Computer modeling of the infrared spectra of zeolite catalysts

The paper describes the applications of computer modeling methods to the interpretation of the infrared spectra of zeolite frameworks. The correlation of the breathing vibration of ring structures in zeolitic lattices with their infrared spectra was investigated by the molecular dynamics method. The calculations reveal that in periodic zeolite lattices the ring-breathing vibrations participate in many normal modes. Despite the fact that the ring-breathing vibrations are calculated to have characteristic frequencies, no general correlation of these frequencies with band positions in the infrared spectra was found. Ab initio quantum-chemical calculations were employed to examine the band observed at 885 cm(-1) in the infrared spectra of activated zeolite beta [J. Phys. Chem. B 104 (2000) 286]. In agreement with the assignment proposed from the experiments, the calculations show that the observed band belongs to a vibration of -O-Al(OH)-O- sites of the zeolite and ascribe this vibration to the antisymmetric stretching vibration of the O-Al-O bridge. (C) 2001 Elsevier Science B.V. All rights reserved.