Studies on the system Al2O3-V2O5-MoO3

Studies on the three-component system Al₂O₃-V₂O₅-MoO₃ have shown the existence of a new compound with molecular formula AlVMoO₇. The synthesis conditions and X-ray characteristics of this compound and its melting temperature, 690±10°C, are reported.

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Zusammenfassung Einleitende Untersuchungen am Dreikomponentensystem Al₂O₃-V₂ O₅-MoO₃ zeigten die Existenz einer neuen, noch nicht publizierten Verbindung der Formel AlVMoO₇. Die Synthese der Verbindung sowie ihre röntgenographischen Eigenschaften wurden beschrieben. Ihr Schmelzpunkt beträgt 690±10°C.

     

Phase diagram of V2O5-MoO3-Ag2O

Phase equilibria in the V₂O₅-Ag₂O system were investigated at a constant pressure of oxygen (0.2 atm) and the phase diagram found under these conditions was compared with the results of the authors who investigated the same system in vacuum and at an oxygen pressure of 1 atm. On the basis of all these results, an attempt was made to construct the hypothetical diagram of V₂O₅-Ag₂O-O₂.     

Phase diagram of the V2O5-MoO3-Ag2O system

The phase diagram of the MoO₃-Ag₂O system was constructed. A comparison of the phase diagram presented here with the phase diagram of MoO₃-Ag₂MoO₄ system presented in [2] revealed some discrepancies.It was found that phase equilibrium in MoO₃-Ag₂O system could be reached only after cooling the previously melted mixtures of silver and molybdenum oxides.

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Zusammenfassung Es wurde das Phasendiagramm des Systemes MoO₃-Ag₂O erstellt. Der Vergleich dieses Phasendiagrammes mit dem des in (2) beschriebenen Systemes MoO₃-Ag₂MoO₄, ergeben sich einige Unterschiede.Man fand, da\ ein Phasengleichgewicht im System MoO₃-Ag₂O nur nach Abkühlen des zuvor geschmolzenen Gemisches aus Silber- und MolybdÄnoxides erreicht werden kann.

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The author wishes to thank Professor M. Figlarz from Université de Picardie, Amiens for giving the possibility of carrying out in his laboratory a part of the experiments described.     

Studies on the System AIVMoO7-V2O5

The phase equilibria in the system AlVMoO₇-V₂O₅ were investigated over the whole component concentration range up to 1000°C. A phase diagram was constructed from the results of DTA and XRD methods. This revised version was published online in July 2006 with corrections to the Cover Date.     

Studium der Reaktionen von TlNO3-V2O5 in Fester Phase

The solid-state reactions of TlNO₃ with V₂O₅ in the molar ratios of 6∶5 and 2∶3 were studied by DTA, DTG and TG in the temperature ranges 20–550° and 20–400°, respectively, in a nitrogen atmosphere. For the molar ratio of 6∶5, thallium pentavanadate (Tl₃V₅O₁₄) was formed as the final product of reaction at 550°. The reaction proceeds stepwise, and Tl₂V₆O₁₆ and TlVO₃ were identified as intermediates. For the molar ratio of 2∶3, impure thallium hexavanadate (Tl₂V₆O₁₆) was obtained as the final product of reaction.

     

Phase Equilibrium in the SeO2–Bi2O3 System

The subject of the present study is the system SeO₂-Bi₂O₃ that comprises two oxides with low melting points. All batches are thermal treatment in quartz ampoules, which are evacuated and sealed at a pressure P=0.1 Pa. On the basis of DTA (differential thermal analysis) and X-ray data, the most probable liquidus line of the system has been plotted. The eutectic composition lies about 90 mol% SeO₂,with on eutectic temperature at 230°C. Above 20 mol% Bi₂O₃ the liquidus temperature extremely increases. The formation of three compounds is proved:Bi₂Se₃O₉ and Bi₂Se₄O₁₁ are melting incongruently at 540 and 350°C respectively and Bi₂SeO₅ congruently at 915°C. This revised version was published online in July 2006 with corrections to the Cover Date.     

Investigation on the TeO2–MoO3–V2O5 System. II. Properties of the obtained glasses

Some of the properties of glasses obtained in the systems TeO₂–MoO₃ and TeO₂–MoO₃–V₂O₅ had been studied. A good correlation between the properties and the phase diagram of the TeO₂–MoO₃ system was established. The glass resistance-composition function varied between 6.85 · 10⁹ ohm · cm and 2.93 · 10¹⁰ ohm · cm. The isolines of the properties (softening temperature, density, resistance at room and higher temperatures and activation energy) of the glasses obtained from the TeO₂–MoO₃–V₂O₅ system were ploted. The electrical resistance is influenced by the concentration of V₂O₅ and MoO₃ and by temperature. The glass absorption characteristics of thin layers were determined in the visible range.     

Non-isothermal crystallization kinetics of V2O5-MoO3-Bi2O3 glasses

Characteristic temperatures, such as T _g (glass transition), T _x (crystallization temperature) and T _l (liquidus temperature) of glasses from the V₂O₅-MoO₃-Bi₂O₃ system were determined by means of differential thermal analysis (DTA). The higher content of MoO₃ improved the thermal stability of the glasses as well as the glass forming ability. The non-isothermal crystallization was investigated and following energies of the crystal growth were obtained: glass #1 (80V₂O₅·20Bi₂O₃) E _G=280 kJ mol^-1, glass #2 (40V₂O₅·30MoO₃·30Bi₂O₃) E _G=422 kJ mol^-1 and glass #3 (80MoO₃·10V₂O₅·10Bi₂O₃) E _G=305 kJ mol^-1. The crystallization mechanism of glass #1 (n=3) is bulk, of glass #3 (n=1) is surface. Bulk and surface crystallization was supposed in glass #2. The presence of high content of a vanadium oxide acts as a nucleation agent and facilitates bulk crystallization. This revised version was published online in August 2006 with corrections to the Cover Date.     

Electrical conductivity of g-Bi2O3-V2O5 solid solution

The total conductivity (σ_T) in bcc γ-Bi₂O₃ doped with V₂O₅ system has been measured in the composition range between 1 and 7 mol% V₂O₅ at different temperatures. Phase transitions for different addition amounts depending on the temperature were investigated by quenching the samples. According to the XRD and DTA/TG results, this bcc type solid solution was stable up to about 720°C and the solubility limit was found at ˜7 mol% V₂O₅ in γ-phase. This system showed predominantly an oxide ionic conduction. As the V₂O₅ addition increased, the ionic conduction increased up to 5 mol% V₂O₅ at which the highest conductivity was found to be 8.318·10^-2 Ω^-1 cm^-1 at 700°C and then decreased. It has been proposed that γ-Bi₂O₃ phase contains a large number of oxide anion vacancies and incorporated vanadium cations at tetrahedral sites which affect the oxygen sublattice of the crystal structure. This revised version was published online in August 2006 with corrections to the Cover Date.     

Phase formation in the Ag2O-ZnO (CdO)-V2O5 systems

The phase composition of the Ag₂O-ZnO(CdO)-V₂O₅ systems has been studied. Two new orthovanadates have been synthesized: AgZnVO₄ (monoclinic space group P21/n, a = 5.68710, b = 12.54080, c = 5.65947 Å, β = 116.209°) and AgCd₄(VO₄)₃ (orthorhombic space group Pnma, a = 9.82438 b = 7.01250, c = 5.37393 Å). One double metavanadate Ag₂Cd(VO₃)₄ has been synthesized. A continuous solid solution formulated as Ag_{3 ? 2x} Cd_{3 + x} (VO₄)₃ has been found to exist between AgCd₄(VO₄)₃ and already described AgCdVO₄. The Ag₂O-ZnO (CdO)-V₂O₅ systems have been triangulated in the subsolidus region.     

Studies on the Fe2(MoO4)3-V2O5 system

The phase equilibria established in solid state in the whole range of component concentrations in the Fe₂(MoO₄)₃-V₂O₅ system were studied by DTA and X-ray powder diffraction. This system is not a real two-component system.

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Zusammenfassung Im gesamten Konzentrationsbereich der Komponenten des Systems Fe₂(MoO₄)₃-V₂O₅ wurde das im festen Aggregatzustand festgestellte Phasengleichgewicht mittels DTA und Pulverröntgendiffraktionsverfahren untersucht. Dieses System ist kein wirkliches Zweikomponentensystem.

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F₂(₄)₃-V₂O₅ . , .

     

硫酸铯/乙醇双水相体系的相平衡

采用自制的相平衡研究装置，测定了硫酸铯/乙醇双水相体系在0、10、20和40 ℃四个温度下的等温平衡溶解度，并且获得了醇相溶液和水相溶液的折光率数据，发现温度对该体系的液-液和固-液相平衡均没有显著影响.利用“湿渣结线法”确定出四个温度下平衡固相均为无水盐，同时给出了该体系的完整相图，在相图中观察到五个相区，为该体系的进一步应用研究提供了参考数据.     

Thermal expansion of phases formed in the system Nb2O5-MoO3

Studies on thermal expansion of phases formed in the system Nb₂O₅-MoO₃ (WO₃) have been carried out in the high-temperature X-ray diffraction attachment. In the case of Nb₁₄Mo₃O₄₄, Nb₁₂MoO₃₃ and Nb₁₂WO₃₃ the structure that consists of ReO₃ type blocks, the direction of minimal thermal expansion is consistent with direction in which the chains of corner-sharing polyhedra spread to infinity. On the contrary, for Nb₂Mo₃O₁₄, the structure of which resembles the structure of tetragonal tungsten bronzes, the maximal thermal expansion direction is consistent with above mentioned direction. This revised version was published online in July 2006 with corrections to the Cover Date.     

A search for new phases in the system Fe2O3-V2O5-WO3

Studies on the three-component system Fe₂O₃-V₂O₅-WO₃ have shown the occurrence of a new, compound with molecular formula FeVW₂O₁₀. Its X-ray characteristics and its melting temperature, 865±10 °C, have been established.

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Zusammenfassung Einleitende Untersuchungen am Dreikomponentensystem Fe₂O₃-V₂ O₅-WO₃ zeigten das Auftreten einer neuen, noch nicht publizierten Verbindung der Formel FeVW₂O₁₀. Die Verbindung wurde röntgenographisch beschrieben, ihr Schmelzpunkt beträgt 865 ±10°C.

     

V2O5-MoO3-SiO2表面复合氧化物催化剂的制备与表征

采用表面改性法制备了V2O5-SiO2,MoO3-SiO2,V2O5-MoO3-SiO2复合氧化物催化剂,并用TPR和IR技术研究了催化剂的表面结构及V=O,M0=O的活性,同时用化学吸附IR技术研究了催化剂样品对异丁烷的化学吸附性能.实验结果表明:这些复合氧化物催化剂对异丁烷都有较高的化学吸附能力;SiO2能缓解表面Lewis碱位V=O和Mo=O的氧化能力,有利于选择氧化.     

CsCl-TmCl3-HCl-H2O(25 ℃)的相平衡及其固相化合物

The equilibrium solubilities of the quaternary system CsCl-TmCl₃-HCl-H₂O was determined at 25 ℃ and the corresponding equilibrium diagram was constructed. The diagram is a complicated system with limited solid solutions and formation of a new compound 3CsCl·2TmCl₃·14H₂O. The new compound has been characterized by XRD, TC-DTG and fluorescence spectrometry. Results show that upconversion spectrum exhibits at 335 nm when exciting at 860 nm, and fluorescence spectrum exhibits at 295 nm and 385 nm when exciting at 240 nm. The compound loses its crystal water by four steps at 50 to 250 ℃. Using a heat conduction calorimeter, the standard molar enthalpy of dissolution of 3CsCl·2TmCl₃·14H₂O was determined to be (-11.601 ± 0.050) kJ·mol^-1 at 298.15 K.     

四元体系RbCl-CeCl3-HCl-H2O(25 ℃)的相平衡及其新相化合物

测定了四元体系RbCl-CeCl3-HCl-H2O在25℃时的溶度数据, 绘制了相应的溶度图. 该四元体系是由3个固相区RbCl(原始盐), RbCl·CeCl3·4H2O, CeCl3·7H2O(原始盐)组成的复杂体系, 其中RbCl·CeCl3 ·4H2O是固液同成分溶解度的化合物. 在相平衡结果指导下, 制备了化合物RbCl·CeCl3 ·4H2O, 并对其进行了X射线粉末衍射鉴定和热重分析, 结果表明, 该化合物在84～216 ℃通过两步失去其结晶水. 用RD496-Ⅲ-2000微量热计测定了298.15 K下新相化合物在水中的溶解焓(-23.70±0.11) kJ·mol-1, 计算出其标准摩尔生成焓为(-2735.6±1.1) kJ·mol-1.     

Yb2O3对Bi2O3-MoO3催化剂性能的影响

在Bi2O3-MoO3复合氧化物催化剂中加入Yb2O3，可明显提高异丁烯转化率和生成甲基丙烯醛的选择性，用XRD、FT-Raman光谱和SEM技术研究了催化剂的组成和性质，Bi2O3—MoO3催化剂的成分主要是α-Bi2Mo3O12，添加镱后出现了Yb2Mo3O12的吸收峰；且Bi2O3-MoO3-Yb2O3催化剂的FT—Raman光谱图在363cm^-1处出现了Yb—O伸缩振动峰，同时既Bi2O3-MoO3催化剂的铝-氧振动发生红移，表明镱的加入使铝-氧键的振动减弱，使Bi2O3-MoO3-Yb2O3催化剂有较高传递晶格氧给予异丁烯的能力，导致异丁烯转化率和生成甲基丙烯醛的选择性均显著提高。     

IR-spectral investigation of the structure of glasses in the Fe2O3-V2O5 system

The structure of glasses in the Fe₂O₃-V₂O₅ system in the 0–50 mol% Fe₂O₃ range is studied by IR-spectroscopy. It is found that the introduction of Fe₂O₃ favours the transformation of the VO₅-groups into VO₄ ones. This effect may be shown with the aid of IR-spectra, owing to the fact that these glasses are characterized by two high-frequency bands at 1020 and 930 cm^–1. The first is determined by the vibrations of the short V=O nonbridging bonds in the VO₅-groups, while the second is assigned to the vibrations of the V—O-bonds in deformed VO₄-tetrahedra.

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IR-spektroskopische Strukturuntersuchung von Gläsern des Systems Fe₂O₃-V₂O₅

Zusammenfassung Die Struktur von Gläsern des Systems Fe₂O₃-V₂O₅ in dem Bereich von 0–50 Molprozent Fe₂O₃ wurde mit Hilfe der IR-Spektroskopie untersucht. Zusatz von Fe₂O₃ begünstigt die Umwandlung der VO₅- in VO₄-Gruppen. Das kann in den IR-Spektren durch zwei Banden bei 1020 und 930 cm^–1 festgestellt werden. Die erste wird durch Schwingungen der kurzen V=O-Nichtbrücken-bindungen in den VO₅-Gruppen verursacht, die zweite wird auf Schwingungen der V—O-Bindungen in dem deformierten VO₄-Tetraeder zurückgeführt.

     

CeCl3-CdCl2-H2O和CeCl3-CdCl2-HCl-H2O的相平衡

测定了三元系CeCl₃-CdCl₂-H₂O (25 ℃)和四元系CeCl₃-CdCl₂-HCl(～8.4％)-H₂O(25 ℃) 的相平衡溶度数据,绘制了相应的溶度图.该三元系是由5个固相区CdCl₂&;#8226;2.5H₂O(原始盐)、CdCl₂&;#8226;H₂O(原始盐)、6CdCl₂&;#8226;CeCl₃&;#8226;14H₂O、4CdCl₂&;#8226;CeCl₃&;#8226;12H₂O、CeCl₃&;#8226;7H₂O(原始盐)组成的复杂体系.该四元系是由5个固相区CdCl₂&;#8226;H₂O(原始盐)、9CdCl₂&;#8226;CeCl₃&;#8226;19H₂O、6CdCl₂&;#8226;CeCl₃&;#8226;14H₂O、4CdCl₂&;#8226;CeCl₃&;#8226;12H₂O、CeCl₃&;#8226;7H₂O(原始盐)组成的复杂体系.其中6CdCl₂&;#8226;CeCl₃&;#8226;14H₂O在该三元系是介稳化合物.9CdCl₂&;#8226;CeCl₃&;#8226;19H₂O 、6CdCl₂&;#8226;CeCl₃&;#8226;14H₂O和4CdCl₂&;#8226;CeCl₃&;#8226;12H₂O用X射线粉末衍射及TG-DTG和DSC等方法进行了研究,并对X射线粉末衍射进行了指标化.