Synthesis of borosilicalite-1 with more than four boron per unit cell from fluoride containing media.

Autor: F. Testa, R. Chiappetta, F. Crea, R. Aiello, A. Fonseca, J. Bertrand, G. Demortier, J. Guth, L. Delmotte, J. Nagy
Zdroj: Journal of Porous Materials; Jun2007, Vol. 14 Issue 2, p191-204, 14p
Abstrakt: Abstract  More than four boron per unit cell has been introduced into the framework of silicalite-1, using fluorine containing media. The initial gels were of composition 9MF–xH3BO3–10SiO2–1.25TPABr–330 H2O with M = NH4, Na, K and Cs and x = 0.1–10. The syntheses were carried out in hydrothermal conditions at 170C. The amount of incorporated TPA+ ions remains quasi constant (3.5–3.8/u.c.) up to 4 B/u.c., while it decreases with increasing boron content. The amount of tetrahedral B/u.c. can be as high as 8 in presence of K+ or Cs+ ions in the as-synthesized samples. It is observed that the preferential countercations to framework negative charges related to the presence of tetrahedral boron, [SiOB]−, are TPA+, K+ and Cs+ ions. It is interpreted, that the −4.0 ppm versus BF3.OEt2 NMR line stems from tetrahedral framework boron, while the −2.9 ppm NMR line represents both extraframework and/or tetracoordinated deformed framework boron in the structure. [ABSTRACT FROM AUTHOR]
Databáze: Complementary Index
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