In situ observation of nucleation and crystal growth in zeolite synthesis. A small-angle x-ray scattering investigation on Si-TPA-MFI

Article Abstract:

Small-angle x-ray scattering techniques and electron microscopy are used in studying crystal growth during the hydrothermal synthesis of the zeolite Si-TPA-MFI. Zeolites are crystalline and microporous substances used as molecular sieves, catalysts and ion-exchange agents. Results indicated that crystal formation is accompanied by the consumption of primary units and their aggregates. It has been observed that the accumulation of 2.8-nm-sized primary units is an important step in the nucleation process.

Analysis, Growth, Crystals, Nucleation, Nucleation (Chemistry), Crystal growth

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Zincosilicate CIT-6: a precursor to a family of *BEA-type molecular sieves

Article Abstract:

Zincosiliate CIT-6 which possesses the *BEA-type structure is prepared in hydrothermal conditions in the presence of tetraethylammonium hydroxide, Li+ and Zn(super 2+). It is shown that as-made CIT-6 can be converted to a hydrophobic Si-CIT-6 with little defects. Al-containing CIT-6 with different water absorption vapor from zeolite beta can also be prepared by inserting Al into CIT-6 extracted at low temperature.

Silicates, Molecular sieves

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Si-MFI crystallization using a "dimer" and "trimer" of TPA studied with small-angle X-ray scattering

Article Abstract:

The formation of precursors in the crystallization of Si-MFI from clear solutions using as the structure-directing agent bis(tripropylammonium) hexamethylene dihydroxide and bis(tripropylammonium-N-N'-hexamethylene)-N",N"-dipropylammonium trihydroxide are investigated. The result confirms that a common mechanism is proposed for organic-mediated crystallization of high-silica zeolites.

Science & research, All Other Basic Inorganic Chemical Manufacturing, Industrial inorganic chemicals, not elsewhere classified, Zeolites, Silicon, Electric properties

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