Wyniki wyszukiwania - Biblioteka Nauki

1

Phosphorus losses in VPO catalysts

100%

Stoch J. , Stoch A. , Mikołajczyk M. , Brożek A.

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1998

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tom Vol. 72, nr 12

2606-2609

EN

During oxidation of n-butane to maleic anhydride on VPO catalysts phosphorus is carried out from the catalyst by gas phase. The transport medium is likely an organic compound of phosphorus. An active role of phosphorus in the n-butane transformation is suggested.

2

Sedimentological and technological studies of Abu Tartur black shales, Western Desert, Egypt

100%

Sediek K. N. , Amer A. N.

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2001

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tom Vol. 35

141-152

EN

Newly conventional combination of sedimentological and technological studies aid in estimation of the resource potential of the Upper Cretaceous clays of Duwi Formation Abu Tartur plateau Western Desert, Egypt. This formation consists of interbedded black to Grey shale, phosphatic and glauconitic sandstones. The granulometric, mineralogical, and geochemical analyses were carried out on the black clays, which provided detailed information about textural parameters, composition and paleoenvironment of deposition The technological studies of black shale is new for its interesting enrichments in various rare metals as nickel , chromium and vanadium . This investigation is a laboratory study for extraction of vanadium from black shales by hydrochloric acid processing to produce leach solutions of vanadium, aluminum and magnesium chlorides. The effects of various factors affecting the leaching process such as temperature, acid concentration, particle size and stirring speed as well as the kinetics of the leaching process were studied. The most favorable conditions for the extraction of the vanadium present in the black shale are temperature 100° C, acid concentration 6 M by weight, grain size 17 žm and leaching time 90 min.

PL

Badania sedymentologiczne i technologiczne miały za cel oszacowanie potencjalnych możliwości wykorzystania czarnych iłów ze złoża Abu Tartur leżącego na pustyni zachodniej w Egipcie. Złoże to zawiera czarny przechodzący w szary łupek, glaukonitowy i fosforanowy piaskowiec. Zostały przeprowadzone analizy granulometryczne, mineralogiczne i geochemiczne czarnych iłów. Wyniki analiz dostarczyły dokładne informacje o teksturze, składzie i paleosrodowisku złoża. Badania technologiczne czarnego łupka zostały przeprowadzone z uwagi na bogatą zawartość w nich metali rzadkich takich jak nikiel, chrom i wanad. Badano w skali laboratoryjnej, proces ekstrakcji wanadu kwasem solnym, otrzymując roztwór zawierający chlorki wanadu, glinu i magnezu. Wpływ różnych parametrów takich jak temperatura, stężenie kwasu solnego, uziarnienie nadawy, prędkość mieszania, na kinetykę procesu ługowania został przebadany. Najlepsze warunki ekstrakcji wanadu z czarnego łupka uzyskano stosując temperaturę 100oC, stężenie kwasu solnego 6M, granulację nadawy 17 žm i czas ługowania 90 minut

3

Application of recycled natural aluminasilicate doped with vanadium for the decontamination of the air

100%

Marcewicz-Kuba A. , Olszewska D.

Polish Journal of Chemical Technology

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2007

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tom 9

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nr 2

65-67

EN

This paper reports studies on the influence of vanadium concentration on the catalytic activity of DESONOX catalysts (in DESOX reaction) based on modified montmorillonite from Jelsovy Potok. The investigation of the influence on the physicochemical properties of the catalysts on their behaviour has also been studied.

4

Determination of vanadium content in soils by slurry sampling electrothermal atomic absorption spectrometry using KO300G as the stabilizing agent

100%

Barałkiewicz D. , Gramowska H. , Ren K. , Mleczek M.

Open Chemistry

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2006

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tom 4

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nr 2

363-374

EN

A direct and sensitive method for the determination of vanadium concentrations in soil is developed using ultrasonic slurry sampling electrothermal atomic absorption spectrometry (USSSETAAS). The surfactant, KO300G, is used as the stabilizing agent. The precision and accuracy of the method are investigated. The detection limits are 0.6 and 0.7 µg 1−1 for SRM Montana Soil 2711 and SRM Soil - S, respectively. The method is applied to determine the vanadium content in 10 soil samples from the Wielkopolska region.

5

Structural properties of transparent Ti-V oxide semiconductor thin films

75%

Sieradzka K. , Kaczmarek D. , Morgiel J. , Domaradzki J. , Prociow E. , Adamiak B.

Open Physics

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2013

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tom 11

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nr 2

251-257

EN

Transparent oxide semiconducting thin films based on mixed Ti-V oxides were prepared using a modified reactive magnetron sputtering method. Based on structural investigations performed with the help of x-ray diffraction and transmission electron microscopy analysis, two distinct regions in the prepared thin film have been observed: a nanocrystalline TiO2-V2O3-V2O5 mixed composition, and a thin layer consisting of amorphous phase and nanocystalline TiO2 phase deposited directly at the substrate. Optical measurements show excellent transmission in the visible spectral range of 73%, on average. Resistivity of the thin film was found at the order of 105 Ω cm at room temperature. The preparation of mixed Ti-V oxides provides a combination of high transparency and semiconducting properties.

6

Large scale multi-configuration Hartree-Fock calculation of the hyperfine structure of the ground state of vanadium

75%

Scharf O. , Gaigalas G.

Open Physics

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2006

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tom 4

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nr 1

42-57

EN

The hyperfine structure of the ground state of vanadium, 51VI, is calculated in the nonrelativistic framework of the multi-configuration Hartree-Fock approximation. A configuration state function limiting algorithm is used to make the calculations feasible and to study the influence of core, valence and core-valence correlations in detail. The obtained configuration state function space captures the most important orbital correlations within 2%. Further correlations are included through configuration interaction calculation. The atomic state functions are used to evaluate the magnetic dipole hyperfine factor A and the electric quadrupole factor B. It turns out that the ab initio calculation can not capture the core polarization of the 2s shell. It introduces an error that is higher than the Hartree-Fock approximation. However, the detailed correlations being observed suggest the introduction of a wrong correlation orbital due to the algorithm being used. Neglecting this orbital leads to good agreement with 2% deviation from the experimental values for the A factors.

7

Problemy w analizie specjacyjnej wanadu

75%

Pyrzyńska K. , Wierzbicki T.

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2005

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tom nr 1

20-22

8

Extraction of vanadium compounds from the used vanadium catalyst with the potassium hydroxide solution

75%

Mazurek K. , Białowicz K. , Trypuć M.

Polish Journal of Chemical Technology

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2010

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tom 12

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nr 1

23-28

EN

The paper presents the results of the research on the degree of the recovery of vanadium(V) from the used vanadium catalyst with the use of KOH solution. The extraction was performed at 293 - 323 K, for 0.5 to 4 h and the catalysts of the variable grain diameter. The concentration of the extracting solution was varied in the range 5 - 20%. The optimal ratio of solid to liquid phase S/L was determined. Additionally the degree of the recovery of total iron ions was presented.

9

Biochemical and medical importance of vanadium compounds

75%

Korbecki J. , Baranowska-Bosiacka I. , Gutowska I. , Chlubek D.

Acta Biochimica Polonica

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2012

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tom 59

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nr 2

195-200

EN

Vanadium belongs to the group of transition metals and is present in the air and soil contaminants in large urban agglomerations due to combustion of fossil fuels. It forms numerous inorganic compounds (vanadyl sulfate, sodium metavanadate, sodium orthovanadate, vanadium pentoxide) as well as complexes with organic compounds (BMOV, BEOV, METVAN). Depending on the research model, vanadium compounds exhibit antitumor or carcinogenic properties. Vanadium compounds generate ROS as a result of Fenton's reaction or of the reaction with atmospheric oxygen. They inactivate the Cdc25B2 phosphatase and lead to degradation of Cdc25C, which induces G2/M phase arrest. In cells, vanadium compounds activate numerous signaling pathways and transcription factors, including PI3K-PKB/Akt-mTOR, NF-κB, MEK1/2-ERK, that cause cell survival or increased expression and release of VEGF. Vanadium compounds inhibit p53-dependent apoptosis and promote entry into the S phase of cells containing functional p53 protein. In addition, vanadium compounds, in particular organic derivatives, have insulin-mimetic and antidiabetic properties. Vanadium compounds lower blood glucose levels in animals and in clinical trials. They also inhibit the activity of protein tyrosine phosphatase 1B. By activating the PI3K-PKB/Akt pathway, vanadium compaunds increase the cellular uptake of glucose by the GLUT4 transporter. The PKB/Akt pathway is also used to inactivate glycogen synthase kinase-3. The impact of vanadium compounds on inflammatory reactions has not been fully studied. Vanadium pentoxide causes expression of COX-2 and the release of proinflammatory cytokines in a human lung fibroblast model. Other vanadium compounds activate NF-κB in macrophages by activating IKKβ.

10

Selected problems in speciation analysis of vanadium in water samples

75%

Pyrzyńska K.

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2006

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tom Vol. 51, No. 3

339-350

EN

Two most commonly vanadium forms, VflV) and V(V), have different loxicity and nutritious properties. Speciation of vanadium is necessary in environmental samples. The objective of this paper is to highlight some aspects of vanadium speciation analysis, such as stability of species and possibility of their redistribution, as well as separation techniques and analytical methods.

PL

Biologiczna rola wanadu i jego toksyczność zależą głównie od formy chemicznej, wjakiej występuje w analizowanych próbkach. W pracy przedstawiono główne problemy związane 2 analizą specjacyjną wanadu, głównie V(IV) i V(V), takie jak trwałość form specjacyjnych w roztworach, przygotowanie roztworów wzorcowych o zdefiniowanej formie chemicznej oraz metody rozdzielania i oznaczania wanadu.

11

Catalytic spectrophotometric determination of vanadium and its application to some natural and agricultural products

63%

Feng Q.-L. , Wen D.-Y.

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2006

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tom Vol. 51, No. 2

319-325

EN

A simple and highly sensitive spectrophotometric method for the determination ofvana-dium(V) has been proposed. The method is based on catalytic oxidation of 1,8-dihydroxy-naphthalene-3,6-disiulfonic acid and phenylhydra/.inc with potassium chlorate. The molar absorptivity was 7.8 x 106 at the wavelength of 506 nm, detection range was 0.2-5.0 ng mL-1. The new method is simple and provides high sensitivity and good selectivity. It has been successfully applied to the determination of trace amounts of vanadium in spring water, black bean, corn, tea leaves, and Rhodiola schalinensis A leaves.

PL

Opracowano prostą i czułą spektofotometryczną metodę oznaczania wanadu( V). Metoda polega na katalitycznym utlenianiu kwasu l,8-dihydroksynaftaleno-3,6-disuIfonowego i fenylohydrazyny za pomocą chloranu potasowego. Molowy współczynnik absorpcji przy długości fali 506 nm wynosił 7 x 106, a zakres stężeń w którym prowadzono pomiary 0.2—5,0 ng mL-1. Nowa metoda jest prosta, selektywna i bardzo czulą. Zastosowano ją z powodzeniem do oznaczania śladowych ilości wanadu w wodzie źródlanej, czarnej fasoli, kukurydzy, herbacie i liściach Rhodiola schalinensis A.

12

Effect of heat treatment parameters on the properties of low-alloy cast steel with microadditions of vanadium

63%

Kalandyk B. , Zapała R.

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2008

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tom Vol. 8, iss. 3

137-140

EN

This article examines the effect of prolonged time of holding at the temperature of 620°C on the processes of secondary phase precipitation and mechanical properties of low-alloy cast steel with an addition of vanadium subjected to two variants of heat treatment, i.e. U:1150°C+H:950°C+O:620°C and H:950°C+O:620°C. To determine an impact of the applied heat treatment operations, testing of mechanical properties and microstructural examinations of the cast steel with 0,21 and 0,27%C were carried out.

13

Oxidative desulfurization of synthetic diesel using vanadium based catalysts

63%

Fabiś G. , Czajkowska S.

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2011

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tom Vol. 55, nr 3-4

151-157

EN

Oxidative desulfurization (ODS) of synthetic diesel was carried out at mild conditions (at atmospheric pressure and temperature of 80 °C) in the presence of V1O5/AI2O3 and V-MCM-41 catalysts, using hydrogen peroxide (H1O2) or rm-butyl hydroperoxide (TBPH) as an oxidant. Obtained results show that removal of benzothiophenic compounds is more effective in the presence of TBHP. Moreover, it has been observed that conversion of sulfur compounds is not a function of textural properties of the catalysts.

14

The mechanism of L-arginine oxidation by quinquevalent vanadium in the presence of cationic surfactant in sulphuric acid media. A kinetic study

63%

Dubey S. , Pandey A.

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2001

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tom Vol. 49, No. 2

183-191

EN

The oxidation is first order each in [substrate] and the [oxidant]. The reaction follows an acid catalysed path, exhibiting second order dependence in [H+]. Bunnett's plot indicates that water acts as a nucleophile. Protonated form of oxidant has been postulated as the reacting oxidizing species. The rate studied at four different temperatures enabled us to calculate activation parameters. A suitable mechanism has been proposed.

15

ESR study of monolayer vanadium oxide catalysts supported of different supports in relation to catalytic oxidation of methanol

63%

Haber J. , Nowak P. , Serwicka E. M. , Wachs I. E.

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2000

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tom Vol. 48, No. 4

337-346

EN

Vanadia monolayers deposited on various oxide supports (Zr02, Nb(2)O(5), TiO2, Al(2)O(3) and Si0(2) have been investigated with the aid of electron spin resonance. The results show that the electronic structure of reduced vanadyl species generated during methanol chemisorption depends on the nature of the supporting matrix. This is shown by changes of theBeta(2) bonding coefficient calculated from the experimentally determined ESR parameters. I t is demonstrated that the catalytic activity in methanol oxidation, ex-pressed in terms of turnover frequency (TOF), can be correlated with the latter parameter and increases with the ionicity of the vanadyl in-plane Pi-bonding system.

16

Vanadium-containing Mesoporous Molecular Sieves: Synthesis, Properties and Catalytic Performance in Oxidative Activation of Light Alkanes

63%

Cortés Corberán V. , Sulikowski B.

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2008

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tom Vol. 82, nr 9

1823-1837

EN

Vanadium-containing mesoporous molecular sieves (MMS) are quasi-crystalline solids with interesting catalytic properties in the oxidative activation of light alkanes. In the present work, the methods of their synthesis, physico-chemical properties and catalytic behaviour in the oxidative dehydrogenation and selective oxidation of C2-C4 alkanes are reviewed. It is concluded that, as with conventional supported vanadium contacts, the catalytic performance in these reactions is related to the number and environment of vanadium centres, and the best selectivity and yield are obtained over isolated vanadium sites exhibiting tetrahedral coordination.

17

Fretting analysis of modulated TiC/VC multilayers on M2 HSS steels.

51%

Fouvry S. , Kapsa P. , Vincent L. , Wendler B. , Kula P.

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1998

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tom R. XIX, nr 4

990-993

EN

Resistance to fretting wear has been widely studied the last two decades. It has been shown that single TiN coatings on M2 HSS steels reduce the fretting damage about one order of magnitude and it is expected on the basis of theoretical considerations that hard multilayer coatings should present still greater resistance to wear. In the present paper hard modulated TiC/VC carbide multilayer coatings with lambda = 40 nm on M2 HSS steel substrate have been submitted to the fretting wear and the results have been compared with those for single TiC coating and for the M2 HSS substrate itself. The carbide coatings have been deposited with use of an indirect method invented in the Technical University of Łódź, Poland, the fretting tests have been performed in the Laboratory of Tribology and of Dynamic Systems of the Ecole Centrale in Lyon, France, and the results have been elaborated according to the new methodology developed in the latter. It turned out that the fretting wear of the multilayer coating was 25 times less than that of the M2 substrate, much less than that of the single TiC coating and 2.5 times less than that of the commercial TiN coating on the same steel.

18

Extraction of vanadium and potassium compounds from the spent vanadium catalyst from the metallurgical plant

51%

Mazurek K.

Polish Journal of Chemical Technology

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2012

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tom 14

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nr 2

49-53

EN

A spent vanadium catalyst, from the plant of metallurgical type, was leached in a sulfuric acid solution to recover vanadium and potassium compounds. The effect of time, temperature, concentration of acid, catalyst particle size and phase ratio was studied. Additionally the concentration of iron, copper, zinc, arsenic and lead compounds was determined. The flow sheet for the proposed process of spent vanadium catalyst leaching is presented.

19

Extractive-spectrophotometric determination of vanadium(IV/V) in catalysts using 4-(2pyridylazo)-resorcinol and tetrazolium violet

51%

Gavazov K. , Lekova V. , Patronov G. , Turkyilmaz M.

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2006

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tom Vol. 51, No. 2

221-227

EN

An extractive-spectrophotometric method for determination of V{V) and V(IV) has been developed. V(V) was converted to ternary ion-associate complex with 4-(2-pyridylazo)-resorcinol and tetrazolium violet. In the presence of diaminocyclohexanetetraacetic acid and NH4F as the masking agents determination of V(V) was highly selective, and V(IV) was among the masked ions. Due to this fact V(1V) could be determined indirectly from the difference in the absorbance measured in the presence and absence of the oxidizing agent, which oxidised V(IV) to V(V). The factors influencing determination of V(V) in the presence of large excess of V{IV) have been investigated. The method was applied to the determination of V(IV/V) in catalysts used for oxidation of SO2 to SO3.The precision and accuracy were satisfactory (RSD ≤ 1.9%). Detection limit of V(V) was 3.3 ngmL-1. Beer's law was obeyed up to V(V) concentration of 1.45 μg mL-1 in dichloroethane extract. The corresponding molar absorptivity coefficient was 3.05 x 104L mol4 cm-1.

PL

Opracowano ekstrakcyjną, spektrofotometryczną metodę oznaczania V{V) i V(1V). V(V) by! przekształcony w trzeciorzędowy kompleks z 4-(2-pirydylazo)rezorcinolem i fioletem tetrazoliowym. W obecności kwasu diaminocycloheksanotetraoctowego i NH4F jako czynnika maskującego oznaczanie V(V) okazało się wysoce selektywne. V(IV) był maskowany, w związku z tym móg! być oznaczany pośrednio z różnicy między absorbancją roztworów zawierających i niezawierąjących utleniacza. Badano czynniki wpływające na oznaczanie V(V) w obecności dużego nadmiaru V(IV). Opracowaną metodę zastosowano do oznaczania V(IV/V) w katalizatorach użytych do utleniania SO2, do SO3. Precyzja i dokładność były zadowalające (względne odchylenie standardowe < 1,9%). Granica wykrywalności wynosiła 3.3 ngmL-1. Prawo Beer'a było zachowane do stężenia 1,45 μg mL-1 w ekstraktach dichloroetanowych. Molowy współczynnik absorpcji wynosił 3.05 x 104L mol4 cm-1.

20

Vanadium - an essential, benefical and toxic element

51%

Anke M. , Muller R. , Schafer U. , Seifert M.

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2006

|

tom Nr 16

9-10