ROLE OF 18-CROWN-6 AND 15-CROWN-5 ETHERS IN THE CRYSTALLIZATION OF POLYTYPE FAUJASITE ZEOLITES

Phases obtained during crystallization of the cubic and the hexagonal end-member of the family of faujasite polytype zeolites and of their intergrowths from aluminosilicate hydrogels containing 15-crown-5 ether, 18-crown-6 ether, or a mixture of these ethers were characterized by XRD, IR, SEM, Si-29 and C-13 MAS NMR, TGA, and nitrogen. adsorption. The siting of crown ethers in the intracrystalline voids of the zeolites is derived from TGA and nitrogen adsorption data. The EMT content of FAU/EMT intergrowths is determined by multiphase Rietveld refinement of XRD patterns. Correlations between gel composition, crystallization kinetics, and EMT content of end products are established. A molecular model for crystallization consistent with the observed correlations is proposed.