The development of strong acidity in hexafluorosilicate-modified Y-type zeolites

Journal Article · Sat Aug 01 00:00:00 EDT 1992 · Journal of Catalysis; (United States)

DOI:https://doi.org/10.1016/0021-9517(92)90086-W· OSTI ID:7241415

Lonyi, F; Lunsford, J H ^[1]

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1. Texas A and M Univ., College Station (United States)

Catalysts have been prepared by treating a parent Na, NH{sub 4}-Y(54) zeolite containing 54 Al{sub f}/u.c. with ammonium hexafluorosilicate (AHFS). The resulting zeolites, containing between 39 and 26 Al/u.c., were crystalline but were relatively inactive for the cracking of n-hexane at 400 C. After steaming they became active, and their activity was greater than that of a parent zeolite which had been steamed to the same framework aluminum (Al{sub f}) content. To achieve maximum activity by steaming the amount of Al removed from the AHFS-treated zeolite was equivalent to ca. one Al atom per {beta} cage. The enhanced activity of the steamed AHFS-treated material is believed to result from the presence of isolated Al in the framework and a cationic form of extraframework Al which has no affect on acidity or activity. The most active zeolites are characterized by infrared bands at 3,602 and 3,525 cm{sup {minus}1}, which are assigned to hydroxyl groups in the large and small cages, respectively. The zeolites prepared with AHFS retained less than 0.3 wt% fluorine. It is unlikely that this fluorine is responsible for the enhanced acidity of the more active catalysts. Impregnation of the less active catalysts with NH{sub 4}F increased the activity; however, this phenomenon results from dealumination rather than from the electronic effect of fluorine.

• OSTI ID: 7241415
• Journal Information: Journal of Catalysis; (United States), Vol. 136:2; ISSN 0021-9517
• Country of Publication: United States
• Language: English

Related Subjects

37 INORGANIC
ORGANIC
PHYSICAL AND ANALYTICAL CHEMISTRY
02 PETROLEUM
HEXANE
CATALYTIC CRACKING
ZEOLITES
CATALYTIC EFFECTS
PH VALUE
CHEMICAL PREPARATION
FLUORINE
FLUORINE COMPOUNDS
HEAT TREATMENTS
INFRARED SPECTRA
MICROSTRUCTURE
NUCLEAR MAGNETIC RESONANCE
SILICATES
SILICON 29
STEAM
ALKANES
CHEMICAL REACTIONS
CRACKING
CRYSTAL STRUCTURE
DECOMPOSITION
ELEMENTS
EVEN-ODD NUCLEI
HALOGEN COMPOUNDS
HALOGENS
HYDROCARBONS
INORGANIC ION EXCHANGERS
ION EXCHANGE MATERIALS
ISOTOPES
LIGHT NUCLEI
MAGNETIC RESONANCE
MATERIALS
MINERALS
NONMETALS
NUCLEI
ORGANIC COMPOUNDS
OXYGEN COMPOUNDS
PYROLYSIS
RESONANCE
SILICATE MINERALS
SILICON COMPOUNDS
SILICON ISOTOPES
SPECTRA
STABLE ISOTOPES
SYNTHESIS
THERMOCHEMICAL PROCESSES
400201* - Chemical & Physicochemical Properties
020400 - Petroleum- Processing