Jing-Fa Deng

XPS studies on surface electronic characteristics of Ni–B and Ni–P amorphous alloy and its correlation to their catalytic properties

Abstract The Ni–B, Ni–P, Ni–B/SiO2 and Ni–P/SiO2 amorphous alloy samples were prepared by chemical reduction with BH4− or H2PO2−. Their amorphous structures were verified by X-ray diffraction (XRD) and extended X-ray absorption fine structure (EXAFS). Transmission electron microscopy (TEM) was used to determine their morphology and particle size. XPS experiments have been carefully designed to characterize the surface electronic state of the as-prepared samples. By comparing with electron binding energies of the pure Ni, B and P, the XPS spectra demonstrated that boron donated electron to nickel in Ni–B alloy, resulting in electron-enrichment of elemental Ni, while no significant electron transfer between Ni and P in Ni–P alloy was observed. Those results seem reasonable to elucidate the different catalytic behaviors of Ni–P and Ni–B amorphous alloy catalysts, such as the hydrogenation activity and sulfur resistance ability.

Progress in design of new amorphous alloy catalysts

Three new kinds of Ni-based amorphous alloy catalysts, Raney type Ni–P(R–Ni–P), Ni–Co–B, and Ni–B(P)/SiO2, have been prepared by modification of either the rapid quenching method or chemical reduction. Their amorphous structures have been determined by XRD, EXAFS, and DSC. Their catalytic activities and selectivities have been measured during the hydrogenation of various organic compounds, which demonstrate the great improvement on the catalytic properties in comparison with the corresponding amorphous alloy catalysts prepared by the rapid quenching method or chemical reduction previously reported. These new amorphous catalysts also exhibit superior catalytic properties over the traditional catalysts, such as Raney Ni, Ni/SiO2, and Pd/C, making them possible to be used in real industrial catalysis. The relationship between the catalytic properties and the structural properties has been discussed according to various characterizations, including ICP, XPS, EXAFS, XRD, TPD, TPR, hydrogen adsorption, IR, SEM, and TEM, etc. The higher hydrogenation activity of R–Ni–P than the Ni–P amorphous catalyst obtained by rapid quenching is mainly ascribed to the increase of the surface area due to the skeleton structure; the higher activity of Ni–Co–B than the Ni–B amorphous catalyst demonstrates a promoting effect of the additive metal(s); while the higher thermal stability of supported Ni–P(B) than the corresponding unsupported catalysts can be explained by considering the stabilizing effect of the silica support on the amorphous structure.

A convenient alcohothermal approach for low temperature synthesis of CuO nanoparticles

Abstract A convenient alcohothermal route to prepare cupric oxide nanoparticles using copper acetate as the starting material was successfully developed. The influence of reaction temperature on the formation of CuO nanoparticles was investigated. The yield was as high as 100% when the alcohothermal synthesis was carried at 110°C. The particle sizes of the CuO nanoparticles can be controlled to be between ∼3 and 9 nm simply by varying the reaction temperature. The possible formation mechanism of CuO nanoparticles via the alcohothermal method is discussed.

XPS studies on a novel amorphous Ni–Co–W–B alloy powder

Abstract A novel amorphous Ni–Co–W–B alloy powder, which showed higher catalytic activity than Ni–Co–B for the hydrogenation of benzene, was prepared by chemical reduction and characterized by TEM and XRD. The surface composition and the interactions between the components on the surface were studied by XPS. The measurement detected the presence of some oxides and hydroxides, such as NiO, Ni(OH) 2 , Co(OH) 2 , B 2 O 3 and WO 3 associated with their elemental states of Ni, Co, B and W, respectively. The presence of a few number of tungsten atoms leads to more metallic nickel on the surface.

XPS studies of Cu/ZnO/Al2O3 ultra-fine catalysts derived by a novel gel oxalate co-precipitation for methanol synthesis by CO2+H2

Abstract The chemical states of Cu and Zn in an ultra-fine high performance Cu/ZnO/Al2O3 catalyst at various preparation stages for the methanol synthesis by CO2/H2 were investigated by X-ray photoelectron spectroscopy. It was found that copper was presented as metallic state and zinc still as ZnO during reaction or reduction. Moreover, it shows that the metallic Cu can be partially oxidized to Cuδ+ species by pure CO2. The active center of the Cu/ZnO/Al2O3 catalyst for methanol synthesis was discussed.

A practical approach for the preparation of high activity Cu/ZnO/ZrO2 catalyst for methanol synthesis from CO2 hydrogenation

Abstract According to the features of CuC2O4·H2O and the colloid/precipitation theories, a practical approach for the preparation of Cu/ZnO-based catalyst, which had high activity for methanol synthesis, was proposed and verified in experiments. Co-precipitation reaction in the ethanol solution was found to be an effective route for the preparation of a highly active and selective catalyst. The characterization of XRD, N2 physisorption, TEM and the measurement of the copper surface area by nitrous oxide titration revealed that preparation conditions have a significant influence on the structure and surface properties of the precursors and the catalysts, as well as on the catalytic activities for methanol synthesis from CO2 hydrogenation.

Preparation of amorphous NiCoB alloys and the effect of cobalt on their hydrogenation activity

Abstract The bimetallic amorphous alloys Ni Co B were prepared by the chemical reduction of the solution containing both nickel and cobalt salts with aqueous potassium borohydride. Those samples were thoroughly characterized by ICP, BET, DSC, XRD, EXAFS, XPS, TEM and TPR. Superior to the rapid quenching techniques, the content of Co in Ni Co B alloys could be adjusted in a wide range by changing the initial concentration of cobalt salt in the solution. The catalytic activities of the asprepared materials were measured through the hydrogenation of benzene under moderate pressure in liquid phase. By comparing with the activities of the corresponding pure Ni B, Co B and their mixture as well as the Ni Co B amorphous alloys with different contents of Co, both the inhibiting and promoting effects of Co on the hydrogenation activities in Ni Co B amorphous alloys have been observed and discussed according to the amount of the effective metal in the alloys and their structural characters, especially their surface properties.

A high activity Cu/ZnO/Al2O3 catalyst for methanol synthesis: Preparation and catalytic properties

Abstract Cu/ZnO/Al 2 O 3 ultrafine catalysts have been prepared by a novel oxalate gel coprecipitation method. The effect of the post-condition on the structure, surface properties of the catalysts and their precursors as well as the catalytic activities for methanol synthesis from CO/CO 2 hydrogenation have been studied. The results showed that the washing with ethanol or drying directly derived a large specific surface area, highly dispersion ultrafine Cu/ZnO/Al 2 O 3 catalysts, which exhibited a higher catalytic activity and optimum methanol selectivity for methanol synthesis from CO/CO 2 hydrogenation. The reaction route and mechanism of methanol formation were also discussed.

Oxidative Dehydrogenation of Propane over Mesoporous HMS Silica Supported Vanadia

Vanadium-containing mesoporous HMS catalysts have been prepared and characterized for the oxidative dehydrogenation (ODH) of propane. It is demonstrated that the vanadium supported HMS catalysts exhibit a much higher catalytic activity than the literature results obtained over the vanadium supported MCM-41 catalysts in the ODH of propane. The improved catalytic activity of the V-HMS catalysts has been attributed to the presence of high concentration of well-dispersed vanadium species on the surface of the mesoporous HMS materials.

Study on the crystallization process of Ni-P amorphous alloy

Abstract The thin film of Ni P amorphous alloy deposited on the p-type silicon slice was prepared by electroless plating, which was then crystallized by heating it at high temperature from 550 K to 610 K in nitrogen flow for 2 h. Its crystallization process was investigated by using ICP, XRD, XPS, TEM, SEM and STM. No significant changes in the composition and the electronic structure on the surface have been observed during the crystallization process. However the changes in the amorphous structure and the surface area as well as the surface morphology are observed, which are attributed to the deactivation of the amorphous alloy after annealing during the hydrogenation reactions. Experimental results also reveal that the diffusion of the component elements in the Ni P alloy is essential during the crystallization because various crystalline diffraction peaks corresponding to Ni and Ni 3 P are observed simultaneously on XRD patterns. Based on those results, some modifications have been described to improve the thermal stability of the amorphous alloy.