Infra-red structural study of various type L zeolites

Abstract

Infra-red spectra (1300–400 cm^–1 region) of L zeolites which have undergone various treatments are presented. Each treatment causes only small frequency shifts, but the band intensities give useful information on the maintenance of the structure. In particular, the intensity of the 608 cm^–1 band yields the number of entire double D-6 rings. Potassium removal does not destroy these structural units, but reduces their thermal stability. In contrast, aluminium removal decreases their number (because Al atoms leave holes as they are not replaced by Si atoms), but does not alter the thermal stability of the remaining entire units. Comparison with X-ray diffraction patterns shows the greater sensitivity of the i.r. spectra.