Vol. 1, No 3, 1996 pp.
200 - 203
UDC
535.338
INFRARED STUDY OF THE HYDROXYL GROUPS IN SYNTHETIC ZEOLITES: ZSM-5 AND HZSM-5 SILICALITE
B. Đurić-Stanojević, P. Dimitrijević, Lj. Miljković
Department of Physics, University of Niš, P.O.Box 91, 18001 Niš, Yugoslavia
Abstract.
The acidic forms of the synthetic high—silica zeolites ZSM—5 and HZSM—5 silicalite have been investigated by infrared spectroscopy, and their OH stretching vibrations have been determined. For ZSM—5 sample two IR bands have been observed: at 3660 cm-1 and 3720— 3740 cm-1, which correspond to Si—OH —Al groups and hydroxyls at siliceous impurities or terminal silanols on the external surface, respectively. Highly crystalline HZSM—5 zeolite contains only one type of framework hydroxyl group characterized by an IR vibration at ~ 3660 cm-1 therefore with slightly visible 3720 cm-1 band. Another IR band at 3470—3520 cm-1 in both samples has been assigned to physisorbed water molecules.
PROUČAVANJE HIDROKSILNIH GRUPA U SINTETIČKIM ZEOLITIMA ZSM-5 i HZSM-5 SILIKALITU PRIMENOM INFRACRVENE SPEKTROSKOPIJE
Infracrvenom spektroskopijom su proučavane kisele forme sintetičkih, silicijumom obogaćenih zeolita ZSM-5 i HZSM-5 silikalita. Određene su vibracije njihovih OH grupa. Kod ZSM-5 uzorka opažene su dve IC trake: na 3660 cm-1 i na 3720-3740 cm-1, koje odgovaraju Si—OH—Al grupama i hidroksilima na nečistoćama ili terminalnim silanolnim grupama na spoljašnjoj površini, respektivno. Jako kristalan HZSM—5 zeolit sadrži samo jedan tip mrežnih hidroksilnih grupa okarakterisanih IC vibracijama na ~3660 cm-1, pa je zato traka na 3720—3740 cm-1 slabo izražena. IC traka opažena kod oba uzorka na 3470 — 3520 cm-1 pripisuje se fizički adsorbovanim molekulima vode.
