Crystallization of zeolites as formation of inclusion compounds

We consider the process of crystallization of aluminosilica gels under hydrothermal conditions as formation of inclusion compounds. We show that the possibility and direction of crystallization of zeolites, like formation of other types of inclusion compounds, are determined by the principle of maximum utilization of space and the energy factor. We establish the limits on the variation in the packing density of water molecules and organic templates occluded within the zeolite cavities. Using the classical theory of crystal formation, we explain the interconnection established in this paper between the characteristics of the reaction mixture (the nature of the cations, the alkalinity, the water content) and the integral heat of hydration of the zeolite crystals formed upon hydrothermal treatment of aluminosilica gels. For the example of ZSM-5-type zeolites, we consider the combined effect of the geometric and energy factors on the process of zeolite formation.Translated from Teoreticheskaya i Éksperimental'naya Khimiya, Vol. 30, No. 3, pp. 130–142, May–June, 1994.