19F MAS NMR-STUDIES OF CRYSTALLINE MICROPOROUS SOLIDS SYNTHESIZED IN THE FLUORIDE MEDIUM

Highly siliceous TON-, MTT-, and MFI-type zeolites, alumino-, gallo-, titano-, and germanosilicates of MFI-type structure, and aluminophosphates and silicoaluminophosphates of AFI-, AEL-, FAU-, and CHA-type structure, containing various alkylammonium species R+, and synthesized in fluoride medium, were studied by 19F MAS n.m.r. The as-synthesized samples, with a fluorine weight content up to 1.7% were characterized by a single main peak attributed to fluorine anions balancing the charge of the organic cation. The variations of chemical shifts with the nature of the templates were very small. The values ranged from -64 to -75 ppm in silicates and from -119 to -123 ppm in aluminophosphates. After calcination in dry gas, the remaining fluorine (0.1-0.3%) is bonded to Si (peak close to -155 ppm) or to TIII elements (peak close to -140 ppm). When the samples were heated in moist atmosphere, no trace of F was found. © 1990.