Vapor phase transport synthesis of zeolites from sol-gel precursors

A study of zeolite crystallization from sol-gel precursors using the vapor phase transport synthesis method has been performed. Zeolites (ZSM-5, ZSM-4 8, zeolite P, and sodalite) were crystallized by contacting vapor phase org anic or organic-water mixtures with dried sodium silicate and dried sodium alumino-silicate gels. For each precursor gel, a ternary phase system of va por phase organic reactant molecules was explored. The vapor phase reactant mixtures ranged from pure ethylene diamine, triethylamine, or water, to an equimolar mixture of each. In addition, a series of gels with varied physi cal and chemical properties were crystallized using the same vapor phase so lvent mixture for each gel. The precursor gels and the crystalline products were analyzed via scanning electron microscopy, electron dispersive spectr oscopy, X-ray mapping, powder X-ray diffraction, nitrogen surface area, Fou rier transform infrared spectroscopy, and thermal analyses. The product pha se and purity as a function of the solvent mixture, precursor gel structure , and precursor gel chemistry is discussed. (C) 2000 Elsevier Science B.V. All rights reserved.