Abstract: The surface hydroxyl groups and acidic properties of LaDAlY were examined by means of IR spectroscopy with pyridine adsorption and NH₃-TPD method.From the variations of hydroxyl groups, it is shown that La³⁺ ions are located at different positions in NH₄Y and DA1Y.The experiments further indicate that the number of both Bronsted and Lewis acid sites on DA1Y and NH₄Y was decreased after La³⁺ ions-exchanged.The NH₃-TPD results show that the strength of weak acid sites of DA1Y was increased, while the strength of strong acid sites was almost not changed after La³⁺ ions-exchanged, and the number of acid intes was decreased generally.The results are consistent with these obtained by infrared studies.

Key words: LaHY, LaDAlY, Surface hydroxyls in LaDAlY