【作者】 汪靖；

【导师】 龙英才；

【作者基本信息】 复旦大学 ， 物理化学， 2008， 博士

【摘要】 沸石是一类无机骨架型硅铝酸盐微孔晶体材料,独特的离子交换性、择形吸附性、组成和性质易调变性、众多小分子催化反应的高活性和选择性,以及在主客体组装化学中的主体性等,使其在工业过程和高科技材料等许多领域中被广泛应用。近年来,关于沸石合成的新方法与沸石材料的新应用受到了广泛关注。在本文中,分别对具有特殊吸附与催化性能的高硅丝光沸石直接合成,以ZSM-5沸石为基础的催化剂在甲醇脱水催化反应中的应用,以及沸石/金属氧化物主客体材料的制备与应用进行研究。探索沸石合成的新方法,理解沸石复杂的生成机理,并寻找沸石材料在催化与传感器领域的新应用。论文包括三个部分内容:1)高硅丝光沸石直接合成方法探索及机理研究;2)煤化工路线甲醇脱水沸石催化剂制备与研究;3)金属氧化物/沸石复合材料制备与应用。（1）高硅丝光沸石直接合成方法探索与机理研究丝光沸石（MOR）是一种具有一维十二元环孔道的大孔沸石,由于其特殊的孔道结构、优良的热稳定性与耐酸性,在吸附分离、烃类催化裂化、歧化与异构化等工业过程有重要的应用价值。提高丝光沸石的硅铝比能进一步增强其热稳定性与酸性质,进而提升其在若干催化反应中的性能。本文着重对高硅丝光沸石的直接合成进行研究,开发了两种新颖的制备方法:全无机体系干胶自转化法和乙醚导向无胺无氟体系水热合成法。全无机体系干胶自转化法的反应原料是不含有机导向剂和氟化物的干胶,在水蒸气环境中自发转晶。X射线粉末衍射（XRD）表征发现干胶的硅铝比与碱度对合成产物有显著影响,存在一个合适的干胶组成-结晶产物物相分布的相图区域,适宜于纯相高硅丝光沸石的生成。同时,晶种的存在能有效加速丝光沸石晶体生成,抑制杂晶的伴生。在优化条件下,可直接合成硅铝比大于30的高硅丝光沸石。经扫描电镜（SEM）,固体魔角旋转核磁共振谱（MAS NMR）,热重（TG）,低温氮吸附与苯吸附等测试表明产物为1～3×0.2～0.5μm棒状单晶,比表面积378 m²/g,微孔容积0.18 cm³/g,苯吸附量9.0wt%,属于骨架完美,孔道结构开放的大孔丝光沸石。对结晶过程进行研究证实,胶体转化是一个连续过程,在反应开始后即有沸石产物生成,反应初期结晶速率较快,反应中期经过一个较平缓的结晶过程后,胶体迅速完全转化为沸石晶体。对胶体转化过程中的母液成分进行分析发现,随着反应进行,碱性物质不断从胶体解离溶解于母液,母液中Na₂O与SiO₂含量不断提高,与结晶度变化规律一致,反应中期也存在一个平稳过渡区。经固体核磁表征发现胶体中Al始终以四配位形式存在,沸石形成过程中,AlO₄四面体基团优先进入沸石骨架,生成骨架硅铝摩尔比较低的晶体内核,反应后期SiO₄开始进入沸石骨架,已形成的硅铝结构发生重排,Si大量取代Al的位置,形成具有较高硅铝比的结晶产物。SEM表征显示产物形貌从无序的团聚胶体,经微小晶粒并逐渐生成形貌完美的棒状晶体的变化规律。氨气程序升温脱附（NH₃-TPD）表征显示由干胶转晶直接合成得到的高硅丝光沸石的固体酸强度明显高于低硅丝光沸石。而低硅丝光沸石经酸处理脱铝得到硅铝比30左右的高硅样品,其热稳定性与水热稳定性显著下降,远低于直接合成得到的高硅样品,体现出直接合成产物结构的高热与水热稳定性。乙醚导向水热法研究Na₂O-Al₂O₃-SiO₂-H₂O胶体反应物中,乙醚诱导水热合成高硅丝光沸石。表征发现经乙醚的存在能有效加速丝光沸石的结晶过程,抑制杂晶产生,并且有助于提高产物结晶度和硅铝比。反应物胶体中硅铝比与碱度对生成的产物有显著影响。以不同铝源制成的合成原料体系的结晶规律相近,但产物的形貌和硅铝比有差异。在优化的反应条件下合成的高硅丝光沸石硅铝摩尔比达30左右,经N₂吸附与²⁷Al MAS NMR等表征证实该沸石骨架结构完美,孔道开放畅通。与低硅样品相比,乙醚导向合成的高硅丝光沸石、水热稳定性大幅提高,在实际催化体系中可望显现优越的结构稳定性。（2）煤化工路线甲醇脱水沸石催化剂的研究。二甲醚与丙烯作为重要的化工基础原料已得到广泛的应用。其中,二甲醚可通过甲醇加工制得,属于煤化工路线的下游初级产物。ZSM-5沸石催化剂在甲醇脱水反应中显示优良的催化性质。本文在工业ZSM-5沸石粉体的基础上经过改性等化学处理方法制得无粘结剂ZSM-5催化剂,经XRD,XRF,²⁷Al MASNMR,N₂吸附等表征证实该无粘结剂催化剂物理化学性质与原粉体材料基本一致,骨架结构完美、孔道开放。同时,无粘结剂催化剂中还富有平均孔径6.8nm的介孔结构,对反应物与产物分子的扩散十分有利。作为对比的含粘结剂催化剂,其结晶度、比表面积与孔容积等性质则明显低于无粘结剂催化剂。NH₃-TPD表征发现,硅铝比不同的催化剂其强酸强度与强酸中心数量相差不大,随着催化剂硅铝比的降低,弱酸强度与弱酸量均增加。固定床联用色谱在线检测催化装置考评发现,甲醇脱水制二甲醚催化剂的骨架硅铝比对催化反应结果的影响至为关键。低硅催化剂催化能力最佳,在180-250℃温度范围内反应、甲醇转化率和二甲醚选择性均可分别达到90%与100%以上,明显优于其它无粘结剂催化剂以及常规氧化铝催化剂。在进料工业甲醇的浓度波动范围（80-95%）内,低硅催化剂的催化性能基本不受影响。当提高进料液时空速时,低硅催化剂的甲醇转化率相应降低,但二甲醚选择性始终保持100%。在优化的实验条件下,低硅催化剂经800h反应仍保持80%左右的二甲醚得率,显现良好的结构稳定性与突出的催化性能。丙烯作为现代化学工业重要基础原料之一,其产量是衡量一个国家综合国力的重要指标,对其需求量越来越大。制备丙烯的传统方法是采用轻油（石脑油、轻柴油）水蒸气裂解工艺。由于我国石油储量有限,以煤为原料制甲醇,再由甲醇制低碳烯烃的工艺受到重视。本文主要研究了ZSM-5沸石催化剂对甲醇制丙烯（MTP）催化反应的影响规律,探索具有高丙烯选择性催化剂的制备与改性方法,开发高效MTP沸石催化剂。研究发现,影响丙烯收率的关键因素是ZSM-5沸石骨架硅铝比。沸石硅铝比低于100以下时,反应进行不完全,生成较多C₆以上的高碳烃类,丙烯收率较低;将沸石硅铝比提高到300以上时,丙烯选择性大幅提高至40%以上;通过特殊的制备方法合成得到硅铝比1000以上的超高硅ZSM-5沸石,丙烯收率可增加至45%。而全硅Silicalite-1沸石高温反应产物主要为甲烷,烯烃选择性极低。脱铝处理后的高硅与超高硅样品,经XRF与²⁹Si MASNMR表征发现微量的骨架铝原子脱除后以非骨架形式存在于催化剂孔道或笼之中,催化剂骨架为全硅结构。该催化剂在MTP反应中表现出一定的催化活性与烯烃选择性,与完全不含铝原子的全硅催化剂性质显著不同。随着催化剂中硅铝元素比的提高,反应产物中丙烯/乙烯比也相应提高。（3）金属氧化物/沸石复合材料制备与应用沸石巨大的比表面积与孔容积为金属氧化物等客体材料的填装与负载提供了广阔的空间,本文以含Ti,Sn与Li的金属盐为原料制备金属氧化物/沸石复合材料,并探索将其应用于光催化与气敏传感等应用方向。以沸石与高熔点金属氧化物表面湿润度不同的概念,使用浸渍焙烧方法在不同硅铝比ZSM-5沸石表面制备具有纳米结构TiO₂的沸石复合材料,研究发现,载体ZSM-5沸石的骨架硅铝比对负载其上的TiO₂的晶相分布有显著影响,随着载体硅铝比提高,TiO₂中金红石相不断增加,而锐钛矿相则相应减少。在较低负载量下,TiO₂以纳米粒子的形式包覆于沸石载体表面,难以通过XRD检测出,提高负载量,TiO₂粒径不断长大并生成约200×15nm的棒状晶体。焙烧温度对复合材料中TiO₂的状态也有重要影响,在400℃温度以下,无法通过XRD表征发现TiO₂衍射峰,温度达到500℃时则开始生成以锐钛矿相为主的纳米TiO₂结构,继续提高温度到600℃以上,晶体继续长大,并由锐钛矿相向金红石相转变。经苯酚光降解实验发现,TiO₂粒径较小,并且具有较高锐钛矿相含量的复合材料表现出优良的光催化性能。分别以具有一维、二维和三维孔道的STI（含与主孔道交叉的扁平孔道）,FER与Y沸石为载体,制备SnO₂纳米粒子/沸石复合材料。实验发现,在硅铝摩尔比5左右的Y沸石表面能够生成12×60 nm的SnO₂纳米棒,提高Y沸石的硅铝比至20后SnO₂则以10nm以下的纳米粒子为主。由于SnO₂粒径小,以高硅Y为载体的复合材料表现出优良的氢气敏感性与重复性,经气敏检测后由TEM表征发现该材料上的金属氧化物粒子尺寸仍在10nm以下,而低硅载体复合材料经气敏实验后SnO₂纳米棒发生断裂并从表面脱落,造成复合材料中SnO₂有效成分含量降低,致使气敏重复性较差。合适的负载量下,在STI沸石表面形成约10-20nm的SnO₂纳米粒子,在氢气敏感性测试中亦表现出良好的敏感性与重复性。而在FER沸石表面,SnO₂不以分散的纳米粒子形式呈现,而是形成50-300nm独立的纳米团聚体。SnO₂/FER复合材料电阻与纯相FER沸石相当,基本不具对氢气的气敏性。在研究LiCl与FER沸石复合材料过程中,发现在500～600℃温度范围内,LiCl能诱发沸石发生相转变,生成热稳定性相对较差的长石LiAlSi₃O₈,而在800℃则主要生成热稳定性较高的β-石英。LiAlSi₃O₈的量随着LiCl的组装量的提高而增加。金属盐诱导沸石相转变这一特性,可能被用于在较低温度下合成一些通常只有通过高温固相反应制备的硅酸盐类陶瓷材料。更多还原

【Abstract】 Zeolite is one kind of inorganic microporous materials widely applied in industrial processes and high tech materials for its excellent performance on ion-exchange,adsorption,shape-selectivity,structure controllability,catalysis and guest accommodation as host materials,etc.Recently,novel methods of synthesis of zeolites and their applications have attracted many attentions.This thesis is focus on the direct synthesis of high silica MOR type（mordenite） zeolite with particular adsorption and catalytic properties,and on MFI type（ZSM-5） zeolite catalysts applied in methanol dehydration processes,and on the preparation and applications of host/guest materials of zeolite/metal oxides.The main objectives are developing novel methods of zeolite synthesis,understanding the complicated formation mechanism and looking for the new applications of zeolite complex materials in fields of catalysis and sensors.Three parts in this thesis are as follows:1) the study of direct synthesis and the formation mechanism of high silica MOR zeolite;2) research on the preparation and catalytic performance of zeolite catalysts in methanol dehydration process in coal chemical industry;3) preparations and applications of metal oxides/zeolites complex materials.（1） The study of direct synthesis and the formation mechanism of high silica MOR zeoliteMOR type zeolite consists of straight channels with 12-membered ring（12-MR） window（0.65×0.70nm） along[001]direction and possesses high thermal and anti-acidic stability.The zeolite is an important aluminosilicate molecular sieve widely used in adsorption separation and catalysis such as cracking,isomerization, and alkylation of hydrocarbons.In this thesis,we report two novel methods for synthesis of the zeolite:dry gel self-transformation in full inorganic system and hydrothermal synthesis in amine-free and fluoride-free ether-containing reactant system.In chapter 2,the dry gel self-transformation（DGST） method of the zeolite is reported.Identifications of the obtained products with powder X-ray diffraction（XRD） indicate that the molar ratio of silica to alumina（SAR） and the alkalinity in the starting dry gel play essential roles in the crystallization of the zeolite with pure phase. Meanwhile,the existence of seedings effectively accelerates and promotes the zeolite crystallization,and prevents the co-crystallization of other impurity phases.The gel composition region for the zeolite crystallization is investigated and expressed with diagram in detail.Rod shape single crystals with size of 1～3×0.2～0.5μm for the as-synthesized zeolite with SAR up to 30 are prepared from DGST with optimum gel compositions.The synthesized products possess perfect framework and channel system,0.18cm³/g of micropore volume,378m²/g of BET surface area and 9.0wt% of benzene adsorption capacity characterized by scanning electron microscope（SEM）, high-resolution transmission electron microscope（HRTEM） and selected-area electron diffraction（SAED）,²⁷Al magic-angle spinning（MAS） nuclear magnetic resonance（NMR）,and adsorption determination.Investigations on the obtained products with XRD prove that the dry gel transformation is a continuous process with three stages possessing different crystallization rates.In the DGST process,the dissociated alkali from dry gel drops down and dissolves in the water that increases the contents of Na₂O and SiO₂ in mother liquid constantly.The results of²⁷Al MAS NMR and ²⁹Si MAS NMR indicate that the state of Al atom is tetrahedron coordination all along.During the crystallization of the zeolite,[AlO₄]tetrahedron preferentially access to the framework of the zeolite,resulting in the formation of the products with low SAR.In the late-stage of the crystallization,SiO₄ tetrahedron structures begin to settle on the zeolite framework.Great deals of Si atoms replace Al atom in the framework and induce re-structuring the framework for forming the zeolite product with high SAR. The SEM images present the change from the aggregated amorphous dry gel to the single rod crystals with perfect appearance.The high silica MOR zeolite exhibits much more excellent hydrothermal stability and solid acid property than that of the low SAR one,implying that the zeolite prepared by the DGST method possess promising application in adsorption and in catalysis.In chapter 3,the synthesis of high-silica MOR zeolite in the temperature range of 140～180℃is investigated in amine-free and fluoride-free Na₂O-Al₂O₃-SiO₂-H₂O reactant system using different alumina sources in the presence of ether,which plays an effectively promoting role in the crystallization and the increment of SAR for the zeolite.SAR and the alkalinity in the starting reactant gel make essential effects on the crystallization of the pure phase zeolite.The crystallization phenomena in the reactants with different alumina sources are similar,except obvious differences in the morphology and SAR of the as-synthesized zeolite.A pure phase MOR zeolite with SAR up to 30 is obtained in the reactant with optimum compositions under a certain reaction condition.Characterized by nitrogen sorption and ²⁷Al MAS NMR,perfect framework and open channel system of the zeolite have been proved.The high silica MOR zeolite exhibits much more excellent hydrothermal stability than that of the low SAR one.（2） Research on the preparation and catalytic performance of zeolite catalysts in methanol dehydration process in coal chemical industryDimethyl ether and propylene are widely applied in chemical industry as important chemicals.ZSM-5 zeolite possesses outstanding catalytic performance in methanol dehydration due to its particular porous and acid properties.In chapter 5.1,a series of binder-free ZSM-5 catalysts and a binder-containing catalyst are prepared and characterized with XRD,XRF,²⁷Al MAS NMR,N₂ sorption and ammonia TPD.The catalytic activity and selectivity in the dehydration of crude methanol to DME are evaluated in a fixed-bed reactor for the catalysts.The outstanding structural characters such as high zeolite contents,sufficiently open channels and richness in mesopores have been proved on these binder-free catalysts. The influence of the solid-acidity,which closely related to the framework SAR of the catalysts,on the catalytic properties has been discussed.A binder-free catalyst with low framework SAR has been selected for in-depth research.The advantages of high activity and selectivity in wide range of operating temperature,non-sensitivity to water contents in the feed,long life-time and easiness to regeneration make the binder-free catalysts with low SAR good potential in industrial applications.The reason for its excellent performance of the catalyst is discussed.In chapter 5.2,the influences of the chemical characteristics of ZSM-5 zeolite catalysts to its catalytic performance in the reaction of methanol transforming to propylene（MTP） are studied,and a catalyst with super high SAR（>1000） presenting excellent catalytic capacity is prepared.High silica ZSM-5 zeolite（SAR>300） and silicalite-1（without Al） are chosen for comparison.The catalytic evaluation results indicate that the framework SAR of the catalysts plays essential role in selectivity of propylene and ratio of propylene to ethylene（PE）.When the dehydration occurs on the catalyst with SAR less than 100,the reaction is incomplete with amounts of high olefins and aromatics as major products.Increasing the SAR of the catalyst to about 400,the conversion of methanol achieves to 100%and the selectivity of propylene significantly elevates to 40%.In the situation of super high SAR catalyst,the selectivity of propylene further increases to 45%.However,the full-silica catalyst exhibits non-selectivity to olefin but high degree of selectivity to methane.High silica catalyst and super high silica catalyst are post-treated to obtain dealuminated catalysts with full-silica framework,in which the trace Al located in the micropores or the supercages of the zeolites.The fact that the dealuminated catalysts present high conversion of methanol and selectivity to olefin implies the important role of Al whether its chemical states are framework or extra-framework in the MTP reaction.（3） Preparations and applications of metal oxides/zeolites complex materialszeolites are excellent materials to provide wide spaces for assembly and encapsulation of guest materials such as metal oxides,organic functional materials due to its huge surface areas and pore volumes.In chapter 7,Ti,Sn and Li cantaining metal oxides/zeolites complex metarials are prepared,and the applications on photocatalysis and gas sensors are studied.In chapter 7.1,nano TiO₂,one kind of metal oxide with high melting point,is prepared on the surfaces of ZSM-5 zeolites with various SAR by impregnation and calcinations under the guidance of de-wetting effect.The experimental results characterized by XRD,TEM indicate that the SAR of zeolite significantly influences the crystal phase of TiO₂ assembled.The amount of rutile phase increases and anatase decreases with elevating the SAR of the zeolite constantly.Nano TiO₂ particles less than 10nm are indetectable by XRD form on the surface of the zeolite at low loadings. With increasing the loadings,TiO₂ particles grow to large scale and form nano rod shape single crystallites with the size of 200×15nm.Temperature of calcinations in preparing is another important factor for influencing the states of TiO₂ in complex materials.When the temperature lowers to 400℃,no characteristic diffraction peaks of TiO₂ appear.Followed by increasing the temperature to 500℃,TiO₂ grow up with anatase as dominate phase.When the temperature rises to 600℃,the phase of TiO₂ nanoparticles transfer from anatase to rutile constantly and the particle size enlarges. The photocatalytic performance of TiO₂/zeolite complex material is evaluated by phenol photodegradation.The results reveal that the material with small particle size and more anatase phase of TiO₂ present outstanding photocatalytic capability.In chapter 7.2,STI,FER and FAU（Y） zeolites are used as matrix to prepare SnO₂ nano complex materials by impregnation of SnCl₂ solution and subsequently calcination at certain temperatures.XRD and TEM are used to characterize the crystalline phase,the morphology,the particle size and the agglomerative state of the formed nano-materials.SnO₂ nanorods with size of 12×60 nm form on the surface of Y zeolite with low SAR.Increasing the SAR of the zeolite to 20,the particle sizes of SnO₂ grown on the zeolite significantly decrease to less than 10 nm.The complex material based on Y zeolite with high SAR presents excellent sensitivity and repeatability to hydrogen in ppm concentration.On the surface of STI zeolite,SnO₂ nanoparticles about 10-20 nm in size grow up and exhibit high hydrogen sensitivity and repeatability.Unfortunately,SnO₂ aggregates in size of 50-300 nm form on FER zeolites instead of nano particles spread uniformly.The resistance of SnO₂/FER zeolite material is even equal to that of pure FER zeolite,presenting even no hydrogen sensitivity.In chapter 7.3,LiCl/FER zeolite guest/host material is prepared by assemble the guest LiCl into the channels of host FER zeolites with thermal dispersion method.By elevating the calcination temperature,an interaction between the guest and the host occurs and induces a phase transformation of the complex material.Characterization with XRD,FT-IR and TG/DTA/DTG,the process of phase transformation is proved to commence at the temperature of 500℃with the product of LiAlSi₃O₈.With further elevating the temperature,β-quartz appears at the temperature of 800℃as the primary product in the process of phase transformation and the relative content of which increases with decreasing the loadings of LiCl in the guest/host materials.更多还原