MAGIC-ANGLE-SPINNING 29Si-NMR STUDY OF THE STRUCTURE OF ZSM-5 AND ZSM-11 ZEOLITES

Abstract

Abstract Eight magnetically different 29Si-NMR lines are clearly distinguished in the solid state high resolution spectra of HZSM-5 zeolite with a high Si/Al ratio (1000) and some of them are assigned. The resonance line at −105 ppm in both HZSM-5 and HZSM-11 zeolites is attributed to Si atoms in the second coordination sphere of an Al atom, i.e. Si (1 Al). The −115 ppm lines stem from Si atoms in 4-membered rings. The splitting of these lines originates from a probable strain in these small rings. The incorporation of Al atom occurs exclusively in the 5-membered rings.