Synthesis of silica-rich chabazite using conventional Si and Al sources and the low-cost tetraethylammonium (TEA(+)) cation as structure directing molecule

High-silica zeolites with the CHA topology have been synthesized from conventional Si and Al sources in the presence of zeolitic seeds, and using the non-expensive tetraethylammonium (TEA(+)) cation as structure directing agent. Seeds with the CHA topology effectively enabled the crystallization of chabazite but the solid was difficult to obtain pure and almost systematically contaminated by zeolites with the GME framework topology. Better results were obtained when high-silica seeds with the FAU topology were added. Under those conditions, pure chabazite zeolites (CHA) with SiO2/Al2O3 > 13 could be obtained within a few days at 130 degrees C. Kinetic studies revealed that the zeolite chabazite was not formed directly from the D6R units of the faujasite seeds, as generally reported in the literature, but from the dissolution of an intermediate [TEA(+)]FAU zeolite that completely crystallized within less than 12 h. Moreover, pure chabazite zeolites (CHA) could be obtained with amounts of seeds as low as 2.5 wt %, that is, an order of magnitude lower than amounts previously reported in the literature.