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1.
The use of XRD and DTA methods has allowed studies on the interaction of the SbVO5 and MoO3, taking place in the solid state and in the medium of ambient air. The experimental results of XRD and DTA for all the samples
showed the presence of a novel phase, i.e. Sb3V2Mo3O21 apart from various amounts of MoO3 and V9Mo6O40 or SbVO5 and V2O5(s.s.). The SbVO5–MoO3 system is not a real two-component system over the entire range of component concentrations up to the solidus line.
This revised version was published online in July 2006 with corrections to the Cover Date. 相似文献
2.
Coexistence Relations, Preparation and Properties of Ternary Compounds in the System Cu/Mo/O The phase diagram of the ternary system Cu/Mo/O is presented at 773 K. The compounds CuMoO4, Cu3Mo2O9, Cu4Mo5O17, Cu6Mo5O18, Cu4–xMo3O12, and CuxMoO3 are found to be thermodynamical stable. The homogeneity range of Cu4–xMo3O12 runs to x = 0.1–0.2. Single crystals of CuMoO4 and Cu3Mo2O9 were grown by chemical transport reactions with TeCl4, Cl2, HCl, and Br2 as transport agent. The results were compared with thermochemical calculations. The decomposition of CuMoO4 and Cu3Mo2O9 was investigated with thermal analysis and decompositon pressure measurements. 相似文献
3.
The dissociation state of the solutes M2MoO4, M2Mo3O10, M2Mo4O13, M2Mo5O16 (MRb or Cs), Na2CrO4·MoO3, K2CrO4·2 MoO3, Cr2Mo3O12 and V2MoO8 was studied cryoscopically in molten K2 Cr2O7 and KNO3 solvents. The freezing point depression, ΔT, of the solvents was obtained by measuring the cooling curves of the binary salt mixtures over unlimited range of solute concentration. The number of foreign ions obtained ν, showed that the solutes were either simply dissociated in the melt into the probable stable species (MoO4)2?, (Mo3O10)2?, (Mo4O13)2? and (Mo5O16)2? or, in some cases after reactions and rearrangements, into (CrMo2O10)2? heteropolyions. The solute V2MoO8, on the other hand, was found to dissolve without any apparent dissociation. An agreement between the experimental and calculated values of activity, a, based on the Temkin and Random Mixing models and that of Van't Hoff's equation support the proposed simple dissocia- tion scheme for K2Cr2O7Cs2MoO4 system. 相似文献
4.
M.Ya. Hodos E.V. Bazarova A.P. Palkin Kh.Z. Brainina 《Journal of Electroanalytical Chemistry》1984,164(1):121-128
The V2O5+MoO3 system has been examined by a stripping voltammetry technique using a carbon paste electroactive electrode and EPR. The feasibility of establishing the phase composition and the capability oxygen chemisorption has been demonstrated. The processes of electrochemical transformations of the substances to be investigated and of chemisorbed oxygen appearing on their surface as a result of electrochemical water oxidation serve as sources of information. The cathodic signal spectrum of chemisorbed oxygen anables its energetic inhomogeneity to be estimated, while the difference in potentials of the corresponding cathodic and anodic currents, its lability. It has been established that in the system investigated the dominant role in processes of oxygen chemisorption is played by the V4+ surface centres. A model of defect formation in solid solution (MoxV1-x)2O5 is discussed. 相似文献
5.
The V4+ content in V2O5 doped with MoO3 is measured by a spectroscopic method. The influence of the oxygen pressure is also considered. Up to roughly 3.5 at.-% Mo/(Mo+V) the V4+ fraction is equal to the Mo6+ fraction for samples sintered in air. Increase of PO2 gives a decrease in the measured values of the V4+ fraction for the 5, 10 and 33 at.-% Mo-doped samples. 相似文献
6.
New mixed valent molybdenum monophosphates AMo3P2O14 have been synthesized for A = Ag, Rb, Na, Sr. The single crystal X-ray diffraction study of two of them (A = Ag, Sr) shows that they belong to the layer structure type KMo3P2O14. Their structure consists of [Mo3P2O14]∞ layers involving MoO6 octahedra and MoO5 bipyramids, interleaved with A cations forming bicapped trigonal prisms AO8. Bond valence calculations show a localisation of the MoV and MoVI species according to the formula A1MoVoct1MoVIoct2MoVIbipyP2O14 for A = Ag, Na and SrMoVoct1MoVoct2MoVIbipyP2O14. A comparison between the different MoV? MoVI phosphates is made. 相似文献
7.
《Polyhedron》1987,6(10):1813-1821
NaVO3Na2MoO4 solutions acidified with HCl were studied at the atomic V/Mo ratios equal to 3 : 1, 1 : 1, 1 : 3, 1 : 6 and vanadium concentration [V] = 0.1, 0.04, 0.004 and 0.0004 M in the range pH 7-2. Their 51V NMR spectra (measured at Hito = 7 T) were compared with those of VW solutions containing mixed metal complexes of known composition. The VMo5O193− (51V NMR chemical shift relative to VOCl3, δ, −502 ppm), V2Mo4O194− (δ −494), V2Mo4O193− δ −507), V9MoO285− (δ −422, −492, −501, −512, −521.5) and HV9MoO284− polyanions (p.a.) have been found to be dominant mixed species in Na-V-Mo solutions. Along with them the VitxMO13-itxO−itx−340 p.a.(x∼2–3) of the Keggin type (δ −496, −498, −516, −522) are supposed to be formed at pH < 4 in concentrated solutions ([V] > 0.01 M). The V2Mo6O266− p.a., isolated at pH ∼ 5 as the sodium salt (solid state δ −482), seem to be present in concentrated Na-V-Mo solutions only as minor species. On dissolving the salt the V2Mo6O266− p.a. mainly disproportionates into the complexes mentioned. From solutions containing mainly the V9MoO285− p.a. the sodium salt of V10O286− is crystallized. The V9WO286− p.a. are detected in VW solutions at V/W > 1. 17O and 95Mo NMR spectra of some mixed complexes are described. The distribution diagrams for VMo and V-W solutions at [V] = 0.004 M and V/Mo(W) = 1:3, derived from their 51V NMR spectra, are given. 相似文献
8.
The aim of this study is to investigate the influence of some monovalent counter-ions (NH4
+, K+ and Cs+) on thermal behavior of polyoxometalates derived from H3PMo12O40 (HPM) and H4PVMo11O40 (HPVM) by replacing the protons. The IR and UV-VIS-DRS spectra of some acid and neutral NH4
+, K+, Cs+ salts, which derived from HPM and HPVM, confirmed the preservation of Keggin units (KU) structure. The X-ray diffraction
spectra clearly showed the presence of a cubic structure. The non-isothermal decomposition of studied polyoxometalates proceeds
by a series of processes: the loss of crystallization water; the loss of O2 accompanying with a reduction of V5+→V4+ and Mo6+→Mo5+; the loss of constitution water started at 360°C for HPVM salts and 420°C for HPM salts; the decomposition of ammonium ion
over 420°C with NH3, N2 and H2O elimination and simultaneous processes of reduction (V5+→ V4+ and Mo6+→ Mo5+ or Mo4+) associating with endothermic effects; reoxidation of Mo5+, Mo4+ and V4+with a strong exothermic effect; destruction of KU to the oxides: P2O5, MoO3 and V2O5 and the crystallization of MoO3.
This revised version was published online in July 2006 with corrections to the Cover Date. 相似文献
9.
通过高温固相合成法首次合成了La2Mo1.8Ga0.2O9陶瓷样品. 粉末XRD结果表明, 该样品为单一立方相La2Mo2O9结构. 以陶瓷样品为固体电解质、多孔性铂为电极, 采用交流阻抗谱、气体浓差电池、氧泵等方法研究了样品在600~1000 ℃下各种气氛中的离子导电特性. 结果表明, 氧浓差电池电动势的实测值与理论值吻合得很好, 氧离子迁移数为1, 表明该陶瓷样品在该温度下氧气气氛中为一纯氧离子导体; 氧泵(氧的电化学透过)实验结果进一步证实了该样品在氧气气氛中为一纯氧离子导体; 在氧分压p(O2)=10-5~105 Pa的高氧分压气氛中, 电导率与氧分压变化基本无关, 表明在该氧分压范围内样品为纯离子导体, 这与氧浓差电池电动势测定结果相吻合; 在低氧分压为10-5~10-15 Pa范围内, 总电导率随氧分压降低而稍有升高, 表明在该氧分压范围样品为氧离子与电子的混合导体; 在600~1000 ℃下氧离子电导率>10-2 S•cm-1, 显著高于母体La2Mo2O9的氧离子电导率, 1000 ℃时的氧离子电导率为0.07 S•cm-1. 相似文献
10.
Ronny Neumann Prof. Daniella Goldfarb Prof. 《Chemistry (Weinheim an der Bergstrasse, Germany)》2010,16(33):10014-10020
An in‐depth spectroscopic EPR investigation of a key intermediate, formally notated as [PVIVVVMo10O40]6? and formed in known electron‐transfer and electron‐transfer/oxygen‐transfer reactions catalyzed by H5PV2Mo10O40, has been carried out. Pulsed EPR spectroscopy have been utilized: specifically, W‐band electron–electron double resonance (ELDOR)‐detected NMR and two‐dimensional (2D) hyperfine sub‐level correlation (HYSCORE) measurements, which resolved 95Mo and 17O hyperfine interactions, and electron–nuclear double resonance (ENDOR), which gave the weak 51V and 31P interactions. In this way, two paramagnetic species related to [PVIVVVMo10O40]6? were identified. The first species (30–35 %) has a vanadyl (VO2+)‐like EPR spectrum and is not situated within the polyoxometalate cluster. Here the VO2+ was suggested to be supported on the Keggin cluster and can be represented as an ion pair, [PVVMo10O39]8?[VIVO2+]. This species originates from the parent H5PV2Mo10O40 in which the vanadium atoms are nearest neighbors and it is suggested that this isomer is more likely to be reactive in electron‐transfer/oxygen‐transfer reaction oxidation reactions. In the second (70–65 %) species, the VIV remains embedded within the polyoxometalate framework and originates from reduction of distal H5PV2Mo10O40 isomers to yield an intact cluster, [PVIVVVMo10O40]6?. 相似文献
11.
Jadwiga Walczak Elżbieta Filipek Monika Bosacka 《Journal of Thermal Analysis and Calorimetry》1995,45(5):1055-1060
The V9Mo6O40?Cr2(MoO4)3 system has been investigated using the differential thermal analysis (DTA) and X-ray phase diffraction methods. The system has been found not to be a real two-component system over the whole component system. 相似文献
12.
Tien The Nguyen Thang Minh Le Duc Duc Truong Rasmus Fehrmann Anders Riisager Isabel Van Driessche 《Research on Chemical Intermediates》2012,38(3-5):829-846
In this work, the possible synergy effects between Bi2O3, MoO3 and V2O5, and between Bi2Mo3O12 and BiVO4, were investigated. The catalytic activity of the ??mechanical mixture?? of these compounds was measured. The mixture containing 36.96?mol% Bi2O3, 39.13?mol% MoO3 and 23.91?mol% V2O5 (21.43?mol% Bi2Mo3O12 and 78.57?mol% BiVO4), corresponding to the compound Bi1?x/3V1?x Mo x O4 with x?=?0.45 (Bi0.85V0.55Mo0.45O4), exhibited the highest activity for the selective oxidation of propylene to acrolein. The mixed sample prepared chemically by a sol?Cgel method possessed higher activity than that of mechanical mixtures. 相似文献
13.
Porous Capsules with a Large Number of Active Sites: Nucleation/Growth under Confined Conditions
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Somenath Garai Dr. Mirta Rubčić Dr. Hartmut Bögge Prof. Dr. Pierre Gouzerh Prof. Dr. Achim Müller 《Chemistry (Weinheim an der Bergstrasse, Germany)》2015,21(11):4321-4325
This work deals with the generation of large numbers of active sites and with ensuing nucleation/ growth processes on the inside wall of the cavity of porous nanocapsules of the type (pentagon)12(linker)30≡{(MoVI)MoVI5}12{MoV2(ligand)}30. A first example refers to sulfur dioxide capture through displacement of acetate ligands, while the grafted sulfite ligands are able to trap {MoO3H}+ units thereby forming unusual {(O2SO)3MoO3H}5? assemblies. A second example relates to the generation of open coordination sites through release of carbon dioxide upon mild acidification of a carbonate‐type capsule. When the reaction is performed in the presence of heptamolybdate ions, MoO42? ions enter the cavity where they bind to the inside wall while forming new types of polyoxomolybdate architectures, thereby extending the molybdenum oxide skeleton of the capsule. Parallels can be drawn with Mo‐storage proteins and supported MoO3 catalysts, making the results relevant to molybdenum biochemistry and to catalysis. 相似文献
14.
E. G. Il’in A. G. Beirakhov V. G. Yarzhemsky A. E. Gekhman A. K. Buryak 《Russian Journal of Inorganic Chemistry》2018,63(4):492-502
MALDI-TOF was used to study molybdenum dioxide (MoO2) containing a nanosized fraction. The composition of cationic clusters of nonstoichiometric lower molybdenum oxides in the gas phase was determined, and the thermodynamic stabilities and configurations of isomers were calculated for selected symmetric molecular structures and for cations MoSO 8 + and Mo5O 9 + . Molecular orbital analysis was performed for two trigonal-bipyramidal clusters Mo5O8 and Mo5O9. Changes in molybdenum–molybdenum interatomic distances in going from MoO 8 + and Mo5O 9 + cations to neutral clusters are discussed. 相似文献
15.
《Journal of Coordination Chemistry》2012,65(6):705-710
The oxalato complex of a polyoxomolybdovanadate, K6[Mo6V2O24(C2O4)2]·6H2O has been obtained by reaction of potassium molybdate, ammonium vanadate and tartaric or ascorbic acid. Such conversion of dicarboxylate into oxalate ions indicates the catalytic role of molybdenum. Complexes of analogous composition also were obtained in the reactions of MoO3, V2O5 and potassium oxalate, or M 2CO3 (M = Rb, Cs) and oxalic acid. The centrosymmetrical molybdovanadate anion [Mo6V2O24(C2O4)2]6- consists of six MoO6 and two VO6 edge-sharing octahedra to give the n -[Mo6O26]4- structure. All complexes were characterized by powder and single crystal X-ray analyses, ESR and IR spectra and TG and DSC measurements. 相似文献
16.
The phase equilibria established in the V2O5–MoO3–α-Sb2O4 system in the solid state in an air atmosphere were examined by using XRD and DTA methods. The obtained results allowed us
to find that in this system a novel compound is formed involving three oxides. Its formula can be written as Sb3V2Mo3O21. The synthesis of this compound requires picking up the atmospheric oxygen. X-ray characteristics of this compound were determined
and it was found that it melted incongruently at 740°C. The results obtained until now allow us to divide the investigated
V2O5–MoO3–α-Sb2O4 system into five partial subsystems.
This revised version was published online in July 2006 with corrections to the Cover Date. 相似文献
17.
Phase equilibrium studies in Ln2O3MoO2MoO3 systems indicate, for a Ln2O3:Mo ratio of 3:2, the existence of a new molybdenum (V)-rare-earth oxide Ln3MoO7. Ternary oxides have been prepared for Ln ≡ La-Ho and Y. For Ln ≡ La-Eu, Ln3MoO7 compounds form at 1473 K under oxygen partial pressures ranging from 10−7.3 to 10−11.6 atm. For Ln ≡ Gd-Ho and Y compounds form above 1573 K and at 1473 K the stability range is about 10−9 to about 10−10 atm. Lattice parameters deduced from X-ray diffraction patterns are reported. For the large Ln cations, lanthanum to europium, all reflections could be indexed in an orthorhombic C-centred cell isotypic to Nd3NbO7. For Ln ≡ Gd-Ho and Y, strong f.c.c.-type reflections show that the structure is defect fluorite. Stability ranges in terms of oxygen partial pressure and crystal chemical properties are discussed with respect to the rare-earth elements. Magnetic susceptibility measurements of La3MoO7 confirm the oxidation state + 5 for molybdenum. 相似文献
18.
M. Nieves Corella‐Ochoa Dr. Haralampos N. Miras Dr. De‐Liang Long Prof. Leroy Cronin 《Chemistry (Weinheim an der Bergstrasse, Germany)》2012,18(43):13743-13754
Five mixed‐metal mixed‐valence Mo/V polyoxoanions, templated by the pyramidal SeO32? heteroanion have been isolated: K10[MoVI12VV10O58(SeO3)8]?18 H2O ( 1 ), K7[MoVI11VV5VIV2O52(SeO3)]?31 H2O ( 2 ), (NH4)7K3[MoVI11VV5VIV2O52(SeO3)(MoV6VV‐ O22)]?40 H2O ( 3 ), (NH4)19K3[MoVI20VV12VIV4O99(SeO3)10]?36 H2O ( 4 ) and [Na3(H2O)5{Mo18?xVxO52(SeO3)} {Mo9?yVyO24(SeO3)4}] ( 5 ). All five compounds were characterised by single‐crystal X‐ray structure analysis, TGA, UV/Vis and FT‐IR spectroscopy, redox titrations, and elemental and flame atomic absorption spectroscopy (FAAS) analysis. X‐ray studies revealed two novel coordination modes for the selenite anion in compounds 1 and 4 showing η,μ and μ,μ coordination motifs. Compounds 1 and 2 were characterised in solution by using high‐resolution ESI‐MS. The ESI‐MS spectra of these compounds revealed characteristic patterns showing distribution envelopes corresponding to 2? and 3? anionic charge states. Also, the isolation of these compounds shows that it may be possible to direct the self‐assembly process of the mixed‐metal systems by controlling the interplay between the cation “shrink‐wrapping” effect, the non‐conventional geometry of the selenite anion and fine adjustment of the experimental variables. Also a detailed IR spectroscopic analysis unveiled a simple way to identify the type of coordination mode of the selenite anions present in POM‐based architectures. 相似文献
19.
Jiqing Xu Renzhang Wang Chunxiao Guo Guoyu Yang Qingxin Zeng Weiming Bu Ling Ye Yuguo Fan Guangdi Yang 《中国科学:化学(英文版)》2001,44(2):137-146
A nickel-1,10-phenanthroline complex supported on an octamolybdate, [(Ni(phen)2 2(ξ-Mo8O26)], has been hydrothermally synthesized with MoO3, H2MoO4, Ni(OAc)2 6H3O and 1,10-phenathroline (1,10-phen) as raw materials. The crystals of the compound belong to monoclinic P21/n space group,a = 1.2952(2),b = 1.6659(10),c = 1.3956(12) nm, β =106.273(8)°,V = 2.8906(5) nm3,Z = 2. 5604 observable reflections (I >2σ(I)) were used for structure resolution and refinements to converge to finalR 1 = 0.0414,wR 2 = 0.0815. The result of structure determination shows that the compound contains octamolybdate possessing a novel structure type (named as ξ-isomer). The feature of ξ-[Mo8O26]4- is that it is composed of Mo6O6 ring and two MoO6 octahedral located at cap positions on opposite faces. The Mo6O6 ring contains two octahedral and four trigonal-bipyramidal MoVI atoms. Each ξ-[Mo8O26]4- unit is bonded with two [Ni(phen)2]2+ through terminal oxygen atoms of octahedral and neighbouring trigonal-bipyramidal Mo atom in the Mo6O6 ring. IR and UV-Vis spectra of the compound were measured and its electronic structure was studied by EHMO method. 相似文献
20.
Five chemical compounds, CuMoO4, Cu3Mo2O9, Cu2Mo3O10, Cu6Mo4O15, and Cu4?x Mo3O12 (0.10 ? x ? 0.40), were identified in the system Cu2OCuOMoO3 and characterized by DTA, X-ray powder patterns, ir spectra, and magnetic properties. Cupric molybdates CuMoO4 and Cu3Mo2O9 are stable in air up to 820 and 855°C, respectively, melting at these temperatures with simultaneous decomposition (oxygen loss). Congruent mp of cuprous molybdates Cu2Mo3O10 and Cu6Mo4O15, in argon, are 532 and 466°C, respectively. Nonstoichiometric phase Cu4?x Mo3O12 = Cu2+3Cu01?xMo6+3O12, melts in argon between 630 and 650°C depending on the value of x and at 525–530°C undergoes polymorphic transformation. Areas of coexistence of the above-mentioned phases are determined. The μeff of Cu2+ ions and θ values are: 1.80 B.M. and 28°K for CuMoO4, 1.71 B.M. and ? 12°K for Cu3Mo2O9, and 1.74 B.M. and ? 93°K for Cu4?xMo3O12. Below 200°K CuMoO4 becomes antiferromagnetic. Cu2Mo3O10 and Cu6Mo4O15 show weak temperature-independent paramagnetism. 相似文献