The origin of strong acidity in dealuminated zeolite-Y

Conference · Wed Aug 01 04:00:00 EDT 1990 · American Chemical Society, Division of Petroleum Chemistry, Preprints; (United States)

OSTI ID:6957613

Lunsford, J H ^[1]

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

The commercial utilization of dealuminated Y-type zeolites has generated renewed interest in the origin of strong acidity in these materials. It is now evident that a carefully prepared H-Y zeolite, with its full complement of protons but with no extraframework Al, exhibits very little activity for acid-catalyzed reactions such as the dealkylation of cumene or the cracking of hexane. If these zeolites are dealuminated to ca. 32 framework Al concentration corresponds to a Si/Al ratio of 5.0 or a unit cell dimension, a{sub 0}, of 24.54 {angstrom}. Even if zeolites are not purposely dealuminated at the outset, they become dealuminated to an equilibrium level during their regeneration in a catalytic cracking unit. Early theoretical arguments of Dempsey and also of Mikovsky and Marshall suggested that the acid strength was related to the Al distribution in the framework and that only Al{sub f} atoms with no second-neighbor Al{sub f} atoms in the 4-rings are responsible for strong Broensted acidity. The number of aluminum atoms with 0, 1, 2, and 3 aluminum second neighbors in the 4-rings has been calculated by Beagley et al. The dealumination process, whether by steaming or by treatment with SiCl{sub 4}, not only changes the Al{sub f} distribution but also introduces extraframework Al into the zeolite cavities. It is the purpose of this review to summarize these results and to suggest a model of strong acidity that appears to fit much of the available data. The data include catalytic results on faujasite-type zeolites prepared by several methods, poisoning studies, and infrared studies of hydroxyl groups.

• OSTI ID: 6957613
• Report Number(s): CONF-900802--
• Conference Information: Journal Name: American Chemical Society, Division of Petroleum Chemistry, Preprints; (United States) Journal Volume: 35:4
• Country of Publication: United States
• Language: English

Related Subjects

02 PETROLEUM
020400 -- Petroleum-- Processing
37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CHEMISTRY
400201* -- Chemical & Physicochemical Properties
ALKANES
ALUMINIUM
AROMATICS
CATALYSTS
CATALYTIC CRACKING
CHEMICAL REACTION KINETICS
CHEMICAL REACTIONS
CRACKING
CUMENE
DEALKYLATION
DECOMPOSITION
DEHYDRATION
DEMETALLIZATION
ELEMENTS
ENERGY SOURCES
FOSSIL FUELS
FUELS
HEXANE
HYDROCARBONS
INDUSTRIAL PLANTS
INORGANIC ION EXCHANGERS
ION EXCHANGE MATERIALS
KINETICS
MATERIALS
METALS
MINERALS
ORGANIC COMPOUNDS
PETROLEUM
PETROLEUM REFINERIES
PH VALUE
POISONING
PYROLYSIS
REACTION KINETICS
REMOVAL
SEPARATION PROCESSES
SILICATE MINERALS
STEAM
THERMOCHEMICAL PROCESSES
ZEOLITES