Binder-free ZSM-5 Zeolite Catalysts Modified with Framework De-alumination

The adsorption properties of binder-free and binder-containing ZSM-5 zeolite catalysts were compared, and the former one was proved to possess the excellent properties. The binder-free ZSM-5 zeolite catalyst has been treated with HCl solution, steaming, and steaming combined with HCl solution, respectively. The de-alumination behavior and the states of yielded non-framework aluminum on the treated catalysts were studied with Al-27 MAS NMR. Some important properties of the treated catalysts, such as the crystalline structures, compositions, pore structures, and distribution of surface strong (S) and weak (W) acidity, Bronsted (B) and Lewis (L) acidity, have been investigated in detail with X-ray diffraction, XRF, N-2 adsorption, NH3-TPD and pyridine-adsorption in situ infrared spectroscopy, respectively. The nature of strong tuning effect on the properties of the zeolite framework and surface solid acidity has been revealed for the zeolite catalyst treated with steaming, which plays the key role in tuning the S acidity and B acidity.