A localized crystallization to hierarchical ZSM-5 microspheres aided by silane coupling agent.

Hierarchical ZSM-5 microspheres were synthesized from a ZSM-5 synthesis solution with the addition of 3-aminopropyltriethoxysilane (APTES). The time dependent revolution of structure and morphology was investigated by XRD, SEM, TEM, N(2) adsorption-desorption, and (29)Si MAS NMR techniques. The results indicated that amorphous aluminosilicate microspheres with diameter of 8 μm were obtained at the initial stage of the synthesis. With the crystallization going on, the amorphous aluminosilicates gradually crystallized to ZSM-5 structure while preserving the spherical morphology. For the first time, a novel phenomenon of localized crystallization of ZSM-5 has been demonstrated in a conventional zeolitic synthesis solution aided by APTES. Moreover, after removing the amorphous silicic residues, the hierarchical ZSM-5 microspheres showed excellent catalytic properties in benzylation of benzene and catalytic cracking of polypropene.