Characterization of zeolite-cracking catalysts
- Univ. of British Columbia, Vancouver (Canada)
A method has been developed to characterize the NMR-invisible Al, which entails the complexing of non-framework Al with acetylacetone (acac) to form Al(acac){sub 3} complexes. These complexes yield {sup 27}Al-MAS-NMR spectra that can be used for more quantitative interpretation. This method can be applied to zeolites dealuminated by various techniques. In steamed faujasites different extra-framework Al and Si species are observed. The dealuminated samples are soaked in a 38% acac-methanol solution at room temperature under a flow of dry air. After one hour the ethanol and excess acac are evaporated. In hydrothermally dealuminated faujasites additional {sup 27}Al lines in the 50-30 ppm range appear, in addition to the tetrahedral and octahedral lines at 60 and 0 ppm. The {sup 27}Al spectra of acac-treated samples indicate that the NMR-invisible Al is complexed, resulting in an increase in the 0-ppm signal due to octahedral Al. The authors note that care should be exercised in the use of this procedure for quantification of extra-framework Al, as some may still not be observable. Although many steaming procedures leave considerable quantities of extra-framework Al in the interstices, as described above, it should be possible to produce highly dealuminated, clean materials without defects or amorphous Si and Al complexes. Some progress has been made in this direction. Figures show the corresponding Si and Al spectra of dealuminated faujasite with Si/Al ratios are indicated. The {sup 29}Si spectra indicate that all the material is highly crystalline with no amorphous silica present. The {sup 27}Al spectra show only sharp peaks at 50 and 0 ppm, corresponding to tetrahedral-framework Al and octahedral Al. There is no evidence of broad resonance peaks due to amorphous alumina. The addition of acac does not increase the intensity of the octahedral peak.
- OSTI ID:
- 7227197
- Report Number(s):
- CONF-900802--
- Journal Information:
- American Chemical Society, Division of Petroleum Chemistry, Preprints; (United States), Journal Name: American Chemical Society, Division of Petroleum Chemistry, Preprints; (United States) Vol. 35:4; ISSN 0569-3799; ISSN ACPCA
- Country of Publication:
- United States
- Language:
- English
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Related Subjects
020400 -- Petroleum-- Processing
37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CHEMISTRY
400201* -- Chemical & Physicochemical Properties
ALUMINIUM
ALUMINIUM 27
ALUMINIUM ISOTOPES
CATALYSTS
CATALYTIC CRACKING
CHEMICAL PREPARATION
CHEMICAL REACTIONS
CRACKING
DECOMPOSITION
DEMETALLIZATION
ELEMENTS
ENERGY SOURCES
EVEN-ODD NUCLEI
FAUJASITE
FOSSIL FUELS
FUELS
INORGANIC ION EXCHANGERS
ION EXCHANGE MATERIALS
ISOTOPES
LIGHT NUCLEI
MAGNETIC RESONANCE
MATERIALS
METALS
MINERALS
MOLECULAR STRUCTURE
NMR SPECTRA
NUCLEAR MAGNETIC RESONANCE
NUCLEI
ODD-EVEN NUCLEI
PETROLEUM
PYROLYSIS
RESONANCE
SEPARATION PROCESSES
SILICATE MINERALS
SILICON 29
SILICON ISOTOPES
SPECTRA
STABLE ISOTOPES
STRUCTURAL CHEMICAL ANALYSIS
SYNTHESIS
THERMOCHEMICAL PROCESSES
ZEOLITES