Characterization of zeolites by infrared spectroscopy

The mid-infrared spectra have been considered for the zeolites characterization. The preliminary interpretation of the infrared spectra suggests specificity for zeolite structure type, group and for secondary building units like double rings and large pore openings. The major structural groups present in zeolites can be detected from their infrared patterns. The infrared spectrum in the region of 1500-400 cm is a fingerprint of the region indicating structural features of zeolite frameworks. The infrared spectra of zeolites in the 1300-400 cm region appear to consists of two classes of vibrations: (i) those caused by internal vibration of the framework TO4 tetrahedron, the primary building units (PBU) in all zeolite frameworks, which tend to be sensitive to variation in framework structure, (ii) vibration related to external linkage between tetrahedral units which are sensitive to the framework structure and to the presence of secondary building units (SBU) and building blocks of polyhedra such as rings and pores (Table-1).