IR‐ and XRD‐Investigations on Isomorphous Substituted ZSM‐5 Zeolites

Abstract

Abstract Ge–ZSM‐5 zeolites are characterized by XRD and IR Spectroscopy in the spectral range of lattice and hydroxyl vibrations. XRD data confirm the high crystallinity of hydrothermally synthesized Ge–ZSM‐5 samples. The incorporation of germanium into the ZSM‐5 framework is proven by the increase of the unit cell volume from 5342 Å 3 (silicalite I) to 5390 Å 3 (Ge–ZSM‐5, Si/Ge = 4). At the same time the wavenumber of the asymmetric T–O–T stretching vibration band is decreased from 1102 to 1090 cm −1 and the intensity of the double ring vibration band at 550 cm −1 is decreased and losses its structure. In the hydroxyl vibration spectra a new absorption band at ca. 3670 cm −1 is observed the intensity of which increases with growing germanium content. This new absorption band is assigned to terminal Ge–OH groups in the zeolite structure.