Synthesis and characterization of chromium silicalite

Journal Article · Mon Feb 01 04:00:00 EST 1993 · Chemistry of Materials; (United States)

DOI:https://doi.org/10.1021/cm00026a004· OSTI ID:6720629

Mambrim, J S.T.; Pastore, H O; Davanzo, C U; Vichi, E J.S.; Nakamura, Ossamu; Vargas, H ^[1]

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1. Universidade Estadual de Campinas (Brazil)

Infrared spectroscopy (mid-IR), [sup 29]Si and [sup 27]Al magic angle spinning nuclear magnetic resonance (MAS-NMR), powder X-ray diffraction (PXRD), electron paramagnetic resonance (EPR), and photoacoustic spectroscopy (PAS), in combination, have produced useful information about a series of crystalline MFI-type chromium silicalite, synthesized in a fluoride medium. Aluminum is an impurity and occupies framework sites, as evaluated by the [sup 27]Al MAS-NMR. The mid-IR spectra are very similar to the zeolite ZSM-5 with the addition of a weak band at [congruent]680 cm[sup [minus]1], which the authors tentatively assign to symmetric stretching of (Cr-O-Si)[sub n] groups. The samples are crystalline materials and have expanded unit cells, as PXRD measurements pointed out. The as-synthesized sample shows a distribution of Cr sites, detected by EPR, comprising structure and channel occlusion sites; the nonstructural sites being extensively oxidized to Cr(VI) species after calcination in the presence of dioxygen. The changes in the photoacoustically measured physical properties, such as nonradiative relaxation time, the thermal diffusivity and optical absorption coefficient of both calcined and noncalcined chromium silicalite samples are also reported. 52 refs., 13 figs., 5 tabs.

• OSTI ID: 6720629
• Journal Information: Chemistry of Materials; (United States), Journal Name: Chemistry of Materials; (United States) Vol. 5:2; ISSN CMATEX; ISSN 0897-4756
• Country of Publication: United States
• Language: English

Related Subjects

36 MATERIALS SCIENCE
360202* -- Ceramics
Cermets
& Refractories-- Structure & Phase Studies
ABSORPTION SPECTROSCOPY
CALCINATION
CHEMICAL PREPARATION
CHEMICAL REACTIONS
CHROMIUM COMPOUNDS
COHERENT SCATTERING
DECOMPOSITION
DIFFRACTION
ELECTRON SPIN RESONANCE
ENERGY LEVELS
EXCITED STATES
INORGANIC ION EXCHANGERS
ION EXCHANGE MATERIALS
MAGNETIC RESONANCE
MATERIALS
MINERALS
NUCLEAR MAGNETIC RESONANCE
OXYGEN COMPOUNDS
PHOTOACOUSTIC SPECTROSCOPY
PYROLYSIS
RESONANCE
SCATTERING
SILICATE MINERALS
SILICON COMPOUNDS
SPECTROSCOPY
SYNTHESIS
THERMOCHEMICAL PROCESSES
TRANSITION ELEMENT COMPOUNDS
VIBRATIONAL STATES
X-RAY DIFFRACTION
ZEOLITES