There are two OH frequencies at 3620 and 3535 cm-1 on Y zeolite, corresponding to the OH groups situated in supercage and sodalite cage, resp. While on DAlY a new band at 3724 cm-1 appeared which was assigned to Si-OH located in the empty hole resulted from the dealumination. After the adsorption of benzene and cumene on the Y and DA1Y zeolites, the 3620 cm-1 band disappeared, which implies that the adsorption occurred in the supercages. The acidic OH groups absorbed at 3620 cm-1 are the main active sites of the cumene cracking.

Key words: INFRARED SPECTROPHOTOMETRY, BENZENE, ZEOLITE, ADSORPTION, SURFACE CHEMISTRY, HYDROXY GROUP, CATALYST POISONING, CRACKING REACTION, IN-SITU, ISOPROPYL BENZENE P