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1.
The synthesis of aluminosilicate zeolite, SSZ-25, is described using a two-component organic guest molecule strategy. This method has been recently described by us and is quite effective in crystallizing a variety of aluminosilicate zeolites with reduction in template cost. In this instance the original organic guest component used in the discovery of SSZ-25, N',N',N'-trimethyl-2-adamantammonium cation, is used in conjunction with a variety of smaller amines. The amine is the major organic component in the synthesis and the quaternary ammonium compound, while a minor component, is essential for structure direction to the desired zeolite product. Studies here show that the adamantyl component is preferentially taken up during crystal growth. Our studies showed that the use of the multi-organic component approach to synthesis resulted in a faster and cheaper route to crystallizing SSZ-25. The SSZ-25 has been described in the literature as having the MWW topology and as such has two different channel systems accessed by 10-ring openings; the channel systems do not intersect. One set of 10-rings open into large cavities. In this study we used NMR spectroscopy to examine the as-made materials and to see if the two organic components are used in different capacities in the synthesis, probing if the admantyl component is only found in these larger cavities. The crystalline products could be affected by solvent extraction with polar solvents like dimethylformamide: the X-ray powder patterns and elemental analyses changed with solvent treatment. The solvent-treated crystals were studied by NMR spectroscopy, elemental analysis, and argon adsorption. The two-component organic guest approach was also found to be quite flexible not only with regard to the amine, but also towards the quaternary ammonium compounds. Non-adamantyl polycyclic templates could be used, and polar but non-quaternized adamantyl derivatives also succeeded in directing towards SSZ-25 formation. On the other hand. in one instance it was shown that the two-component approach favors SSZ-25 as the kinetic product but at longer run times Ostwald ripening was observed, leading to the disappearance of SSZ-25 and formation of ferrierite zeolite and quartz. 相似文献
2.
Burton AW Elomari S Chan I Pradhan A Kibby C 《The journal of physical chemistry. B》2005,109(43):20266-20275
The synthesis, characterization, and structure elucidation of the borosilicate zeolite SSZ-63 are described. SSZ-63 is synthesized using the 1-cyclodecyl-1-methylpyrrolidinium cation as a structure-directing agent. The structural model for SSZ-63 was determined by comparison of its powder X-ray diffraction pattern with those of zeolite beta and its polytype structures. Whereas conventional zeolite beta may be described as a random intergrowth of polytypes A and B, SSZ-63 is more accurately described as a random intergrowth of polytypes B and C(H) (the hypothetical polytype C proposed by Higgins). Polytype C(H) is essentially an ordered intergrowth (of polytypes A and B) in which one of the crystallographic projections is equivalent to those in polytype A and another projection is equivalent to those in polytype B. Unlike zeolite beta, which possesses significant disorder related to layer shifts along both the a- and b-crystallographic axes, the structure of SSZ-63 has little disorder associated with the translations of layers in the a-direction. DIFFaX simulations of the powder diffraction patterns, electron diffraction, and high-resolution transmission electron microsocopy data all support the proposed model. 相似文献
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Hudson MR Queen WL Mason JA Fickel DW Lobo RF Brown CM 《Journal of the American Chemical Society》2012,134(4):1970-1973
Low-pressure adsorption of carbon dioxide and nitrogen was studied in both acidic and copper-exchanged forms of SSZ-13, a zeolite containing an 8-ring window. Under ideal conditions for industrial separations of CO(2) from N(2), the ideal adsorbed solution theory selectivity is >70 in each compound. For low gas coverage, the isosteric heat of adsorption for CO(2) was found to be 33.1 and 34.0 kJ/mol for Cu- and H-SSZ-13, respectively. From in situ neutron powder diffraction measurements, we ascribe the CO(2) over N(2) selectivity to differences in binding sites for the two gases, where the primary CO(2) binding site is located in the center of the 8-membered-ring pore window. This CO(2) binding mode, which has important implications for use of zeolites in separations, has not been observed before and is rationalized and discussed relative to the high selectivity for CO(2) over N(2) in SSZ-13 and other zeolites containing 8-ring windows. 相似文献
5.
L Wu V Degirmenci PC Magusin BM Szyja EJ Hensen 《Chemical communications (Cambridge, England)》2012,48(76):9492-9494
The dual template synthesis of zeolite SSZ-13 by use of trimethyl-adamantanammonium hydroxide and a diquaternary-ammonium mesoporogen induces considerable mesoporosity without impeding zeolite microporosity. The strongly improved accessibility of Br?nsted sites in mesoporous SSZ-13 increases its stability during application as an acid catalyst in the methanol-to-olefins reaction. 相似文献
6.
Structure-direction in zeolite synthesis 总被引:1,自引:0,他引:1
Raul F. Lobo Stacey I. Zones Mark E. Davis 《Journal of inclusion phenomena and macrocyclic chemistry》1995,21(1-4):47-78
The concepts of structure-direction in the synthesis of clathrasils and high-silica molecular sieves are reviewed. The effects of size, geometry, and chemical nature of the organic structure-directing agent on the crystalline structures that are formed are discussed beginning with clathrasils (0-dimensional pore systems) and ending with 12-ring zeolites with 3-dimensional pore systems. Emphasis is focused on the energetic interactions between the organic guest and the inorganic framework. The energetic stability of porous frameworks is compared to the stability of dense pure-silica phases and the effects of trivalent (Al, B) and divalent (Zn) tetrahedral heteroatoms on the structure of zeolites formed is reviewed. The application of structure-directing concepts are described using the syntheses of ZSM-18 and SSZ-26 as examples, and the control over long-range order in zeolites by structure-directing effects is illustrated by the purposeful variation of the stacking probability of SSZ-33-CIT-1 and FAU-EMT intergrowths. 相似文献
7.
Burton A Elomari S Medrud RC Chan IY Chen CY Bull LM Vittoratos ES 《Journal of the American Chemical Society》2003,125(6):1633-1642
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. 相似文献
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Shayib RM George NC Seshadri R Burton AW Zones SI Chmelka BF 《Journal of the American Chemical Society》2011,133(46):18728-18741
Interactions of fluoride anions and organocations with crystalline silicate frameworks are shown to depend subtly on the architectures of the organic species, which significantly influence the crystalline structures that result. One- and two-dimensional (2D) (1)H, (19)F, and (29)Si nuclear magnetic resonance (NMR) spectroscopy measurements establish distinct intermolecular interactions among F(-) anions, imidazolium structure-directing agents (SDA(+)), and crystalline silicate frameworks for as-synthesized siliceous zeolites ITW and MTT. Different types and positions of hydrophobic alkyl ligands on the imidazolium SDA(+) species under otherwise identical zeolite synthesis compositions and conditions lead to significantly different interactions between the F(-) and SDA(+) ions and the respective silicate frameworks. For as-synthesized zeolite ITW, F(-) anions are established to reside in the double-four-ring (D4R) cages and interact strongly and selectively with D4R silicate framework sites, as manifested by their strong (19)F-(29)Si dipolar couplings. By comparison, for as-synthesized zeolite MTT, F(-) anions reside within the 10-ring channels and interact relatively weakly with the silicate framework as ion pairs with the SDA(+) ions. Such differences manifest the importance of interactions between the imidazolium and F(-) ions, which account for their structure-directing influences on the topologies of the resulting silicate frameworks. Furthermore, 2D (29)Si{(29)Si} double-quantum NMR measurements establish (29)Si-O-(29)Si site connectivities within the as-synthesized zeolites ITW and MTT that, in conjunction with synchrotron X-ray diffraction analyses, establish insights on complicated order and disorder within their framework structures. 相似文献
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由新型铜胺络合物模板剂设计合成活性优异的Cu-SSZ-13分子筛 总被引:2,自引:0,他引:2
以低廉的铜胺络合物为新型模板剂, 成功地合成了含铜的 SSZ-13 沸石分子筛 (Cu-ZJM-1). 在合成过程中, 铜胺络合物既是模板分子, 又是催化活性组分铜物种的直接来源. 理论计算表明, 该模板分子的构型与尺寸恰好与构成 SSZ-13 分子筛结构的 CHA 笼相匹配, 因而可以成功地导向该沸石分子筛结构. 采用 X 射线衍射、扫描电镜、氮气吸附、红外、紫外-可见吸收光谱、差热-热重分析、氨气程序升温脱附及氢气程序升温还原等手段对样品的性质及模板分子的状态进行了系统表征. 结果表明, 所制 Cu-ZJM-1 样品为结晶度很高的 SSZ-13 沸石结构, 硅铝比和铜负载量可调且铜处于高分散状态, 在 NH3 选择催化还原氮氧化物反应中表现出优异的催化性能. 相似文献
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SSZ-60 is a new borosilicate zeolite that may be prepared using N-ethyl-N-(2,4,4-trimethylcyclopentyl)pyrrolidinium or N-ethyl-N-(3,3,5-trimethylcyclohexyl)pyrrolidinium as a structure directing agent; the framework of SSZ-60 was determined by the FOCUS Fourier recycling method, its structure refined in space group P21nm and found to possess a one-dimensional channel system with pores delimited by twelve-rings; the topological structure of SSZ-60 may be derived from a sigma-expansion of the framework of ZSM-23 (MTT). 相似文献
13.
Zones SI Burton AW Lee GS Olmstead MM 《Journal of the American Chemical Society》2007,129(29):9066-9079
This study is a continuation of our efforts to understand the interplay in the self-assembly chemistry for formation of molecular sieves from guest organocations and inorganic silicon oxide. In this particular study we focus on the competitive interplay of the organocations and the synthesis cofactor fluoride anion. The anions play a key role in structure determination, as a function of net solution concentration. They compete with the role for the space-filling organocation in determining which molecular sieve host structure will be specified. In this study we look at this competition in the synthesis for a series of 33 different organocations derived from the piperidine ring system. Derivatives were prepared which both fixed substituents on the carbon and nitrogen centers on the ring. Results were discussed in terms of product selectivity from synthesis as a function of solution concentration for the reactants. A total of 17 different host topologies were found in this series, and a correlation was seen for (a) open-framework lattices (low framework densities) under the most concentrated reaction conditions and then (b) high framework density products once the conditions were more dilute. Some surprising synthesis differences are seen in comparing the performance of these structure directing agents (SDAs) in fluoride media vs hydroxide media (the more conventional environment for zeolite/molecular sieve syntheses involving silicate chemistry). Finally molecular modeling was used to understand some of the trends in product selectivity for closely related guest (SDA) candidates. 相似文献
14.
Rania Charrad Dr. Hanna E. Solt Dr. József Valyon László Trif Dr. Faouzi Ayari Dr. Mourad Mhamdi Jenő Hancsók Dr. Ferenc Lónyi 《ChemistryOpen》2020,9(11):1123-1134
Co/SSZ-13 zeolites were prepared by heating the finely dispersed mixture of NH4-SSZ-13 and different cobalt salts up to 550 °C. Investigations by thermogravimetry – differential scanning calorimetry – mass spectrometry provided new insight into details of the solid-state reaction. Formation of Co carrying hydrate melt or volatile species was shown to proceed from chloride, nitrate, or acetylacetonate Co precursor salts upon thermal treatment. This phase change allows the transport of the Co species into the zeolite pores. The reaction of the NH4+ or H+ zeolite cations and the mobile Co precursors generates vapor or gas products, readily leaving the zeolite pores, and cobalt ions in lattice positions suggesting that solid-state ion-exchange is the prevailing process. The obtained catalysts are of good activity and N2 selectivity in the CH4/NO-SCR reaction. The thermal treatment of acetate or formate salts give solid intermediates that are unable to get in contact and react with the cations in the zeolite micropores. These catalysts contain mainly Co-oxide clusters located on the outer surface of the zeolite crystallites and have poor catalytic performance. 相似文献
15.
Synthesis of a new zeolite structure ITQ-24, with intersecting 10- and 12-membered ring pores 总被引:2,自引:0,他引:2
Castañeda R Corma A Fornés V Rey F Rius J 《Journal of the American Chemical Society》2003,125(26):7820-7821
A new 10- and 12-membered ring zeolite, named ITQ-24, has been synthesized, and its structure has been solved. It has been found that this zeolite structure is topologically identical to that proposed for the hypothetical polymorph C of the SSZ-33/SSZ-26/CIT-1 family. This new zeolite has been achieved by using a rational approach of introducing Ge in the framework that has a directing effect toward zeolite structures with double-four-membered rings as secondary building units. Notoriously, active catalytic centers, such as Ti and Al, have been incorporated into this new zeolite, demonstrating that it is catalytically active for alkylation of aromatics. 相似文献
16.
Greg S. LeeStacey I. Zones 《Journal of solid state chemistry》2002,167(2):289-298
In this communication, we report on the discovery of novel zeolite compositions, SSZ-50. The zeolite has the RTH topology but can be made over a large silica-to-alumina range including no aluminum at all. The surprising capability to produce a broad compositional range comes from the use of a single organo-cation guest molecule in the zeolite synthesis. The molecule is a specific derivative from within a family of 2-aza [4.1.1] bicyclo octanes that were prepared employing a sequence of organic synthesis steps from a starting ketone. Other cage-based zeolites like SSZ-35,-36,-39 and MTN arose from the use of the other derivatives in this series. We also comment on the tendency of a variety of polymethylated organo-cations to produce RTH, the closely related ITE, or the intergrowth structure, SSZ-36. 相似文献
17.
Ionothermal synthesis, the use of an ionic liquid as both solvent and structure-directing agent, has been used to synthesize three different cobalt aluminophosphate zeolites. Two of the materials are isostructural with solids prepared previously and have the AEI and SOD framework types. SIZ-7 is a novel zeolite structures that is closely related to the family of 8-ring zeolites consisting of the MER, GIS, and PHI frameworks. Single-crystal X-ray diffraction of SIZ-7 indicates that the distribution of cobalt among the four possible tetrahedral sites is unequal. 相似文献
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通过静态水热合成法,溴化六甲二铵作为结构导向剂合成出系列低硅铝比的ZSM48沸石分子筛(Si/Al100),所合成样品中最低硅铝比为38.6(ICP-AES),这将拓宽ZSM-48高硅沸石分子筛的应用范围。制备Pt负载双功能催化剂,用于正构十二烷临氢异构催化反应。结果表明,硅铝比的改变可以影响催化剂的活性,投料硅铝比为70的双功能催化剂具有最优的催化性能,但硅铝比改变对异构产物的分布没有明显的影响,其异构产物以支链在中间位的异构体为主。 相似文献
20.
Dr. Veronika Pashkova Dr. Kinga Mlekodaj Dr. Petr Klein Dr. Libor Brabec Dr. Radek Zouzelka Dr. Jiri Rathousky Dr. Venceslava Tokarova Dr. Jiri Dedecek 《Chemistry (Weinheim an der Bergstrasse, Germany)》2019,25(52):12068-12073
The economical and environmentally benign synthesis of SSZ-13 zeolite was possible due to the mechanochemical activation of dry reagents by planetary mill. Contrary to manual grinding in a mortar, the proposed automatized approach is scalable and reproducible. This solvent-free process provided a huge gain in product/gel ratios, significantly minimized reaction space and organic structure-directing agent use, and allowed for the elimination of agitation. Obtained materials were comparable to the product of “classical” syntheses. The use of different silica sources resulted in SSZ-13 zeolites with various characteristics: different Si/Al ratio and crystal size. 相似文献