【作者】 王德举；

【导师】 唐颐；

【作者基本信息】 复旦大学 ， 应用化学， 2011， 博士

【摘要】 沸石具有丰富均一的微孔、较大的比表面积、良好的水热稳定性以及可调的表面性质,广泛应用于吸附、分离和催化等领域。由于沸石孔道狭窄,扩散阻力较大,在涉及大分子或液相反应中不能达到预期的催化效果,主要表现在反应温度偏高,催化剂结焦失活快,在某些反应中还表现为产物选择性下降。近年来,以纳米微孔沸石为基础的多级孔道沸石材料成为研究热点,这种材料具有良好的酸性和水热稳定性,并且含有丰富介孔/大孔,微孔扩散通道短,因此有利于分子的吸附和扩散,在扩散控制型或者涉及大分子的催化反应中表现了很好的催化活性和产物选择性,是极有应用价值的催化材料。工业上合成的沸石粉体通常需要加入粘结剂成型制成具有一定机械强度和形状的颗粒以适应各种应用。粘结剂的引入会降低有效沸石的含量并部分堵塞沸石孔口,造成吸附能力减弱并引入了扩散限制,导致催化活性和选择性下降。为克服上述问题,很多研究致力于研究具有较高机械强度和多级孔道结构的规整沸石材料,这种材料不但可以方便制备和应用,而且能够加强反应物和产物的扩散进而提高催化效率。无粘结剂沸石作为规整沸石材料的典型代表不含惰性粘结剂,沸石含量较高,具有良好的物理化学性能。具有多级孔道结构的无粘结剂沸石由于改善的扩散性能将可能提供一种高效的沸石催化剂。针对沸石材料的发展趋势以及实际应用中面临的问题,本论文重点研究了多级孔道沸石材料(包括小晶粒沸石)的合成和无粘结剂沸石材料的制备,并对制备的沸石材料开展了有针对性的催化反应研究。通过研究拓展了多级孔道沸石材料的制备方法,为高效沸石催化剂的设计合成提供了新的思路。本论文对所开展的研究工作将分为七个章节进行讨论：第二章讨论了晶种导向剂法制备纳米ZSM-5沸石,在水热合成体系中添加自制晶种导向剂成功制备了纳米ZSM-5沸石,考察了晶种导向剂、晶化温度和合成体系硅铝比对合成纳米ZSM-5沸石的影响。结果表明在ZSM-5沸石制备体系中添加晶种导向剂可有效降低有机模板剂的使用量,缩短晶化时间,并能得到纳米尺村寸。的ZSM-5沸石,降低晶化温度和合成体系硅铝比有利于减小纳米ZSM-5沸石晶体尺寸。第三章研究了定向生长纳米棒构成的多级孔道ZSM-5沸石及其在苯酚烷基化反应中催化性能。在不添加任何介观尺寸模板剂的情况下,采用沸石晶种辅助水热转化成功制备了由纳米棒组成的多级孔道类单晶ZSM-5沸石。研究表明多级孔道类单晶ZSM-5沸石的形成符合非经典的定向聚集晶体生长机理。在苯酚烷基化的催化反应中,制备的多级孔道类单晶ZSM-5沸石材料表现了比常规沸石更为优良的苯酚转化率,对位产物的产率以及良好的稳定性。第四章制备了具有多级孔结构和机械强度稳定的规整ZSM-5沸石材料。将含β沸石的硅铝原料成型制备的前躯体进行水热转化,成功制备了一种机械强度很高的具有空心结构的多级孔规整ZSM-5沸石材料。无定型硅铝包覆的β沸石经过水热转化形成了交错生长的ZSM-5沸石,内部的β沸石溶解并输送给外部ZSM-5沸石生长导致生成了ZSM-5沸石颗粒内部的空心结构。所得材料在大分子α-蒎烯的异构化反应中表现了很高的活性。第五章讨论了汽相转化法制备无粘结剂小晶粒ZSM-5沸石,以硅藻土为原料混合部分硅溶胶与少量晶种导向剂进行成型,然后进行汽相转化,成功制备了无粘结剂小晶粒ZSM-5沸石。产物的表征结果表明制备的无粘结剂小晶粒ZSM-5成型沸石具有丰富的孔结构,较大的比表面以及较高的机械强度,酸性质可调,具备用作催化剂和吸附剂的基础。第六章研究了重质裂解汽油加氢裂解增产BTX芳烃的研究,在这一章中,对重质裂解汽油催化加氢裂解增产BTX芳烃的催化剂进行了系统研究。研制了一种贵金属修饰无粘结剂ZSM-5沸石双功能催化剂,在该反应中具有良好的催化性能,表现了很高的反应活性和产物选择性。该工艺可以加氢处理升级重质裂解汽油生产BTX芳烃、液化石油气(LPG)和少量燃料气。第七章研究了基于无粘结剂PtM/ZSM-5催化剂的重整重芳烃催化加氢裂解反应,系统地考察了反应温度、H2/油体积比、反应压力以及空速对重整重芳烃加氢裂解反应的影响规律,优化了反应条件。催化剂稳定性实验表明在优化的反应条件下,C9转化率大于70%,C10+转化率大于50%,BTX(苯,甲苯,乙苯和二甲苯)芳烃产物收率保持在58%以上,且剩余C9重组分中富集了三甲苯,可从中精馏分离三甲苯单体,催化剂稳定性良好。该工艺可实现低值重整重芳烃的转化,增产高附加值的BTX芳烃和三甲苯单体,为大规模处理重整重芳烃提供了一种新的工艺路线。第八章系统研究了以HZSM-5为催化剂环氧乙烷选择性催化氨化制备乙醇胺的反应行为,建立了酸密度与催化活性、酸强度与选择性间的定量与定性关系。结果表明氢型沸石具有比钠型沸石更好的催化活性,产物的选择性主要取决于ZSM-5沸石的晶粒大小。通过表而硅烷化或负载过渡金属氧化物等修饰方法,可以提高催化剂二乙醇胺产物的选择性。开发了一种La203修饰的无粘结剂小晶粒ZSM-5沸石催化剂,在环氧乙烷液相催化氨化反应中表现了高稳定性、高活性与高选择性。更多还原

【Abstract】 Zeolite molecular sieves are widely in the fields of adsorption, separation and catalysis due to their uniform and ordered micropores, large specific surface area, high hydrothermal stability and easily adjustable surface characters. However, the intrinsic molecular-sized micropores of zeolite have diffusion limitations on the chemical reaction rate as well as catalytic performance, especially in catalytic reaction of liquid phase or concerning with heavy molecules. In this case, the catalyst presents high reaction temperature and fast deactivation, sometimes low selectivity for aimed products.Recently, hierarchical porous zeolite materials based on nanozeolites have been attracted considerable research enthusiasm. Such materials not only inherit excellent acidity and hydrothermal stability of zeolite, but also facilitate the diffusion of reactant/product in bulky molecule-involved and/or diffusion-controlled catalytic reactions due to the insertion of meso- and/or macro-porosity and short microporous diffusion channel. Reasonally, they show unique properties in catalytic reactions, such as preferential selectivity to products, high activity, and long lifetime.Zeolite is conventionally obtained in fine powder. As in the case of industrial catalysis, a certain amount of binders are generally used for cementing zeolite crystals into large sticks or granules with mechanical stability. However, the inorganic binders may dilute the active zeolite and partially block the pore system, which give rise to diffusion limitation and inaccessibility of the active species. To overcome these problems, continuous progress is made on the mechanical stable zeolite monoliths with both uniform shape and hierarchical structure. Such monolithic zeolite material facilitates not only practical preparation and application, but also reactant/ product diffusion as well as reaction efficiency. As one of such typical structures, binderless zeolites without inert binders have high zeolite content and show excellent physichemical properties. Furthermore, binderless zeolites with hierarchical porosity of micro/meso/macropores offers perspective as an efficient catalyst in zeolite catalysis for its improved transport properties.Based on the research status and problems of zeolite materials, this thesis mainly focuses on the synthesis of hierarchical porous zeolite materials (including nanozeolites) and binderless zeolites. Meanwhile, the catalytic performances of the as-synthesized materials are also involved in the detailed work. Potentially the routes demonstrated in this thesis could expand the methods for fabrication of hierarchical porous zeolite materials and offer new strategies for industrial zeolite catalysts with high activity. The research work is categorized and discussed in seven chapters of this thesis.Chapter 2 involves the preparation of nanosized ZSM-5 zeolite using seeding director. In this chapter, nanosized ZSM-5 Zeolite was successfully prepared by hydrothermal synthesis with adding the prepared seeding director. The influences of the seeding director, crystallization temperature and the silica/alumina ratio of the synthesis gel were investigated. It was concluded that using seeding director in the hydrothermal preparation of ZSM-5 zeolite could decrease the template dosage, shorten the crystallization time and gain nanosized ZSM-5 zeolite. The crystal size of the resulted nanosized ZSM-5 zeolite is found to decrease with decreasing crystallization temperature and increasing alumina content in the synthesis gel.Chapter 3 discusses the hierarchical structured ZSM-5 zeolite of oriented nanorods and its performance in the alkylation of phenol with isopropanol Hierarchical structured ZSM-5 zeolite of c-axis oriented nanorods has been prepared by a zeolite-seeds assisted hydrothermal synthesis method without adding any type of mesoscale template. The final product has higher mesopore volume and external surface area than the sample prepared conventionally. Due to the shortened microporous channel and opening mesopore, the prepared HZSM-5 catalyst presents high catalytic activity and stability for the alkylation of phenol with isopropanol.Chapter 4 studies shape-controlled synthesis of monolithic ZSM-5 zeolite with hierarchical structure and mechanical stability. Columned ZSM-5 zeolite monoliths with hierarchical structure and excellent mechanical strength were successfully prepared by a hydrothermal transformation method. The intra-particle hollow structure formed during hydrothermal synthesis was attributed to the digestion of innerβzeolite accompanying with the growth of ZSM-5 zeolite shell. The obtained hierarchical ZSM-5 zeolite monoliths showed superior catalytic performance inα-pinene isomerization for their proper acidity and good diffusion, compared with the ZSM-5 zeolite sample prepared from the precursor withoutβzeolite.Chapter 5 involves the preparation of binderless utrafine ZSM-5 zeolite monoliths by vapor-phase transformation method. Using vapor-phase transformation method, binderless monoliths of ultrafine ZSM-5 zeolite crystals was prepared by conversion of the preformed bodies of diatomite and silica sol, which mixed with some zeolite seeding directors. The prepared materials possessed enriched porosity, high surface area, good mechanical strength and tunable acidity which was verified by the characterizations. The products have promised applications in catalyst and adsorbent.Chapter 6 studies production of BTX aromatics by catalytic hydropyrolysis of heavy pyrolysis gasoline. In this chapter, the catalyst was thoroughly studied for hydro-upgrading pyrolysis gasoline to produce light aromatics and light alkanes. An optimized bifunctional catalyst comprising metallic Pt supported on a binderless ZSM-5 zeolite showed significantly improved catalytic property for this reaction with both excellent stability and activity. The reported catalytic process produces a BTX mixture with low ethylbenzene content, LPG and fuel gas from heavy pyrolysis gasoline.Chapter 7 studies the catalytic hydropyrolysis of heavy reformates over binderless Pt/HZSM-5 zeolite. Effects of temperature, ratio of hydrogen to oil, reaction pressure and space velocity of heavy reformates on the reaction were systematically investigated as well as proper process conditions were optimized. At the optimized process conditions, the catalyst possesses very good stability during its life-testing experiment and is able to converted heavy reformats to above 58% yield of BTX aromatics with over 70% conversion of C9 and 50% conversion of C10+, respectively. And the remainder after the separation of BTX aromatics enriched trimethylbenzene (TMB), from which the TMB isomers could be obtained by fractionation. The reported process could convert low valuable heavy reformats to high valuable BTX and TMB aromatics, which offered a new route for treating heavy reformats in large scale.Chapter 8 discusses selective amination of ethylene oxide for preparation of ethanolamine over HZSM-5. TPD, FTIR and catalytic performance showed that HZSM-5 was more active than the sodium form. Relative selectivity of product was mainly controlled by the crystal size of ZSM-5. Surface modification such as silyation or rare earth oxide supporting was effective for enhancing the shape selectivity. Finally, La2O3 modified binderless HZSM-5 zeolite in small crystal size was introduced to the amination of EO in liquid phase, which showed a high selectivity of MEA and DEA and a long-term stability.更多还原