Comparison of factors influencing acidity of hydroxyl groups in zeolites. Quantum chemical study

Journal Article · Thu Jan 11 04:00:00 EST 1990 · Journal of Physical Chemistry; (USA)

DOI:https://doi.org/10.1021/j100364a057· OSTI ID:6731446

Beran, S ^[1]

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1. J. Heyrovsky Institute of Physical Chemistry and Electrochemistry, Prague (Czechoslovakia)

The nonempirical quantum chemical method with a STO-3G basis set is employed to study the effect of changes in the chemical composition of the environment of the {r arrow}Si-OH-Al{l arrow} fragment in zeolites on the acidity of the bridging OH groups modeled by the H-OX-TH{sub 2}-O-SiH{sub 2}-OH-AlH{sub 3} molecule model (T = Si or Al and X = H or Na). It is shown that the substitution of Si by Al (i.e., variation in the Si/Al ratio) is the most important factor influencing the OH group acidity. Its effect on the acidity is approximately twice as great as the effect of substitution of H by Na (i.e., variation in the degree of decationization). The bridging OH groups in immediate proximity to a terminal OH group were calculated to be somewhat more acidic than the OH groups surrounded by only Si or Al atoms. Neutral oxide-like species of metals occluded in the zeolite pores were found to increase the acidity of the adjacent OH groups.

• OSTI ID: 6731446
• Journal Information: Journal of Physical Chemistry; (USA), Journal Name: Journal of Physical Chemistry; (USA) Vol. 94:1; ISSN 0022-3654; ISSN JPCHA
• Country of Publication: United States
• Language: English

Related Subjects

36 MATERIALS SCIENCE
360603 -- Materials-- Properties
37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CHEMISTRY
400200* -- Inorganic
Organic
& Physical Chemistry
ACIDIFICATION
CALCULATION METHODS
CATALYSIS
DATA
HYDROGEN COMPOUNDS
HYDROXIDES
INFORMATION
INORGANIC ION EXCHANGERS
ION EXCHANGE MATERIALS
MATERIALS
MATHEMATICAL MODELS
MECHANICS
MINERALS
NUMERICAL DATA
OXYGEN COMPOUNDS
QUANTUM MECHANICS
THEORETICAL DATA
ZEOLITES