IR STUDIES ON THE ACIDITY OF DEALUMINATED Y-ZEOLITE WITH DIFFERENT PROBE MOLECULES

Dealuminated HY zeolites (D-HY), which are partly reexchanged by La ions (D-LaHY), show two i.r. bands at 3625 cm-1 (high frequency) and 3550 cm-1 (low frequency). In contrast to the findings in D-HY and nondealuminated La-exchanged Y zeolite (LaHY), the LF band of D-LaHY is considerably affected by the adsorption of butadiene, in connection with a strongly increased coking. Sorption experiments with pyridine and ammonia confirm the OH groups belonging to the LF band to be acidic and accessible even to pyridine. This can be further confirmed by an H-D exchange reaction with C6D6 at room temperature.