Effect of Fluoride and Sodium Ions on Structural and Thermal Properties of γ‐Al2O3

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Abstract
The structural properties of alumina as well as its fluoride and sodium modifications were characterized by X‐ray diffraction, infrared spectroscopy and differential thermal analysis. We have shown, that fluoride ions interact with hydroxyls type Ia of γ‐Al2O3 forming Al–F species, which then react at 400 °C forming β‐Al2O3. Morever, F/Al2O3 sample heated up to 400 °C contain two acidic hydroxyls type IIa and III, which are also represented on a differential thermal curve as endoeffect with minima at 470 and 500 °C. For Na/Al2O3 sample the same types of hydroxyls interact with Na+ ions leading to substitution of their protons. After heating at 400 °C this sample contains also hydroxyls type IIa and III, which are represented by two endothermal effects with minima at 450 and 520 °C. Differential thermal analysis shown to be a powerful and simple technique to characterize surface hydroxyl types of Na and F samples supported on γ‐alumina.

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