The morphology of hydrothermally synthesized stilbite type zeolites

Stilbite, stellerite, and barrerite-zeolites having the stilbite framework- were synthesized in a temperature range between 200 and 250 degrees C by hy drothermal conversion of artificial water-free precursor glasses of the res pective 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 com position 1 Na2O-8CaO-9Al(2)O(3)-54SiO(2) with monoclinic symmetry (C2/m, a = 13.61 Angstrom, b = 18.24 Angstrom, c = 11.27 Angstrom, beta = 127.85 degrees, or: F2/m, a = 13.61 Angstrom, b = 18.24 Angstrom, c = 17.8 Angstrom, beta = 90.75 degrees in pseudoorthorhombic setting), Thes e preparation conditions could be successfully applied to the synthesis of zeolites stellerite (glass composition 4Na(2)O-4Al(2)O(3)-28SiO(2), symmetr y Fmmm, a = 13.60 Angstrom, b = 18.22 Angstrom, c = 17.84 Angstrom) and bar rerite (glass composition 4Na(2)O-4Al(2)O(3)-28SiO(2), symmetry Amma, a = 1 3.64 Angstrom, b = 18.20 Angstrom, c = 17.84 Angstrom), 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 mate rial in general while the sodium and/or calcium content of the precursor gl ass was responsible for the formation of the respective zeolite phase in pa rticular. Therefore it could be concluded that stellerite, stilbite, and ba rrerite are members of the same solid-solution series. (C) 1999 Academic Pr ess.