Hydrothermal treatment of an aqueous solution containing tetramethoxysilane, boric acid and ethylenediamine (EN) led to the crystallization of B-MFI (BOR-C) together with small amounts of B-ferrierite. A single-crystal X-ray diffraction study was performed on two small prismatic crystals of BOR-C with the unit cell dimensions: a = 19:869, b = 19:661, c = 13:207A, V = 5159A3, and a = 19:875, b = 19:669, c = 13:218A, V = 5167A3 (space group Pnma) using a laboratory diffractometer equipped with a CCD detector and a synchrotron radiation source, respectively. In both cases the unit cell volume and the B/Si occupancy agree with about 15% substitution of B for Si in the framework T-sites, corresponding to 14 B/u.c. Three independent EN molecules were located, one (EN1) is located in the sinusoidal 10-ring channel parallel to the [100] direction, lying on the (010) plane, the other two (EN2 and EN3) in the straight 10-ring channel. The negative charge of the framework is counterbalanced by the EN molecules in the form of divalent cations.
B-containing molecular sieves crystallized in the presence of ethylenediamine. Part II: crystal structure of as-synthesized B-MFI.
ALBERTI, Alberto;ZANARDI, STEFANO
2003
Abstract
Hydrothermal treatment of an aqueous solution containing tetramethoxysilane, boric acid and ethylenediamine (EN) led to the crystallization of B-MFI (BOR-C) together with small amounts of B-ferrierite. A single-crystal X-ray diffraction study was performed on two small prismatic crystals of BOR-C with the unit cell dimensions: a = 19:869, b = 19:661, c = 13:207A, V = 5159A3, and a = 19:875, b = 19:669, c = 13:218A, V = 5167A3 (space group Pnma) using a laboratory diffractometer equipped with a CCD detector and a synchrotron radiation source, respectively. In both cases the unit cell volume and the B/Si occupancy agree with about 15% substitution of B for Si in the framework T-sites, corresponding to 14 B/u.c. Three independent EN molecules were located, one (EN1) is located in the sinusoidal 10-ring channel parallel to the [100] direction, lying on the (010) plane, the other two (EN2 and EN3) in the straight 10-ring channel. The negative charge of the framework is counterbalanced by the EN molecules in the form of divalent cations.I documenti in SFERA sono protetti da copyright e tutti i diritti sono riservati, salvo diversa indicazione.
