Hierarchical Porous Zeolite Composite with a Core−Shell Structure Fabricated Using β-Zeolite Crystals as Nutrients as Well as Cores

Abstract

A hierarchical porous zeolite composite possessing β-zeolite cores and Y-zeolite polycrystalline shells (denoted as BFZ) is synthesized by a two-step hydrothermal crystallization procedure and characterized by X-ray diffraction (XRD), N2 adsorption−desorption, scanning electron microscopy (SEM), high resolution transmission electron microscopy (HRTEM), selected area electron diffraction (SAED), energy-dispersive spectrometry (EDS), NMR, intelligent gravimetric analyzer (IGA), and in situ infrared (IR) spectrometry of pyridine. The results show that a hierarchical pore structure with the pore size centered around 6.9, 10.3, and 16 nm is created in the composite. A more than 2 orders of magnitude gas transport improvement is, therefore, achieved in the composite as compared with the corresponding physical mixture. The conversion of liquid-phase hydrogenation of benzene over H-BFZ supported by 3 wt % Ru is much higher than those over H-Y or H-β-zeolites supported by the same Ru loading due to the improved diffusion and acid accessibility as well as the enhanced Ru dispersion because of the introduction of hierarchical pores.