29 results on '"Camblor, Miguel A."'
Search Results
2. 2-Isopropyl-1,3-dimethylimidazolium as a versatile structure-directing agent in the synthesis of zeolites.
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Yu, Huajian, Rojas, Alex, Gao, Zihao Rei, Gómez-Hortigüela, Luis, Villaescusa, Luis A., Li, Jian, Paillaud, Jean-Louis, and Camblor, Miguel A.
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X-ray powder diffraction ,RIETVELD refinement ,MOLE fraction ,DIFFRACTION patterns ,ZEOLITES - Abstract
An organic cation lacking specificity in its structure-directing action offers the possibility, through the screening of other structure-directing parameters, to synthesize a variety of zeolites. In this work we show that the organic structure-directing agent 2-isopropyl-1,3-dimethylimidazolium (2iPr13DMI) can produce up to seven different zeolite phases depending on water concentration, the presence of inorganic impurities, crystallization temperature and time, and germanium molar fraction. The obtained phases are very different in terms of pore system, connectivity of the zeolite structure and structural units. At the pure SiO
2 side, ZSM-12 and SSZ-35 dominate, with ZSM-12 being favored by the presence of potassium impurities and by less concentrated conditions. The introduction of Ge at low levels favors SSZ-35 over ZSM-12 and as the Ge fraction increases it successively affords CSV, -CLO and two distinct UOS zeolites, HPM-11 and HPM-6. These two zeolites have the same topology but distinct chemical compositions and display powder X-ray diffraction patterns that are much different from each other and from that of as-synthesized IM-16 (UOS reference material). They also show different symmetry at 96 K. Rietveld refinements of the three as-made UOS materials mentioned are provided. HPM-6 and HPM-11 are produced in distinct, non-adjacent crystallization fields. The frequent cocrystallization of the chiral STW zeolite, however, did not afford its synthesis as a pure phase. Molecular mechanics simulations of the location of the organic cation and host–guest interactions fail to explain the observed trends, but also considering the intrinsic stability of the zeolites and the effect of germanium help to rationalize the results. The study is completed by DFT calculations of the NMR chemical shifts of13 C in UOS (helping to understand splittings in the spectrum) and19 F in CSV (supporting the location of fluoride inside the new [44 52 ], which is an incomplete double 4-ring). [ABSTRACT FROM AUTHOR]- Published
- 2023
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3. Synthesis of Extra‐Large Pore, Large Pore and Medium Pore Zeolites Using a Small Imidazolium Cation as the Organic Structure‐Directing Agent.
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Gao, Zihao Rei, Balestra, Salvador R. G., Li, Jian, and Camblor, Miguel A.
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HOST-guest chemistry ,CATIONS ,HYDROTHERMAL synthesis - Abstract
One common strategy in the search for new zeolites is the use of organic structure‐directing agents (OSDA). Typically, one seeks to achieve a high specificity in the structure‐directing effect of the OSDA. This study shows, however, that an OSDA lacking strong specificity towards any particular zeolite may provide opportunities for discovery when other synthesis parameters are systematically screened. Thus, 1‐methyl‐2‐ethyl‐3‐n‐propylimidazolium has allowed to crystallize the new large/medium pore zeolite HPM‐16 as well as the recently reported extra‐large pore ‐SYT and the medium/small pore and chiral STW. The sophisticated OSDA originally affording ‐SYT and the new simple OSDA have very little in common, both in terms of size, shape and flexibility, while both may still direct the synthesis of the same zeolite. In fact, molecular simulations show that the new OSDA is located in three different positions of the ‐SYT structure, including the discrete 8MR where the original organic could not fit. [ABSTRACT FROM AUTHOR]
- Published
- 2021
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4. HPM‐16, a Stable Interrupted Zeolite with a Multidimensional Mixed Medium–Large Pore System Containing Supercages.
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Gao, Zihao Rei, Balestra, Salvador R. G., Li, Jian, and Camblor, Miguel A.
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THERMAL stability ,ELECTRON diffraction - Abstract
HPM‐16 is a highly porous germanosilicate zeolite with an interrupted framework that contains a three‐dimensional system of 12+10×10(12)×12+10‐membered ring (MR) pores. The 10(12) MR pore in the b direction is a 10 MR pore with long 12 MR stretches forming 30 Å long tubular supercages. Along one direction the 10 MR pores are fused, meaning that the separation between adjacent pores consists of a single tetrahedron that is, additionally, connected to only three additional tetrahedra (a Q3). These fused pores are thus decorated by T‐OH groups along the whole diffusion path, creating a hydrophilic region embedded in an otherwise essentially hydrophobic environment. The structure is built from highly porous 12×12×12 MR uninterrupted layers that are connected to each other through Q3 producing a second system of 10×10×10 MR pores. This zeolite can be extensively degermanated yielding a material with high thermal stability, despite its interrupted nature. [ABSTRACT FROM AUTHOR]
- Published
- 2021
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5. HPM‐14: A New Germanosilicate Zeolite with Interconnected Extra‐Large Pores Plus Odd‐Membered and Small Pores.
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Gao, Zihao Rei, Li, Jian, Lin, Cong, Mayoral, Alvaro, Sun, Junliang, and Camblor, Miguel A.
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ELECTRON diffraction ,SCANNING transmission electron microscopy ,X-ray powder diffraction ,ZEOLITES ,TETRAHEDRAL molecules - Abstract
HPM‐14 is a new extra‐large pore zeolite synthesized using imidazolium‐based organic structure‐directing agents (SDAs), fluoride anions, and germanium and silicon as tetrahedral components of the framework. Owing to the presence of stacking disorder, the structure elucidation of HPM‐14 was challenging, and different techniques were necessary to clarify the details of the structure and to understand the nature of the disorder. The structure has been solved by three‐dimensional electron‐diffraction technique (3D ED) and consists of an intergrowth of two polymorphs possessing a three‐dimensional channel system, including an extra‐large pore opened through windows made up of sixteen tetrahedral atoms (16‐membered ring, 16MR) as well as two additional sets of odd‐membered (9MR) and small (8MR) pores. The intergrowth has been studied by scanning transmission electron microscopy (Cs‐STEM) and powder X‐ray diffraction simulations (DIFFaX), which show a large predominance of the monoclinic polymorph A. [ABSTRACT FROM AUTHOR]
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- 2021
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6. Structure–direction towards the new large pore zeolite NUD-3.
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Chen, Fei-Jian, Gao, Zihao Rei, Li, Jian, Gómez-Hortigüela, Luis, Lin, Cong, Xu, Le, Du, Hong-Bin, Márquez-Álvarez, Carlos, Sun, Junliang, and Camblor, Miguel A.
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ZEOLITES ,DISEASES - Abstract
The new zeolite NUD-3 possesses a three-dimensional system of large pore channels that is topologically identical to those of ITQ-21 and PKU-14. However, the three zeolites have distinctly different frameworks: a particular single 4-membered ring inside the denser portion of the zeolite is missing in PKU-14, disordered in ITQ-21 and fully ordered in NUD-3. We document these differences and use molecular simulations to unravel the mechanism by which a particular structure directing agent dication, 1,1′-(1,2-phenylenebis(methylene))bis(3-methylimidazolium), is able to orient this inner ring. [ABSTRACT FROM AUTHOR]
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- 2021
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7. IDM‐1: A Zeolite with Intersecting Medium and Extra‐Large Pores Built as an Expansion of Zeolite MFI.
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Villaescusa, Luis A., Li, Jian, Gao, Zihao, Sun, Junliang, and Camblor, Miguel A.
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BUILDING additions ,ELECTRON diffraction ,X-ray powder diffraction ,ZEOLITES ,THERMAL stability - Abstract
IDM‐1 is a new silica zeolite with an ordered and well‐defined framework constructed by alternating pentasil layers and interrupted layers, giving rise to an intersecting system of straight medium pores and undulating extra‐large lobed pores. This unique structure was solved by rotation electron diffraction and refined against synchrotron powder X‐ray diffraction data. Despite the presence of both Si(OSi)3(OH) and Si(OSi)2(OH)2 sites, this new zeolite presents high thermal stability, withstanding calcination even to 1000 °C. The location of defects at specific sites of the structure results in alternating hydrophobic SiO2 and hydrophilic SiO(2−x)(OH)2x intracrystalline regions. This peculiar combination of intersecting medium and extra‐large pores and alternating regions of different chemical character may provide this zeolite with unique catalytic properties. [ABSTRACT FROM AUTHOR]
- Published
- 2020
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8. Synthesis of a germanosilicate zeolite HPM-12 using a short imidazolium-based dication: structure-direction by charge-to-charge distance matching.
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Lu, Peng, Gómez-Hortigüela, Luis, Gao, Zihao, and Camblor, Miguel A.
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NUCLEAR magnetic resonance spectroscopy ,CHEMICAL shift (Nuclear magnetic resonance) ,ZEOLITES ,DISTANCES ,CATIONS ,GERMANIUM ,CRYSTALLIZATION - Abstract
A short imidazolium based dication, with only three methylene units in the spacer linker, selectively directs the crystallization of zeolite HPM-12 (*UOE) as long as there is enough germanium present in the synthesis gel. The integrity of the dication is proved by dissolution of the zeolite and
1 H and13 C NMR spectroscopy, where significant effects of organic dication concentration and the presence and concentration of HF need to be taken into account. For the as-made HPM-12 zeolite, a large shift of 9 ppm of one resonance in the13 C MAS NMR spectrum is due to the particular conformation of the dication imposed by confinement in the zeolite framework, as found by DFT calculations. The structure-directing ability of this kind of dication with varying length of the linker suggests that matching of the distance between positive charges (imidazolium moieties) and negative charges (double four rings in which fluoride resides) plays a crucial role during crystallization. [ABSTRACT FROM AUTHOR]- Published
- 2019
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9. Synthesis of Pure Silica MWW Zeolite in Fluoride Medium by Using an Imidazolium‐Based Long Dication.
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Lu, Peng, Gómez‐Hortigüela, Luis, and Camblor, Miguel A.
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ZEOLITES ,FLUORIDES ,IMIDAZOLES ,INORGANIC synthesis ,HYDROGEN ,RESONANCE - Abstract
As the spacer length in 1,2‐dimethylimidazolium‐based dications increases beyond a specific point (six methylene units), they fail in structure‐directing towards STW zeolites in any synthetic conditions. These dications can instead produce, under fluoride concentrated conditions, either *BEA [in the case of the eight‐methylene‐unit structure‐directing agent (SDA)] or MWW (ten methylene units) zeolites. For any length of the dication, the default zeolite (MTW) is a relatively dense zeolite containing a unidimensional channel, whereas the zeolite demanding most specificity (STW, *BEA or MWW) is more porous, affording a larger concentration of the dication to be occluded. This work provides the first reported fluoride synthesis of pure silica MWW zeolites. Charge balance of the organic dications in this zeolite was achieved by combining "structural" silanolates, regular "connectivity defects" and occluded fluoride. Molecular mechanics calculations showed a perfect fit of the decamethylenebis(dimethylimidazolium) dication in the sinusoidal intralayer pore system of MWW. The calculations showed also that the dication is able to stabilize the interlayer space without disturbing the hydrogen‐bonding system that holds the layers together in the as‐made material. The 19F magic‐angle spinning (MAS) NMR presented two distinct resonances at −71 and −83 ppm, which, on the basis of DFT calculations, we tentatively assigned to fluoride occluded in [4662] and [415262] cages of the MWW structure, respectively. The same DFT study determines a different chemical shift of one methyl 13C nuclear magnetic resonance according to the imidazolium ring residing in the sinusoidal channels or in the large cup cavities, thus explaining an experimentally observed splitting of that resonance. Pure silica MWW zeolite was synthesized for the first time through the fluoride route by using dimethylimidazolium‐based long dications in highly concentrated conditions. DFT calculations suggested that the F− anions reside in both [415262] and [4662] cages, giving rise to two distinct 19F NMR signals. [ABSTRACT FROM AUTHOR]
- Published
- 2019
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10. Synthesis of pure silica MFI zeolites using imidazolium-based long dications. A comparative study of structure-directing effects derived from a further spacer length increase.
- Author
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Lu, Peng, Gómez-Hortigüela, Luis, and Camblor, Miguel A.
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ZEOLITES ,SILICA ,CYCLOBUTANE - Abstract
Length-dependent structure direction of linear methylimidazolium-based dications towards MFI zeolite, previously known only for the tetramethylene spacer, has also been found for octamethylene and decamethylene spacers. This works only under highly concentrated conditions, whereas dilution always tends to favor TON, a default structure that is the only zeolite obtained with the other reported dications (with tri-, penta-, and hexamethylene spacers). The locations and conformations of the dications have been studied by molecular mechanics simulations. As longer dications introduce lower density of positive charges in the zeolite, the density of connectivity defects also decreases. Finally, these long dications cannot easily place each charged imidazolium ring in the two possible orientations (either parallel or perpendicular to 4MR close to F
− sites) found for the tetramethylene case. Hence, although the three MFI materials display two19 F NMR resonances at similar chemical shifts, their relative intensities strongly vary as a function of the spacer length. [ABSTRACT FROM AUTHOR]- Published
- 2018
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11. Influence of Flexibility on the Separation of Chiral Isomers in STW‐Type Zeolite.
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Bueno‐Perez, Rocio, Balestra, Salvador R. G., Camblor, Miguel A., Min, Jung Gi, Hong, Suk Bong, Merkling, Patrick J., and Calero, Sofia
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MOLECULAR dynamics ,ATMOSPHERIC temperature ,NANOPOROUS materials ,ZEOLITES ,SILICA - Abstract
Abstract: Molecular simulation, through the computation of adsorption isotherms, is a useful predictive tool for the selective capacity of nanoporous materials. Generally, adsorbents are modelled as rigid frameworks, as opposed to allowing for vibrations of the lattice, and this approximation is assumed to have negligible impact on adsorption. In this work, this approach was tested in an especially challenging system by computing the adsorption of the chiral molecules 2‐pentanol, 2‐methylbutanol and 3‐methyl‐2‐butanol in the all‐silica and germanosilicate chiral zeolites STW and studying their lattice vibrations upon adsorption. The analysis of single‐ and multicomponent adsorption isotherms showed the suitability of STW‐type zeolites as molecular sieves for chiral separation processes, which pose a challenging task in the chemical and pharmaceutical industries. Moreover, new experimental adsorption data validate the force field employed. The results reveal that the lattice vibrations of the all‐silica framework are sorbate‐independent, while those of germanosilicate STW show host–guest coupling modulated by uptake and sorbate type that disrupts the chiral recognition sites. This study indicates that the effects of intrinsic flexibility on the selective capacity of nanoporous materials may range from low to high impact, and some of them could not have been foreseen even after examination of the structural dynamics of an empty framework. [ABSTRACT FROM AUTHOR]
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- 2018
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12. NOn the Porous Silicate HPM-5.
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Jo, Donghui, Mayoral, Alvaro, Hong, Suk Bong, and Camblor, Miguel A.
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ALUMINUM silicates ,MESOPOROUS materials ,MESOPORES ,MOLECULAR dynamics ,ANIONS - Abstract
HPM-5, a porous aluminosilicate with an intricate and so far unsolved structure, has been synthesized by using 1,2,3-trimethylimidazolium in hydroxide medium in the absence of fluoride anions. It consistently displays an ill-defined XRD pattern with broad and overlapped reflections and contains a large concentration of defects, as evidenced by IR and
29 Si MAS NMR spectroscopy.1 H MAS NMR spectroscopy confirmed the existence of highly deshielded protons (δ = -11.6 ppm) assigned to hydrogen atoms in relatively strong Si-O-H. . . .O-Si hydrogen bonds (O···O distance ≈ 2.64 Å) The calcined material shows limited microporosity (0.07-0.09 cm3 g -1 ). The results of a high-resolution transmission electron microscopy study suggest HPM-5 may be far more complicated than "standard" layered zeolites and may consist of low-density layers profusely decorated by holes. The resulting lace-like layers may be too unstable to withstand reactions characteristic of more conventional layered materials (both delamination and expansion by silylation); although the derivatives show an increase in the specific surface area, the layers are apparently disassembled and, at most, only ribbons remain. [ABSTRACT FROM AUTHOR]- Published
- 2017
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13. Framework Reduction of GeO2 Zeolites During Calcination.
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Villaescusa, Luis A. and Camblor, Miguel A.
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ZEOLITES , *CALCINATION (Heat treatment) , *GERMANIUM , *ORGANIC cation transporters , *OXIDATION - Abstract
zeolites with AST-topology causes reduction of the framework, hence structural destruction, in a notable extension. This is due to the impossibility for the organic cation occluded inside to react with ambient oxygen. As the temperature increases, reoxidation in air of the reduced framework causes episodes of weight-gain. When calcination is carried out in N2, weight losses close to 70% imply a loss of Ge due to sublimation of germanium monoxide, GeO. The nature of the organic cation occluded determines the nature and oxidation state of the final residue after calcination in N2: for tetramethylammonium the residue is GeO2 while trimethyl-terc-butylammonium, thanks to its larger C content, yields metallic Ge. Framework organoreduction is not unique to GeO2-AST zeolites but also occurs during the calcination in air of other germanium-containing zeolites with larger pore openings. [ABSTRACT FROM AUTHOR]
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- 2016
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14. Time Evolution of an Aluminogermanate Zeolite Synthesis: Segregation of Two Closely Similar Phases with the Same Structure Type.
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Villaescusa, Luis A. and Camblor, Miguel A.
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CHEMICAL synthesis , *ZEOLITES , *METALLURGICAL segregation , *FLUORIDES , *CRYSTALLIZATION , *TRIETHYLAMINE , *TRANSMETHYLATION - Abstract
A synthesis of zeolite-like aluminogermanates using N,N,N-trimethyl-terc-butylammonium (TMTBA) and fluoride evolved from an initially crystallized zeolite with the AST Zeolite Framework Type and very little Al in it into an Al-free GeO2 phase with the same structure but a slightly smaller unit cell. In spite of both zeolites having the same framework type, same symmetry, a much similar unit cell size and almost the same framework composition, phase segregation occurred at intermediate crystallization times as the initial AST phase was gradually replaced by the new one. For reaction mixtures with a high Al content complete replacement of the large cell by the smaller cell phase was accomplished. The solids have been characterized by powder X-ray diffraction (XRD), Rietveld refinement from synchrotron diffraction data, multinuclear Nuclear Magnetic Resonance (NMR) of both intact and disolved solids and infrarred spectroscopy. The study reveals TMTBA can degrade under the crystallization conditions to initially yield triethylamine (tMA), whereas transmethylation between TMTBA and tMA produces tetramethylammonium (TMA), as probed by liquid NMR. The TMA cation can also structure-direct to AST zeolites but with a smaller unit cell volume and no Al in the framework. Phase segregation occurs despite the lack of structural mismatch because both crystallization events are decoupled, occurring at different moments and from largely different solutions. When both TMTBA and TMA cations are intentionally added at the start, no phase segregation but crystallization of a solid solution occurs instead. [ABSTRACT FROM AUTHOR]
- Published
- 2016
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15. Efficient Removal of Volatile Organic Compounds by FAU-Type Zeolite Coatings.
- Author
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Diboune, Mathieu, Nouali, Habiba, Soulard, Michel, Patarin, Joël, Rioland, Guillaume, Faye, Delphine, Daou, T. Jean, and Camblor, Miguel A.
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VOLATILE organic compounds ,ZEOLITES ,SURFACE coatings ,MICROPOROSITY ,ADSORPTION capacity - Abstract
Silicone and pure organic binders were used to develop FAU-type zeolite coatings applied on pre-treated aluminum substrates by using a spraying method and then cured under specific conditions. The influence of the amount of binder on adhesion properties of zeolite coatings was first investigated to determine the optimum ratio between zeolite and binder. Zeolite coatings were then elaborated with a high zeolite content (between 70 and 80 wt.%) to ensure high adsorption capacities. The amount of binders involved in different zeolite coatings was sufficient to achieve interesting adhesion and cohesion properties. The accessibility of zeolite microporosity was studied by nitrogen adsorption-desorption measurements, which revealed a very small or no loss of the micropore volume for the optimized coatings. Volatile Organic Compounds (VOCs) adsorption measurements were carried out using n-hexane as probe molecule. FAU-type zeolite in powder form adsorbs 180 mg/g
anhydrous zeolite , whereas the amounts of n-hexane adsorbed by zeolite coatings ranged from 131 to 175 mg/ganhydrous zeolite . [ABSTRACT FROM AUTHOR]- Published
- 2020
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16. Synthesis of Hierarchical Zeolites with Morphology Control: Plain and Hollow Spherical Beads of Silicalite-1 Nanosheets.
- Author
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Moukahhal, Kassem, Lebeau, Bénédicte, Josien, Ludovic, Galarneau, Anne, Toufaily, Joumana, Hamieh, Tayssir, Daou, T. Jean, and Camblor, Miguel A.
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ZEOLITES ,DISSOLUTION (Chemistry) ,SILICA - Abstract
Binderless pure silica zeolites (zeosils) spheres and hollow spheres with a diameter of 20 µm composed of silicalite-1 nanosheets particles were prepared by pseudomorphic transformation of spherical silica beads using different temperatures (110, 130, and 150 °C) and treatment times (1–5 days) in order to adapt the local dissolution rate of silica to the crystallization rate of silicalite-1 nanosheets allowing to preserve the initial morphology of the silica beads. Fully crystalline beads of 20 µm were obtained at 110 °C for 5 days, whereas hollow spheres similar in size were synthesized at higher temperatures. The crystallization process seems to begin at the outer surface of the amorphous silica beads and spreads with the time in the interior of the beads leading to a dissolution of the inner amorphous part of the beads to create zeosil hollow spheres for the highest treatment temperatures (130 and 150 °C). The dissolution rate of the inner amorphous part of the beads increases by increasing the hydrothermal treatment temperature from 130 to 150 °C. The silicalite-1 beads synthesized at 110 °C for 5 days showed to be promising for rapid molecular decontamination by adsorbing n-hexane in larger amount than the silicalite-1 conventional big crystals in powder forms. [ABSTRACT FROM AUTHOR]
- Published
- 2020
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17. A stable aluminosilicate zeolite with intersecting three-dimensional extra-large pores
- Author
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Qing-Fang Lin, Zihao Rei Gao, Cong Lin, Siyao Zhang, Junfeng Chen, Zhiqiang Li, Xiaolong Liu, Wei Fan, Jian Li, Xiaobo Chen, Miguel A. Camblor, Fei-Jian Chen, National Natural Science Foundation of China, Ministerio de Ciencia, Innovación y Universidades (España), Swedish Research Council, Knut and Alice Wallenberg Foundation, Lin, Qing-Fang [0000-0001-9057-5091], Gao, Zihao Rei [0000-0003-0331-3515], Lin, Cong [0000-0003-0021-5055], Fan, Wei [0000-0002-8581-2651], Li, Jian [0000-0003-2221-2285], Chen, Xiaobo [0000-0001-9180-0190], Camblor, Miguel Ángel [0000-0001-9591-3432], Chen, Fei-Jian [0000-0001-9345-9459], Lin, Qing-Fang, Gao, Zihao Rei, Lin, Cong, Fan, Wei, Li, Jian, Chen, Xiaobo, Camblor, Miguel Ángel, and Chen, Fei-Jian
- Subjects
Multidisciplinary ,Crystalline porous materials ,Zeolites - Abstract
Anyone can then access the published paper FREE OF CHARGE by clicking on this link. Cualquier persona puede acceder al documento publicado de forma GRATUITA, accediendo a través del enlace: https://www.science.org/stoken/author-tokens/ST-242/full, [EN] Zeolites are crystalline porous materials with important industrial applications, including uses in catalytic and adsorption-separation processes. Access into and out of their inner confined space, where adsorption and reactions occur, is limited by their pore apertures. Stable multidimensional zeolites with larger pores able to process larger molecules are in demand in the fine chemical industry and for the oil processing on which the world still relies for fuels. Currently known extra-large-pore zeolites display poor stability and/or lack pore multidimensionality, limiting their usefulness. We report ZEO-1, a robust, fully connected aluminosilicate zeolite with mutually intersecting three-dimensional extra-large plus three-dimensional large pores. ZEO-1 is stable up to 1000°C, has an extraordinary specific surface area (1000 square meters per gram), and shows potential as a catalytic cracking catalys., National Natural Science Foundation of China (grant numbers: 21601004, 21776312, 22078364), the Natural Science Foundation of the Higher Education Institutions of Anhui Province, China (grant numbers: KJ2020A0585), and the Spanish Ministry of Science Innovation and Universities (MICIU) (PID2019-105479RB-I00 project, AEI, Spain and FEDER, EU). The cRED data was collected at the Electron Microscopy Center (EMC), Department of Materials and Environmental Chemistry (MMK) in Stockholm University with the support of the Swedish Research Council (Grant No. 1444205) and the Knut and Alice Wallenberg Foundation (KAW, 2012-0112) through the 3DEM-NATUR project. Use of the Advanced Photon Source at Argonne National Laboratory was supported by the U. S. Department of Energy, Office of Science, Office of Basic Energy Sciences, under Contract No. DE-AC02-06CH11357. W.F. gratefully acknowledges support from the U.S. Department of Energy, Office of Science, Basic Energy Sciences, Materials Sciences and Engineering Division, under Award # DE-SC0019170.
- Published
- 2021
18. HPM‐16, a Stable Interrupted Zeolite with a Multidimensional Mixed Medium–Large Pore System Containing Supercages
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Zihao Rei Gao, Salvador R. G. Balestra, Jian Li, Miguel A. Camblor, Ministerio de Ciencia e Innovación (España), Stockholm University, Knut and Alice Wallenberg Foundation, Gao, Zihao Rei, Balestra, Salvador R. G., Li, Jian, Camblor, Miguel Ángel, Gao, Zihao Rei [0000-0003-0331-3515], Balestra, Salvador R. G. [0000-0002-2163-2782], Li, Jian [0000-0003-2221-2285], and Camblor, Miguel Ángel [0000-0001-9591-3432]
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Materials science ,Communication ,Three-dimensional electron diffraction ,Diffusion ,General Medicine ,General Chemistry ,Ring (chemistry) ,Communications ,Catalysis ,Large pore ,Zeolites | Hot Paper ,Structure solution ,Chemical engineering ,Interrupted framework ,Highly porous ,Zeolites ,Tetrahedron ,Thermal stability ,Zeolite ,Degermanation - Abstract
[EN] HPM-16 is a highly porous germanosilicate zeolite with an interrupted framework that contains a three-dimensional system of 12+10 10(12) 12+10-membered ring (MR) pores. The 10(12) MR pore in the b direction is a 10 MR pore with long 12 MR stretches forming 30 long tubular supercages. Along one direction the 10 MR pores are fused, meaning that the separation between adjacent pores consists of a single tetrahedron that is, additionally, connected to only three additional tetrahedra (a Q3). These fused pores are thus decorated by T-OH groups along the whole diffusion path, creating a hydrophilic region embedded in an otherwise essentially hydrophobic environment. The structure is built from highly porous 12 12 12 MR uninterrupted layers that are connected to each other through Q3 producing a second system of 10 10 10 MRpores. This zeolite can be extensively degermanated yielding a material with high thermal stability, despite its interrupted nature., The authors are grateful for financial support to the Spanish Ministry of Science Innovation and Universities (MICIU) (PID2019-105479RB-I00 project, AEI, Spain and FEDER, EU). SRGB also thanks MICIU for a Juan de la Cierva- Formación Research Contract (FJC2018-035697-I code reference). Synchrotron experiments were performed at beamline BL04 (MSPD) at the Spanish ALBA Synchrotron with the collaboration of ALBA staff, and special thanks are due to A. Manj n and A. Missiul. Centro T cnico Inform tico-CSIC, Trueno cluster facility of SGAI-CSIC is acknowledged for running the calculations. We also deeply thank C. Márquez- Álvarez for his kind help in characterization. The cRED data were collected at the Electron Microscopy Center (EMC), Department of Materials and Environmental Chemistry (MMK) in Stockholm University with the support of Knut and Alice Wallenberg (KAW) foundation-financed project 3DEM-NATUR.
- Published
- 2021
19. Dication Containing Three Aromatic Ring Structure-Directs toward a Chiral Zeolite, Spans Three Cavities, and Effectively Traps Water
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Zihao Rei Gao, Salvador R. G. Balestra, Luis Gómez-Hortigüela, Jian Li, Carlos Márquez-Alvarez, Miguel A. Camblor, Ministerio de Ciencia e Innovación (España), Agencia Estatal de Investigación (España), Balestra, Salvador R. G., Gómez-Hortigüela Sainz, Luis, Li, Jian, Márquez Álvarez, Carlos, Camblor, Miguel Ángel, Gao, Zihao Rei, Balestra, Salvador R. G. [0000-0002-2163-2782], Gómez-Hortigüela Sainz, Luis [0000-0002-4960-8709], Li, Jian [0000-0003-2221-2285], Márquez Álvarez, Carlos [0000-0003-2749-4269], Camblor, Miguel Ángel [0000-0001-9591-3432], and Gao, Zihao Rei [0000-0003-0331-3515]
- Subjects
General Chemical Engineering ,Cations ,Materials Chemistry ,Imidazolium ,Zeolites ,General Chemistry ,Cavities ,Molecular structure - Abstract
[EN] The chiral zeolite STW has been synthesized using a large dication containing three aromatic rings (two imidazolium moieties plus a benzene one). The integrity of the occluded organics is proven by 1H and 13C liquid NMR of the zeolite dissolved in HF/D2O. Molecular simulations strongly suggest that each aromatic ring is located in a different cavity so that each dication crosses two medium pore 10-membered-ring (MR) windows. This is confirmed by Rietveld refinement against synchrotron powder X-ray diffraction data, which suggests that there is also trapped water in the cavities, explaining a significant excess of H found in this material. The presence of water is very soundly confirmed by Fourier-transform infrared experiments, which also show that this water cannot leave the zeolite even after heating at 180 °C under vacuum. Molecular simulations allow us to conclude that this is due to the blockage of the 10 and 8MR windows by the occluded organics. The peculiar situation of an organic structure-directing agent spanning three cavities has important implications for the structure-direction concept that are briefly discussed. Several chiral derivatives of this dication have also been studied, and their possibility to enantioselectively direct the crystallization of STW has been analyzed., This article is part of projects PID2019-105479RB-I00 and PID2019-107968RB-I00 funded by MCIN/AEI/10.13039/501100011033, Spain. S.R.G.B. was supported by grant FJC2018-035697-I funded by MCIN/AEI/10.13039/501100011033. Centro Técnico Informático-CSIC, Trueno, and CESGA (Supercomputing Center of Galicia) cluster facilities are acknowledged for running the calculations. OpenAccess funding is provided by CSIC.
- Published
- 2022
20. A 3D extra-large-pore zeolite enabled by 1D-to-3D topotactic condensation of a chain silicate.
- Author
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Jian Li, Zihao Rei Gao, Qing-Fang Lin, Chenxu Liu, Fangxin Gao, Cong Lin, Siyao Zhang, Hua Deng, Mayoral, Alvaro, Wei Fan, Song Luo, Xiaobo Chen, Hong He, Camblor, Miguel A., Fei-Jian Chen, and Jihong Yu
- Subjects
- *
ZEOLITES , *ION exchange resins , *METAL-organic frameworks , *MOLECULES , *VOLATILE organic compounds - Abstract
Zeolites are microporous silicates with a large variety of applications as catalysts, adsorbents, and cation exchangers. Stable silica-based zeolites with increased porosity are in demand to allow adsorption and processing of large molecules but challenge our synthetic ability. We report a new, highly stable pure silica zeolite called ZEO-3, which has a multidimensional, interconnected system of extra-large pores open through windows made by 16 and 14 silicate tetrahedra, the least dense polymorph of silica known so far. This zeolite was formed by an unprecedented one-dimensional to three-dimensional (1D-to-3D) topotactic condensation of a chain silicate. With a specific surface area of more than 1000 square meters per gram, ZEO-3 showed a high performance for volatile organic compound abatement and recovery compared with other zeolites and metal-organic frameworks. [ABSTRACT FROM AUTHOR]
- Published
- 2023
- Full Text
- View/download PDF
21. Synthesis of 3D Large-Pore Germanosilicate Zeolites Using Imidazolium-Based Long Dications
- Author
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Luis Gómez-Hortigüela, Miguel A. Camblor, Peng Lu, Alvaro Mayoral, Yaping Zhang, Ministerio de Economía y Competitividad (España), National Natural Science Foundation of China, Gómez-Hortigüela Sainz, Luis [0000-0002-4960-8709], Camblor, Miguel Ángel [0000-0001-9591-3432], Gómez-Hortigüela Sainz, Luis, and Camblor, Miguel Ángel
- Subjects
Germanosilicate ,Materials science ,Intergrowth ,Scanning electron microscope ,General Chemical Engineering ,02 engineering and technology ,Fluoride medium ,010402 general chemistry ,01 natural sciences ,law.invention ,Crystal ,law ,Scanning transmission electron microscopy ,Materials Chemistry ,Calcination ,Crystallization ,High-resolution transmission electron microscopy ,Zeolite ,Alkyl ,chemistry.chemical_classification ,General Chemistry ,Imidazolium-based dications ,021001 nanoscience & nanotechnology ,0104 chemical sciences ,Crystallography ,Zeolite beta polymorphs ,Structure-directing agents ,chemistry ,Zeolites ,0210 nano-technology - Abstract
[EN] Introduction of small molar fractions of Ge in a synthesis system otherwise yielding the monodimensional large-pore zeolite MTW produced three 3D large-pore materials as the Ge fraction increased: *BEA, HPM-8, and HPM-7. HPM-8 is a zeolite consisting of an intergrowth of polymorphs D and E of the zeolite Beta family with a large predominance (>80%) of polymorph D, according to DIFFaX simulations and high-resolution scanning transmission electron microscopy analysis. After calcination, HPM-8 becomes remarkably stable upon contact with ambient air. HPM-7 likely possesses the POS topology, which is related to polymorph C. The density of double 4-ring (D4R) units in the crystallized materials increases from *BEA to HPM-8 to HPM-7, that is, as the Ge fraction increases. Interestingly, molecular mechanics show that in both HPM-7 and HPM-8, the organic dications prefer to site with their imidazolium rings in close contact with the D4R units as a consequence of a stronger confinement in this position. Indeed, the structure-directing role of these long dications can be explained as a consequence of the appropriate distance match between adjacent D4R units in both zeolite frameworks (and hence the negative charges associated with the occluded fluoride) and the imidazolium rings of these organic dications (and hence the positive charges), which is dictated by the length of the alkyl spacers, thus driving the crystallization pathway toward these particular germanosilicate zeolites., Ministry of Science, Innovation and Universities (projects MAT2016-77496-R and MAT2015-71117-R) and the National Natural Science Foundation of China (NSFC-21850410448, NSFC- 21835002). P.L. is grateful to the China Scholarship Council (CSC) for a fellowship and to the Dalian Institute of Chemical Physics for permission to leave. A.M. and Y.Z. acknowledge The Centre for High-resolution Electron Microscopy (CℏEM), supported by SPST of ShanghaiTech University under contract No. EM02161943. The authors are also indebted to L.A. Villaescusa (Valencia) for helpful comments and suggestions. Centro Técnico Informático-CSIC is acknowledged for running the calculations, and Biovia for providing the computational software.
- Published
- 2019
22. Sandwich-type zeolite intergrowths with MFI and the novel extra-large pore IDM-1 as ordered end-members
- Author
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Luis A. Villaescusa, Jian Li, Alvaro Mayoral, Zihao Rei Gao, Miguel A. Camblor, Ministerio de Ciencia, Innovación y Universidades (España), Ministerio de Economía y Competitividad (España), Swedish Research Council, Knut and Alice Wallenberg Foundation, Generalitat Valenciana, Gobierno de Aragón, National Natural Science Foundation of China, ShanghaiTech University, Agencia Estatal de Investigación (España), European Commission, Diputación General de Aragón, Mayoral, Álvaro [0000-0002-5229-2717], Camblor, Miguel Ángel [0000-0001-9591-3432], Mayoral, Álvaro, and Camblor, Miguel Ángel
- Subjects
General Chemical Engineering ,Mixtures ,Materials Chemistry ,Zeolites ,General Chemistry ,Layers ,Diffraction ,Materials - Abstract
Stacking faults are two-dimensional planar defects frequently arising in zeolites, modifying their properties and potentially affecting their performance in catalysis and separation applications. In classical zeolite intergrowths, a topologically unique zeolite layer may often pile up after some spatial transformation (lateral translation, rotation, and/or reflection) that may occur in different amounts or directions with about similar probabilities, leading to a difficult to control disorder. Here, we present a new kind of zeolite intergrowth that requires an additional topologically distinct layer rather than a spatial transformation of a unique one. Stacking of the so-called pentasil layers produces the well-known medium pore zeolite MFI. Intercalation in strict alternation of a topologically distinct second layer sandwiched between pentasil layers expands the structure to produce the new extra-large pore IDM-1. Stacking disorder modulates the structural expansion along the stacking direction. The disordered materials have been studied by simulation of the X-ray diffraction patterns using the program DIFFaX and by Cs-corrected highresolution electron microscopy. We show that disorder does not occur at random but in extended domains and can be controlled all the way from MFI to IDM-1 by just varying the concentration of the synthesis mixture., The authors thank funding from the Spanish Ministry of Science, Innovation and Universities, under Projects MAT2015-71117-R (MINECO/FEDER, UE), PID2019-105479RB-I00 and RTI2018-101599-B-C22 (MCUI/AEI/FEDER, UE), the Swedish Research Council (VR), and the Knut and Alice Wallenberg Foundation (KAW). L.A.V. also thanks the Generalitat Valenciana (project PROMETEO/2018/024). A.M. acknowledges the Spanish Ministry of Science (RYC2018-024561-I) and the Regional government of Aragon (DGA E13_20R), the National Natural Science Foundation of China (NFSC-21850410448 and NSFC-21835002), and the Centre for High-resolution Electron Microscopy (CℏEM), supported by SPST of ShanghaiTech University under contract No. EM02161943.
- Published
- 2021
23. HPM-14, a New Germanosilicate Zeolite with Interconnected Extra-Large Pores Plus Odd-Membered and Small Pores
- Author
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Cong Lin, Junliang Sun, Alvaro Mayoral, Miguel A. Camblor, Zihao Rei Gao, Jian Li, Ministerio de Economía y Competitividad (España), Ministerio de Ciencia, Innovación y Universidades (España), National Natural Science Foundation of China, Swedish Research Council, Knut and Alice Wallenberg Foundation, ShanghaiTech University, Gao, Zihao Rei [0000-0003-0331-3515], Camblor, Miguel Ángel [0000-0001-9591-3432], Gao, Zihao Rei, and Camblor, Miguel Ángel
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010405 organic chemistry ,Three-dimensional electron diffraction ,Foundation (engineering) ,Library science ,General Chemistry ,Stacking faults ,010402 general chemistry ,01 natural sciences ,Catalysis ,Extra-large pores ,0104 chemical sciences ,Structure solution ,Research council ,Political science ,Zeolites ,Christian ministry - Abstract
HPM-14 is a new extra-large pore zeolite synthesized using imidazolium-based organic structuredirecting agents, fluoride anions and germanium and silicon as tetrahedral components of the framework. Due to the presence of stacking disorder, the structure elucidation of HPM-14 was challenging, and different techniques were necessary to clarify the details of the structure and to understand the nature of the disorder. The structure has been solved by three-dimensional electron diffraction technique (3D ED) and consists of an intergrowth of two polymorphs possessing a three-dimensional channel system, including an extra-large pore opened through windows made up of sixteen tetrahedral atoms (16-membered ring, 16MR) as well as two additional sets of oddmembered (9MR) and small (8MR) pores. The intergrowth has been studied by scanning transmission electron microscopy (Cs-STEM) and powder X-ray diffraction simulations (DIFFaX), which show a large predominance of the monoclinic polymorph A., The authors acknowledge financial support by the Spanish Ministry of Science, Innovation and Universities (MAT2015-71117-R and PID2019-105479RB-I00 projects, AEI, Spain and FEDER, EU), the National Natural Science Foundation of China (No. 21871009, 21621061, 21527803, 21471009, NFSC-21850410448, NSFC- 21835002), the Swedish Research Council (VR) and the Knut and Alice Wallenberg Foundation (KAW), and the Centre for High-resolution Electron Microscopy (ChEM), supported by SPST of ShanghaiTech University under contract No. EM02161943. A.M. also acknowledges funding by the Spanish Ministry of Science, Innovation and Universities through the Ramon y Cajal Program (RYC2018-024561-I).
- Published
- 2020
24. Structure–direction towards the new large pore zeolite NUD-3
- Author
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Jian Li, Cong Lin, Fei-Jian Chen, Miguel A. Camblor, Zihao Rei Gao, Carlos Márquez-Álvarez, Hong-Bin Du, Le Xu, Junliang Sun, Luis Gómez-Hortigüela, Ministerio de Economía y Competitividad (España), Ministerio de Ciencia, Innovación y Universidades (España), National Natural Science Foundation of China, Swedish Research Council, Knut and Alice Wallenberg Foundation, Consejo Superior de Investigaciones Científicas (España), Chen, Fei-Jian [0000-0001-9345-9459], Gao, Zihao Rei [0000-0003-0331-3515], Li, Jian [0000-0003-2221-2285], Gómez-Hortigüela Sainz, Luis [0000-0002-4960-8709], Lin, Cong [0000-0003-0021-5055], Xu, Le [0000-0002-9727-7713], Du, Hong-Bin [0000-0002-5293-2323], Márquez Álvarez, Carlos [0000-0003-2749-4269], Sun, Junliang [0000-0003-4074-0962], Camblor, Miguel Ángel [0000-0001-9591-3432], Chen, Fei-Jian, Gao, Zihao Rei, Li, Jian, Gómez-Hortigüela Sainz, Luis, Lin, Cong, Xu, Le, Du, Hong-Bin, Márquez Álvarez, Carlos, Sun, Junliang, and Camblor, Miguel Ángel
- Subjects
Materials science ,Metals and Alloys ,Structure directing agents (SDAs) ,zeolites ,General Chemistry ,Ring (chemistry) ,Catalysis ,Surfaces, Coatings and Films ,Electronic, Optical and Magnetic Materials ,Large pore ,Dication ,chemistry.chemical_compound ,Crystallography ,chemistry ,Materials Chemistry ,Ceramics and Composites ,NUD-3 ,Methylene ,Zeolite - Abstract
[EN] The new zeolite NUD-3 possesses a three-dimensional system of large pore channels that is topologically identical to those of ITQ-21 and PKU- 14. However, the three zeolites have distinctly different frameworks: a particular single 4-membered ring inside the denser portion of the zeolite is missing in PKU-14, disordered in ITQ-21 and fully ordered in NUD-3. We document these differences and use molecular simulations to unravel the mechanismbywhich a particular structure directing agent dication, 1,10-(1,2-phenylenebis(methylene))bis(3-methylimidazolium), is able to orient this inner ring., Spanish Ministry of Science Innovation and Universities (MAT2015-71117-R, PID2019-105479RB-I00 and PID2019-107968RB-I00 projects, AEI, Spain and FEDER, EU), the National Natural Science Foundation of China (No. 22071099, 21673115, 21527803, 21871009, and 21601004), top talent cultivation program of Anhui Educational Committee (gxgwfx2018051), and the Swedish Research Council (VR) and the Knut and Alice Wallenberg Foundation (KAW). Synchrotron experiments were performed at beamline BL04 (MSPD) at ALBA Synchrotron with the collaboration of ALBA staff, and special thanks are given to A. Manjo´n for support in collecting the data and for helpful comments and suggestions. Z. R. G. specially thanks Yingxia Wang of Peking University for her kind suggestions and help with this paper. Centro Te´cnico Informa´tico- CSIC is acknowledged for running the calculations, and BIOVIA for providing the computational software. We acknowledge support of the publication fee by the CSIC Open Access Publication Support Initiative through its Unit of Information Resources for Research (URICI).
- Published
- 2020
25. A stable aluminosilicate zeolite with intersecting three-dimensional extra-large pores.
- Author
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Lin, Qing-Fang, Gao, Zihao Rei, Lin, Cong, Zhang, Siyao, Chen, Junfeng, Li, Zhiqiang, Liu, Xiaolong, Fan, Wei, Li, Jian, Chen, Xiaobo, Camblor, Miguel A., and Chen, Fei-Jian
- Subjects
- *
ALUMINUM silicates , *ZEOLITES , *CATALYSTS , *POROUS materials , *HOLES - Abstract
Zeolites are crystalline porous materials with important industrial applications, including uses in catalytic and adsorption-separation processes. Access into and out of their inner confined space, where adsorption and reactions occur, is limited by their pore apertures. Stable multidimensional zeolites with larger pores able to process larger molecules are in demand in the fine chemical industry and for the oil processing on which the world still relies for fuels. Currently known extra-large-pore zeolites display poor stability and/or lack pore multidimensionality, limiting their usefulness. We report ZEO-1, a robust, fully connected aluminosilicate zeolite with mutually intersecting three-dimensional extra-large plus three-dimensional large pores. ZEO-1 is stable up to 1000°C, has an extraordinary specific surface area (1000 square meters per gram), and shows potential as a catalytic cracking catalyst. [ABSTRACT FROM AUTHOR]
- Published
- 2021
- Full Text
- View/download PDF
26. Synthesis of Pure Silica MWW Zeolite in Fluoride Medium by Using an Imidazolium-Based Long Dication
- Author
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Peng Lu, Miguel A. Camblor, Luis Gómez-Hortigüela, Ministerio de Economía y Competitividad (España), Camblor, Miguel Ángel [0000-0001-9591-3432], Gómez-Hortigüela Sainz, Luis [0000-0002-4960-8709], Camblor, Miguel Ángel, and Gómez-Hortigüela Sainz, Luis
- Subjects
DFT calculation ,MWW zeolite ,010402 general chemistry ,Ring (chemistry) ,01 natural sciences ,Catalysis ,chemistry.chemical_compound ,Molecular mechanics ,Structure directing agent ,Methylene ,Zeolite ,Porosity ,010405 organic chemistry ,Chemistry ,Organic Chemistry ,Resonance ,Pore system ,General Chemistry ,0104 chemical sciences ,Dication ,Crystallography ,Density functional calculations ,Fluoride media ,Zeolites ,Fluoride ,Structure-direction ,Zeolite synthesis - Abstract
[EN] As the spacer length in 1,2-dimethylimidazolium-based dications increases beyond a specific point (six methylene units), they fail in structure-directing towards STW zeolites in any synthetic conditions. These dications can instead produce, under fluoride concentrated conditions, either *BEA [in the case of the eight-methylene-unit structure-directing agent (SDA)] or MWW (ten methylene units) zeolites. For any length of the dication, the default zeolite (MTW) is a relatively dense zeolite containing a unidimensional channel, whereas the zeolite demanding most specificity (STW, *BEA or MWW) is more porous, affording a larger concentration of the dication to be occluded. This work provides the first reported fluoride synthesis of pure silica MWW zeolites. Charge balance of the organic dications in this zeolite was achieved by combining “structural” silanolates, regular “connectivity defects” and occluded fluoride. Molecular mechanics calculations showed a perfect fit of the decamethylenebis(dimethylimidazolium) dication in the sinusoidal intralayer pore system of MWW. The calculations showed also that the dication is able to stabilize the interlayer space without disturbing the hydrogen-bonding system that holds the layers together in the as-made material. The F magic-angle spinning (MAS) NMR presented two distinct resonances at −71 and −83 ppm, which, on the basis of DFT calculations, we tentatively assigned to fluoride occluded in [46] and [456] cages of the MWW structure, respectively. The same DFT study determines a different chemical shift of one methyl C nuclear magnetic resonance according to the imidazolium ring residing in the sinusoidal channels or in the large cup cavities, thus explaining an experimentally observed splitting of that resonance., Financial support provided by the Spanish Ministry of Economy and Competitiveness (projects MAT2015-71117-R and MAT2016-77496-R) is acknowledged. P. L. is grateful to the China Scholarship Council (CSC) for a fellowship and to the Dalian Institute of Chemical Physics for permission to leave. Centro Técnico Informático-CSIC is acknowledged for running the calculations, and Biovia is acknowledged for providing the computational software.
- Published
- 2019
27. Synthesis of pure silica MFI zeolites using imidazolium-based long dications. A comparative study of structure-directing effects derived from a further spacer length increase
- Author
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Luis Gómez-Hortigüela, Peng Lu, Miguel A. Camblor, Ministerio de Economía y Competitividad (España), Gómez-Hortigüela Sainz, Luis [0000-0002-4960-8709], Camblor, Miguel Ángel [0000-0001-9591-3432], Gómez-Hortigüela Sainz, Luis, and Camblor, Miguel Ángel
- Subjects
Materials science ,Chemical shift ,02 engineering and technology ,Fluorine-19 NMR ,010402 general chemistry ,021001 nanoscience & nanotechnology ,Ring (chemistry) ,01 natural sciences ,0104 chemical sciences ,Dilution ,Inorganic Chemistry ,Crystallography ,Zeolites ,Ton ,0210 nano-technology ,Zeolite - Abstract
[EN] Length-dependent structure direction of linear methylimidazolium-based dications towards MFI zeolite, previously known only for the tetramethylene spacer, has also been found for octamethylene and decamethylene spacers. This works only under highly concentrated conditions, whereas dilution always tends to favor TON, a default structure that is the only zeolite obtained with the other reported dications (with tri-, penta-, and hexamethylene spacers). The locations and conformations of the dications have been studied by molecular mechanics simulations. As longer dications introduce lower density of positive charges in the zeolite, the density of connectivity defects also decreases. Finally, these long dications cannot easily place each charged imidazolium ring in the two possible orientations (either parallel or perpendicular to 4MR close to F sites) found for the tetramethylene case. Hence, although the three MFI materials display two F NMR resonances at similar chemical shifts, their relative intensities strongly vary as a function of the spacer length., Financial support provided by the Spanish Ministry of Economy and Competitiveness (projects MAT2015-71117-R and MAT2016-77496-R) is acknowledged. P. L. is grateful to the China Scholarship Council (CSC) for a fellowship and to the Dalian Institute of Chemical Physics for permission to leave. Centro Técnico Informático-CSIC is acknowledged for running the calculations, and Biovia is acknowledged for providing the computational software.
- Published
- 2018
28. The Si-Ge substitutional series in the chiral STW Zeolite Structure Type
- Author
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Said Hamad, Reus Tiago Rigo, Salvador R. G. Balestra, Miguel A. Camblor, Sofia Calero, Ángel Rabdel Ruíz-Salvador, Rocio Bueno-Perez, Ministerio de Economía y Competitividad (España), Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (Brasil), Camblor, Miguel Angel, and Camblor, Miguel Angel [0000-0001-9591-3432]
- Subjects
Range (particle radiation) ,Condensed Matter - Materials Science ,Yield (engineering) ,Materials science ,Renewable Energy, Sustainability and the Environment ,Inverse ,Materials Science (cond-mat.mtrl-sci) ,FOS: Physical sciences ,02 engineering and technology ,General Chemistry ,010402 general chemistry ,021001 nanoscience & nanotechnology ,Kinetic energy ,01 natural sciences ,Molecular physics ,0104 chemical sciences ,Chiral ,Metastability ,Zeolites ,General Materials Science ,Density functional theory ,Resilience (materials science) ,0210 nano-technology ,Zeolite ,Isomorphous substitution - Abstract
The whole compositional range (Gef = Ge/(Ge+Si)= 0 to 1) of zeolite STW has been synthesized and studied by a comprehensive combined experimental--theoretical approach. The yield of zeolite goes through a maximum and then drops at the GeO2 side of the series, following the inverse of the calculated free energy curve. The unit cell generally expands, roughly linearly, as the Gef increases, but a notable resilience to expansion is observed at the high silica side. This can be attributed to the more rigid character of SiO2 and the ability of Ge units to deform. Density functional theory calculations provide a new assignment of the previously controversial 19F MAS NMR resonances for occluded fluoride, which is based not only in the number of Ge atoms in the double-4-ring units but also on the way they are associated (namely, no Ge, isolated Ge, Ge pairs or closed Ge clusters). While we found an overall good agreement between the experimental and theoretical trends in preferential occupation by Ge of different crystallographic sites, the theoretical models show more sharp and abrupt tendencies, likely due both to limitations of the approach and to kinetic factors that allow metastable configurations to actually exist., The authors thank the Spanish Ministry of Science and Competitiveness for funding (Projects MAT2015-71117-R and CTP2016-80206-P). R. T. Rigo thanks CAPES (Brazil) for a PhD fellowship (process 99999.012012/2013-00). S. R. G. Balestra thanks the Spanish State Secretariat for Research, Development and Innovation for his Predoctoral fellowship (BES-2014-067825 from CTQ2013-48396-P).
- Published
- 2018
- Full Text
- View/download PDF
29. Stepped Propane Adsorption in Pure-Silica ITW Zeolite.
- Author
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Jung Gi Min, Luna-Triguero, Azahara, Youngchul Byun, Balestra, Salvador R. G., Vicent-Luna, Jose Manuel, Calero, Sofia, Suk Bong Hong, and Camblor, Miguel A.
- Subjects
- *
GAS absorption & adsorption , *PROPANE , *ZEOLITES , *TEMPERATURE effect , *CATALYSTS - Abstract
Gas adsorption over zeolites is at the basis of important applications of this class of microporous crystalline solids, notably as separation media and catalysts, but it may also be complex and not straightforward to understand. Here we report that for temperature below 323 K propane adsorption on the small-pore pure-silica zeolite ITW exhibits a clear step (pseudosaturation). This is absent in the case of propene and the other small linear alkanes. An intermediate plateau, clearly observed in the 293 K isotherm, always occurs when one molecule of propane is loaded in every other cage, i.e., at half-saturation. The simulation results show a swelling of the ITW structure upon propane adsorption. The strong dependence of available pore volume on the adsorbate loading level implies that adsorption cannot occur on the void structure while saturation can only be reached on highly loaded structures. To account for this unprecedented adsorption phenomenon, we propose the term "guest-modulated effect". [ABSTRACT FROM AUTHOR]
- Published
- 2018
- Full Text
- View/download PDF
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