THE INFLUENCE OF DEALUMINATION ON THE INFRARED SPECTRA OF H-ZSW-5

The influence of hydrothermal dealumination on the infrared spectra of H-ZSM-5 has been studied on framework end OH stretching vibrations. A linear dependence was found between the number of framework aluminium per unit cell and the wavenumber of the asymmetric T-O-T stretching vibrations. Dealumination leads to a decrease of the number of strong acidic OH groups. A short hydrothermal(-1) treatment causes an increasing band intensity at about 3665 cm(-1) due to non-framework aluminium species. By comparing dealuminated H-ZSW-5 before end after the acid leaching, we suggest an interaction between non-framework aluminium species end terminal OH groups.