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Abstract: Previous investigations have shown that an all-silica BEA-type (Si-BEA) material is difficult to be nucleated in basic media and that the fluorosilicic precursors formed in near neutral media play an important role in its formation. The present study reports on the synthesis of this microporous material under basic conditions by using TEA2SiF6 as an additional silica source that provides preformed fluorosilicate species. The effect of the amount of TEA2SiF6 on the purity of the final product, crystallization kinetics and morphological features of Si-BEA were systematically studied. The investigation showed that above a certain concentration corresponding to TEA2SiF6/SiO2 =0.07 pure Si-BEA was obtained and further increase in the concentration improved substantially the crystallization kinetics. The increase in TEA2SiF6 content led also to a gradual increase of the size of the pyramidal (h 0l) face coupled with the decrease of pinacoidal (001) one. Thus, the morphology of the zeolite crystals can be varied from well developed truncated bipyramids to plate-like crystals with dominating pinacoidal faces. A consequence of this morphological changes is the number the pore openings of the channel systems running along the a- and c-axes per total external surface. The framework defectness and water content in the synthesized materials were studied by 29Si NMR spectroscopy and TG analysis, respectively. This combined study revealed that materials with a high level of hydrophobicity, due to the specific effect of fluorine anions, have been synthesized under basic conditions. [Copyright &y& Elsevier]

This feature article highlights recent developments in nanosized zeolites and addresses the question: what will be next? Until recently the limiting step to practical applications was determined by the challenging synthesis of nanosized zeolites in high yield and adequate form. The advances in the synthesis of nanozeolites that provide the basis for future developments and for diverse practical applications are reviewed. The main trends and challenges in processing, characterization and applications of nanosized zeolites are summarized. Particular attention is paid to the processing of nanosized zeolites in terms of their further use. The extending applications of nanosized zeolites in nanotechnology, medicine, pharmaceutical, and food industry, are discussed. [ABSTRACT FROM AUTHOR]

Abstract: Core–shell zeolite composites possessing a mordenite core and a shell of intergrown silicalite-1 crystals were synthesized. A classical hydrothermal treatment of mordenite crystals with a silicalite-1 precursor mixture did not result in the formation of an extended silicalite-1 layer on the mordenite surface. The incompatibility between the core crystals and the shell precursor was circumvented by adsorption of nanoseeds on the core surface, which upon a subsequent hydrothermal treatment induced the formation of a well intergrown shell. The kinetics of shell growth was studied at 150 and 200°C and the optimum conditions further used for the preparation of composites subjected to XRD, SEM, TG/DTA, EDS and X-ray fluorescence analyses. The integrity of the shell layer was tested by N2 adsorption measurements on materials comprising Na- and Na,H-mordenite and a non-calcined tetrapropylammonium (TPA)-containing shell, the latter being non-permeable for the N2 molecules. These measurements showed that 96–98% of the mordenite crystals were covered with a defect-free TPA-silicalite-1 shell after a single hydrothermal treatment. A characteristic feature of the obtained composites is the relatively large single crystal core and the very thin polycrystalline shell. Thus, the relatively large active part of the composite is covered by a tiny shell that ensures fast kinetics. [Copyright &y& Elsevier]