Publications

From the27Al MAS NMR and 2D 3QMAS NMR experiments, it can be concluded that during the steaming process of zeolite omega, some part of the framework tetrahedral Al species are gradually distorted. The 30ppm broad hump in the 1D27Al spectra is mainly due to appearance of the distorted tetrahedral Al. With the dealumination process going on, penta-coordinated Al species are formed and contribute also to the 30ppm broad hump. There exists the trend that the formation of penta-coordinated Al occurs with the consumption of the distorted tetrahedral Al species. Because the same phenomenon of the27Al NMR signals has also been observed in other zeolites, such as mordenite, ZSM-5 and Y, it could be regarded as a general procedure in the process of dealumination of acidic zeolites. © 2004 Elsevier B.V. All rights reserved.

Boron-doping commercial magnesia-supported ruthenium catalysts for ammonia synthesis were conveniently prepared in a similar process of the preparation of supported amorphous alloy Ru-B catalysts using RUCl3· nH2O as precursor. Activity evaluation results showed that the cesium-promoted catalyst exhibited significantly high activity for ammonia synthesis at atmospheric pressure, whereas the non-promoted catalyst had almost no activity in the same conditions. The catalysts were characterized by XRD, XPS and TEM. © 2004 Elsevier B.V. All rights reserved.

Boron substituted omega (MAZ) was directly synthesized and the synthesis conditions were systemically investigated, focusing on reducing the template usage by employing ageing and seeding processes. Boron substituted zeolite omega was characterized by11B,27Al,29Si and 2D27Al 3Q MAS NMR to study the structure and dealuminization process. The result suggested that boron adulteration is a good way to improve the Si/Al ratio of omega.

Titania supported palladium-copper bimetallic catalysts (Pd-Cu/TiO2) are prepared by liquid-phase chemical reduction method and then applied in the catalytic reduction of nitrite ions in drinking water. The nitrite conversion and selectivity to N2influenced by metal molar ratio (Pd:Cu), H2flow rate, CO2flow rate, pH value of solution and reaction temperature are also discussed in detail with physical characterizations methods such as XPS, XRD, in situ FT-IR. It is discovered that bimetallic Pd-Cu/TiO2catalyst has higher activity than monometallic Pd/TiO2catalyst in the catalytic reduction of nitrite ions and a mechanism is proposed to explain this promoting effect of bimetallic catalyst in this paper. © 2004 Elsevier B.V. All rights reserved.

Photocatalytic reduction of nitrate in the presence of hole scavenger has been studied by using TiO2-supported bimetallic catalysts for the first time. Compared with monometallic catalysts, bimetallic catalysts, especially Ni-Cu/TiO2catalyst, show more excellent photocatalytic reduction activity. Furthermore, the effects of metal weight ratio, total metal content, different hole scavengers and pH value of the solution are also investigated. It is found that pH value of reaction solution plays an important role in the photocatalytic reduction of nitrate ions. A mechanism is proposed to discuss enhancement effect of the bimetallic catalyst in photocatalytic reduction of nitrate ions in this paper. © 2004 Elsevier B.V. All rights reserved.

Supported metal catalysts have been applied in many current industrial processes. The morphology of metal particles coated on support has been proven to affect the performance of catalysts greatly. In this study, a simple photodeposition process will be introduced to coat palladium onto titanium dioxide with an emphasis on the morphology control and size distribution of palladium particles. The effect of pH on the morphology of palladium particles was systemically investigated. It is found that the deposited palladium particles can be controlled to have narrow particle size distribution and homogeneous dispersion by a simple pH-controlled process during photodeposition. Experimental results demonstrate that the adsorption competition between OH-and PdCl42-or it s hydrolytic anions can efficiently keep local concentration of palladium ions on titanium dioxide extremely low to control the morphology of deposited palladium particles on titania. The as-prepared Pd/TiO2particles are found to be crystallitic stable indicated by TEM, XRD and XPS measurements. © 2004 Elsevier B.V. All rights reserved.

Photocatalytic reduction of nitrate ions was examined by using Cu/MgTiO3-TiO2catalyst in the presence of sodium oxalate as hole scavenger. Many factors such as catalyst calcination temperature, Cu:Mg atom molar ratio, different hole scavengers and different concentrations of sodium oxalate were tested to search for the optimal reaction conditions. X-ray diffraction (XRD) and Transmission Electron Micrograph (TEM) were performed to characterize the composite semiconductors catalyst. Our results indicated that Cu/MgTiO3-TiO2catalyst calcined at 873 K showed the highest photocatalytic activity and nitrate conversion reached 39.2% after 2 h irradiation. The enhanced effect for photocatalytic nitrate reduction activity was most likely to result from the formation of composite semiconductor MgTiO3-TiO2and the transformation of TiO2crystalline phase. © 2004 Elsevier B.V. All rights reserved.

A caesium-promoted ruthenium catalyst supported on nanocrystalline magnesia with high activity for ammonia synthesis was conveniently prepared by using hydrated ruthenium trichloride and hexahydrate magnesium nitrate as precursors, whereas dechlorination post-treatment and ready-made magnesia were not necessary.

Titania supported palladium-copper bimetallic catalysts (Pd-Cu/TiO 2) are prepared by the liquid phase chemical reduction method and then applied in the liquid phase catalytic reduction of nitrate ions (NO 3 -). Compared with the conventional impregnation method that needs the post-thermal reduction to prepare the supported metallic catalysts, the liquid phase chemical reduction at room temperature can inhibit the aggregation of metal active components and have been proved to exhibit high catalytic activity in this work. The conversions of NO3 - are 29.18% and 54.12% over the catalysts treated at 873 and 298 K, respectively. The conversion of NO3 - and selectivity to N2 influenced by the effect of the support, the loading of Pd + Cu, the molar ratio of Pd to Cu, the H2 flow rate, the addition of CO2 and the pH value of solution are also discussed in detail with the surface characterizations by X-ray photoelectron spectrum (XPS), X-ray diffraction (XRD), in situ FT-IR and transmission electron microscopy (TEM). A mechanism has been proposed that Cu2O component involved the reaction course and acted as the active center for nitrate-to-nitrite conversion. The spilt-over hydrogen on Pd is suggested to reduce the adjacent Cu2O into metal Cu, and on the latter the conversion of NO3 - to NO2 - occurs. However, in strongly acidic solution, copper is dissolved from the Pd-Cu/TiO2 catalyst and released into the solution in the form of copper(II) ions, so the reduction of Cu 2O to Cu is inhibited and the nitrate reduction cannot be accomplished. © 2003 Elsevier B.V. All rights reserved.

Supported metal catalysts have been used extensively in many current industrial processes. The morphology of coated metal on a support is usually an important factor affecting the efficiency of the catalyst. In this study, the investigation is focused on a photocatalytic process to coat silver clusters on titania (P-25 TiO2) with an emphasis on the morphology control of coated silver clusters. For the first time, the particle size and the deployment intervals of silver clusters are controlled with an innovative method that involves the in-situ formation of water-insoluble transitory species such as AgBr, AgCl, or Ag2O on the surface of titanium dioxide. Experimental results demonstrated that the transitory particles function as physical spacers, which temporarily occupy some of the active site on the titanium dioxide surface and act as reservoirs for Ag+ions to keep the local Ag+concentration on TiO2extremely low. The silver clusters coated on titania are found to be stable in the spherical silver-3c syn crystalline form indicated by TEM, XRD, and XPS measurements.