Nucleation promotion of zeolite crystals by in situ formation of silver-based heterogeneous nuclei

The size of zeolite crystals can be controlled by modifying the nucleation frequency by the addition of silver-based promoters. Nanoparticles of silver oxide can be formed in the alkaline solutions used in zeolite synthesis and can act as effective heterogeneous nuclei for the crystallization of zeolites in a wide range of topology and composition (zeolites LSX, X, Y, A, L, and beta). The presence of silver oxide does not affect the normal nucleation mechanism of zeolites from gels and provides a number of additional seeds proportional to the amount of silver oxide precursors introduced in the synthesis systems. The yield of zeolite crystallization is not significantly affected by the presence of the nucleation promoters. The volume of the crystals formed can be decreased by a factor 20 in the appropriate conditions. The effectiveness of the nucleation promotion is not affected by the presence of organic cations but is largely reduced in extremely alkaline media, in which silver oxides are significantly soluble.

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► Silver oxide germs formed in situ are effective seeds for zeolite crystallisation.
► Seeded heterogeneous nucleation allows to control zeolite crystal size.
► Crystal size of zeolites as different as LSX and beta can be controlled.