Feiyue Zhang

The effect of positioning cations on acidity and stability of the framework structure of Y zeolite.

The investigation on the modification of NaY zeolite on LaHY and AEHY (AE refers Ca and Sr and the molar ratio of Ca and Sr is 1:1) zeolites was proformed by XRD, N2-physisorption (BET), XRF, XPS, NH3-TPD, Py-IR, hydrothermal stability, and catalytic cracking test. These results indicate that HY zeolite with ultra low content Na can be obtained from NaY zeolite through four exchange four calcination method. The positioning capability of La3+ in sodalite cage is much better than that of AE2+ and about 12 La3+ can be well coordinated in sodalite cages of one unit cell of Y zeolite. Appropriate acid amount and strength favor the formation of propylene and La3+ is more suitable for the catalytic cracking of cyclohexane than that of AE2+. Our results not only elaborate the variation of the strong and weak acid sites as well as the Brönsted and Lewis acid sites with the change of exchanged ion content but also explore the influence of hydrothermal aging of LaHY and AEHY zeolites and find the optimum ion exchange content for the most reserved acid sites. At last, the coordination state and stabilization of ion exchanged Y zeolites were discussed in detail.

Synthesis of (Ag,F)-modified anatase TiO2 nanosheets and their enhanced photocatalytic activity

A series of TiO2 nanosheets are prepared with different amounts of AgNO3 and HF solution through a solvothermal process. The samples are characterized by X-ray diffraction (XRD), X-ray fluorescence spectroscopy (XRF), X-ray photoelectron spectroscopy (XPS), transmission electron microscopy (TEM), laser Raman spectroscopy (LRS), electron paramagnetic resonance (EPR), and UV-vis diffuse reflectance spectroscopy (UV-vis DRS). From the results it is clear that the added HF solution inhibits the crystallite size growth in the [001] direction, and induces the formation of the TiO2 nanosheets with highly exposed (001) facets. There is a strong interaction between the Ag nanoparticles and the TiO2 support. The (Ag,F)-modified TiO2 catalyst exhibits high activity of MB photodegradation under both UV light and visible light irradiation. Two mechanisms of photocatalysis under UV light and visible light irradiation were discussed and proposed. It is indicated that the strong interaction between the Ag nanoparticles and the TiO2 support improves the photocatalytic activity of TiO2 nanosheets.