Lihui Dong

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.

A Study of Different Doped Metal Cations on the Physicochemical Properties and Catalytic Activities of Ce20M1Ox (M=Zr, Cr, Mn, Fe, Co, Sn) Composite Oxides for Nitric Oxide Reduction by Carbon Monoxide

This work is mainly focused on investigating the effects of different doped metal cations on the formation of Ce20 M1 Ox (M=Zr, Cr, Mn, Fe, Co, Sn) composite oxides and their physicochemical and catalytic properties for NO reduction by CO as a model reaction. The obtained samples were characterized by using N2 physisorption, X-ray diffraction, laser Raman spectroscopy, UV/Vis diffuse reflectance spectroscopy, inductively coupled plasma atomic emission spectroscopy, X-ray photoelectron spectroscopy, temperature-programmed reduction by hydrogen and by oxygen (H2 -TPR and O2 -TPD), in situ diffuse reflectance infrared Fourier transform spectroscopy, and the NO+CO model reaction. The results imply that the introduction of M(x+) into the lattice of CeO2 increases the specific surface area and pore volume, especially for variable valence metal cations, and enhances the catalytic performance to a great extent. In this regard, increases in the oxygen vacancies, reduction properties, and chemisorbed O2 (-) (and/or O(-) ) species of these Ce20 M1 Ox composite oxides (M refers to variable valence metals) play significant roles in this reaction. Among the samples, Ce20 Cr1 Ox exhibited the best catalytic performance, mainly because it has the best reducibility and more chemisorbed oxygen, and significant reasons for these attributes may be closely related to favorable synergistic interactions of the vacancies and near-surface Ce(3+) and Cr(3+) . Finally, a possible reaction mechanism was tentatively proposed to understand the reactions.

Influences of doping and thermal stability on the catalytic performance of CuO/Ce20M1Ox (M = Zr, Cr, Mn, Fe, Co, Sn) catalysts for NO reduction by CO

For NO reduction by CO with CuO/Ce20M1Ox (M = Zr, Cr, Mn, Fe, Co, Sn) catalysts, the results imply that for fresh catalysts, the doping variable valence Mx+ is more conducive to an increase in the oxygen vacancies, the content of unsaturated metal cations on the surface, and the reduction capacity. The Cu/CeMn and Cu/CeSn samples exhibited better potential; after aging, the samples doped with Cr6+, Mn4+, and Co3+ had poor physicochemical properties, but doping with Zr4+, Fe3+, and Sn4+ resulted in better thermal stability. The Cu/CeSn sample exhibited the best catalytic properties and thermal stability, which are closely related to its structure retention, oxygen vacancies, the content of the surface chemical adsorption oxygen and surface unsaturated metal cation, and reduction capacity, whether it is fresh or aged. Finally, in order to further understand the interaction between the CO and NO probe molecules with the catalyst surface, a possible reaction mechanism for NO reduction by CO on a Cu/CeSn catalyst is tentatively proposed.