Abstract: Effects of temperature on the acidity of zeolites were studied by using IRspectrometry. The experimental results show that the acidities (acid strength) of the zeolites are increased as temperature increases. The increase of the acidities of the diffrent -OH groups has the following order: acidic -OHgroups located in the big cavities (supercages in the zeolite Y and main channels in the ZSM-5) > Si-OH on the external surface or on the defect positions > acidic -OH groups located in the small cages (D-6 membered rings in the zeolite Y), The changes of the acidities are linear with increasing temperature over the temperature range employed in the study.

Key words: Infrared spectra, Temperature, Acidity, Y type zeolite, ZSM-5