Abstract:

B-ZSM-5 zeolites with different crystal sizes were synthesized by adjusting hydrothermal synthesis temperature. Ti-ZSM-5 samples were prepared by gas-solid reaction using acid-treated B-ZSM-5 as precursors with gaseous TiCl4. The samples were characterized by scanning electron microscopy (SEM), X-ray powder diffraction (XRD), Fourier-transforminfrared (FT-IR) spectra, ultraviolet-visible (UV-Vis) spectroscopy, inductively coupled plasma atomic emission spectrometry (ICP-AES), Raman spectra, nitrogen adsorption-desorption, and 1,2,4-trimethylbenzene adsorption. The catalytic performance of Ti-ZSM-5 for phenol hydroxylation was investigated. Results showed that all the precursors were agglomerated by the small cuboids particles and had MFI topology structure, but there were some differences in the crystal size, the amount of framework titanium species, and pore volume. The optimized temperature range of the low-temperature crystallization stage is from 333 to 353 K for the synthesis of B-ZSM-5. Moreover, Ti-ZSM-5 sample using this B-ZSM-5 as the precursor has a better catalytic performance for phenol hydroxylation, because of the smaller cuboids particles, the larger pore volume and surface area. In phenol hydroxylation, when the molar ratio of phenol to hydrogen peroxide was 3, the conversion of phenol was 20.5%.

Key words: Ti-ZSM-5, Low-temperature crystallization, Gas-solid isomorphous substitution, Phenol hydroxylation