A procedure was developed in our laboratory to synthesis non-agglomerated silicalite nanocrystals within days, instead of weeks as
required in the literatures. This was achieved by concentrating the precursor sol, aging at 80oC for about a day, followed by a short hydrothermal reaction at 175oC. In this study, the same procedure has been extended to the synthesis of aluminum containing ZSM-5 zeolite nanocrystals.
However, before applying the method to ZSM-5 system, some details of the previous procedures were further investigated to clarify the controlling parameters. For example, the proper way to concentrate the precursor sol, the selection of temperature and duration in the first aging stage, as well as that in the second hydrothermal reaction stage.
After clarifying the controlling parameters, the method was applied to the synthesis of ZSM-5. In addition to the Si/Al ratio, the effect of TPAOH
ratio in the starting recipe was also investigated. It was found that the size
of the resulted nanozeolite increases with the amount of aluminum incorporated. On the other hand, there exists an optimum TPAOH/SiO2 ratio leading to the smallest particles size. Under appropriate conditions,non-agglomerated ZSM-5 (silicalite) nanocrystals of 140, 110 and 50 nm
for Si/Al of 50, 100 and infinite, respectively, were achieved with a total synthesis time shorted than 2 days.||en_US|