Fourier-transform infrared and inelastic neutron-scattering study of hy zeolites

A combination of FTi.r. and INS spectroscopy is used in a vibrational study of the bending and stretching vibrations of the acidic hydroxyl groups of Y zeolites. The influence of the number of acidic Bronsted sites and the Si/Al ratio is discussed. Out-of-plane hydroxyl bending modes are assigned to vibrations centered around 419 cm-1 and in-plane hydroxyl bending modes are assigned to vibrations centered around 1089 cm-1. Upon dealumination, these bands are shifted by approximately 30 cm-1 to lower values. The less intense bands at 319,470,565,765, and 1130 cm-1 are assigned to proton- coupled framework vibrations. Upon dealumination, the mode at 319 cm-1 is shifted to lower frequencies and the modes at 565 and 1130 cm-1 are shifted to higher frequencie