Synthesis of zeolite beta Part 2.—Formation of zeolite beta and titanium-beta via an intermediate layer structure

Lohse, U.; Altrichter, B.; Fricke, R.; Pilz, W.; Schreier, E.; Garkisch, Ch.; Jancke, K.

doi:10.1039/a603690b

Cited by 16 publications

(8 citation statements)

References 9 publications

(4 reference statements)

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“…The X-ray powder pattern of the TEA aluminosilicate is also characteristic of a layered structure with a very strong basal reflection at 2θ = 5.4° (Figure ). The resolution of the pattern is high compared to that previously reported by Lohse et al, particularly in the region corresponding to 2θ values between 15° and 40°. However, the similarity between the two diffractograms indicates that we have prepared the same material.…”

Section: Resultsmentioning

confidence: 53%

“…In some cases, lamellar compounds are formed prior to the crystallization of a three-dimensional network and have been regarded as precursors of three-dimensional microporous frameworks. − During the crystallization of zeolite beta with tetraethylammonium (TEA + ) cations, Lohse et al observed that a crystalline layered material was obtained at short synthesis times, while prolonging the crystallization period led to the formation of pure zeolite beta. From these observations, the authors concluded that zeolite beta is formed via a layered aluminosilicate, by direct transformation of the latter to a three-dimensional framework.…”

Section: Introductionmentioning

confidence: 99%

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Layered Intermediates in Zeolite Synthesis: Are Structures Related?

Tuel

1999

Chem. Mater.

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Layered organic-inorganic compounds have been found during the crystallization of zeolites ZSM-48 and beta with hexamethonium and tetraethylammonium cations, respectively. These materials are obtained from gels with relatively high concentrations in organic species but are not stable under hydrothermal conditions. While highly crystalline solids are formed after short synthesis periods, their structure gradually collapses with synthesis time until a completely amorphous compound is formed. The stability of these materials can be increased by lowering the synthesis temperature, but zeolites start to crystallize only after the complete degradation of the layered structures. Even though the synthesis conditions, the gel compositions, and the structure of the final zeolite are different, the two layered materials seem to possess very similar structures, the main difference resulting from the nature of the interlayer organic molecules. These intermediate compounds display interesting intercalation properties toward long alkylammonium cations. Silica layers can be swollen at low temperature without any modification of their crystallinity. Spectroscopic characterization of the materials as well as their evolution over the whole crystallization period tends to indicate that zeolites are not formed via layered intermediates, as was previously claimed. Actually, these solids only provide the synthesis medium with silicate and aluminosilicate species necessary for the crystallization of the zeolite, whose structure is directed by the organic species present in the solution.

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Section: Resultsmentioning

confidence: 53%

Section: Introductionmentioning

confidence: 99%

Layered Intermediates in Zeolite Synthesis: Are Structures Related?

Tuel

1999

Chem. Mater.

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“…On the other hand, Beta360 was already in acid form. The improvement in adsorption, hence, can be due to the increase of acidity of hydrophobic BEAs caused by surface and structural modifications induced by mild thermal treatments in humid air as described, for instance, in . In particular, the results showed in suggest that at 550°C in humid air the number of silanol present on the zeolite surface increases.…”

Section: Resultsmentioning

confidence: 89%

Factors affecting drug adsorption on beta zeolites

et al. 2013

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The adsorption behaviour of three commonly used drugs, namely ketoprofen, hydrochlorothiazide and atenolol, from diluted aqueous solutions on beta zeolites with different SiO2/Al2O3 ratio (i.e. 25, 38 and 360) was investigated by changing the ionic strength and the pH, before and after thermal treatment of the adsorbents. The selective adsorption of drugs was confirmed by thermogravimetry and X-ray diffraction. The adsorption capacity of beta zeolites was strongly dependent on both the solution pH and the alumina content of the adsorbent. Such a remarkable difference was interpreted as a function of the interactions between drug molecules and zeolite surface functional groups. Atenolol was readily adsorbed on the less hydrophobic zeolite, under pH conditions in which electrostatic interactions were predominant. On the other hand, ketoprofen adsorption was mainly driven by hydrophobic interactions. For undissociated molecules the adsorption capability increased with the increase of hydrophobicity.

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“…Hypothetically, the two-dimensional layer structure could then transform directly to the three-dimensional structure via further condensation of the gallophosphate sheets. Such a transformation of two-dimensional layered structures to three-dimensional open-framework structures has been observed to occur during the synthesis of zeolite β, and a direct solid-state transformation of a one-dimensional chain aluminophosphate to a two-dimensional layered aluminophosphate structure has been observed . Such a possibility seems especially likely given the many structural relationships between the members of the ULM- n family. , ULM-3, -4, -5, -8, and -16 are all constructed from the same basic hexameric units, constructed from three PO 4 tetrahedra, two GaO 4 F trigonal bipyramids, and one GaO 4 F 2 octahedron connected via corner-sharing oxygen atoms.…”

Section: Resultsmentioning

confidence: 97%

Time-Resolved In-Situ Energy and Angular Dispersive X-ray Diffraction Studies of the Formation of the Microporous Gallophosphate ULM-5 under Hydrothermal Conditions

et al. 1999

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The hydrothermal synthesis of the large-pore oxy-fluorinated gallophosphate ULM-5 has been followed in situ using time-resolved energy dispersive and angular dispersive X-ray diffraction. A variety of synthetic parameters such as temperature, reagent stoichiometry, source materials, and pH have been studied, and their effect on the crystallization determined. The nature of the phosphorus source used, either orthophosphoric acid or phosphorus pentoxide, is found to have a profound influence on the reaction pathway. Using orthophosphoric acid, ULM-5 is found to form very rapidly following a short induction period. A kinetic analysis of the crystallization of ULM-5 using orthophosphoric acid under isothermal hydrothermal conditions has been performed. Comparison of the experimentally determined extent of reaction (α) versus time data with those predicted by various theoretical models indicates that over a wide range of temperatures and pH the crystallization can be modeled by a three-dimensional diffusion-controlled process. This process occurs at a rate essentially independent of temperature and pH. In contrast, using phosphorus pentoxide, the formation of ULM-5 is found to proceed via the formation of either of two distinct crystalline intermediate phases, which subsequently react to form the ULM-5 final product at a rate which is strongly dependent on temperature. The relative quantities of each intermediate phase formed depend critically on the precise reagent stoichiometry used. Conditions have been identified in which ULM-5 can be formed exclusively via either intermediate phase. The mechanism of transformation of intermediate to product phases appears to be either a direct solid−solid transformation, or via the dissolution or amorphorization of only a small quantity of material at the surface of the intermediate crystallites.

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Synthesis of zeolite beta Part 2.—Formation of zeolite beta and titanium-beta via an intermediate layer structure

Cited by 16 publications

References 9 publications

Layered Intermediates in Zeolite Synthesis: Are Structures Related?

Layered Intermediates in Zeolite Synthesis: Are Structures Related?

Factors affecting drug adsorption on beta zeolites

Time-Resolved In-Situ Energy and Angular Dispersive X-ray Diffraction Studies of the Formation of the Microporous Gallophosphate ULM-5 under Hydrothermal Conditions

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