复合固体超强酸催化剂SO_4~(2-)_4-WO_3-ZrO_2的结构研究

已报导，经适当处理的SO42-ZrO2和WO3－ZrO2具有超强酸性［1］．在此基础上将SO42-和WO3同时负载于ZrO2表面，发现其表面酸性有明显增强，得到的固体超强酸504－W0s－Zro。在很宽的焙烧温度范围内（700七00“C）都具有HO三一16．04的酸强度，吸附毗院的红外光谱研究表明，其表面同时具有强的L酸性和B酸性问，140“C时，对正乙烷裂解及异构化的催化活性比SO4－－ZrO。和WO3－ZI02都高，表现出相当的协同效应同．本文用XRD，DTA－TG，比表面测定等技术研究催化剂的组成、结构形态及其随焙烧温度的变化．并与504－Zro：和WO。…     

Selective synthesis and characterization of single-crystal silver molybdate/tungstate nanowires by a hydrothermal process

Selective synthesis of uniform single crystalline silver molybdate/tungstate nanorods/nanowires in large scale can be easily realized by a facile hydrothermal recrystallization technique. The synthesis is strongly dependent on the pH conditions, temperature, and reaction time. The phase transformation was examined in details. Pure Ag(2)MoO(4) and Ag(6)Mo(10)O(33) can be easily obtained under neutral condition and pH 2, respectively, whereas other mixed phases of Mo(17)O(47), Ag(2)Mo(2)O(7,) Ag(6)Mo(10)O(33) were observed under different pH conditions. Ag(6)Mo(10)O(33) nanowires with uniform diameter 50-60 nm and length up to several hundred micrometers were synthesized in large scale for the first time at 140 degrees C. The melting point of Ag(6)Mo(10)O(33) nanowires were found to be about 238 degrees C. Similarly, Ag(2)WO(4), and Ag(2)W(2)O(7) nanorods/nanowires can be selectively synthesized by controlling pH value. The results demonstrated that this route could be a potential mild way to selectively synthesize various molybdate nanowires with various phases in large scale.     

Effect of WO3 particle size on the type and concentration of surface oxygen

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Multi-element trace analysis of tungsten

Investigations carried out in order to determine traces of 25 elements in tungsten in the lower g/g range are reported on. Atomic absorption spectrometry and plasma atomic emission spectrometry as well as solution photometry and activation analysis were the main techniques used.     

光度分析中协同系数补偿方法的研究──三次标准加入法同时测定钼、钨和钛

本文在两次标准加入法[1]的基础上，提出了三组份同时测定的三次标准加入法，并应用于钼、钨和钛的流动注射同时测定。测定条件：［水杨基荧光酮（SAF）］＝1．25　×10-4mol／L，［溴化＋六烷基三甲基铵（CTMAB）」＝2．5×10－3mol／L，pH1．35，25℃，采样、进样时间分别为10s和18s，进样频率128次／h。为消除组份间协同作用引起的吸光度加合性的偏离，定义了三组份协同系数。将其引入三组份同时测定方法，补偿了吸光度对线性的偏离。补偿后钼、钨和钛的测定范围分别为0．05～0．35，0．25～1．00，0．025～0．30mg／L。测定了钢样及模拟样品中钼、钨和钛含量，结果较好。     

Ultra trace analysis of refractory metals by solid state mass spectrometry — A comparison of GDMS,SSMS and SIMS

The analytical performance of a glow discharge quadrupole mass spectrometer is demonstrated using sintered tungsten as an example. The inherent problem of molecular interferences in glow discharge mass Spectrometry has been considerably reduced using neon as a complementing discharge gas. Particular attention has been paid to time dependences. Analytical figures of merit are presented.     

Metal carbonyl derivatives of lanthanides. CpLuCl2-induced synthesis of the trinuclear tungsten cluster [Na(DME)3]2[W3(CO)14]

The cluster [Na(DME)₃]₂[W₃(CO)₁₄] (1) was prepared by treating CpLuCl₂ with an equimolar mixture of Na₂W(CO)₅ and Na₂W₂(CO)₁₀ in DME and characterized by X-ray analysis (MoK radiation, 653 reflections,R = 0.125). The crystals are rhombic,a=18.749(4) Å,b=15.074(3) Å,c=9.505(3) Å,Z = 2, space groupC _mmm. The W-W distance in the W-W-W chain is 2.79 Å. The carbonyl ligands at the tungsten atoms are eclipsed. Compound 1 is the first example of a homometallic carbonyl cluster of an early transition metal. It is suggested that CpLuCl₂ interacts with Na₂W(CO)₅ to afford the highly reactive species CpLu (CO)₅ which further reacts with Na₂W₂(CO)₁₀ to form1. Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 3, pp. 582–585, March, 1993.     

Syntheses,molecular structures,and thermal decomposition of cyclopentadienyldicarbonylmanganese chalcogenide derivatives

Transmetallation of the dichalcogenide complexes [CpMn(CO)₂]₂(-X₂) (X = S or Se) with M(CO)₅(thf) (M = Cr or W) afforded new heterometallic complexes CpMn(CO)₂(-Se₂)Cr(CO)₅, CpMn(CO)₂(-Se₂)[Cr(CO)₅]₂, CpMn(CO)₂(-X₂)[W(CO)₅]₂ (X = S or Se), and CpMn(CO)₂(-Se₂)[Cr(CO)₅][W(CO)₅]. According to the X-ray diffraction data, their molecular structures contain the cyclic MnX₂ fragments coordinated by one or two M(CO)₅ groups via the X atoms. Study of thermal decomposition of the manganese complexes with different Mn : M : X ratios (M = Cr, W; X = S, Se, Te) by differential scanning calorimetry (DSC) and thermogravimetry demonstrated that this process took place at rather low temperatures (100—400 °C) and was accompanied by complete elimination of the CO groups followed by elimination of the Cp groups. At any metal to chalcogen ratio, the resulting inorganic chalcogenides contained no impurities of metal oxides and carbides.     

Oxidation products of the niobium tungsten oxide Nb4W13O47: A high-resolution scanning transmission electron microscopy study

Nb₄W₁₃O₄₇, a member of the solid solution series Nb_8−nW_9+nO₄₇ (0?n?5), crystallizes in a threefold superstructure of the tetragonal tungsten bronze structure. While the oxidation of this reduced phase at T_OX=1200 °C leads to a separation into the thermodynamically stable phases, lower oxidation temperatures result in products that comprise new structural elements and ordering variants. The characterization of the oxidation products obtained at T_OX=1000 °C was performed by scanning transmission electron microscopy applying a high-angle annular dark field detector. At the selected imaging conditions (Z contrast), not only the metal positions are revealed by this technique but valuable additional information about the elemental distribution can be obtained simultaneously.     

Beiträge zur Chemie der Alkylverbindungen von Übergangsmetallen. 58. Zur Kenntnis von 2-(Dimethylaminomethyl)ferrocenyl-Verbindungen des Vanadiums,Molybdäns,Wolframs, Thoriums und Urans

Contributions to the Chemistry of Transition Metal Alkyl Compounds. 58 On 2-(Dimethylaminomethyl)ferrocenyl Compounds of Vanadium, Molybdenum, Tungsten, Thorium, and Uranium Earlier results according to which dimethylaminomethylferrocenyl groups (FcN) are able to form stable organometallic chelate compounds were confirmed by synthesis of the heterobimetallic chelate compounds (FcN)₂VO · Li(acac) II , (FcN)MoO₂(acac) III , (FcN)WOCl₃ IV , (FcN)Th(acac)₃ V , and (FcN)UO₂(acac) VI from the corresponding metal acetylacetonates or oxidchlorides and (FcN)Li I . The new compounds were characterized by elemental analysis, the i.r., ¹H-n.m.r., and electron spectra and by their effective magnetic moments.