Abstract
In this study, hierarchical zeolite ZSM-5 materials were hydrothermally synthe-sized by using a novel tri-block structure directing agent (SDA) and different silicon sources and were further functionalized then loaded with palladium for the catalytic selective phenol hydrogenation. The tri-block SDA contains repeated propylene oxide units with both ends connented to three quaternary ammonium groups. The effects of the kinetic parameter of the synthesis on the morphology and lamellar structure of the resulting ZSM-5 and MFI zeolites were investigated by tuning the precursors with different silicon and aluminum sources. In the TEOS-Al(OsBu)3 synthesis system, lamellar stacking and flower-like morphology was formed. On the other hand, highly uniform self-pillared structure containing almost exclusively tetrahedrally coordinated framework aluminum was obtained in the water glass-aluminum sulfate synthesis system. For the deposition of Pd nanoparticles, the Pd(II) ions were coordinated with vinyl groups on zeolite surface and highly dispersed Pd nanoparticles were form after reduction. The Pd@ZSM-5 catalyst exhibited higher phenol conversion and cyclo-hexanone selectivity under room temperature and atmospheric pressure than reference catalysts including commercial Pd/C and conventional ZSM-5-supported catalyst did. The superior catalytic activity in mainly attributed to shorter diffusion path length, hydrophobic surface and small and highly dispersed Pd nanoparticles.