Effect of Sodium Concentration on the Synthesis of Faujasite by Two-step Synthesis Procedure

T he relationship between the concentration of sodium cations and the properties of faujasite(FAU) zeolite was investigated using a two-step synthesis procedure including (1) formation of amorphous aluminosilicate precursors and separation of amorphous nanoparticles, and (2) transformation of these amorphous particles into zeolite crystals by treatment with alkali solutions(NaOH). Three representative samples including two nano-sized zeolites and one micron-sized zeolite were prepared using different concentrations of sodium hydroxide. The crystallization process of these zeolites was studied in detail by Fourier transform infrared(FTIR) spectrometry, nuclear magnetic resonance spectroscopy(NMR), X-ray diffraction(XRD), scanning electron microscopy (SEM), transmission electron microscopy(TEM), and N 2 adsorption. The results indicated that minor changes in the concertation of inorganic cations can significantly shorten the induction period and crystallization time and thus affect the morphology, size and chemical composition of the zeolite crystals.