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Properties of hydroxyl groups in the magnesium-montmorillonite structure

I. Horváth, E. S San'ko, E. A Paukshtis, and E. N Yurchenko

Institute of Inorganic Chemistry, Centre of Chemical Research, Slovak Academy of Sciences, 842 36 Bratislava

 

Abstract: Thermal decompn. and the acid-base properties of OH groups in Mg-montmorillonite were studied by thermoanal. methods and IR spectroscopy. In the temp. range 200-700° the OH groups of montmorillonite structure are characterized by 5 absorption bands with ̅v(OH)/cm-1 = 3740, 3710, 3675, 3640, and 3595. Thermally most stable are the OH groups with  ̅v(OH) = 3675 and 3595 cm-1, the least stable are those with ̅v(OH) = 3710 cm-1. Acid-base properties of the OH groups were investigated by the adsorption of pyridine, ND3, and benzonitrile vapors. On the surfaces of samples heated at various temps. at 200-700°, strong protonic centers are absent or not possible for larger mols. Only the most stable OH groups of the structure in configurations Al-OH-Al and Al-OH-Mg manifested acidity sufficient for the protonation of NH3. The formation of pyridine and benzonitrile donor-acceptor complexes occurred via surface Mg2+ ions mainly after the heat treatment at 500-600°.

Full paper in Portable Document Format: 364a515.pdf

 

Chemical Papers 36 (4) 515–522 (1982)

Wednesday, February 26, 2020

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