Synthesis, characterisation and HDN activity of iron–vanadium sulphide prepared with the use of a chelating agent

The influence of the use of ethylenediamine in the preparation of iron–vanadium catalyst for toluene hydrogenation (HYD) and pyridine hydrodenitrogenation (HDN) has been studied. Both HYD and HDN activities increased significantly with Fe incorporation to vanadium sulphide and the beneficial effect of ethylenediamine was shown. Possible explanations for the enhancements in HYD and HDN conversion are discussed.     

Dehydrogenation of propane over a silica-supported vanadium oxide catalyst

The dehydrogenation of propane over a silica-supported vanadium oxide catalyst was investigated at 823 K under atmospheric pressure in the presence/absence of CO₂. The yield of propene and the selectivity to propene were higher in the dehydrogenation in the presence of CO₂ than those in the dehydrogenation in the absence of CO₂. On the other hand, the yield of aromatics and the selectivity to aromatics were much higher in the dehydrogenation in the absence of CO₂ than those in the dehydrogenation in the presence of CO₂. TPR measurements, NH₃ desorption studies and in-situ UV–vis studies on the catalyst were also performed to elucidate the effects of CO₂ on the behavior of the vanadium oxide in the catalyst during the dehydrogenation of propane.     

浅谈五氧化二钒的市场状况和生产工艺

介绍了五氧化二钒的运用领域,并对目前国内、外五氧化二钒的生产及消费状况进行了分析;列举了五氧化二钒不同的生产工艺,并分别讲述了各种工艺流程的技术特点;最后对五氧化二钒产品的市场进行了预测和展望。     

Photochemical reduction of nitrate to ammonia using layered hydrous titanate/cadmium sulphide nanocomposites

The photocatalytic activity of H₂Ti₄O₉/CdS nanocomposites incorporating CdS particles, less than 0·8 nm thick, in the interlayer of H₂Ti₄O₉ was evaluated for the reduction of NO₃⁻ with and without methanol. NO₃⁻ was photochemically reduced by bandgap illumination in the presence of H₂Ti₄O₉/CdS nanocomposites with and without methanol although unsupported CdS showed no noticeable photocatalytic activity for NO₃⁻ reduction. The oxidation of CdS in H₂Ti₄O₉/CdS to SO₄^2- was accompanied by NO₃⁻ reduction without methanol, whereas addition of methanol was useful to promote the NO₃⁻ reduction and depress the oxidation of CdS. The catalytic activity of H₂Ti₄O₉/CdS greatly increased with doping Pt particles in the interlayer.     

Discharge characteristics of silver vanadium oxide cathodes

The discharge characteristics of silver vanadium oxide (SVO) as a cathode in lithium–silver vanadium oxide (Li–SVO) primary battery was studied under various operating conditions. The cathode yielded a capacity of 260 mAh g⁻¹ at a current density of 0.08 mA cm⁻², although the theoretical capacity of this material is 315 mAh g⁻¹. The pulse discharge characteristics were studied under conditions that simulate battery operation inside an implantable cardio-verter defibrillator (ICD). The variation of the ohmic resistance of the system was studied as a function of depth of discharge. Rate capability and impedance studies indicated high diffusion limitations for this system especially at high depth of discharge. Morphological changes during discharge were also discussed using scanning electron microscopic studies.     

钒磷氧非均相催化合成苯乙酮乙二醇缩酮

研究了苯乙酮与乙二醇在钒磷氧非均相催化剂作用下的缩合反应，考察了反应时间、醇酮比、催化剂用量和带水剂用量等因素对苯乙酮乙二醇缩酮收率的影响。结果表明，在回流条件下，苯乙酮为0．10mol，乙二醇为0．12mol，催化剂用量为0．20g，带水剂环己烷用量为6mL，反应2．5h后，缩酮收率可达到81．5％，且催化剂重复使用性能良好。产品经熔点仪和红外光谱仪进行了表征。     

Photocatalytic reduction of the environmental pollutant Cr over a cadmium sulphide powder under visible light illumination

The photocatalytic reduction of the pollutant Cr^VI over CdS in different crystalline states under visible light illumination was investigated. The photocatalytic activity of heat-treated (HT) and non-heat-treated (NHT) CdS was systematically compared. The Cr^VI, contained in an aqueous solution of 200 μg/ml, was almost totally eliminated within 30 min when NHT CdS was used as catalyst and displayed a much higher activity than that of HT CdS. The addition of a hole-scavenger such as ethanol, which acted optimally at 10–20%, remarkably improved the activity of HT CdS. The macroscopic difference in photocatalytic activity between NHT and HT CdS was microscopically explained by the differences in their morphological structures, surface states, and light responses which were determined by means of X-ray diffraction, static adsorption and UV-visible spectra. The adsorbance and adsorption state of Cr^VI was determined on the CdS surface and its photoreducibility was proven by X-ray photoelectron spectroscopy and temperature-programmed desorption. The photoreduction rate of pollutant Cr^VI, either during experiments indoors or during experiments in sunlight was remarkably improved. 99.3% of the Cr^VI was reduced from a solution of 200 μg/ml concentration during 1 h of sunlight irradiation. Applications are given for the photocatalytic elimination of Cr^VI in waste water under sunlight irradiation.     

Intercalation of lithium in r.f.-sputtered vanadium oxide film as an electrode material for lithium-ion batteries

Vanadium oxide films were prepared by r.f.-sputtering using an argon sputter gas and a V2O5 target. The films were characterized by scanning electron microscopy, atomic force microscopy, X-ray diffraction, X-ray photoelectron spectroscopy and electrochemical techniques. The oxide film as deposited is amorphous; they are heat-treated in the range 300–700°C in oxygen atmosphere and are composed of orthorhombic V2O5 crystals. At higher heat-treatment temperatures (600–700°C) the crystallization of the oxide proceeded significantly with ab-direction parallel to the substrate. The oxide film undergoes a reversible lithium intercalation and deintercalation process. The kinetics of the intercalation process of lithium into amorphous V2O5 film was studied using an a.c. impedance method. Furthermore, a rocking-chair type V2O5 film/LixV2O5 film cell could be charge–discharge cycled over 300 times at a current of 10A at 25°C.     

Preparation, characterization, and electrochemical properties of lithium vanadium oxide nanoribbons

Highly uniform lithium vanadium oxide nanoribbons were successfully prepared in large quantities using a facile hydrothermal approach without employing any surfactants or templates. The as-prepared products were up to hundreds of micrometers in length, about 200 nm in width, and 20 nm in thickness. These nanoribbons and nafion composite were employed to modify glassy carbon electrode, which displayed excellent electrochemical sensitivity and rapid response in detecting dopamine in phosphate buffer solution. Lithium ions can greatly increase the electron transfer between the electrode and biological materials, and significantly increase the reversibility of electrochemical process. A linear relationship between the concentrations of dopamine and its oxidation peak currents was obtained. The linear range for the detection of dopamine was 2.0 × 10⁻⁶ to 1.0 × 10⁻⁴ M with a detection limit of 1.0 × 10⁻⁷ M. In addition, the good reproducibility and long-term stability of the sensor make it valuable for further application.     

Synthesis and electrochemical performance of lithium vanadium oxide nanotubes as cathodes for rechargeable lithium-ion batteries

A new kind of cathode materials for rechargeable lithium-ion batteries, lithium vanadium oxide nanotubes synthesized by a combined sol-gel reaction and hydrothermal treatment procedure is reported in this paper. SEM, TEM, XRD and XPS techniques were performed to investigate the morphology and structure of the resulting materials. The results confirmed that the synthetic materials are composed of uniformly open-ended multiwalled nanotubes with a length from 1 to 3 μm. The inner and the outer diameters of the obtained nanotubes vary from 30 to 50 nm and 50 to 120 nm, respectively. The electrochemical performance as a cathode material was examined and evaluated by cyclic voltammetry, galvanostatic charge-discharge cycling and AC impedance spectroscopy techniques. The results indicated that the resultant lithium vanadium oxide nanotubes have a high initial discharge capacity of 457 mAh g⁻¹ in the potential range of 1.0-4.0 V (vs. Li/Li⁺) and good cycling performance. The improved electrochemical performance of the products should be due to its special one-dimensional multiwalled tubular structure and the contribution of lithium-ions.     

Coextraction of vanadium and manganese from high-manganese containing vanadium wastewater by a solvent extraction-precipitation process

High-manganese containing vanadium wastewater (HMVW) is commonly produced during the vanadium extraction process from vanadium titano-magnetite. HMVW cannot be reused and discharged directly, and is harmful to the environment and affect product quality due to heavy metals in the wastewater. The wastewater is usually treated by lime neutralization, but valuable metals (especially V and Mn) cannot be recovered. In this study, an efficient and environmentally friendly method was developed to recover valuable metals by using a solvent extraction-precipitation process. In the solvent extraction process, 98.15% of vanadium was recovered, and the V₂O₅ product, with a purity of 98.60%, was obtained under optimal conditions. For the precipitation process, 91.05% of manganese was recovered as MnCO₃ which meets the III grade standard of HG/T 2836-2011. Thermodynamic simulation analysis indicated that MnCO₃ was selectively precipitated at pH 6.5 while Mg and Ca could hardly be precipitated. The results of X-ray diffraction and scanning electron microscopy demonstrated that the obtained V₂O₅ and MnCO₃ displayed a good degree of crystallinity. The treated wastewater can be returned for leaching, and resources (V and Mn) in the wastewater were utilized efficiently in an environmentally friendly way. Therefore, this study provides a novel method for the coextraction of V and Mn from HMVW.     

锂一次电池正极材料钒酸银的研究进展

钒酸银正.极材料目前已广泛应用于可植入式心脏复律除颤器电源中,是一种极具研究和开发价值的电极材料.本文介绍了钒酸银放电过程的电化学还原机理,归纳总结了固相法,溶胶凝胶法、水热法、微波法等方法制备钒酸银的研究成果和各方法的优缺点,概述了对钒酸银进行改性研究的成果,并对今后钒酸银主要的研究方向和发展趋势进行了展望.     

CO2氧化乙苯脱氢制苯乙烯钒基氧化物催化剂研究进展

与现有乙苯直接脱氢工艺技术相比,CO₂氧化乙苯脱氢工艺具有缓解直接脱氢热力学平衡限制、苯乙烯选择性高、能耗低和二氧化碳资源化利用等显著优势,有望成为一条从乙苯生产苯乙烯的绿色工艺路线。为此,在总结乙苯直接脱氢反应体系和现有工业技术特点、面临的问题和发展方向的基础上,本文较为全面地分析了CO₂氧化乙苯脱氢的特点和反应机理,探讨了现有催化剂体系普遍快速失活的关键原因,表明高性能催化剂研究依然是推进CO₂氧化乙苯脱氢工业化应用的关键。鉴于钒基氧化物催化剂表现出较高的活性,成为近年来CO₂氧化乙苯脱氢相关研究关注的重点。为此,从钒物种含量及其聚集态结构、催化剂的氧化还原和酸碱性、催化剂表面积炭及其作用等角度,综合分析了活性中心结构、反应机理等方面的相关研究进展,认为孤立态V⁵⁺及其含量可能是决定钒基氧化物催化剂活性的关键,其稳定性主要取决于催化剂的氧化还原特性,而积炭对催化剂活性和稳定性的影响则与其组成和石墨化程度密切相关。基于上述认识,认为强化CO₂的高效活化、抑制V⁵⁺的深度还原等是今后钒基氧化物催化剂研究的重点发展方向,而利用移动固定床或提升管反应器等进行工艺优化,对推进CO₂氧化乙苯脱氢工业化应用具有重要的研究价值。     

Hydrogen adsorption capacity of vanadium oxide nanotube from pure and mixture gas environment through molecular simulation

The effects of temperature and pressure on the adsorption capacity of vanadium oxide nanotube (VONT) were investigated by Monte Carlo (MC) simulation. Hydrogen adsorption was an increasing function of pressure and in about 50 MPa VONT showed the maximum total hydrogen capacity of 5.17, 4.67 and 4.56 wt%. at 250, 275 and 300 K, respectively. On increasing the temperature to room temperature, 75% decrease in the initial adsorption capacity was observed.

Appraising adsorption of the same number of hydrogen molecules from pure and hydrogen/nitrogen mixture at 300 K indicated that under 10 MPa, changes in adsorption capacities were inconsequential after N₂ addition to the environment.     

Liquid phase oxidation of dibenzothiophene with alumina-supported vanadium oxide catalysts: An alternative to deep desulfurization of diesel

Alumina-supported vanadium oxide catalysts were prepared by different methods as thermal spreading, incipient wetness impregnation of ammonium metavanadate and sol–gel synthesis of alkoxide precursors, with different vanadium loadings, in order to increase the performance in oxidative desulfurization (ODS) of dibenzothiophene. The catalysts were characterized by several techniques: X-ray diffraction, UV–vis DRS, Raman spectroscopy, FT-IR of adsorbed pivalonitrile, and TPR. As additional experimental techniques, SEM–EDX and N₂ adsorption–desorption were applied, to obtain elemental analyses and textural properties. Results evidenced the presence of different superficial V species, which depend on both vanadium loading and preparation method, while significant differences in ODS activity were observed due to the catalysts preparation method.     

Corrosion mechanism of MgO-C bricks used as linings in a vanadium extraction converter

To extend the service life of MgO-C bricks used as linings in vanadium extraction converters, their corrosion mechanism was investigated using stationary immersion and rotary crucible methods at 1673 K. The effects of oxides in vanadium slag were studied using the slag invasion method. The results showed that a decarburization layer was formed but was not effectively sintered under vanadium extraction conditions, resulting in it having a loose structure and poor binding strength. When slag-splashing technology was applied to protect the converter, the decarburization layer and slag-splashing layer easily fell off due to scouring by the molten pool. Consequently, the poor strength of the decarburization layer was the main reason for the poor anti-erosion performance of the MgO-C bricks and the weak effect of slag-splashing technology. In addition, higher contents of SiO₂ and TiO₂ in vanadium slag could form low melting point compounds and increase the thickness of the decarburization layer, thereby accelerating the MgO-C brick corrosion rate. Higher contents of FeO in the vanadium slag not only formed low melting point compounds but also caused a decarburization reaction with the MgO-C bricks. However, with increases of V₂O₃ in the slag, the formation of high melting point compounds decreased the corrosion rate and corrosion depths.     

Metal-oxide boundary effects in vanadium oxide – Rh(111) inverse model catalysts: a RAIRS, STM and TPD study

The formation and the reactivity of V-oxide/Rh(111) inverse catalyst surfaces has been investigated by reflection absorption infra red spectroscopy (RAIRS), varaiable-temperature scanning tunneling microscopy (VT-STM) and thermal programed desorption (TPD), The oxidation of metallic V island structures deposited on Rh(111) at room temperature has been monitored in situ at 200 °C and 400 °C by VT-STM and RAIRS, leading to small-island and large-island morphologies, respectively. The different reactivities of the generated inverse catalyst surfaces have been probed using the adsorption and oxidation reaction of CO. It is shown that the small-island V-oxide/Rh(111) catalyst exhibits enhanced reactivity in the oxidation of CO and is more easily subjected to oxide reduction. This is ascribed to the significant influence of the metal-oxide phase boundary on the catalyst activity. This paper is dedicated to Konrad Hayek.     

Impact response of epoxy systems containing short fibres and/or oxide particles as reinforcements

This work looks at the role played by constant levels of fibre and/or particles in epoxy matrices on impact responses during dynamic loading. In order to delineate the differing roles of reinforcements, hybrid composites containing different amounts of fibres and particles were prepared. Maximum loads and energies were used to distinguish the responses during and following impact. Scanning electron microscopy (SEM) was used to characterize the surface features before and after failure. Furthermore, such microscopic analyses were also employed to substantiate the deductions arrived at based on mechanical data analysis, which included the deduced parameter in the form of energy for propagation. The experimental results pointed to the fact that the total energy and load generally rise as the fibre content in the epoxy system increases. The hybrids, on the other hand, displayed a trend where the normalized load and the total energy increased as the fibre content in the hybrid was raised from 1 to 5 vol%. This was most evident when the differing levels of fillers and fibres were fixed at a total of 7 vol%. In addition, comparison was made between two sets of compositions of fibres and particles in the composites. The results showed that the higher fibre content in the hybrid allowed greater load bearing and energy absorption and the difference in recorded levels increased with higher fibre content in one hybrid set. Fractography studies indicated flatter surface features for systems with only particles added, whereas the ‘all‐fibre’ bearing systems displayed ‘fast‐fracture’ features resembling ‘river patterns’. Copyright © 2004 Society of Chemical Industry     

An assessment of zinc oxide nanosheets as a selective adsorbent for cadmium

Zinc oxide nanosheet is assessed as a selective adsorbent for the detection and adsorption of cadmium using simple eco-friendly extraction method. Pure zinc oxide nanosheet powders were characterized using field emission scanning electron microscopy, energy dispersive spectroscopy, X-ray diffraction, X-ray photoelectron spectroscopy, and Fourier transform infrared spectroscopy. The zinc oxide nanosheets were applied to different metal ions, including Cd(II), Cu(II), Hg(II), La(III), Mn(II), Pb(II), Pd(II), and Y(III). Zinc oxide nanosheets were found to be selective for cadmium among these metal ions when determined by inductively coupled plasma-optical emission spectrometry. Moreover, adsorption isotherm data provided that the adsorption process was mainly monolayer on zinc oxide nanosheets.     

Synthesis of nanodispersed oxides of vanadium, titanium, molybdenum, and tungsten on mesoporous silica using atomic layer deposition

The advantages of the atomic layer deposition (ALD) method for preparation of tungsten, vanadium, titanium, and molybdenum oxide catalyst supported on mesoporous silica are discussed, with emphasis on the importance of synthesis conditions on dispersion, structure and activity of the resulting materials. A suite of complementary techniques such as DRS-UV/Vis, BET, ¹H-NMR, XRD, and TEM were used to study the structural properties of the supported metal oxides, and probe reactions such as 2-butanol dehydration and ethanol partial oxidation were used to demonstrate the potential advantages of the ALD-prepared catalysts. Specifically, highly dispersed oxides of titanium, molybdenum, and tungsten oxide on mesoporous silica were synthesized using the ALD method. It is also demonstrated that attainment of high dispersions of vanadium oxide on mesoporous silica requires the presence of at least a single layer of titanium oxide due to the well-known poor interaction between vanadia and silica. The highly dispersed catalysts prepared here by ALD methods exhibited superior catalytic performance relative to those prepared using conventional incipient wetness impregnation.