Synthesis of gismondine-type zeolites by the hydrothermal method

Gismondine, amicite, garronite, and gobbinsite—zeolites with the same structure type of the double-connected 4-ring chain group—were synthesized by long-term hydrothermal treatment of synthetic water-free glasses of the same compositions as the respective zeolite phases, in a temperature range between 200 and 250°C at 1 kbar H2O pressure. Gismondine was formed from glass of the composition 4CaO–4Al2O3–8SiO2 with tetragonal symmetry, and the preparation conditions could be successfully applied to the synthesis of zeolites amicite (monoclinic, glass composition 2Na2O–2K2O–4Al2O3–8SiO2), garronite (tetragonal, glass composition Na2O–2.5CaO–3Al2O3–10SiO2) and gobbinsite (tetragonal, glass composition 5Na2O–5Al2O3–22SiO2). The formation of these zeolite phases under the chosen p-T-t conditions was only dependent on the chemical composition of the glassy starting product. This behavior could be explained by a supersaturation–crystallization process, which, in principle, is applicable to synthesis of this class of materials.