Turkish Journal of Physics

IR and ESR Studies of Acid-Base and Electron-Acceptor Properties of H-Pentasil and Aluminium Oxide




The acid and basic centres of H-pentasil samples heated at 773, 923 and 1073 K were characterized by IR spectroscopy of adsorbed CO, CD_{3}CN and CDCl_{3}. It was established that all found centers with Q_{L:CO} 36-38, 40-44 and 49-55 kJ/mole in H-pentasil due to extra -frame Al^{3+} cations and that they are similar to L-centres of Al_{2}O_{3} by nature. The basic centers with PA 860, 900 and 950 kJ/mole were found for the first time in pentasil type zeolites. Acceptor centers of the type coordinatively unsaturated Al^{3+} ions were identified for samples of H-pentasil and Al_{2}O_{3} on the basis of ESR spectra of the adsorbed nitroxide radical. It was shown that the concentration of these centres depends on the heated temperature of samples and is maximum for samples dehydroxylated at 850 K.

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