Adsorption of pyridine on dealuminated zeolite HY

Infrared spectra showed that over 80% of aluminum atoms on the surface of z eolite HY were extracted by a exposure of SiCl4 vapor at elevated temperatu res. The dealumination of the HY surface resulted in an appreciable change in its acidic properties. Infrared spectra of adsorbed pyridine indicated t he formation of various kinds of Lewis acid sites on the delauminated HY su rfaces. Although the total number of the surface Bronsted acid site decreas ed in the SiCl4-induced dealumination process, the nature of these remainin g Bronsted acid sites was unchanged spectroscopically.