The Faujasite Family of Molecular Sieve Zeolites: Part I—Synthesis and Characterization

Sodium zeolites X and Y (SiO2/Al2O3 ratio varying between 2.15 and 4.40), belonging to the faujasite family of molecular sieve zeolites, were synthesized at 80°-150°C from gels of different alkali and silica concentrations. Free gel, zeolite A and zeolite NaP* were found to be the most common impurities likely to be obtained while crystallizing zeolites X and Y from sodium aluminosilicate gels. Formation and/or persistence of these impurities were found to be dependent on the water content of the starting gel, or the time of crystallization. Synthesis of “ultrastable” Y zeolite was achieved by stepwise (though incomplete) removal of Na+ ions from a NaY sample. The compositional breaks and the associated problems of an uniform nomenclature for the entire range of the faujasite family of zeolites are discussed.