Location of Ge and extra-framework species in the zeolite ITQ-24

Pinar, Ana B.; McCusker, Lynne B.; Baerlocher, Christian; Schmidt, Joel E.; Hwang, Son‐Jong; Davis, Mark E.; Zones, Stacey I.

doi:10.1039/c4dt03831b

Cited by 15 publications

(7 citation statements)

References 34 publications

(59 reference statements)

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“…As a typical IWR structure, ITQ-24 zeolite discovered by Corma et al, was first synthesized in the presence of germanium species using hexamethonium as an organic template . Because of its unique three-dimensional 12 × 10 × 10-membered ring pore structure (aperture size of 5.8 × 6.8, 4.6 × 5.3, and 4.6 × 5.3 Å), it has attracted much attention recently. , − However, when a large amount of germanium species exist in the IWR framework, its thermal and hydrothermal stabilities are remarkably reduced. In addition, the use of germanium species in the synthesis is costly, which strongly hinders the applications of IWR zeolite in industrial chemical processes. , To solve this problem, alternatively Ge-free synthesis routes were developed for synthesis of IWR zeolite by introduction of boron species instead of germanium.…”

Section: Introductionmentioning

confidence: 99%

Direct Synthesis of Aluminosilicate IWR Zeolite from a Strong Interaction between Zeolite Framework and Organic Template

et al. 2019

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A large amount of zeolite structures are still not synthetically available or not available in the form of aluminosilicate currently. Despite significant progress in the development of predictive concepts for zeolite synthesis, accessing some of these new materials is still challenging. One example is the IWR structure as well. Despite successful synthesis of Ge-based IWR zeolites, direct synthesis of aluminosilicate IWR zeolite is still not successful. In this report we show how a suitable organic structure directing agent (OSDA), through modeling of an OSDA/zeolite cage interaction, could access directly the aluminum-containing IWR structure (denoted as COE-6), which might allow access to new classes of materials and thus open opportunities in valuable chemical applications. The experimental results reveal that the COE-6 zeolites with a SiO2/Al2O3 ratio as low as 30 could be obtained. Very interestingly, the COE-6 zeolite has much higher hydrothermal and thermal stabilities than those of the conventional Ge–Al–IWR zeolite. In methanol-to-propylene (MTP) reaction, the COE-6 zeolite exhibits excellent selectivity for propylene, offering a potential catalyst for MTP reaction in the future.

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Section: Introductionmentioning

confidence: 99%

Direct Synthesis of Aluminosilicate IWR Zeolite from a Strong Interaction between Zeolite Framework and Organic Template

et al. 2019

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“…The main advantages of the use of fluoride media are that they lower the number of crystal defects after calcination, reduce the quantity of solvent needed in the synthesis gel, and increases the silica‐to‐alumina ratio (SAR) of the resultant products . Fluoride media also enable the introduction of germanium into the zeolitic framework, for example, in the syntheses of ITQ‐24 and ITQ‐37 . It is important to tailor properties such as acidity and basicity to introduce a variety of heteroatoms into zeolites, for example, to enable their use in catalysis, and these heteroatom‐containing zeolites have an increasing importance in industry …”

Section: Introductionmentioning

confidence: 99%

Organic Structure‐Directing Agents in SAPO Synthesis: The Case of 2‐Ethyl‐1,3,4‐trimethylimidazolium

Vinaches

Pergher

2017

Eur J Inorg Chem

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Structure direction is a key topic in zeolite synthesis. In this work, the organic cation 2‐ethyl‐1,3,4‐trimethylimidazolium was studied for the first time in the synthesis of SAPO zeolite. Concentrated gels and fluoride media were chosen for the synthesis. To understand the formation of the main products, CHA and LTA zeotypes, several statistical calculi were performed, and the results showed that the structure direction of the LTA zeotype was mainly caused by to the organic cation. For SAPO‐CHA, the temperature and a combination of dilution and synthesis time also influenced the formation. The CHA zeotype was studied thoroughly by other techniques such as thermogravimetry, high‐power decoupled (HPDEC) magic‐angle spinning (MAS) NMR spectroscopy, and nitrogen sorption. We calculated that this zeotype contains one cation per unit cell and observed that the fluoride medium also directs the structure. The silicon atoms in SAPO‐CHA are present in three states [SiO(4X), SiO(3X), and SiO(1X)], aluminium atoms were found in tetrahedral and octahedral coordination environments, and the phosphorus atoms also had tetrahedral geometries. Textural analysis confirmed the formation of a microporous material with a Brunauer–Emmett–Teller (BET) surface are of 510 m2 g–1 and an external surface of 110 m2 g–1.

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“…The existence of Q 3 groups in PKU-22 was also detected by the solid-state 29 Si MAS NMR, though the signals are broad and weak (Figure a) due to the low Si content and the influence of surrounding Ge atoms. The resonance peaks at −93.8 to −96.3 ppm were assigned to Q 3 units [(−TO) 3 Si–OH, T for Si or Ge], and broad peaks from −99.1 to −103.1 ppm can be attributed to Q 4 units [(−TO) 4 Si, T for Si or Ge]. , This assignment is confirmed by the 1 H– 29 Si CP MAS NMR spectrum (Figure b). The relative intensities of the peaks at −93.8 to −96.3 ppm are enhanced, implying they are related to silanol groups.…”

Section: Resultsmentioning

confidence: 54%

Synthesis and Characterization of a Layered Silicogermanate PKU-22 and Its Topotactic Condensation to a Three-Dimensional STI-type Zeolite

Chen

Huang

Wang

et al. 2017

Crystal Growth & Design

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A new layered silicogermanate, PKU-22, was hydrothermally synthesized under fluoride conditions using the tetraethylammonium (TEA+) cation as the structure directing agent (SDA). The crystal structure was determined by single crystal X-ray diffraction. Structure analysis reveals that PKU-22 is constructed by sti layers stacking along the [100] direction in an ···AAAA··· manner, with TEA+ cations occurring in the interlayer spaces and F– anions residing within the layer and connecting to Ge atoms, which also act as the charge compensation species. In situ temperature-variable powder X-ray diffraction results indicated that PKU-22 could be transferred into a three-dimensional STI-type zeolite PKU-22a on heating. It is interesting that the TEA+ cations remain intact in the structure of the condensed product. Solid-state NMR, inductively coupled plasma atomic emission spectroscopy, thermogravimetric-differential scanning calorimetry, and carbon, hydrogen, and nitrogen elemental analyses were applied to aid the structure analysis of PKU-22 and illustrate its transformation. The scheme of the topotactic condensation of PKU-22 to PKU-22a is proposed.

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Location of Ge and extra-framework species in the zeolite ITQ-24

Cited by 15 publications

References 34 publications

Direct Synthesis of Aluminosilicate IWR Zeolite from a Strong Interaction between Zeolite Framework and Organic Template

Direct Synthesis of Aluminosilicate IWR Zeolite from a Strong Interaction between Zeolite Framework and Organic Template

Organic Structure‐Directing Agents in SAPO Synthesis: The Case of 2‐Ethyl‐1,3,4‐trimethylimidazolium

Synthesis and Characterization of a Layered Silicogermanate PKU-22 and Its Topotactic Condensation to a Three-Dimensional STI-type Zeolite

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