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The catalytically relevant Nb2Mo3O14 phase has been prepared in bulk and silica-supported forms via the so-called "multiple molecular precursors method" from water-soluble oxo-oxalato complexes of Nb and Mo, (NH4)3[NbO(ox)3].H2O, and (NH4)2[MoO3(ox)].H2O. Thermal treatment of the mixed Nb-Mo precursor has been optimized for the formation of the pure Nb2Mo3O14 phase, either as bulk oxide or a silica-supported phase with high specific surface area. A characterization of the bulk phase obtained via the conventional ceramic route has also been carried out and a comparison has been made with the precursors route. According to this route, the Nb2Mo3O14 phase is shown to be formed in a pure form at 700 degrees C (i.e., 100 degrees C below the lowest temperature reported so far for the formation of the phase by the ceramic method). The supported samples have appreciable specific surface areas of 60-70 m(2) g(-1), much larger than those reached in the previous attempts under vacuum in sealed vials. The SEM and EDX analyses reveal a high dispersion of the desired phase on the silica support. 相似文献
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通过高温固相反应合成了铌酸盐KCa2Nb3O10及Cr3+和Mo6+掺杂(摩尔分数5%)的KCa2Nb3O10,并通过离子交换反应制备出HCa2Nb3O10及Cr3+和Mo6+掺杂的HCa2Nb3O10,采用X射线衍射、原子吸收光谱、扫描电镜等对所制得的样品进行了表征.在甲醇为电子给体、Pt为助催化剂的情况下,研究了催化剂HCa2Nb3O10及Cr3+和Mo6+掺杂的HCa2Nb3O10在紫外光辐射下分解水产氢的光催化活性,并讨论了引起催化剂活性差异的原因. 相似文献
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Zusammenfassung Mittels homogenisierter Sinter-und Schmelzproben wird die Bildung von lückenlosen Mischreihen zwischen Nb3Sn mit Mo3Si, Mo3Ge und Nb3Ge nachgewiesen.Mit 1 Abbildung 相似文献
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Yafarova Liliia V. Silyukov Oleg I. Myshkovskaya Tatiana D. Minich Iana A. Zvereva Irina A. 《Journal of Thermal Analysis and Calorimetry》2021,143(1):87-93
Journal of Thermal Analysis and Calorimetry - Protonation and hydration processes of layered perovskite-like oxide KCa2Nb3O10 during the reaction with nitric acid solutions with different... 相似文献
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《Comptes Rendus Chimie》2016,19(10):1337-1351
The sulphidation process of two catalysts (Mo/Al2O3 and CoMo/Al2O3) has been investigated by time-resolved X-ray Absorption Spectroscopy. With the unique edge jumping capability available at the SOLEIL synchrotron, studies of cobalt and molybdenum species have been conducted simultaneously on the same bimetallic catalyst. A methodology combining Principal Component Analysis and Multivariate Curve Resolution with Alternating Least Squares methods unravels a 3-stepped or 4-stepped sulphidation process for the bimetallic and monometallic catalysts, respectively. An oxysulphide-based molybdenum species has been identified as an intermediate for Mo/Al2O3 and a MoS3-like species has been observed for both catalysts. 相似文献
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ChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 100 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a “Full Text” option. The original article is trackable via the “References” option. 相似文献
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The existence of the charge transfer excited triplet state [Mo5+-O-] produced by UV-irradiation of Mo/SiO2 catalysts, and its reactivity are evidenced by experiments of photoluminescence, photoinduced metathesis, and photoreduction
of CO. Mo5+ ions can be produced separately by thermal activation and O- ions by further adsorption of N2O on those Mo5+ ions. The latter of which are adsorbed on Mo6+ ions are found to be more reactive than O2- of [Mo6+ =O2-] bond. They are able either to add a molecule such as CO or C2H4, or to abstract hydrogen from H2, CH4 or trans-dicyanoethylene, or a CN group form tetracyanoethylene (TCNE). The Mo5+ ions are able to coordinate gas phase ligands when their coordination sphere possesses vacant sites. This is the case for
tetracoordinated Mo5+
4c ions arising from reduction of tetrahedral Mo6+ ions (Eq. (7)). These Mo5+
4c ions are similar to those produced by UV-irradiaiion (Eq. (2)). In addition, if the adsorbed molecule has a sufficiently
large electron affinity, such as TCNE or O2, an electron transfer can occur (Eq. (9) and (17)). The [Mo5+-O-] bond obtained by thermal activation is more difficult to evidence than that obtained with UV-activation because it is not
detectable by EPR. However, the EPR results obtained at low temperature show that the O- ions adsorbed on Mo/SiO2 catalysts as well as the [Mo5+-O-] excited triplet state obtained by UV-irradiation of 1Mo6+=O2] interact with methanol (Eq. (16)). They are consistent with the mechanism of methanol oxidation occurring at high temperature
(Eq. (4)). 相似文献
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Zusammenfassung Es wird ein isothermer Schnitt im System Nb2O5 -Li2O-Sc2O3 untersucht. Dabei wurde die neue Verbindung Li0.5Sc0.5Nb2O6 gefunden. Die Röntgenreflexionsaufnahmen ergaben unter Annahme eines orthorhombischen Gitters die Parameter a=1433.6/2/ pm, b=572.96/6/ pm und c=505.76/4/ pm.Bei 1453 K wurde der LiNbO3-Homogenitätsbereich bestimmt, der sich vom binären System Li2O-Nb2O5 bis zu 5 mol% Sc2O3 im Dreikomponentensystem erstreckt. Im Homogenitätsbereich wurde die Variation der Gitterkonstanten gemessen. Das Volumen der Elementarzelle nimmt mit steigendem Sc2O3-Gehalt zu.
An isothermal section was investigated in the system Nb2O5-Li2O-Sc2O3. The new compound Li0.5Sc0.5Nb2O6 was found The x-ray reflection pattern could be indexed with the assumption of an orthorhombic lattice with the parameters of a=1433.6(2) pm, b=572.96(6) pm, c=505.76(4) pm.The LiNbO3-homogeneity range was determined at 1453 K. It extends from the binary Li2O-Nb2O5 to 5 mole-% Sc2O3 in the ternary system. The variation of the lattice constants of LiNbO3 was measured in the homogeneity range. The volume of the unit cell increases with increasing content of Sc2C3.
Nb2O5-Li2O-Sc2O3, Li0,5 Sc0,5Nb2O6. , $ = 1433,6/2/ , =572,96/6/ =505,76/4/ . 1453 LiNbO3, $ Li2O-Nb25 $ 5 %. $ . .相似文献
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The reaction of Mo2(O3CCF3)4 with (CH3)3SiI and PPh3 gave the title complex [Mo3(O2CCF3)2I4]-(HPPh3)2 which was characterized by X-ray crystallography. Crystal data for [Mo2(O2CCF3)2I4](HPPh3)2: space group $ {\rm P}\bar 1 $, a = 10.953(4) Å, b = 12.784(3) Å, c = 19.829(4) Å, α = 100.68(2)°, β = 91.16(2)°, γ = 112.98(2)°, V = 2498.6(10) Å3, Z = 2, with final residuals R = 0.0887 and Rw = 0.0965. There are two independent molecules in each asymmetric unit. The molybdenum, oxygen, and fluoride atoms in one of the two independent molecules are disordered, such that the primary set is 53% occupied, and the secondary set 47%. 相似文献