钒钛物料中钒钛化学物相分析现状及最新进展

主要概述了钒钛炉渣原料中价态钒(V2+,V3+,V4+,V5+),低价钛(Ti 2+,Ti 3+),金属钒(MV),氮化钒(VN),碳化钒(VC),碳化钛(TiC),氮化钛(TiN)及钢铁材料里固溶钒(Vsol),氮化钒(VN),碳化钒(VC),固溶钛(Tisol),碳化钛(TiC),氮化钛(TiN)等的化学物相分析的现状流程及最新进展,为从事钒钛化学物相分析方法研究者提供了参考依据。     

Spectrophotometric determination of vanadium as vanadium(IV) pyridine thiocyanate

A spectrophotometric determination of vanadium as vanadium(IV) pyridine thiocyanate is described. The blue complex is formed in acidic aqueous solution and extracted into pyridine-chloroform. Absorbance is measured at 7.40 mμ. The range of best accuracy for 1-cm cells is from about 80 to 240 μg of vanadium per ml, and sensitivity is 0.4 μg of vanadium per cm² at 7.40 mμ. The vanadium may be present initially as vanadium(IV) or vanadium(V), which is reduced to vanadium(IV) by the large excess of thiocyanate ion added. Several elements interfere in the determination ; a separation procedure involving mercury cathode electrolysis is suggested.     

Structure and electronic properties of Li-doped vanadium oxide nanotubes

The influence of Li-doping on the mixed-valent vanadium oxide nanotubes has been investigated using electron energy loss spectroscopy. In particular, the electron diffraction profiles and the vanadium L excitation edges have been studied. We observe that the structure of the vanadium oxide nanotubes is stable against electron transfer upon Li-doping. Excitations at the vanadium L edges show features which are associated with a reduction of the vanadium valency.     

Synthesis and magnetic properties of two-dimensional vanadium(IV) oxide nanostructures on silica surface

Vanadium(IV) oxide nanolayers on silica surface were prepared for the first time. Samples characterized by different degrees of surface coverage by vanadium(IV)-oxygen groups were studied. Samples containing only vanadium(IV) ions and both vanadium(IV) and vanadium(V) ions were obtained. The size effect on the phase transition parameters was determined by studying magnetic properties of vanadium(IV) oxide nanolayers. The phase transition temperature ranges from 140 to 220 K, depending on surface concentration of vanadium(IV) ions and their environment.     

Determination of vanadium species in environmental samples

The distribution of vanadium between different oxidation states plays an important role in its environmental chemistry. As its two most commons forms, vanadium(IV) and vanadium(V) have different toxicity, speciation analysis of this element is necessary for environmental and biological samples. This paper presents recent research on the determination of vanadium species. Some important problems concerning stability of vanadium forms and proposed separation techniques are discussed.     

Multiple Metal–Metal Bond or No Bond? The Electronic Structure of V2O2

Detailed knowledge of the electronic structure of vanadium oxide clusters provides the basis for understanding and tuning their significant catalytic properties. However, already for the simple four‐atom V₂O₂ molecule, there are contradictory reports in the literature regarding the electronic ground state and a possible vanadium–vanadium bond. We herein show through a combination of experimental (matrix isolation) studies and theoretical results that there is a multiple vanadium–vanadium bond in this benchmark vanadium oxide molecule.     

Application of HPLC to measure vanadium in environmental,biological and clinical matrices

Vanadate and vanadium compounds exist in many environmental, biological and clinical matrices, and despite the need only limited progress has been made on the analysis of vanadium compounds. The vanadium coordination chemistry of different oxidation states is known, and the result of the characterization and speciation analysis depends on the subsequent chemistry and the methods of analysis. Many studies have used a range of methods for the characterization and determination of metal ions in a variety of materials. One successful technique is high performance liquid chromatography (HPLC) that has been used mainly for measuring total vanadium level and metal speciation. Some cases have been reported where complexes of different oxidation states of vanadium have been separated by HPLC. Specifically reversed phase (RP) HPLC has frequently been used for the measurement of vanadium. Other HPLC methods such as normal phase, anion-exchange, cation-exchange, size exclusion and other RP-HPLC modes such as, ion-pair and micellar have been used to separate selected vanadium compounds. We will present a review that summarizes and critically analyzes the reported methods for analysis of vanadium salts and vanadium compounds in different sample matrices. We will compare various HPLC methods and modes including sample preparation, chelating reagents, mobile phase and detection methods. The comparison will allow us to identify the best analytical HPLC method and mode for measuring vanadium levels and what information such methods provide with regard to speciation and quantitation of the vanadium compounds.     

Direct Determination of Vanadium in Water Samples,Human Hairs,Vegetables, and Foods by Graphite Furnace Atomic Absorption Spectroscopy

At present,the considerable attention was greatly paid to the determination of vanadium from the point of vanadium as a kind of biological nutrient element or one kind of industrial sources of pollution. In the paper,we employed graphite furnace AAS (GFAAS) method to determine directly the vanadium in samples, using optically controlled raising temperature combining with pyrolytic coating tube to atomize vanadium under the conditions of stable temperature for the determination of vanadium in samples.     

Reduction of vanadium(V) by L-ascorbic acid at low and neutral pH: kinetic, mechanistic, and spectroscopic characterization

L-Ascorbic acid interacts with vanadium(V) over the pH range of 0.4-7.0 to form three different coordination complexes. Both inner- and outer-sphere electron-transfer pathways are proposed to form vanadium(IV) complexes with L-ascorbate or dehydroascorbate, respectively. Effects of the pH on the coordination of L-ascorbic acid to the vanadium(V) center were observed and are presumably related to the speciation of the vanadium(V) ion. Three vanadium(IV) complexes were observed using ambient-temperature electron paramagnetic resonance spectroscopy. Two of these complexes are proposed to be vanadium(IV) L-ascorbate complexes, and one is consistent with a vanadium(IV) dehydroascorbic acid complex proposed earlier. These reduction reactions will occur under physiological conditions and could be important to the reduction of vanadium(V)-containing coordination complexes used as insulin-enhancing agents for treatment of diabetes.     

Flüssig-Flüssig-Extraktion von Vanadium mit ausgewählten zweizähnigen Chelatbildnern

Liquid-Liquid Extraction of Vanadium with Bidentate Ligands The extraction of vanadium(V) as well as vanadium(IV) with thenoyltrifluoracetone, 1-phenyl-3-methyl-4-benzoylpyrazol-5-one, N-benzoyl-N-phenylhydroxylamine, maltol, di-2-ethylhexylphosphoric acid, and selected 8-quinolinols was studied in comparison with corresponding thioanalogue compounds. In the reaction of vanadium(IV) with 7-methyl-8-quinolinol vanadium(IV) and vanadium(V) compounds were isolated side by side.     

莫来石的低温合成与结构研究

通过在高岭土中引入质量分数为1%～5%的钒以后,在700℃左右的较低温度下观察到莫来石相的生成,并结合酸、碱抽提反应过程制得较纯的莫来石.进一步研究了低温莫来石点阵参数的测定方法,发现低温钒-莫来石的晶胞体积比常规的高温莫来石大,表明钒进入了莫来石的骨架结构.另外,低温莫来石的形成动力学可表述为钒-高岭石低温共熔体迁移过程.     

Reaktionen und thermisches Verhalten oxofreier Vanadium(IV)-Komplexe. Kristallstrukturen von Methoxo-oxo[thenoyltrifluoraceton-salicylhydrazonato(2−)]vanadium(V) und Methoxo-oxo[benzoylaceton-salicylhydrazonato(2−)]vanadium(V)

Reactions and Thermal Behaviour of Nonoxo Vanadium(IV) Complexes. Crystal Structures of Methoxo-oxo[thenoyltrifluoroacetone-salicylhydrazonato(2–)]vanadium(V) and Methoxo-oxo[benzoylacetone-salicylhydrazonato(2–)]vanadium(V) The persistence of non-oxo vanadium(IV) complexes in dichlormethane/methanol/water solutions was studied by UV/VIS spectroscopy. The reaction products methoxo-oxo-[thenoyltrifluoroacetone-salicylhydrazonato(2–)]vanadium(V) and methoxo-oxo[benzoylacetone-salicylhydrazonato(2–)]vanadium(V) were isolated and characterized by X-ray analysis. The thermal behaviour of non-oxo vanadium(IV) complexes was checked.     

Organometallic vanadium-based heterogeneous catalysts for ethylene polymerization. Study of the deactivation process

Slurry polymerizations of ethylene over vanadium catalysts (based on VCl₄ and VOCl₃) and their MgCl₂(THF)₂-supported equivalents were studied. Unsupported vanadium catalysts were found to be unstable while the vanadium active sites deposited on the MgCl₂(THF)₂ complex are stable. A sharply outlined correlation was found between the concentration of vanadium(III) and catalyst productivity. The high activity and stability of the vanadium catalyst when supported on the magnesium complex is attributed to the increase of resistance to reduction of active vanadium(III) to inactive vanadium(II) by an organoaluminium co-catalyst.     

Flow-injection chemiluminescent determination of vanadium(IV) and total vanadium by means of catalysis on the periodate oxidation of purpurogallin

A flow-injection chemiluminescent (CL) method is proposed for the successive determination of nanogram levels of vanadium(IV) and total vanadium. The method is based on the catalytic effect of vanadium(IV) on the oxidation of purpurogallin by periodate to produce light emission at 4 °C. The presence of hydrogen carbonate enhanced the light emission arising from the vanadium(IV)-catalyzed reaction. Since vanadium(V) did not catalyze the CL reaction of purpurogallin, vanadium(V) was determined after being reduced to vanadium(IV) by using an on-line silver-reducing column. Calibration curves for vanadium(IV) and (V) were linear in the range 0.1–10 ng ml⁻¹ with sampling rate of about 50 h⁻¹. The limit of detection for signal-to-noise ratio of 2 was 0.05 ng ml⁻¹ and the relative standard deviations were 1.4 and 1.6% for ten determinations of 2.0 ng ml⁻¹ vanadium(IV) and (V), respectively. Interferences from metal ions could be eliminated by the use of O,O′-bis(2-aminoethyl)ethyleneglycol- N,N,N′,N′-tetraacetic acid and diphosphate as masking agents. The proposed method was successfully applied to the determination of vanadium(IV) and total vanadium in fresh water samples.     

The determination of small amounts of vanadium in the presence of large amounts of uranium

To eliminate the color interference of large amounts of uranium in the determination of vanadium by the Hamner method, the vanadium was separated prior to titration by the extraction of vanadium cupferrate with chloroform. The chloroform extract was evaporated with sulfuric acid and the excess cupferron removed by oxidation with nitric acid and perchloric acid. The vanadium was reduced with ferrous ammonium, sulfate solution, the excess ferrous ion oxidized with ammonium persulfate, and the vanadium (IV) titrated with 0.02 N potassium permanganate. As little as 1.02 mg of vanadium in the presence of 5 g of uranium oxide was determined accurately by this method.     

Flow injection analysis for oxidation state speciation of vanadium(IV) and vanadium(V) in natural water.

A sensitive and simultaneous spectrophotometric flow injection method for the determination of vanadium(IV) and vanadium(V) is proposed. The method is based on the effect of ligands such as 2,4,6-tris(2-pyridyl)-1,3,5-triazine (TPTZ) and diphosphate on the conditional redox potential of iron(III)/iron(II) system. A four-channel flow system is assembled. In this flow system, diluted hydrochloric acid (1.0 x 10(-2) mol dm(-3)) as a carrier for standard/sample, acetate buffer (pH 5.5) as a carrier for diphosphate solution, an equimolar mixed solution of iron(III) and iron(II) and a TPTZ solution are delivered, so that the baseline absorbance can be established by forming a constant amount of iron(II)-TPTZ complex (lambda(max) = 593 nm). Vanadium(IV) and/or vanadium(V) (400 microL) and diphosphate (200 microL) solutions are simultaneously introduced into the flow system; in this system the diphosphate solution passes through a delay coil. The potential of the iron(III)/iron(II) system increases in the presence of TPTZ, and therefore vanadium(IV) is easily oxidized by iron(III) to vanadium(V) to produce an iron(II)-TPTZ complex (a positive peak for vanadium(IV) appears). On the other hand, the potential of the redox system decreases in the presence of diphosphate, so that vanadium(V) can be easily reduced by iron(II) to vanadium(IV). In this case, the amount of iron(II) decreases according to the amount of vanadium(V). As a result, the produced iron(II)-TPTZ complex decreases (a negative peak for vanadium(V) appears). In this manner, two peaks for vanadium(IV) and vanadium(V) can be alternately obtained. The limits of detection (S/N = 3) are 1.98 x 10(-7) and 2.97 x 10(-7) mol dm(-3) for vanadium(IV) and vanadium(V), respectively. The method is applied to the simultaneous determination of vanadium(IV) and vanadium(V) in commercial bottled mineral water samples.     

Fluorinated β-diketones in the development of a gas chromatographic procedure for the determination of vanadium

Volatile, fluorinated β-diketonates of vauadium(III) have been examined for their suitability in determining vanadium by gas chromatography. Substituents in the β-diketones influence the air sensitivity of the vanadium(III) chelates, the extent of irreversible adsorption in the chromatographic column, and the ease with which excess of ligand can be separated from the derivative after solvent extraction. Derivatization involves reduction of vanadium to vanadium(III) with sodium dithionite in aqueous solution followed by chelation and extraction of the vanadium(III) chelates. A method for quantifying trace concentrations of vanadium in petroleum oils with 1,1,1,2,2-pentafluoro-6,6-dimethylheptane-3,5-dione as reagent is presented.     

钒化合物抗糖尿病作用的研究进展*

在糖尿病的治疗研究中,体内和体外的研究表明,钒化合物可以降低I型和II型糖尿病血糖,促进葡萄糖转运和糖原合成,具有“类胰岛素作用”。本文综述了近年来钒化合物在降低和改善糖尿病症状的生物效应及其通过胰岛素信号通路在降糖作用的分子机制的研究进展。     

Preparation and characterization of vanadium(IV) oxide supported on SBA-15 and its catalytic performance in benzene hydroxylation to phenol using molecular oxygen

Preparation of dispersed transition metal oxides catalyst with low oxidation state still remains a challenging task in heterogeneous catalysis.In this study,vanadium oxides supported on zeolite SBA-15 have been prepared under hydrothermal condition using V 2 O 5 and oxalic acid as sources of vanadium and reductant,respectively.The structures of samples,especially the oxidation state of vanadium,and the surface distribution of vanadium oxide species,have been thoroughly characterized using various techniques,including N 2-physisorption,X-ray diffraction(XRD),transmission electron microscopy(TEM),X-ray photoelectron spectroscopy(XPS),UV-visible spectra(UV-Vis) and UV-visible-near infrared spectra(UV-Vis-NIR).It is found that the majority of supported vanadium was in the form of vanadium(IV) oxide species with the low valence of vanadium.By adjusting hydrothermal treatment time,the surface distribution of vanadium(IV) oxide species can be tuned from vanadium(IV) oxide cluster to crystallites.These materials have been tested in the hydroxylation of benzene to phenol in liquid-phase with molecular oxygen in the absence of reductant.The catalyst exhibits high selectivity for phenol(61%) at benzene conversion of 4.6%,which is a relatively good result in comparison with other studies employing molecular oxygen as the oxidant.     

利用硫酸氧钒制备钒炭催化剂用于烟气脱硫

利用硫酸氧钒制备钒炭催化剂用于烟气脱硫。研究发现,负载在活性炭上的硫酸氧钒极易被氧化为五价钒硫酸盐,这些五价钒硫酸盐具有很高的氧化SO₂的活性,极大地促进了SO₂在活性炭上的脱除。而且,通过煅烧可以将五价钒硫酸盐分解为五价钒氧化物,最佳煅烧温度为500℃,由于煅烧后用于储存硫酸的微孔孔容增加,SO₂的吸附容量得到了进一步提高,由此表明,利用硫酸氧钒可以制备传统的V₂O₅/AC催化剂。为了获得完全氧化的钒物种,对煅烧后的催化剂进行了空气中预氧化,但由于含氧官能团的形成、炭载体的烧蚀以及钒的还原,预氧化不利于脱硫。此外,研究中得到初步证据证明脱硫过程中V₂O₅/AC催化剂中五价钒氧化物转变成了五价钒硫酸盐,结合五价钒硫酸盐所表现出的氧化SO₂的能力,推测SO₂在V₂O₅/AC上的脱除遵循以下机理:五价钒氧化物先转变为五价钒硫酸盐,后者催化氧化SO₂为硫酸。