Synthesis of NaA/X Composite Zeolites in Hydrothermal Reaction System

The NaA/X composite zeolites were successfully synthesized under hydrothermal treatment without template. On the basis of many experiments, this paper discusses the effect of composition of raw material and the condition of gel formation on the synthesis of NaA/X composite zeolites according to X-ray diffraction analysis. Investigation shows that the optimum n(SiO₂):n(Al₂O₃) is 2.8 in this hydrothermal reaction system. The proper basicity conditions are molar ratios n(H₂O):n(Na₂O) = 25–30 and n(Na₂O):n(SiO₂) = 1.6–3.0. Scanning electron microscope analysis shows that the particle size of the as synthesized composite zeolite was uniform of about 150 nm. The calcium ion exchange capacity (based on CaCO₃/anhydrous zeolite) of the products was 300 mg/g, the magnesium ion exchange capacity of the products was much better than zeolite 4A, X and high aluminum P zeolites.