Combined Alkali‐Organoammonium Structure Direction of High‐Charge‐Density Heteroatom‐Containing Aluminophosphate Molecular Sieves

The charge density mismatch concept was applied to the synthesis of high‐charge‐density silicoaluminophosphate SAPO‐69 (OFF) and SAPO‐79 (ERI) and zincoaluminophosphate PST‐16 (CGS), PST‐17 (BPH), PST‐19 (SBS), and ZnAPO‐88 (MER) molecular sieves. Combined alkali‐organoammonium structure direction in these systems is thus enabled. Structure direction is treated from the perspective of stabilizing an ionic framework, the relationships between reaction charge density (OH^?/H₃PO₄), alkali and organoammonium content, and ionicity of tetrahedral framework atoms in successful structure direction are presented.     

模板剂种类、浓度、硅源对SAPO-5分子筛结构性质的影响

研究了模板剂种类、浓度及硅源等因素对ＳＡＰＯ５分子筛结构、性质及酸催化性能的影响．结果表明，在合成ＳＡＰＯ５分子筛时，较合适的模板剂为三乙基胺或四乙基氢氧化铵．模板剂对分子筛结构的影响在于其空间效应，对酸性的影响在于其对硅反应性能和骨架硅含量的改变．不同硅源对分子筛骨架中的硅含量和酸性有较大的影响．得到较强酸性ＳＡＰＯ５分子筛催化剂的条件是：采用三乙胺模板剂和正硅酸乙酯．     

凝胶中硅含量对SAPO-5分子筛合成及其性能的影响

通过改变反应物凝胶中的硅含量，用水热法合成了系列ＳＡＰＯ－５分子筛，并用ＸＲＤ、ＳＥＭ和ＭＡＳＮＭＲ分别研究了不同硅含量的分子筛结构和形貌．以正己烷的催化裂解为模型反应，用微反色谱研究了不同硅含量的ＳＡＰＯ－５分子筛的催化性能．结果表明，分子筛骨架中的硅含量随反应物中硅含量的增加而增加；硅开始进入ＳＡＰＯ－５分子筛骨架时，是以取代单个磷原子而进行的；当反应物中硅含量较高时，硅进入分子筛骨架是通过两个硅原子取代一对铝和磷原子，从而在ＳＡＰＯ－５中形成富硅区．硅进入分子筛骨架，虽然未改变分子筛的晶体结构，但改变了分子筛的晶形晶貌．ＳＡＰＯ－５分子筛中存在３种酸中心，即弱酸、中强酸和强酸中心．在正己烷催化裂解中，较低温度时，催化活性中心主要是中强酸中心；当反应温度较高时，弱酸中心也可充当活性中心．在强酸中心上易发生结炭现象．     

A Family of Molecular Sieves Containing Framework‐Bound Organic Structure‐Directing Agents

Organic structure‐directing agents (OSDAs), such as quaternary ammonium cations and amines, used in the synthesis of zeolites and related crystalline microporous oxides usually end up entrapped inside the void spaces of the crystallized inorganic host lattice. But none of them is known to form direct chemical bonds to the framework of these industrially important catalysts and adsorbents. We demonstrate that ECR‐40, currently regarded as a typical silicoaluminophosphate molecular sieve, constitutes instead a new family of inorganic‐organic hybrid networks in which the OSDAs are covalently bonded to the inorganic framework. ECR‐40 crystallization begins with the formation of an Al–OSDA complex in the liquid phase in which the Al is octahedrally coordinated. This unit is incorporated in the crystallizing ECR‐40. Subsequent removal of framework‐bound OSDAs generates Al‐O‐Al linkages in a fully tetrahedrally coordinated framework.     

Time‐Resolved In Situ MAS NMR Monitoring of the Nucleation and Growth of Zeolite BEA Catalysts under Hydrothermal Conditions

Time‐resolved ¹³C, ²³Na, ²⁷Al, and ²⁹Si MAS NMR has been applied in situ for monitoring the hydrothermal synthesis of zeolite BEA. Isotopic labelling with ²⁹Si and ¹³C isotopes has been used to follow the fate of siliceous species and structure directing agent ((¹³CH₃−CH₂)₄NOH). Two mechanistic pathways, namely solution‐mediated and solid–solid hydrogel rearrangement have been distinguished for two synthesis procedures studied. The mechanisms of structure‐directing behavior of TEA⁺ cations in two reaction pathways have been elucidated. The results show that multinuclear MAS NMR can serve as a superior tool for monitoring hydrothermal synthesis of various solids including zeolites, zeotypes, mesoporous materials, metal–organic frameworks and so on and for the design of novel outstanding materials for different applications.     

SAPO-34分子筛合成中的主客体电荷平衡与硅分布(英文)

SAPO-34分子筛的硅磷酸铝组成与菱沸石笼结构孔道促进了甲醇高效转化为乙烯、丙烯(MTO)的反应,以其为催化剂的工业过程不断取得进步.然而,MTO反应过程中SAPO-34分子筛的迅速失活成为困扰该过程的重要问题.研究发现,反应中形成的多环芳烃阻塞了SAPO-34分子筛晶粒表面的笼结构孔道,甲醇分子难以向晶体内部扩散,致使分子筛在其活性中心未曾充分利用之前便己失活.为此,纳米晶粒SAPO-34的合成引起了人们的广泛兴趣,通过提高分子筛晶体的利用率有限地延长了催化剂的MTO反应寿命.但反应后催化剂的结焦量明显增加,说明引起SAPO-34结焦的因素不因晶粒的减小而受到抑制.我们曾研究了无硅A1P04-34分子筛的MTO反应,发现初始活性良好的催化剂在未结焦的情况下却因为活性中心的缺失而失活.显然,SAPO-34的MTO反应活性及其结焦均与其酸性密切相关,而酸性取决于其结构中的硅含量与硅分布.我们通过单晶结构解析获得了二乙胺(DEA)与哌嗪(PIPZ)导向合成SAPO-34的晶体结构,并从文献获得了四乙基氢氧化铵(TEAOH)、三乙胺(TEA)、吗啉(MOR)为模板剂合成SAPO-34的晶体结构.按照SAPO-34结构中菱沸石笼内形成的模板剂阳离子的电荷数(R)对不同模板剂导向合成的SAPO-34加以分类:TEAOH,TEA(R~+);DEA,MOR(2R~+);PIPZ(2R~(2+)).它们不因SAPO-34合成条件的变化而改变.依据分子筛骨架负电荷与SAPO-34菱沸石笼内模板剂阳离子正电荷平衡的原则(主客体电荷平衡),模板剂的类型决定SAPO-34骨架负电荷数,即引入硅形成的酸中心密度;酸中心的强度则取决于合成体系中硅的加入量.由此可以给出不同类型模板剂导向合成SAPO-34骨架中的最低硅含量(形成隔离硅原子).R~+型模板剂SiO_2/Al_2O_3为0.11;2R~+型模板剂为0.22;2R~(2+)型模板剂为0.44.合成体系中硅加入量的增加,会在SAPO-34骨架中形成"硅岛"结构.然而,我们的研究表明,"硅岛"的形成同样受到主客体电荷平衡原则的制约.通过结构分析发现,一个独立的"五硅岛"至少为6个相邻的菱沸石笼所分享,而每个"五硅岛"仅能形成3个负电荷.以R~+型模板剂导向合成的SAPO-34为例,需要6个骨架负电荷来平衡6个菱沸石笼中的R~+电荷,因此,除了"五硅岛"的3个负电荷,还要在这些笼骨架上形成3个"孤立"硅原子.该类模板剂导向合成SAPO-34,形成"五硅岛"的最低SiO_2/Al_2O_3摩尔比(硅含量)为0.45.进一步分析可知,在相邻的7个菱沸石笼之间可以分别形成"八硅岛"、"十一硅岛",而"十四硅岛"只能形成于相邻的10个菱沸石笼之间.同理,每种"硅岛"的形成都要伴随相应数目的"孤立"硅原子共同来平衡菱沸石笼内的R~+电荷.对于以2R~+型模板剂导向合成的SAPO-34,仍然是6个相邻的菱沸石笼分享"五硅岛",但是,每个菱沸石笼内的正电荷阳离子数增加了一倍,为满足主客体电荷平衡,需要形成更多"孤立"硅原子.由此可见,随着菱沸石笼内模板剂电荷数的增加,骨架的负电荷密度增大,给SAPO-34带来了更多酸中心,无论硅以"孤立"硅原子形式分布,还是形成"硅岛".同时,"硅岛"伴随"孤立"硅原子的共同存在也使我们理解了~(29)Si MAS NMR中的一个独特现象:在硅含量很高时形成了"硅岛",可是却存在着很强的属于"孤立"硅原子的谱峰.     

Themed Issue Dedicated to Professor Ruren Xu onthe Occasion of his 90th Birthday

Aluminophosphate(AlPO) and silicoaluminophosphate(SAPO) molecular sieves are an important class of open-framework crystalline materials with wide applications thanks to their molecular-scale selectivity, moderate/strong acidity and excellent (hydro)thermal stability. In recent decades, the manufacturing of new microporous solids with ordered structures has been widely investigated and many effective methods have been developed, which enriches the material types and broadens their applications beyond the traditional use as catalysts and adsorbents. However, the development on the synthesis of AlPO/SAPO molecular sieves is still insufficient and lags behind the needs of applications. Herein, we summarize the work on the seed-assisted synthesis of AlPO/SAPO molecular sieves compared with the zeolite synthetic system, aiming to prompt the synthesis and application of AlPO/SAPO molecular sieves.     

Facile Synthesis,Characterization, and Catalytic Behavior of a Large‐Pore Zeolite with the IWV Framework

Large‐pore microporous materials are of great interest to process bulky hydrocarbon and biomass‐derived molecules. ITQ‐27 (IWV) has a two‐dimensional pore system bounded by 12‐membered rings (MRs) that lead to internal cross‐sections containing 14 MRs. Investigations into the catalytic behavior of aluminosilicate (zeolite) materials with this framework structure have been limited until now due to barriers in synthesis. The facile synthesis of aluminosilicate IWV in both hydroxide and fluoride media is reported herein using simple, diquaternary organic structure‐directing agents (OSDAs) that are based on tetramethylimidazole. In hydroxide media, a zeolite product with Si/Al=14.8–23.2 is obtained, while in fluoride media an aluminosilicate product with Si/Al up to 82 is synthesized. The material produced in hydroxide media is tested for the hydroisomerization of n‐hexane, and results from this test reaction suggest that the effective pore size of zeolites with the IWV framework structure is similar to but slightly larger than that of ZSM‐12 (MTW), in fairly good agreement with crystallographic data.     

Al-MCM-48分子筛对苯酚与乙酸异丙酯异丙基化反应的催化性能(英文)

Al-MCM-48 molecular sieves (Si/Al molar ratios = 25, 50, 75, and 100) were synthesized hydrothermally using cetyltrimethyl-ammonium bromide as the structure directing template. The orderly arrangement of mesopores was evident from the low angle X-ray diffraction patterns and transmission electron microscopy images. The catalytic performance of the materials was evaluated in the vapor phase isopropylation of phenol with isopropyl acetate. Phenol conversion decreased with the increase in the Si/Al ratio of the catalysts. The major reaction product was 4-isopropyl phenol with 78% selectivity. The delocalization of phenolic oxygen electron pair over the aromatic ring promoted para-selective alkylation. Such delocalization could be aided by the hydrophilic surface of the molecular sieves. Although an ester was used as the alkylating agent, phenyl isopropyl ether was not formed in the reaction.     

SSZ-33分子筛的合成、表征及其对汽车尾气中碳氢化合物的捕集性能

采用碘化N,N,N-三甲基-8-氨基-三环[5.2.1.02.6]癸烷为结构导向剂, 通过过程控制方法, 经3-4 d成功合成了高性价比的B-SSZ-33分子筛. 以B-SSZ-33为母体, 经过Al(NO3)3溶液后处理制得了Al-SSZ-33分子筛. 采用X射线衍射(XRD), 傅里叶变换红外(FT-IR)光谱, 扫描电子显微镜(SEM), 热重(TG)分析, 电感耦合等离子体原子发射光谱(ICP-AES), N2吸附/脱附, 27Al核磁共振(27Al NMR)和NH3程序升温脱附(NH3-TPD)等手段对合成的B-SSZ-33、Al-SSZ-33样品进行了物理化学性能表征. 并以甲苯作为汽车尾气中碳氢化合物的探针分子, 通过甲苯程序升温脱附测试来考察样品的碳氢捕集性能. 结果表明: 后处理过程中Al同晶取代B, 从而制得了含骨架Al的Al-SSZ-33; 在甲苯的程序升温脱附测试中, 由于Al-SSZ-33相对于B-SSZ-33具有较强的酸性位, 且表面孔口由于骨架外硅铝物种的修饰, 限制了甲苯的扩散, 致使脱附速率最大时的温度(Tmax)和脱附最终的温度(Tend)均升高, 从而形成了新型汽车尾气捕集催化剂的雏形.     

Dendrimers and Hyperbranched Polyesters as Structure‐Directing Agents in the Formation of Nanoporous Silica

Anionic dendritic macromolecules (hyperbranched polyesters and polyamidoamine (PAMAM) dendrimers) and amine‐functionalized PAMAM dendrimers have been used as structure‐directing agents in the synthesis of nanoporous silica structures. When utilizing carboxylates as structure‐directing agents the incorporation of the negatively charged species into a SiO₂ framework was achieved via a sol‐gel synthesis route using a quaternized aminosilane as co‐structure‐directing agent to yield silica materials of various morphologies and high surface areas. Amine dendrimers as porogens gave materials with high surface areas, revealing increasing pore sizes corresponding to the increasing size of the porogen. The resulting materials have been characterized by X‐ray diffraction (XRD), N₂ adsorption/desorption (BET), scanning electron microscopy (SEM), infrared spectroscopy (IR), and thermogravimetric analysis (TGA).     

Two Aluminophosphate Molecular Sieves Built from Pairs of Enantiomeric Structural Building Units

Herein we report the synthesis and structures of two new small‐pore aluminophosphate molecular sieves PST‐13 and PST‐14 with mutually connected 8‐ring channels. The structure of PST‐13, synthesized using diethylamine as an organic structure‐directing agent, contains penta‐coordinated framework Al atoms bridged by hydroxy groups and thus edge‐sharing 3‐ and 5‐rings. Upon calcination, PST‐13 undergoes a transformation to PST‐14 with loss of bridging hydroxy groups and occluded organic species. The structures of both materials consist “nonjointly” of pairs of previously undiscovered 1,5‐ and 1,6‐open double 4‐rings (d4rs) which are mirror images of each other. We also present a series of novel chemically feasible hypothetical structures built from 1‐open d4r (sti) or 1,3‐open d4r (nsc) units, as well as from these two enantiomeric structural building units.     

Fabrication of SAPO‐34 with Tuned Mesopore Structure

Crystalline SAPO‐34 molecular sieves with hierarchical network were synthesized employing polyethylene glycol (PEG) as the meso‐generating agent via a self‐assembly strategy. XRD, FESEM, N₂ adsorption‐desorption and FT‐IR spectroscopic analyses showed that PEG co‐template has a decisive role in tailoring the pore structure and producing a tuned structure from microporous towards the mesoporous structure. Also, addition of PEG favored the formation of more uniform and smaller crystals than the conventional SAPO‐34. In fact, PEG did not only control the size of crystals due to its crystal growth inhibiting (CGI) effect but also modified the morphology of the crystals and improved CSD (crystal size distribution) along with induction of mesopores into the porous structure. The modified SAPO‐34 would be recommended for selective formation of light olefins through the acid‐catalyzed reactions, such as the conversion of methanol to olefins/propylene (MTO/MTP) and propane dehydrogenation (PDH) to produce olefins with higher selectivity and catalyst stability than the conventional SAPO‐34.     

SAPO-34分子筛晶化过程中硅进入骨架的方式和机理

采用 Ｘ Ｒ Ｄ, Ｓ Ｅ Ｍ, Ｉ Ｒ 和 Ｎ Ｍ Ｒ 等手段考察了 Ｓ Ａ Ｐ Ｏ３４ 分子 筛的晶化过 程,深入研 究了晶化过程中硅进入 Ｓ Ａ Ｐ Ｏ３４ 晶格 骨架的方式和机理． 结果表明 ,在 Ｓ Ａ Ｐ Ｏ３４ 分子筛的整个晶化过程中没有 Ａｌ Ｐ Ｏ３４ 分 子筛晶相生成． 在 初始 凝 胶的 制备 过 程中, 模板 剂 的添 加和 混 合凝 胶的 老 化处 理对 Ｓ Ａ Ｐ Ｏ３４ 晶化过程的进行起着关键性的作用． 晶化前 期（ ＜ ２５ ｈ） , 硅原子直接参与晶核的形成和晶粒的长大过程,形成 Ｓｉ（４ Ａｌ） 结构,此阶段基本上 可以排除硅取代磷机理的作用; 晶化后期（ ＞ ２５ ｈ） ,少量硅以取代方式进入分子 筛骨架形成 Ｓｉ（ ｎ Ａｌ）（ ｎ ＝ ０ ～４） 多种硅结构     

Water-Induced Structural Dynamic Process in Molecular Sieves under Mild Hydrothermal Conditions: Ship-in-a-Bottle Strategy for Acidity Identification and Catalyst Modification

Water is the most important substance in nature. Imitating the formation of natural materials, molecular sieves have been synthesized under hydrothermal conditions and applied in industry. Herein, we reveal an unforeseen observation on a very special water-induced structural dynamic process of these materials. Dynamic and reversible breaking and forming of T-O-T bonds in silicoaluminophosphate (SAPO) occurs through interactions between gaseous water and the molecular-sieve framework under mild hydrothermal conditions and is confirmed by detection of the incorporation of ¹⁷O from H₂¹⁷O into molecular-sieve framework. Encapsulation of the bulky molecules trimethylphosphine and pyridine (kinetic diameters much larger than the pore size of SAPO-34) into CHA cavities consolidated the water-induced dynamic process. Consequently, new insights into the dynamic features of molecular sieves in water are provided. The ship-in-a-bottle strategy based on these findings also open new fields for fine acidity identification and gives extra boost in shape-selective catalysis.     

AlMCM-41介孔分子筛的合成及表征

以拟薄水铝石为铝源、水玻璃为硅源、十六烷基三甲基溴化铵为模板剂,在110℃时水热晶化合成了含Al的MCM-41介孔分子筛.采用X射线衍射(XRD)、N2吸附-脱附、固体29Si、27Al魔角旋转核磁共振技术(MASNMR)、扫描电镜(SEM)及吡啶吸附傅里叶变换红外(FTIR)光谱技术对AlMCM-41分子筛进行了表征.结果表明:AlMCM-41分子筛具有六方排列的孔道结构,同时具有很高的相对结晶度、比表面积和孔容,且孔分布单一;AlMCM-41分子筛中Si原子在骨架内键合的程度更高,使AlMCM-41分子筛具有更好的骨架晶化程度;同时具有四配位骨架铝,使AlMCM-41介孔分子筛具有适当的酸性.     

Hydrolysis of POAl bonds in AlPO4 and SAPO molecular sieves

It is shown for three AlPO₄ and SAPO molecular sieves (structures SAPO-5, AlPO₄-17, SAPO-17, and SAPO-44) that the framework is attacked by water in the temperature range between ca. 323 and 473 K. The structural damage is more severe in the presence of ions such as NH⁺₄ or Na⁺, probably due to a shift in POAl hydrolysis equilibrium.     

Synthesis and Surface Acidity of Alpo4–5 and Sapo–5 Molecular Sieves

Aluminophosphate molecular sieves, AlPO₄ ? 5 and SAPO?5, were synthesized and characterized by XRD, SEM, ²⁹Si and ¹³C NMR, and TGA. Ammonia TPD indicates the moderately acidic nature of SAPO?5 and the non-acidic nature of AlPO₄?5. The activity of the cumene cracking reaction at 350°C for SAPO?5 is similar to that of LaY, while AlPO₄?5 and amorphous AlPO₄ show no activity.     

Morphology‐Reserved Synthesis of Discrete Nanosheets of CuO@SAPO‐34 and Pore Mouth Catalysis for One‐Pot Oxidation of Cyclohexane

Discrete nanosheets of silicon‐doped AlPO₄ molecular sieves (SAPO‐34) with a thickness of ≈7 nm have been prepared through morphology‐reserved synthesis with a lamellar aluminum phosphate as precursor. Cages of the nanosheets are in situ incorporated with copper oxide clusters. The CuO@SAPO‐34 nanosheets exhibit a large external surface area with a high number of (010) channel pores on the surface. Due to the thin morphology, copper oxide clusters occupy the outmost cages with a probability >50 %. The distinctive configuration facilitates a new concept of pore mouth catalysis, i.e., reactant molecules larger than the pores cannot enter the interior of the molecular sieves but can interact with the CuO clusters at “the mouth” of the pore. In heterogeneous catalysis, CuO@SAPO‐34 nanosheets have shown top performance in one‐pot oxidation of cyclohexane to adipic acid by O₂, a key compound for the manufacture of nylon‐66, which is so far produced using non‐green nitric acid oxidation.     

Synthesis of a Specified,Silica Molecular Sieve by Using Computationally Predicted Organic Structure‐Directing Agents

Crystalline molecular sieves are used in numerous applications, where the properties exploited for each technology are the direct consequence of structural features. New materials are typically discovered by trial and error, and in many cases, organic structure‐directing agents (OSDAs) are used to direct their formation. Here, we report the first successful synthesis of a specified molecular sieve through the use of an OSDA that was predicted from a recently developed computational method that constructs chemically synthesizable OSDAs. Pentamethylimidazolium is computationally predicted to have the largest stabilization energy in the STW framework, and is experimentally shown to strongly direct the synthesis of pure‐silica STW. Other OSDAs with lower stabilization energies did not form STW. The general method demonstrated here to create STW may lead to new, simpler OSDAs for existing frameworks and provide a way to predict OSDAs for desired, theoretical frameworks.