P-derived organic cations as structure-directing agents: synthesis of a high-silica zeolite (ITQ-27) with a two-dimensional 12-ring channel system

Recently, efforts have been made to synthesize large-pore, multidimensional zeolite frameworks as a basis for new catalysts to improve various hydrocarbon conversions. A new aluminosilicate zeolite, ITQ-27, has been prepared using the phosphorus-containing structure-directing agent, dimethyldiphenylphosphonium. Its crystal structure was determined in its calcined form by direct methods (FOCUS) on synchrotron powder diffraction data (lambda = 0.8702 A) after the unit cell and space group were determined from tilt electron diffraction experiments on individual microcrystals. The material crystallizes in space group Fmmm, where a = 27.7508(5) A, b = 25.2969(7) A, and c = 13.7923(4) A. The final model, refined by Rietveld methods, comprises seven unique T-sites forming a framework with straight 12-MR channels that are connected by 14-MR openings between them. (Corresponding 12-ring pore dimension is 6.94 A x 6.20 A.) Since access from one 14-MR opening to the next is through the 12-MR channel, the structure is best described as a two-dimensional, 12-MR framework.     

Synthesis and Structure Determination of SCM-15: A 3D Large Pore Zeolite with Interconnected Straight 12×12×10-Ring Channels

A new germanosilicate zeolite named SCM-15 (Sinopec Composite Material No. 15), the first zeolite containing a 3-dimensional (3D) channel system with interconnected 12-, 12-, and 10-ring channels (pore sizes: 6.1×7.2, 6.1×7.4, and 5.2×5.9 Å), has been synthesized using neutral 4-pyrrolidinopyridine as organic structure-directing agents (OSDAs). Its structure has been determined by combining single-crystal electron diffraction (SCED) and synchrotron powder X-ray diffraction (SPXD) data. The unique open framework structure of SCM-15 is related to that of FOS-5 ( BEC ), ITQ-7 ( ISV ), PKU-16 ( POS ), ITQ-26 ( IWS ), ITQ-21, Beta polymorph B, and SU-78B, since all these framework structures can be constructed from similar chains which are connected through shared 4-ring or double 4-ring (d4r) units. Based on this relation, six topologically reasonable 3D large or extra-large pore hypothetical zeolites are predicted.     

ITQ-15: the first ultralarge pore zeolite with a bi-directional pore system formed by intersecting 14- and 12-ring channels, and its catalytic implications

The pore topology of ITQ-15 zeolite consists of an ultra-large 14-ring channel that is intersected perpendicularly by a 12-ring pore; acid sites have been introduced in its framework and this unique structure shows advantages over unidirectional ultralarge pore zeolites for diffusing and reacting large molecules.     

Synthesis design and structure of a multipore zeolite with interconnected 12- and 10-MR channels

A new molecular sieve, ITQ-38, containing interconnected large and medium pores in its structure has been synthesized. The rational combination of dicationic piperidine-derivative molecules as organic structure directing agents (OSDAs) with germanium and boron atoms in alkaline media has allowed the synthesis of ITQ-38 zeolite. High-resolution transmission electron microscopy (HRTEM) has been used to elucidate the framework topology of ITQ-38, revealing the presence of domains of perfect ITQ-38 crystals as well as very small areas containing nanosized ITQ-38/ITQ-22 intergrowths. The structure of ITQ-38 is highly related to ITQ-22 and the recently described polymorph C of ITQ-39 zeolite. It shares a common building layer with ITQ-22 and contains the same building unit as the polymorph C of ITQ-39. All three structures present similar framework density, 16.1 T atoms/1000 ?(3).     

Synthesis and structure of the bidimensional zeolite ITQ-32 with small and large pores

A new bidimensional zeolite containing 8R and 12R pores, denoted as ITQ-32, has been synthesized and its structure solved from powder X-ray diffraction data. This zeolite presents a relatively large pore volume (0.16 cm3/g) and pore apertures of 3.5 x 4.3 A and can be prepared as a nearly pure silica zeolite and as aluminosilicate. In the latest case, acidic properties are developed.     

Synthesis of ITQ-2 zeolite under static conditions and its properties

Zeolite ITQ-2 can be synthesized by swelling the layers of MCM-22 precursor. It has a single delami-nated structure of MWW with thickness of 2.5 nm. It shows disordered properties in long range and ordered in short range, which is a promising catalytic ma…     

分子动力学模拟1-丁烯和正丁烷在MCM-22分子筛中的扩散行为

应用分子动力学方法研究了1-丁烯和正丁烷在MCM-22型分子筛(ITQ-1)中的扩散行为. 得到了两种物质在ITQ-1分子筛两个独立孔道中的均方位移曲线、自扩散系数和扩散轨迹. 计算结果表明, 在温度为400 K时, 1-丁烯或正丁烷在十元环孔道中的扩散明显低于在超笼中的扩散, 吸附质在超笼的底部和顶部的扩散明显低于在超笼中心的扩散; 1-丁烯和正丁烷在ITQ-1分子筛的超笼中两者扩散速率较为相似, 而在十元环中, 两者的扩散速率差别较大.可以推测, 选择性催化主要发生在十元环中.     

Synthesis and structure determination of a new microporous zeolite with large cavities connected by small pores

A new small-pore germanosilicate zeolite, named as ITQ-49, has been synthesized using a new ditetraalkylphosphonium dication as an organic structure-directing agent, and its structure has been solved by direct methods applied to the powder X-ray diffraction pattern of the calcined solid. This new zeolite crystallizes in the space group Immm with cell parameters a = 19.6007(8) ?, b = 18.3274(7) ?, and c = 16.5335(6) ?. The pore topology of ITQ-49 consists of large, nonspherical cavities that are connected to each other through small eight-membered-ring windows, resulting in a unidirectional small-pore zeolite that has a relatively large adsorption capacity. Also, ITQ-49 contains double four-membered-ring units where Ge is preferentially located, and fluoride anions are placed inside these units.     

芳香类化合物在ITQ-1分子筛中吸附特性的蒙特卡罗模拟

用巨正则统计系综蒙特卡罗模拟研究了苯、甲苯以及间二甲苯分子在ITQ-1分子筛中的吸附特性.从这3种分子的粒子分布云图上,可发现分子的扩散和吸附主要在十二元环超笼内发生,在十元环通道内的吸附和扩散则相对较难.从一系列不同压力下的蒙特卡罗模拟还预测了3种分子的吸附等温线,预测结果与实验结果相符.这3种分子在一定压力下,都可通过十元环通道或连接十二元环超笼的十元环窗口到达分子筛孔道内部,达到较好的吸附平衡状态.     

Sorption thermodynamics of CO2, CH4, and their mixtures in the ITQ-1 zeolite as revealed by molecular simulations

The thermodynamic properties and siting of carbon dioxide and methane sorbed in the siliceous form of zeolite MCM-22, ITQ-1, were studied by means of grand canonical Monte Carlo simulation. ITQ-1 comprises two independent pore systems of different geometry. It was found to be CO(2)-selective toward CO(2)/CH(4) gas mixtures, its equilibrium selectivity being distinctly higher in its sinusoidal channel pore system than in the large cavity system over a wide range of pressures starting from the Henry law regime, at the three temperatures considered. A maximum in selectivity is observed at low temperature, high pressure, and methane-rich gas-phase composition.     

The Grand Canonical Monte Carlo Simulations of Benzene and Propylene in ITQ-1 Zeolite

Thealkylationofbenzenewithpropylenetoproducecumene,astartingmaterialfortheproductionofacetoneandphenol,isveryimportantinhydrocarbonprocess.ComparedwithsomemineralacidsincludingAlCl,andothers,zeolitesseemtobemorecleancatalysts,moreoveF,theycaneffectivelyreducetheamountoflessdesiredproductssuchasdiisopropylbenzenes.SeveralzeoIitesincludingH-ZSM-5,USYflandMCM-22havebeentestedforthereactionoftheaIkylationofbenzenewithpropylene,andithasbeenfoundthatP,USYandMCM-22areveryreactiveI.ZeoIiteMC…     

MCM-22和ITQ-2分子筛负载型催化剂加氢裂化性能的对比研究

 以MCM-22和ITQ-2分子筛为载体, WNi为活性组分,制得两种负载型催化剂,考察了两种催化剂的加氢裂化性能,并通过N2吸附、氨程序升温脱附和原位红外光谱对催化剂进行了表征. 减压瓦斯油加氢裂化反应结果表明, WNi/ITQ-2的加氢裂化活性高于WNi/MCM-22, 并且前者的反应温度相对较低. WNi/ITQ-2具有高催化活性是因为ITQ-2分子筛具有空旷的次级结构和较多的可接近的酸性位; 中油选择性高是因为空旷的次级结构使裂化产物快速离开酸性位而避免了二次裂化.     

多级孔无铝Beta分子筛的合成与表征

研究了氟介质条件下,合成参数对前驱体黏度和无铝Beta分子筛晶化过程的影响.X射线衍射结果表明,高水硅比可降低前驱体的黏度,但抑制分子筛的晶化.当合成体系中加入成核促进剂(二氧化锗)和晶化促进剂(高氯酸根或磷酸根)后,即使水硅摩尔比高达20~30,在150℃水热合成4 d,仍可获得高结晶性、微米级球形或多面体形无铝Beta分子筛.热重和能谱分析结果表明,极少量高氯酸根和磷酸根可进入分子筛孔道,并影响模板剂四乙基铵根离子的热分解过程.氮气吸附-脱附、扫描电子显微镜、透射电子显微镜和选区电子衍射分析结果表明,所得无铝Beta分子筛具有多级孔结构,介孔尺寸在3.4~3.8 nm之间,由纳米晶体或纳米棒堆积而成.     

1-丁烯在MCM-22分子筛中的吸附与扩散：Monte Carlo与动力学模拟研究

采用巨正则Monte Carlo方法和分子动力学方法研究了1-丁烯在MCM-22分子筛中的吸附现象和扩散行为,得到了1-丁烯吸附在该分子筛孔道中的相互作用能和在不同孔道中的扩散轨迹和扩散系数.结果表明1-丁烯在MCM-22分子筛中主要存存两个相互作用能区间,1-丁烯优先吸附在十元环孔道中;1-丁烯的扩散和移动主要发生在十二元环超笼的中部,十元环孔道中的1-丁烯扩散速度明显小于十二元环超笼系统中的扩散速度.     

The synthesis,characterization, and structure solution of SSZ-58: a novel two-dimensional 10-ring pore zeolite with previously unseen double 5-ring subunits

The synthesis, structure solution, and characterization of the novel zeolite SSZ-58 are described. SSZ-58 was synthesized under hydrothermal conditions using 1-butyl-1-cyclooctylpyrrolidinium cation as a structure-directing agent. The framework topology of SSZ-58 was determined with the FOCUS Fourier recycling method. SSZ-58 possesses 12 tetrahedral atoms in the asymmetric unit of its highest topological symmetry, and to date it is the most complex zeolite structure solved from powder data. Rietveld refinement of synchrotron powder X-ray diffraction data in space group Pmma confirmed the proposed model. SSZ-58 contains layers of atoms that are linked together by double five-membered rings (D5R), or 5(2)4(5) subunits, that have not been observed before in any zeolite or zeotype structures. SSZ-58 possesses a two-dimensional channel system consisting of 10-membered ring pores that intersect to form large cavities circumscribed by 12- and 16-membered ring pores.     

以季磷化合物为模板剂合成超大孔分子筛ITQ-33

以四丁基氢氧化磷为模板剂, 在中温水热条件下, 利用浓溶胶法合成了具有一维18元环孔道的含铝硅锗酸盐分子筛ITQ-33. 系统研究了ITQ-33的合成条件, 并利用原位变温X射线衍射(XRD), 扫描电子显微镜(SEM), 固体核磁共振波谱(NMR), 电感耦合等离子体发射光谱(ICP), 氮气吸附-脱附程序升温脱附(TPD), 热重(TG)及元素分析等手段对其结构、 稳定性及催化性能进行了表征. 结果表明, 以季磷化合物为模板剂可以合成含铝的ITQ-33纯相, 产物具有较高的热稳定性, 其骨架结构可以稳定至400℃以上, 煅烧后的ITQ-33具有Lewis酸位点, 在酸催化方面有潜在的应用价值.     

A Stable Extra‐Large‐Pore Zeolite with Intersecting 14‐ and 10‐Membered‐Ring Channels

The development of inorganic frameworks with extra‐large pores (larger than 12‐membered rings) has attracted considerable attention because of their potential applications in catalysis, the separation of large molecules, and so forth. We herein report the synthesis of the new extra‐large‐pore zeolite NUD‐2 by using the supramolecular self‐assembly of simple aromatic organic cations as structure‐directing agents (SDAs). NUD‐2 is a high‐silicon‐content germanosilicate with interconnecting 14×10‐membered‐ring channels. The SDAs in NUD‐2 can be removed by calcination in air at 550 °C to yield permanent pores with a BET surface area of 500 m²g^?1. Both germanium and organic cations in NUD‐2 can also be removed by treatment with acid at lower temperature, thus not only affording recycling of germanium and SDAs, but also providing a highly stable siliceous zeolite. In addition, aluminum ions can be incorporated into the framework of NUD‐2. The NUD‐2 structure is yet another extra‐large‐pore zeolite synthesized by using the supramolecular self‐assembling templating approach, thus demonstrating that this approach is a general and applicable strategy for synthesis of new large‐ and extra‐large‐pore zeolites.     

Supercritical CO2 as a superior solvent for the cyclization of diallylmalonate catalyzed by palladium-containing zeolites

Palladium-containing zeolites catalyze the cycloisomerization of diethyl diallylmalonate to dimethylcyclopentenes. When the reaction is carried out in toluene, the performance of the palladium catalyst depends on the pore size of the zeolites. At 60 °C, palladium adsorbed on large pore size Beta zeolite (pore size ∼7.4 Å) is more active than medium pore size ZSM-5 (pore size ∼5.4 Å). This lower activity of ZSM-5 compared to Beta is attributable to the restricted diffusion of reagent and products through the ZSM-5 channels as compared to Beta zeolite. However, due to the gas-like diffusion characteristic of the supercritical state, the activity of ZSM-5 increases and becomes identical to that of Beta zeolite using supercritical CO₂ as medium.     

11-丁烯在MCM-2222分子筛中的吸附与扩散: Monte Carlo与动力学模拟研究

采用巨正则Monte Carlo方法和分子动力学方法研究了11-丁烯在MCM-2222分子筛中的吸附现象和扩散行为, 得到了11-丁烯吸附在该分子筛孔道中的相互作用能和在不同孔道中的扩散轨迹和扩散系数. 结果表明11-丁烯在MCM-2222分子筛中主要存在两个相互作用能区间, 11-丁烯优先吸附在十元环孔道中; 11-丁烯的扩散和移动主要发生在十二元环超笼的中部, 十元环孔道中的11-丁烯扩散速度明显小于十二元环超笼系统中的扩散速度.     

An Organic Zeolite With 10 Å Diameter Pores Assembles From a Soluble and Flexible Building Block by Non-Covalent Interactions

Two similar molecular building blocks, which both contain a hydrogen-bonded nitro group, have been prepared and crystallised. One structure has more flexibility with a butyl side chain which allows an open framework organic zeolite to form with large 10 Å diameter pores, whereas the other structure has less flexibility with an aryl side chain and is close packed. The pore size is comparable with those of the aluminophosphate VPI-5 (12 Å). It is concluded that some flexibility in the design of the building block for porous organic molecular materials was beneficial.