Preparation of silver nanowires in ion-track membranes

Polycarbonate (PC) membranes were irradiated with swift heavy ions and latent tracks were created along the ions' trajectories. Nanopores, diameters between 100 and 500 nm, were obtained after illuminating the membranes with UV light and etching in NaOH solution. Silver nanowires were produced in the etched ion-track membranes by electrochemical deposition. The morphology and crystallinity of the silver nanowires were studied by means of scanning electron microscopy (SEM), X-ray diffraction (XRD), transmission electron microscopy (TEM), and selected area electron diffraction (SAED). Under certain conditions (deposition voltage 25 mV, current density 1-2 mA.cm(-2), temperature 50 degrees C, electrolyte 0.1 mol.L-1 AgNO3), single-crystalline silver nanowires with preferred orientation along the [111] direction can be synthesized.

Coking kinetics on the catalyst during alkylation of fcc off-gas with benzene to ethylbenzene

The production of ethylbenzene from the alkylation of dilute ethylene in fee off-gases with benzene has been commercialized in China over a newly developed catalyst composed of ZSM-5/ZSM-11 co-crystallized zeolite. The duration of an operation cycle of the commercial catalyst could be as long as 180 days. The conversion of ethylene could attain higher than 95%, while the amount of coke deposited on the catalyst was only about 10 wt.%. Thermogravimetry (TG) was used to study the coking behavior of the catalyst during the alkylation of fee off-gas with benzene to ethylbenzene. Based on effects of reaction time, reaction temperature, reactants and products on coking during the alkylation process, it is found that the coking rate during the alkylation procedure follows the order: ethylbenzene > ethylene > propylene > benzene for single component, and benzene-ethylene > benzene-propylene for bi-components under the same reaction condition. Furthermore, the coking kinetic equations for benzene-ethylene, benzene-propylene and ethylbenzene were established. (C) 2003 Elsevier B.V. All rights reserved.

Direct reduction of SO2 to elemental sulfur by the coupling of cold plasma and catalyst (I)

The direct reduction of SO2 to elemental sulfur in flue gas by the coupling of cold plasma and catalyst, being a new approach for SO2 reduction, was studied. In this process, CO2 can be disassembled to form CO, which acts as the reductant under the cold plasma. With the coupling of the cold plasma and the catalyst, sulfur dioxide was selectively reduced by CO to elemental sulfur with a byproduct of metal sulfate, e.g., FeSO4. In the present work, Fe2O3/gamma-Al2O3 was employed as the catalyst. The extent of desulfurization was more than 80%, and the selectivity of elemental sulfur is about 55%. The effects of water vapor, temperature, and the components of simulated flue gas were investigated. At the same time, the coupling of thermogravimetry and infrared method and a chemical analysis method were employed to evaluate the used catalyst. In this paper, we will focus on the discussion of the catalyst. The discussions of the detail of plasma will be introduced in another paper.

A mechanism for enhanced photocatalytic activity of silver-loaded titanium dioxide

In this paper, silver-loaded TiO2 photocatalyst was prepared by photochemical impregnation method and characterized by transmission electron microscopy (TEM), diffuse reflectance spectra (DRS), photooxidation of phenol and photoreduction of Cr(VI). Electron paramagnetic resonance (EPR) was used to detect photoproduced paramagnetic radicals. The correlation of photocatalytic activity and photogenerated reactive species was discussed, and the mechanism of silver-loaded TiO2 for enhancement of photocatalytic activity was elucidated. The results show that deposited silver on TiO2 Surface acts as a site where electrons accumulate. The better separation between electrons and holes on the modified TiO2 surface allowed more efficiency for the oxidation and reduction reactions. The enhanced photocatalytic activity was mainly attributed to the increased amounts of O-2(.-) reactive species and surface Ti3+ reactive center on silver-loaded TiO2 photocatalyst. (C) 2004 Published by Elsevier B.V.

Pd/sulfated alumina - a new effective catalyst for the selective catalytic reduction of NO with CH4

Sulfated alumina (SA) is firstly found to be an effective support for Pd catalyst used in the SCR of NO with methane. The sulfation is important to increase support's acidity which is essential for the reduction of NO over Pd catalysts. On consideration of the lower cost and easier availability of SA, we believe that SA is more promising to act as the commercial support for Pd catalyst used in the SCR of NO with methane.

The reaction route and active site of catalytic decomposition of hydrazine over molybdenum nitride catalyst

The catalytic properties of the passivated, reduced passivated, and fresh bulk molybdenum nitride for hydrazine decomposition were evaluated in a microreactor. The reaction route of hydrazine decomposition over molybdenum nitride catalysts seems to be the same as that of Ir/gamma-Al2O3 catalysts. Below 673 K, the hydrazine decomposes into N-2 and NH3. Above 673 K, the hydrazine decomposes into N-2 and NH3 first, and then the produced NH3 further dissociates into N-2 and H-2. From the in situ FT-IR spectroscopy, hydrazine is adsorbed and decomposes mainly on the Mo site of the Mo2N/gamma-Al2O3 catalyst. (C) 2004 Elsevier Inc. All rights reserved.

Synthesis and characterization of carbon black supported Pt-Ru alloy as a model catalyst for fuel cells

A set of bimetallic Pt-Ru catalysts prepared by co-impregnation of carbon black with ruthenium(III) chloride hydrate and hydrogen hexachloroplatinate(IV) hydrate were investigated by temperature-programmed reduction (TPR), chemisorption of hydrogen, transmission electron microscopy (TEM), microcalorimetry of adsorbed CO and a structure-sensitive reaction (n-hexane conversion). The results showed that the volumetric capacities for CO and H-2 adsorption is influenced in the bimetallic Pt-Ru catalysts by the formation of a Pt-Ru alloy. The n-hexane reaction revealed that the reaction mechanism for the pure Pt catalyst mainly occurs via cyclic isomerization and aromatization due to the presence of bigger Pt surface ensembles, whereas the Pt-Ru catalysts exhibited predominantly bond-shift isomerization by the diluting effect of Ru metal addition. The differential heats of CO chemisorption on Pt-Ru catalysts fell between the two monometallic Pt and Ru catalysts extremes. (C) 2004 Elsevier B.V. All rights reserved.

An improved palladium-based DMFCs cathode catalyst

A novel carbon-supported palladium-rich Pd3Pt1/C catalyst prepared by a modified polyol process showed a better cell performance than Pt/C in direct methanol fuel cells, which may be attributed to palladium's inactivity to methanol electro-oxidation while exhibiting good performance to oxygen reduction reaction.