Seed-induced synthesis of hierarchical architectures of ZSM-5 nanocrystalline aggregates by the solid state crystallization

Abstract

A seed-induced rapid synthesis of hierarchical ZSM-5 aggregates was achieved by the solid state conversion method in an inorganic system. No secondary mesoporogen was introduced to construct supplementary pore. The physical and chemical properties of the products were characterized by using XRD, SEM, TEM, XRF and N2 adsorption–desorption techniques. The results revealed that the synthesized samples typically exhibit the uniform spherical zeolite ZSM-5 aggregates composed of loosely packed nanocrystals. It was clearly found that the morphology, mesoporosity and particle size of synthesized samples were directly affected by the type of the seed and synthesis conditions. The well-dispersed hierarchical ZSM-5 aggregates were synthesized at NaOH/SiO2 = 0.15, 20 ≤ SiO2/Al2O3 ≤ 40 with the acid of zeolite seed solution in guiding the structure. In addition, the crystal growth of zeolite samples synthesized with zeolite seed solution was studied at 433, 453, and 473 K. The results suggested that the activation energies for the induction, transition and crystallization stages were 91.44, 104.37 and 77.68 kJ∙mol−1, respectively. The method provides a cost-effective and industrially applicable route to synthesize hierarchical ZSM-5 aggregates.