The oxygen exchange from O2/C18O2 with surfaces of vanadium pentoxide and alkali metal-promoted vanadium pentoxide catalysts

1978 ◽  
Vol 56 (24) ◽  
pp. 3078-3083 ◽  
Author(s):  
David Victor Fikis ◽  
Keith Walter Heckley ◽  
William John Murphy ◽  
Robert Anderson Ross
Keyword(s):  
Alkali Metal ◽  
Vanadium Pentoxide ◽  
Concentration Level ◽  
Oxygen Exchange ◽  
Circulation System ◽  
X Ray Diffraction ◽  
X Ray ◽  
Oxygen Exchange Reaction ◽  
Metal Sulphates ◽  
Activity Series

The oxygen exchange reaction between O2/C18O2 and the surfaces of vanadium pentoxide and promoted vanadium pentoxide catalysts has been studied in a circulation system using a quartz differential reactor. Isotopic compositions were analysed with an in-line mass spectrometer. Alkali metal sulphates, Li to Cs, were added to the pentoxide as individual promoters at a concentration level of 9 mol % and the effect of variation of promoter concentration was examined with melts containing potassium sulphate at additional levels of 1, 2, and 5 mol%. The structures of the solids were studied by X-ray diffraction and by ATR and transmission infrared spectroscopy. The latter results have been used to explain the two activity series for the exchange rates: (i)V2O5 < Na < Li < K < Rb < Cs (melts) and (ii) V2O5 < 1 mol% < 2 mol% < 5 mol% < 9 mol% (K), in terms of additive effects on the relative abundance and strength of identified vanadium/oxygen linkages in the surfaces of the catalysts.

New mixed-valent alkali chain sulfido ferrates A1+x[FeS2] (A = K, Rb, Cs; x = 0.333–0.787)

2020 ◽  
Vol 235 (8-9) ◽  
pp. 275-290
Author(s):  
Michael Schwarz ◽  
Pirmin Stüble ◽  
Katharina Köhler ◽  
Caroline Röhr
Keyword(s):  
Alkali Metal ◽  
General Structure ◽  
Variable Number ◽  
Monoclinic Space Group ◽  
X Ray Diffraction ◽  
Modulated Structure ◽  
Space Group ◽  
X Ray ◽  
Local Coordination ◽  
Natural Pyrite

AbstractFour new mixed-valent chain alkali metal (A) sulfido ferrates of the general structure family ${A}_{1+x}\left[{\text{Fe}}_{x}^{\text{II}}{\text{Fe}}_{1-x}^{\text{III}}{\text{S}}_{2}\right]$ were synthesized in the form of tiny green-metallic needles from nearly stoichiometric melts reacting elemental potassium with natural pyrite (A = K) or previously prepared Rb2S/Cs2S2 with elemental iron and sulfur (A = Rb/Cs). The crystal structures of the compounds were determined by means of single crystal X-ray diffraction: In the (3+1)D modulated structure of K7.15[FeS2]4 (space group Ccce(00σ3)0s0, a = 1363.87(5), b = 2487.23(13), c = 583.47(3) pm, q = 0,0,0.444, R1 = 0.055/0.148, x = 0.787), a position modulation of the two crystallographically different undulated ${}_{\infty }{}^{1}\left[{\text{FeS}}_{4/2}\right]$ tetrahedra chains and the surrounding K cations is associated with an occupation modulation of one of the three potassium sites. In the case of the new monoclinic rubidium ferrate Rb4[FeS2]3 (x = $\frac{1}{3}$; space group P21/c, a = 1640.49(12), b = 1191.94(9), c = 743.33(6) pm, β = 94.759(4)°, Z = 4, R1 = 0.1184) the undulation of the tetrahedra chain is commensurate, the repetition unit consists of six tetrahedra. In the second new Rb ferrate, Rb7[FeS2]5 (x = 0.4; monoclinic, space group C2/c, K7[FeS2]5-type; a = 2833.9(2), b = 1197.36(9), c = 744.63(6) pm, β = 103.233(4)°, Z = 4, R1 = 0.1474) and its isotypic mixed Rb/Cs-analog Rb3.6Cs3.4[FeS2]5 (a = 2843.57(5), b = 1226.47(2), c = 759.890(10) pm, β = 103.7170(9)°, R1 = 0.0376) the chain buckling leads to a further increased repetition unit of 10 tetrahedra. For all mixed-valent ferrates, the Fe–S bond lengths continuously increase with the amount (x) of Fe(II). The buckling of the chains is controlled through the local coordination of the S atoms by the variable number of A cations of different sizes.

Synthèse et caractérisation des oxypentafluorouranates(VI) NH4UOF5, KUOF5, RbUOF5 et CsUOF5

1978 ◽  
Vol 56 (14) ◽  
pp. 1874-1880 ◽  
Author(s):  
Philippe Joubert ◽  
Roland Bougon ◽  
Bernard Gaudreau
Keyword(s):  
Infrared Spectroscopy ◽  
Solid State ◽  
Alkali Metal ◽  
Vibrational Spectroscopy ◽  
Uranium Atom ◽  
The Other ◽  
Metal Fluoride ◽  
X Ray Diffraction ◽  
X Ray ◽  
Raman And Infrared Spectroscopy

The oxypentafluorouranates(VI) MUOF5, where M = NH4, K, Rb, Cs, have been synthetized from reaction of UOF4 with the ammonium or corresponding alkali metal fluoride in liquid SO2. According to X-ray diffraction, Raman and infrared spectroscopy, and from an isomorphism with the corresponding hexafluorouranates(V) MUF6, two different environments around the uranium atom are observed. In CsUOF5 the five fluorine atoms and the oxygen around the uranium result in a pseudo-octahedral surrounding whereas for the other complexes (M = NH4, K, Rb) each uranium is surrounded by eight light atoms forming a dodecahedron. In this structure the dodecahedra are linked together by fluorine atoms to form infinite chains. The UOF5− ion has been characterized by vibrational spectroscopy in the solid state. The proposed assignment, which was made with the assumption of a C4v symmetry of the UOF5− ion, was confirmed by a force constant calculation. From these data and contrary to the values reported for comparable oxypentafluoroanions, the axial fluorine is found to be less ionic than the equatorial ones.

EFFECT OF ANNEALING ON THE PROPERTIES OF VANADIUM PENTOXIDE FILMS PREPARED BY SOL–GEL METHOD

2014 ◽  
Vol 21 (02) ◽  
pp. 1450027 ◽  
Author(s):  
YAQIANG LIU ◽  
XUELIAN DU ◽  
XUEQIN LIU
Keyword(s):  
Vanadium Pentoxide ◽  
Annealing Temperature ◽  
Substrate Surface ◽  
Sol Gel ◽  
Amorphous Structure ◽  
Spectral Transmittance ◽  
X Ray Diffraction ◽  
X Ray ◽  
Tauc Plot ◽  
Silicon Substrate Surface

The vanadium pentoxide ( V 2 O 5) films were obtained by using sol–gel procedure and then were annealed at different temperature in air. The effect of different annealing temperatures on the composition, the microstructure, the surface morphology and the optical properties of the films were characterized by methods such as by X-ray diffraction, Raman spectroscopy, scanning electron microscopy and spectral transmittance. The results revealed that the film annealed at 150°C has amorphous structure and dense with a smooth surface and the films annealed at 300°C and 450°C have a polycrystalline V 2 O 5 structure with preferred growth orientation along (001) planes, the c-axis and perpendicular to the silicon substrate surface. From the spectral transmittance we determined the absorption edge using the Tauc plot. The results indicated that optical bandgap of V 2 O 5 thin films decreased with annealing temperature.

scholarly journals Vanadium Chemical Compounds Forms in Wastes of Vanadium Pentoxide Production

Materials ◽  
2020 ◽  
Vol 13 (21) ◽  
pp. 4889
Author(s):  
Anton Volkov ◽  
Ulyana Kologrieva ◽  
Anatoly Kovalev ◽  
Dmitry Wainstein ◽  
Vladimir Vakhrushev
Keyword(s):  
Vanadium Pentoxide ◽  
Photoelectron Spectroscopy ◽  
Converter Slag ◽  
Fluorescence Analysis ◽  
Vanadium Content ◽  
X Ray Diffraction ◽  
Oxidation Degree ◽  
X Ray ◽  
Secondary Ions ◽  
Optimal Technology

A big amount of solid wastes or dump sludges is generated after leaching vanadium (V) from a roasted mixture. As the vanadium content in these tailings is comparable to its concentration in traditional vanadium sources such as titanomagnetite ores or a vanadium converter slag, these wastes could be recycled to extract additional vanadium. Therefore, this research was aimed on studies of vanadium-containing sludges resulting from hydrometallurgical production of vanadium pentoxide to find an optimal technology for V extraction. The material composition of industrial and synthetic sludge samples was studied by X-ray fluorescence analysis (XRF), X-ray diffraction (XRD), secondary ions mass spectroscopy (SIMS), and X-ray photoelectron spectroscopy (XPS, ESCA). The paper demonstrates the presence of vanadium in sludges, not only in spinels in 3+ oxidation degree, but also in other compounds containing V4+ and V5+. It was found that vanadium substitutes a set of elements in minerals except spinel. The dependence between the content of insoluble vanadium compounds and V oxidation degree was determined.

Synthesis and Characterization of Large Single Crystals of Silicon and Germanium Clathrate-II Compounds and a New Tin Compound with Clathrate Layers

2000 ◽  
Vol 626 ◽  
Author(s):  
Svilen Bobev ◽  
Slavi C. Sevov
Keyword(s):  
Alkali Metal ◽  
Single Crystals ◽  
Alkali Metals ◽  
Measured Temperature ◽  
X Ray Diffraction ◽  
X Ray ◽  
Mixed Alkali ◽  
Pauli Paramagnetism ◽  
Silicon And Germanium

ABSTRACTWe have synthesized large single crystals of clathrate-II compounds with frameworks of silicon and germanium by employing mixed alkali metal countercations. The combinations of alkali metals are rationally selected in order to fit the different cages of the clathrate-II structure. This approach leads to the following stoichiometric and fully “stuffed” compounds: Cs8Na16Si136, Cs8Na16Ge136, Rb8Na16Si136 and Rb8Na16Ge136. The structures and the corresponding Si-Si and Ge-Ge distances are elucidated and established with high accuracy from extensive single crystal X-ray diffraction work. The compounds are stoichiometric, metallic, and are very stable at a variety of extreme conditions such as heat, concentrated acids, hydrothermal treatment etc. No evidence was found for vacancies in the silicon and germanium networks or partial occupancies of the alkali metal sites. The stoichiometry of these fully “stuffed” clathrates is consistent with the measured temperature independent Pauli paramagnetism, supported also by the conductivity measurements on single crystals and thermopower measurements on pellets. A new compound with novel clathrate-like structure forms when small and large cations are combined with tin. The new materials, A6Na18Sn46 (A = K, Rb, Cs), are made of clathrate layers and the interlayer space filled with Sn4-tetrahedra and alkali-metal cations. Its formula can be rationalized as A6Na6Sn34 + 3·Na4Sn4 (one clathrate layer and three tin tetrahedra). The compound is stable in air and is being currently tested at other conditions. Detailed measurements of its transport properties are under way.

Electrochemical preparation and properties of the mixed-crystalline hexavanadates MxM′4−xV6O16, M, M′ = NH4, K, Rb, Cs

1990 ◽  
Vol 68 (8) ◽  
pp. 1283-1292 ◽  
Author(s):  
E. Andrukaitis ◽  
P. W. M. Jacobs ◽  
J. W. Lorimer
Keyword(s):  
Chemical Analysis ◽  
Alkali Metal ◽  
Mixed Crystals ◽  
Continuous Series ◽  
Alkali Metal Cations ◽  
X Ray Diffraction ◽  
Ammonium Ions ◽  
Electrochemical Preparation ◽  
X Ray ◽  
End Members

Coherent deposits of oriented, crystalline MxM′4−xV6O16+δ, with M, M′ = K, Rb, Cs, or NH4, 0.0 ≤ x ≤4.0 and 0.00 ≤ δ ≤ 0.13, have been prepared electrochemically on various conducting substrates from metavanadate solutions containing ammonium or alkali metal cations, singly or in combination. Chemical analysis and X-ray diffraction show that the deposits consist of a continuous series of mixed crystals based on the isomorphic end members M4V6O16 and M′4V6O16.The deposits can be oxidized electrochemically, with removal of M and M′ atoms, and the products can be used as cathodes for insertion of lithium, with the largest capacity achieved about 1.0 mol% of total vanadium. Cycling of the electrodes improves capacity, with insertion of lithium reaching 25 mol% of total vanadium. This gain in capacity results from further removal of alkali metal or ammonium ions from the electrode during the oxidation step of the cycling process.The results extend the range of composition of homogeneous phases in the system (NH4)2O–K2O–V2O4–V2O5. Keywords: alkali metal hexavanadates, electrochemical preparation.On a préparé des dépôts cohérents qui contiennent des cristaux orientés de MxM′4−xV6O16+δ, avec M, M′ = K, Rb, Cs ou NH4, 0,0 ≤ x ≤4,0 et 0,00 ≤ δ ≤ 0,13, par la méthode de voltammétrie cyclique sur des substrats divers et dans des solutions de metavanadates qui contiennent des cations des métaux alcalins ou d'ammonium seuls ou des combinations de tels ions. L'analyse chimique et la diffraction des rayons X ont démontré que les dépôts comprennent une série continue de cristaux mixtes basée sur les membres terminaux M4V6O16 et M′4V6O16.

Na4OI2 — ein neuer Alkalimetallchalkogenidhalogenid-Typ/Na4OI2 — a New Type of Alkali Metal Chalcogenide Halide

1989 ◽  
Vol 44 (3) ◽  
pp. 373-374 ◽  
Author(s):  
Horst Sabrowsky ◽  
Karin Hippler ◽  
Petra Vogt
Keyword(s):  
Alkali Metal ◽  
X Ray Diffraction ◽  
Metal Chalcogenide ◽  
X Ray ◽  
New Type

The colourless compound Na4OI2: has been prepared and characterized by X-ray diffraction techniques. Na4OI2: crystallizes in a tetragonal body-centered lattice with a = 467.7(1) pm, c = 1602.0(3) pm (Z = 2) and is isotypic to K2NiF4.

Na3OCl und Na3OBr, die ersten Alkalimetallchalkogenidhalogenide / Na3OCl and Na3OBr, the First Alkali Metal Chalcogenide Halides

1988 ◽  
Vol 43 (2) ◽  
pp. 238-239 ◽  
Author(s):  
Horst Sabrowsky ◽  
Karin Paszkowski ◽  
Dagmar Reddig ◽  
Petra Vogt
Keyword(s):  
Alkali Metal ◽  
Lattice Constant ◽  
X Ray Diffraction ◽  
Metal Chalcogenide ◽  
X Ray

The colourless compounds Na3OCl and Na3OBr have been prepared and characterized by X-ray diffraction techniques. Na3OCl crystallizes in a cubic primitive lattice with a = 450.0(3) pm (Z = 1). Na3OBr is isotypic with Na3OCl and its lattice constant is a = 457.3(5) pm. The structures are related to the anti-perowskitetype

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