F Ghoroghchian - Faculty of Chemistry, Teacher training university, Tehran, Iran
H Kazemian - R&D Lab. Of SPAG Co., Technology incubator, Sci & Technol. Park of Tehran University, Tehran, Iran,
F farhadi - R&D Lab. Of SPAG Co., Technology incubator, Sci & Technol. Park of Tehran University, Tehran, Iran,
h Aghabozorg - Faculty of Chemistry, Teacher training university, Tehran, Iran

The synthesis of zeolites is carried out under hydrothermal conditions. An aluminate solution and a silicate solution are mixed together in an alkaline medium to form a milky gel or in some instances, clear solutions. Synthesis proceeds at elevated temperatures (60-200 °C) where crystals form through a nucleation step. Nucleation and growth kinetics can depend on the dissolution of the solid reagents and formation of aluminosilicates precursors. Kühl found that crystallization of some structures was dependent on the degree of pre polymerization of the silica source. Mintova and Valtchev recently investigated the colloidal distribution of silicalite-1 synthesis mixtures containing different silica sources. Impurities in silica or alumina sources are likely to influence crystallization kinetics and framework composition.

zeolite, silica source, crystallization