IR spectroscopic investigation of internal silanol groups in different zeolites with pentasil structure

Various isomorphically substituted high-silica zeolites, including ZSM-5, beta, ferrisilicates, gallosilicates and borosilicates, were investigated by diffuse reflectance IR spectroscopy. The narrow band at 3735 cm–1 and the broad band at 3500 cm–1 were assigned to internal silanol groups. These defect sites in the as-synthesized Na-forms of zeolites arise during the template decomposition.