三章研究催化剂量OP乳化剂或甘油对FER沸石结晶过程的促进作用。以THF为模板剂的水热产物除FER沸石之外,MTN,MFI,MOR以及α-石英等杂晶相也极易与其共生。这使该沸石的纯相须在较窄碱度、硅铝比、温度及反应时间等条件下进行,严重制约其规模化生产。以XRD,SEM,²⁷Al,¹³C CP MASNMR,XRF,低温氮吸附等来表征加入催化剂量OP乳化剂或甘油的反应物体系中不同温度和不同时间的结晶产物,发现其对沸石结晶过程具有明显的促进作用,使结晶温度明显降低,晶化时间缩短,且有效抑制杂晶相的伴生。产物FER沸石为单晶团簇体,比表面和孔容积等吸附性质优良。发现于我国北京地区的一种新天然矿物资源STI沸石,品位高,储量大,且开采成本低,是十分值得研究和开发应用的微孔材料。但因其结构热稳定性差,系统的性质和应用研究较少。在第四章中,以离子交换结合控制焙烧的方法对天然STI沸石骨架结构进行了一系列超稳化改性,使其结构热稳定性达到1000℃以上。研究还发现该天然沸石在不同浓度盐酸热溶液中具有优良的耐酸性。在此基础上,进一步研究了结构超稳化高硅STI沸石的阳离子交换性能及阳离子型STI沸石的结构热稳定性。还以超稳化高硅STI沸石为基底沸石,分别以盐酸脱铝和氟硅酸铵脱铝补硅方法制备高硅STI沸石,并对其吸附性质与结构热稳定性进行了研究。这些研究为开发其在吸附分离,离子交换和催化方面的工业应用奠定了基础。第五章则从沸石骨架改性和催化应用的角度出发,对商品化无粘结剂ZSM-5沸石催化剂进行改性研究,并将其应用于稀乙醇脱水制乙烯（ETE）催化反应中。对比无粘结剂和有粘结剂ZSM-5沸石催化剂的吸附性质,证实前者的优良品质。分别采用盐酸处理、水蒸气处理及水蒸气-盐酸相结合处理的方法对无粘结剂ZSM-5沸石催化剂进行骨架改性研究,揭示了水蒸气对沸石骨架的深度脱铝作用以及强烈调变沸石结构和表面性质的本质。分别以低硅有粘结剂与无粘结剂HZSM-5沸石分子筛（SAR=30）为催化剂,研究其在ETE反应中的表现,发现后者具有较高的反应活性。对比三种不同硅铝比（SAR=435,92,31）的无粘结剂HZSM-5沸石催化剂在ETE反应中的表现,发现反应活性随骨架硅铝比增大而降低,低硅HZSM-5沸石催化剂对乙烯具有较高选择性和产率。而水蒸气-盐酸处理相结合改性的的低硅无粘结剂HZSM-5沸石催化剂ETE反应催化性能最佳。第六章简单介绍煤系高岭土转化为沸石分子筛的研究工作。煤矸石（主要矿物成分是高岭石,又称煤系高岭土）是采煤过程中的废弃物,若不加以有效利用,既浪费资源,又严重污染环境。本章采用无机导向法,以煤系高岭土和水玻璃为原料,在水热体系中合成NaY沸石。煤系高岭土经高温焙烧后成为活性偏高岭土,可作为无机导向剂母液和溶胶-凝胶合成原料液的主要铝源。分别采用硅溶胶和水玻璃为主要补充硅源,均可制成纯相纳米NaY沸石分子筛的聚晶。产物孔道完美开放,吸附性质优于市售全化工原料合成的商品NaY沸石分子筛。其中,完全以煤系高岭土-水玻璃为原料的合成产物吸附性质更优。更多还原

【Abstract】 Zeolites are a kind of microporous crystalline aluminosilicate materials with framework structures.The materials possess some excellent properties,such as uniform distributions of pore size,high surface area and pore volume,good thermal and hydrothermal stability,and easy tuning on the compositions,structures and properties.The materials can be widely used in industrial catalysis,adsorption separation and ion exchange.The synthesis of zeolite is the foundation for further research on properties and applications.Manufacturing zeolites by simple route from some raw materials with low-pollution and low cost is always the hot research points for many zeolite specialists.Therefore,in this thesis,the major research topics are focused on the new process for making some zeolites with wide applications in various sol-gel reactant systems,or for modifying some zeolites with low cost.Chapter 1 reviews the synthesis,modification and application of zeolites.Some synthesis methods of zeolites,such as hydrothermal synthesis,solvent-thermal synthesis and dry gel conversion,as well as the application of organic template, mineralization agent and microwave heating,are briefly introduced.Modification of zeolites,called as the secondary synthesis,can make the materials own some better properties on surface acidity,thermal and hydrothermal stability with methods of ion exchange,framework de-aluminium,replacement of some framework atoms, modification of channels and external surface.The modified zeolites can be applied in adsorption,catalysis and ion exchange,as well as in high-tech areas as advanced materials in recent years.Chapter 2 introduces a novel method for the synthesis of high-silica FER zeolite in THF/H₂O binary vapor phase with vapor phase transport（VPT）,and the investigations on the crystallization kinetics and mechanisms in detail as well.Two sections in Chapter 2 introduce the crystallization process of seeded Na₂O-SiO₂-Al₂O₃ dry gel（SDG） in THF/H₂O binary vapor.In the first section,the gel and the products are characterized with XRD,SEM,N₂ adsorption and ¹³C CP MAS NMR for investigating the gel transformation process,and the roles of THF,H₂O and the added seeds are also discussed.In the second section,XRD,FT-IR,SEM,TEM,HRTEM and SAED are used to observe the crystallization process from the macroscopic view, and it has been found that the initial large globoids of SDG composed of nano-scale amorphous globules firstly diminish and disperse into smaller particles with high reaction activity in the beginning of the reaction gradually.FER zeolite crystallites appear at the reaction time of 10.5h,and in the zeolite crystallites further grow in the period from 6h to 35.5h.The reaction rapidly finishes at 36h,and the crystallinity remains till 72h without the structure collapse,which is defined as the re-crystallization stage.In the last section of the chapter,²⁷Al,²⁹Si,¹³C CP MAS NMR,NH₃-TPD and N₂ adsorption are used to investigate the coordination changing of[SiO₄]and[AlO₄]tetrahedrons in dry gel at the molecule level.At the same time, the interactions of template THF molecules with these tetrahedrons and formed zeolite framework are also studied.It is found that THF molecules diffuse from the surface of the gel particles and react with the tetrahedrons,which are then as the centers of FER cages to form the precursors and further construct the zeolite framework.Therefore,the nucleation and the growth process of the zeolite from dry gel can be understood in detail.Chapter 3 introduces the promoting roles of catalytic amount of OP emulsion agent or glycerol in the crystallization process ofFER zeolite as additives in a reactant system of THF-Na₂O-SiO₂-Al₂O₃-H₂O.The target zeolite in the reactant system usually easily co-crystallizes with some impure phases such as MTN,MFI,MOR andα-quartz,leading to that pure FER only crystallizes in a restricted composition region of alkalinity and Si/Al ratio,and a narrow range of reaction temperature and reaction time as well.These limit the scale-up production of FER zeolite.XRD,SEM,²⁷Al, ¹³C CP MAS NMR,XRF and N₂ adsorption are used to characterize the crystallization products in the reactant system with catalytic amount of OP emulsion agent or glycerol,and the obvious promoting role of the additives is found in the zeolite crystallization process,which can lower the reaction temperature,shorten the reaction time and effectively restrict the growth of impure phase.The zeolite products present a form of poly-crystals composed of tiny single crystallites,and possess high surface area and pore volume.STI zeolite is a new natural mineral resource found in Beijing area,with high quality and storage,which is worth to be studied and exploited as useful microporous materials.Because the framework thermal stability of the zeolite is very poor,the detailed research on properties and application is little to be reported.In Chapter 4, the methods of ion exchange and controlled calcinations are used to modify the zeolite framework,and the ultra-stable products with the framework thermal stability higher than 1000℃are recieved.It has been found that the natural zeolite possesses excellent anti-acidity property in hot HCl solutions with different concentrations. Based on this finding,the properties of ion exchange and thermal stabilities of the modified ultra-stable STI zeolite with various cation-types are further studied.The ultra-stable STI zeolite as the basic material has been modified with HCl solution and ammonium hexafluorosilicate solution,respectively,to get the samples with higher Si/Al ratios.The adsorption properties and the framework thermal stability are also determined.All the research works above create a foundation for further industrial application in the adsorption separation,ion exchange and catalysis.Chapter 5 introduces the modification studies of a commercial binder-free ZSM-5 zeolite catalyst,which can be used in the catalysis of diluted ethanol dehydration to prepare ethylene（ETE）.The adsorption properties of binder-free and binder-containing ZSM-5 zeolite catalysts are compared,indicating that the former one possesses the excellent properties.The methods of HCl solution treatment,steam treatment,steam combined with HCl solution treatment are taken to modify the framework of binder-free zeolite catalyst,and the reason of the deep de-alumunium and strong tuning on the zeolite framework and surface properties is also revealed. The ETE reactions on the low-silica binder-containing and binder-free zeolite catalysts with SAR of 30 are compared,and it has been found that the latter one possesses the higher reaction activity.Three binder-free zeolite catalysts with different SAR are also studied in the ETE reaction,and the reaction activity lowers as the increase of framework SAR.The low-silica HZSM-5 zeolite catalyst possesses the highest ethylene selectivity and yielding.The modified low-silica binder-free zeolite catalyst prepared with the combined treatment of steam and HCl solution shows the excellent catalysis properties in the ETE reaction.Chapter 6 briefly introduces the research work of coal-based kaolinite transforming to zeolites.The main mineral composition of coal gangue is kaolinte, which is also called coal-based kaolinite,and is the castoff in the excavating process of coal.Without used effectively,the coal-based kaolinite must pollute the environment as a waste.In this chapter,the inorganic directing method is used to synthesize NaY zeolite hydrothermally with the coal-based kaolinite and water glass as the raw materials.The kaolinite transforms to metakaolin after calcination at high temperature,which can be used as the main aluminium source in preparing raw sol-gel materials for the further synthesis.The silica sol and water glass are used as supplementary silica source,respectively,and the crystallite clusters composed of many pure nano-sized NaY zeolite are synthesized.The adsorption properties of the prepared NaY zeolite are better than that of the commercial one synthesized with all chemical raw materials.更多还原