Orientation of Chemical Properties by Direct Synthesis of Molecular Sieves

Abstract

This subject was discussed on the basis of a broad collective experimental experience and not only that of the presented papers (1). The classical concept of a nuclei as a critically sized “species” allowing spontaneous growth in a system by virtue of lowering the free energy of the “solution” — was accepted. This may occur spontaneously in a supersaturated system or by the addition of such material promoters from an external source. The issue of whether the latter are nuclei or seeds was discussed at length, and depending on the specific zeolite or synthesis slurry in question, both mechanisms may be invoked. Nuclei in this case are structureless in the sense that such a source may induce crystal growth of many different structures in several different gel systems, whereas seeds are viewed as being structure specific. They direct the crystallization to only one structure — that of the seed.