MORPHOLOGY OF HYDROTHERMALLY SYNTHESIZED STILBITE TYPE ZEOLITES

摘要

Stilbite, stellerite, and barrerite-zeolites having the stilbite framework-were synthesized at 200-250 C by hydrothermal conversion of artificial water-free precursor glasses of the respective same composition at 1 kbar H2O pressure. No template materials and no sol-gel-like preparation technique was applied. Stilbite was formed from glass of the composition 1Na2O-8CaO-9Al2O3-54SiO2 with monoclinic symmetry (C2/m, a=13.61 angstroms, b=18.24 angstroms, c=11.27 angstroms, beta=127.85 degrees, or: F2/m, a=13.61 angstroms, b=18.24 angstroms, c=17.8 angstroms, beta=90.75 degrees in pseudoorthorhombic setting). These preparation conditions could be successfully applied to the synthesis of zeolites stellerite (glass composition 4CaO-4Al2O3-28SiO2, symmetry Fmmm, a=13.60 angstroms, b=18.22 angstroms, c=17.84 angstroms) and barrerite (glass composition 4Na2O-4Al2O3-28SiO2, symmetry Amma, a=13.64 angstroms, b=18.20 angstroms, c=17.84 angstroms). The investigations showed, that the formation of these zeolites with the same type of crystal lattice was dependent only on the chemical composition of the starting material in general while the Na and/or Ca content of the precursor glass was responsible for the formation of the respective zeolite phase in particular. Therefore it could be concluded that stellerite, stilbite, and barrerite are members of the same solid-solution series. 9 refs.