Synthesis of high-silica FAU-, EMT-, RHO- and KFI-type zeolites in the presence of 18-crown-6 ether

FAU-, EMT-, RHO- and KFI-type zeolites were synthesized by heating an aqueous alkaline aluminosilicate gel containing 18-crown-6 ether as an organic template with either sodium, or sodium and cesium, or potassium and strontium cations. The products were characterized by elemental analysis, scanning electron microscopy, powder X-ray diffraction, thermal analysis, solid-state nuclear magnetic resonance spectroscopy, and n-hexane adsorption. The 18-crown-6 ether is incorporated in each structure. Its presence turns out to be necessary to crystallize EMT-type materials and, in the other cases, it allows reproducible preparations of well crystallized materials with high Si/Al ratios (3.7–4.6). The retrieval of the 18-crown-6 ether from the EMT-type zeolite is possible with solvothermal treatments.