- Use of ionic liquids (ILs) for the IL-anion size-dependent formation of Cr, Mo and W nanoparticles from metal carbonyl M(CO)6 precursors
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Stable chromium, molybdenum and tungsten nanoparticles are obtained reproducibly by thermal or photolytic decomposition under argon from mononuclear metal carbonyl precursors M(CO)6 (M = Cr, Mo, W) suspended in the ionic liquids BMim+BF4-, BMim +OTf- and BtMA+Tf2N- (BMim+ = n-butyl-methyl-imidazolium, BtMA+ = n-butyl-trimethyl-ammonium, Tf2N = N(O2SCF 3)2, OTf = O3SCF3) with a very small and uniform size of 1 to 1.5 nm in BMim+BF4- which increases with the molecular volume of the ionic liquid anion to ～100 nm in BtMA+Tf2N- [characterization by transmission electron microscopy (TEM), dynamic light scattering and transmission electron diffraction (TED) analysis]. The Royal Society of Chemistry.
- Redel, Engelbert,Thomann, Ralf,Janiak, Christoph
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- MOLYBDENUM METAL BY THE ALUMINOTHERMIC REDUCTION OF CALCIUM MOLYBDATE.
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A process is discussed for extracting molybdenum metal in well consolidated form and in good yield from calcium molybdate by open aluminothermic reduction. Post reduction processing by electron beam melting and by molten salt electrorefining for the removal of aluminum is also described. The final metal is said to compare very favorably with commercial molybdenum obtainable by other routes.
- Mehra,Bose,Gupta
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- Phase and structural transformations in the Ni65Mo 20Cr15 alloy at changing the temperature of heat treatment
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The ternary Ni65Mo20Cr15 alloy was studied using TEM after heat treatment at different temperatures. It has been shown that the tendency to phase separation which exists in the Ni/Mo diffusion couple at high temperatures leads to precipitation of crystalline particles of Mo atoms in the liquid solution. At lowering the heat treatment temperature to 1200 C, a phase transition ordering - phase separation occurs in the Ni/Mo diffusion couple, which results in dissolution of the particles of Mo atoms. At 650 C, there takes place precipitation of Ni2Mo phase particles, which can initiate intercrystalline embrittlement of Hastelloy-type alloys.
- Ustinovshikov
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- Structure of Mo7S8: A new binary sulfide synthesized by self molybdenum intercalation
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A new Mo7S8 binary sulfide structure and its crystal growth are reported. It is the first example of Mo atoms in the channels of the Chevrel phases. The single crystal structure determination indicates extra molybdenum atoms located in the chalcogen site that is centered at the rhombohedral unit-cell origin. The nature and valence state of these extra atoms are discussed through chemical and physical properties. 1998 Elsevier Science Ltd.
- Belin, Stephanie,Chevrel, Roger,Sergent, Marcel
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- A novel growth mode of Mo on Au(111) from a Mo(CO)6 precursor: An STM study
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The growth of a submonolayer of metallic Mo prepared by chemical vapor deposition (CVD) of Mo(CO)6 on Au(111) was studied by scanning tunneling microscopy (STM). At low coverage, nanoscale Mo clusters grow at the elbow sites and in the fcc regions of the reconstructed Au surface. When the coverage increases, rather than decorating uniformly all elbows as found in physical vapor deposition (PVD), the Mo clusters aggregate but do not coalesce, forming ramified cluster islands. Within the islands, the clusters preferentially aggregate along the fcc troughs and the domain boundaries. At step edges, Mo clusters are found to grow at both upper and lower step edges. Differences between CVD and PVD are attributed to differences in the mobility of the nascent Mo species leading to growth. We hypothesize that the difference in mobility for the CVD process is due to the presence of CO from the precursor molecules. Oxidation of the Mo islands leads to their spreading, proving that the Mo clusters are either three-dimensional above or embedded in the surface of the gold substrate.
- Song, Zhen,Cai, Tanhong,Rodriguez, Jose A.,Hrbek, Jan,Chan, Ally S.Y.,Friend, Cynthia M.
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- Electrode reactions on synthetic diamond and cubic boron nitride in ionic melts
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The behavior and corrosion resistance of synthetic diamond and cubic boron nitride in chloride, chloride-oxide, and oxide salt melts at 750-900°C were studied by potentiometric and voltammetric methods.
- Novoselova,Gab
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- Visible Laser-Induced Nucleation and Growth of Cr, Mo, and W Films from the Hexacarbonyls. Reactivity of CO on Film Surfaces
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Continuous visible laser irradiation is used to deposit Cr, Mo, and W films from the hexacarbonyls by thermal excitation.Detailed analyses of the films by scanning Auger microscopy show that the Mo and Cr films are spatially inhomogeneous, having clean metal centers surrounded by contaminated metal rings.W films are completely pure.Depth profiles reveal that, prior to formation of clean Mo and Cr, an interfacial layer of contaminated material is deposited which becomes progressively metal rich as thickness increases.If such a layer is formed for W, it is very thin.The measured composition profiles are compared to calculated surface temperature distributions in order to extract information on the kinetics of CO dissociation and desorption during growth.The temperature and mechanism simulations show that CO desorption dominates above about 450 K, ensuring that pure metal is deposited.Below that temperature contamination occurs.Previous investigations of film growth from metal hexacarbonyls have led to the conclusion that film purity will only be high at temperatures exceeding 800 K, where recombinative desorption of CO is fast.The origins of the large discrepancy in temperatures are discussed.Chemical processes leading to growth of metal oxycarbide material at the film edges and film-substrate interface are explored using data from the catalysis literature.The strong parallels found between the laser-deposited material and supported catalysts formed from the hexacarbonyls suggest that the oxycarbide films may have significant Lewis acid-base character, leading to faster CO and metal-CO bond dissociation rates.Thus, formation of contaminated material appears to depend on local surface composition as well as temperature.
- Houle, F. A.,Singmaster, K. A.
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- The cluster size dependence of thermal stabilities of both molybdenum and tungsten nanoclusters
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We measured, for the first time, the oxidation enthalpies of both molybdenum (Mo) and tungsten (W) nanoclusters at several cluster sizes. We observed that the oxidation enthalpies of both Mo and W nanoclusters went down to the corresponding bulk values, r
- Kim,Huh,Park,Jeong,Lee
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- Mechanistic understanding, gamma phase formation and morphological behaviour of the Reduction?Diffusion processed U-Mo alloy
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Reduction?Diffusion (R-D) process has been attempted to synthesize U-Mo alloy powder for the first time, and the mechanism of alloy formation has been investigated. Calciothermic reduction of uranium dioxide in the presence of the alloying element Mo, followed by high temperature soaking; subsequent leaching to remove the calcia slag yields U-Mo alloy in powder form. Experiments were carried out to synthesize U-10 wt%Mo alloy powder. The alloy powder products were characterized by Scanning Electron Microscopy and X-ray Diffraction. Complete stabilization of the metastable isotropic gamma phase has been achieved in U-10 wt%Mo powder synthesized by R-D process, where the final soaking was carried out at 1300 °C and 4 h. Attempts were made to understand the mechanism of formation of U-Mo alloy by R-D process on two fronts, i.e. alloying within a single particle, and particle-to-particle homogenization. The intended application of the alloy powders is in high uranium density dispersion fuels for high flux nuclear research and test reactors.
- Gupta, Sonal,Kumar, Raj,Majumdar, Sanjib,Sonber, Jitendra,Satpati,Sahu
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- Carbothermic reduction of copper, nickel, and cobalt oxides and molybdates
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The carbothermic reduction of NiO, CoO, CuO, MoO3, and the MMoO4 (M = Ni, Co, Cu) molybdates has been studied by thermogravimetry. The results demonstrate that the reactivity of the molybdates with solid carbon, the sequence of reduc
- Lebukhova,Karpovich
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- Metal-Drug Interactions: Synthesis and Spectroscopic Characteristics, Surface Morphology, and Pharmacological Activity of Ephedrine–HCl Complexes with Mo(V), Nb(V), Ga(III), and Ge(IV)
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Four new Mo(V), Nb(V), Ga(III), and Ge(IV) ephedrine complexes, [Mo(Eph)2(Cl)4].Cl, [Nb(Eph)2(Cl)3], [Ga(Eph)2(Cl)3], and [Ge(Eph)2(Cl)2] are synthesized and characterized. Composition and coordination behavior of ephedrine drug towards Mo(V), Nb(V), Ga(III), and Ge(IV) ions are deduced from microanalysis, IR spectra, molar conductance, magnetic and thermal analysis data. These support coordination of the eph ligand in its neutral state. Ephedrine has two powerful chelating sites, OH and NH, that determine its uni- or bidentate mode of action. IR spectra indicate that Mo(V) and Ga(III) coordinate to ephedrine via nitrogen atom of the NH group as a unidentate chelator with six and five coordination geometry, respectively. On the other hand, Eph ligand behaves as a monoanionic bidentate no chelating agent via the NH and deprotonated OH groups in Nb(V) and Ge(IV) complexes. Mo(V) complex demonstrates electrolytic properties, the other complexes are non-electrolytes in DMSO solutions. TG/DTG analysis makes it possible to calculate the number of solvent molecules in and outside the coordination sphere, and estimate stability of the synthesized complexes. The Eph complexes are screened in vitro for antibacterial (Escherichia coli, Pseudomonas aeruginosa, Bacillus subtilis and Staphylococcus aureus) and antifungal (Aspergillus flavus and Candida albicans) activities. Anti-cancer action of the Mo(V) and Ga(III) complexes is assessed against the human hepato cellular carcinoma (HepG-2) tumor cell line (IC50 >1000 μg/mL).
- El-Habeeb,Refat
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- Electrochemical and Chemical Behavior of Extra Molybdenum Atoms into the Chevrel Phase Host Network
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In this paper, we present a comparative electrochemical study of copper insertion into series of Mo6Se8-xSx phases which are obtained through different synthesis processes. We show that α-, β-, and HT-forms can reversibly accommodate copper at room temperature. The variation of the integral copper insertion rate is a function of the sulfur content and the synthesis type of pseudobinaries. While the mechanism of copper intercalation is quite similar for the different Mo6Se8-xSx for a given x, there is a drastic difference for α- and β-Mo6S8 compound. This behavior is explained on the basis of structural considerations. If the extra Mo atoms, present in the lattice channels of the β form and HT-Mo6Se8-xSx, are not displaced by this copper intercalation, they are shown to be mobile through cationic exchange reactions and chemical deinsertion at higher temperature.
- Kaidi,Belin,Boulanger,Lecuire,Sergent,Chevrel
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- A novel route to the synthesis of nanosized metallic molybdenum at moderate temperature and its catalytic properties
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Nanosized metallic molybdenum could be synthesized from MoO3 and KBH4 by solid-state reaction at moderate temperature. The crystallinity, morphology, surface properties of as-synthesized metallic molybdenum were investigated by powder X-ray diffraction (XRD), transmission electron microscopy (TEM), X-ray photoelectron spectral (XPS). The results of its catalytic activity test show that the as-synthesized nanosized metallic molybdenum is superior to the noble metal catalyst 0.3% Pd/Al2O 3 for the selective hydrogenation of alkadienes at higher temperature and pressure.
- Li, Yuanzhi,Luo, Guangfu,Fan, Yining,Chen, Yi
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- Temperature-Programmed Reduction of MoO3 and MoO2
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The reduction of MoO3 and MoO2 is studied by temperature-programmed reduction (TPR).TPR patterns appear to be highly dependent on H2O content of the reducing mixture, sample size, precalcination temperature, and heating rate.Activation energy values for reduction have been calculated from TPR series with various heating rates.A consistent interpretation of the complex TPR results is constructed, in which the extent of H2 dissociation catalyzed by low-valent Mo atoms plays a central role.The formation of these Mo catalytic sites is found to depend on H2O pressure, concentration of surface defects, and surface area.Reduction of MoO3 to MoO2 and of MoO2 to Mo metal both can be catalyzed, in which case the rate-determining step is either H2 dissociation, when the formation of catalytic sites is limited, or Mo-O bond breaking, when excess catalytic sites are present.Reduction of MoO3 to MoO2 can also take place noncatalyzed, with oxygen diffusion as rate determining step.MoO2 and Mo metal are also formed, as intermediates, in temperature-programmed sulfiding (TPS) of MoO3.MoO2 production is faster in H2/H2S than in H2 due to a different reduction mechanism involving H2S as primary reactant.The formation of metal is also faster, due to a higher porosity of the MoO2 formed in situ.
- Arnoldy, P.,de Jonge, J. C. M.,Moulijn, J. A.
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- Preparation and characterization of molybdenum disulphide catalysts
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Molybdenum disulphide has been prepared by atmospheric-pressure hydrogen reduction of molybdenum trisulphide in the temperature range 400-750°C for 4 h and characterized. Chemical analysis of the product confirmed the S to Mo ratio 2.00 as desired for MoS2, consistent with its thermogravimetric analysis data in an air atmosphere. MoS2 prepared under these reducing conditions possessed a hexagonal structure with n-type diamagnetic semiconducting behavior and a lower surface area. The catalytic activity of the MoS2 was studied for liquid-phase hydrogenation of nitrobenzene. X-ray studies on MoS3 when reduced at 750°C for 48 h indicated that MoS2 so formed is unstable, resulting in the formation of its over-reduced products Mo2S3 and Mo.
- Srivastava,Avasthi
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- Thermal reduction of AlVMoO7
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The TPR (temperature programmed reduction) study of the AlVMoO7, phase, belonging to the Al2O3-V2O5-MoO3 system, has been carried out by means of X-ray diffraction analysis, IR spectroscopy
- Botto,Vassallo
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- High-temperature solid-vapor and liquid-vapor transitions in binary and ternary chalcogenides La2S3, MoS2, Mo2S3 and LiInSe2
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High heating rate thermo-microscopic analysis, analytical atomic-emission technique with inductively coupled plasma and differential dissolution method have been used to investigate solid-liquid and solid-liquid-vapor transitions of refractory chalcogenides La2S3, MoS2, Mo2S3 and LiInSe2. The techniques were effective in determining the total pressure and vapor phase composition over the compounds in large temperature and pressure ranges. As a result, for compounds that evaporate incongruently, the melting points corresponding to their strict stoichiometry, the decomposition pressure-temperature relations, and other new results of the T-x phase diagrams for the La3S4-La2S3, Mo-MoS2, and Li2Se-LiInSe2 systems were obtained.
- Vasilyeva,Nikolaev
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- Simulation of MoS2 crystal structure and the experimental study of thermal decomposition
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In this paper, the theoretical calculations of MoS2 crystal geometries, energy band structure, electron density, electron density difference, density of states and Mulliken overlap population were carried out by density functional theory (DFT).
- Liu, Dachun,Chen, Xiumin,Li, Dianjun,Wang, Fei,Luo, Xiaogang,Yang, Bin
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- SMOOTH ELECTRODEPOSITS OF MOLYBDENUM FROM KF-K//2B//4O//7-K//2MoO//4 FUSED SALT MELTS.
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An adherent and visually smooth deposit of molybdenum has been electrolytically deposited on copper, nickel, molybdenum, stainless steel, mild steel and graphite substrates in a KF-K//2B//4O//7-K//2MoO//4 fused salt melt at temperatures in the range 998-1173 K and current densities in the range 110-660 A m** minus **2. The deposits were not as hard as those obtained from KF-B//2O//3-MoO//3, KF-B//2O//3-Na//2MoO//4, KF-B//2O//3-K//2MoO//4 and KF-Na//2B//4O//7-Na//2MoO//4 fused salt melts, a little harder than the smooth deposits obtained from a KF-Li//2B//4O//7-Li//2MoO//4 fused salt melt, and in spite of the use of a graphite cell, comparable with that of a molybdenum button which was prepared by plasma-arc-melting a commercially available molybdenum sheet.
- Koyama, Koichiro,Hashimoto, Yasuhiko,Terawaki, Kazuo
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- Photo-induced synthesis of molybdenum oxide quantum dots for surface-enhanced Raman scattering and photothermal therapy
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By means of a simple and photo-induced method, four colors of molybdenum oxide quantum dots (MoOx QDs) have been synthesized, using Mo(CO)6 as the structural guiding agent and molybdenum source. The as-prepared MoOx QDs display diverse optical properties due to the different configurations of oxygen vacancies in various nanostructures. Among them, crystalline molybdenum dioxide (MoO2) with a deep blue color shows the most intense localized surface plasmon resonance effect in the near-infrared (NIR) region. The strong NIR absorption endows MoO2 QDs with a high photothermal conversion efficiency of 66.3%, enabling broad prospects as a photo-responsive nanoagent for photothermal therapy of cancer. Moreover, MoO2 QDs can also serve as a novel semiconductor substrate for ultrasensitive surface-enhanced Raman scattering (SERS) analysis of aromatic molecules, amino acids and antibiotics, with SERS performance comparable to that of noble metal-based substrates. The therapeutic applications of MoO2 QDs open up a new avenue for tumor nanomedicine.
- Yu, Haihong,Zhuang, Zhengfei,Li, Dongling,Guo, Yanxian,Li, Yang,Zhong, Huiqing,Xiong, Honglian,Liu, Zhiming,Guo, Zhouyi
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- A study on the kinetics of hydrogen reduction of molybdenum disulphide powders
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In order to achieve direct reduction of molybdenite in presence of a sulphur scavenger such as CaO such that SO2 emission is completely avoided, it is important to maximise the rate of the partial reaction involving molybdenite and hydrogen (without lime) given the low thermodynamic driving force for this reaction. Accordingly, reaction of molybdenum disulphide powders with hydrogen was investigated by thermogravimetric method. Effect of temperature and concentration on the reaction rate was studied under such conditions that resistance to mass transfer arising from external film, between particles and intra-grain was negligible. The operating temperature ranged between 973 and 1173 K while the hydrogen concentration was varied between 30 and 100%. The experimental data obtained under the above conditions were analyzed by applying the shrinking unreacted core model . The reduction reaction was found to be first order with respect to the gaseous reactant. Pre-exponential factor and activation energy have been determined to be 3.91 × 103 cm min-1 and 139.0 kJ mol-1, respectively. Activation energy obtained from a fitted model, agreed well with the values determined from the model-free methods using isothermal measurements.
- Mehdi Afsahi,Sohrabi, Morteza,Vasant Kumar,Ale Ebrahim, Habib
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- Thermoelectric properties of A0.05Mo3Sb 5.4Te1.6 (A = Mn, Fe, Co, Ni)
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Mo3Sb7-xTex was earlier reported to be a promising p-type thermoelectric material for high temperature applications, with Ni0.06Mo3Sb5.4Te1.6 achieving a ZT of 0.93 at 1023 K. In order to investigate the effect of using different transition metal atoms and to further improve the thermoelectric properties, a variety of transition metal atoms (Mn, Fe, Co and Ni) were intercalated into the voids of empty Sb atom cubes. Our results indicate that Fe 0.05Mo3Sb5.4Te1.6 and Ni 0.05Mo3Sb5.4Te1.6 exhibit a higher power factor than Mo3Sb5.4Te1.6. Fe 0.05Mo3Sb5.4Te1.6 demonstrates the highest ZT value at 673 K (ZT = 0.31), significantly higher than Mo 3Sb5.4Te1.6. Thermal analysis proves Ni 0.05Mo3Sb5.4Te1.6 to be phase stable at least until 1250 K in an inert atmosphere, an important prerequisite for high temperature applications.
- Xu, Hong,Kleinke, Katja M.,Holgate, Tim,Rossouw, David,Botton, Gianluigi,Tritt, Terry M.,Kleinke
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- Facile synthesis of interstitial metal nitrides with the filled β -manganese structure
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A new family of nitrides, Ni2-xM′xMo3N (M′=Co or Pd; 0≤x≤1.5), has been prepared pure by nitridation of commercially available crystalline metal oxides under reducing conditions (10% H2 in N2). The simple synthesis employs standard solid-state techniques and does not require the preparation of reactive precursors. Substitution of Ni by Co or Pd leads to a linear increase of the unit cell volume with composition. The temperature, composition, and magnetic-field dependence of the molar magnetisation suggest that the introduction of Co, but not Pd, increases the degree of electron localisation in Ni2-xM′xMo3N. The same synthetic method has also lead to the formation, in mixtures, of the new phases π-Co2Mo3N and Pd2N.
- Prior, Timothy J.,Battle, Peter D.
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- Pentane isomerization over molybdenum oxide prepared by H2 reduction of a hydrogen molybdenum bronze
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Physical and catalytic properties of hydrogen molybdenum bronze, H 1.55MoO3 varied markedly with H2 reduction. The surface area was enlarged from 10 m2/g to 250 m2/g by H2 reduction at 673-723 K. H1.55MoO3 became an active and selective catalyst for pentane isomerization after reduction. H 2-reduced H1.55MoO3 exhibited a comparable isomerization activity to H2-reduced Pt/MoO3.
- Matsuda, Takeshi,Asano, Yoko,Sakagami, Hirotoshi,Takahashi, Nobuo
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- Electrochemical and optical studies of facile synthesized molybdenum disulphide (MoS2) nano structures
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The global energy demand requires high energy conversion and storage devices. In order to enhance the utility of these devices, highly efficient, stable and cost effective catalyst and electrode materials are required. In the present study, the nano-size single phase molybdenum disulphide (MoS2) has been synthesized at 700 °C via reduction-sulphurization method in a specially designed autoclave. The UV–Visible and photoluminescence results are in accordance with the Raman spectroscopy studies, confirming few layers (5–6 layers) of synthesized MoS2 exhibiting a band gap of 2.29 eV. Based on structural and morphological results, the formation mechanism from MoO3 to MoS2 is proposed. The as-synthesized samples are expected to be promising stable catalyst for hydrogen evolution reaction (HER) through water splitting in both acidic and basic medium. The cyclic voltammetry (CV) test for 1000 cycles in basic medium shows enhanced stability of pure phase MoS2. The electrochemical double layer capacitance (EDLC) of 2.8 mFcm?2 reveals that the synthesized material is a promising candidate for double layer capacitors and super-capacitors with high capacitance retention of 1000 CV cycles at fix scan rate.
- Kaur, Navpreet,Mir, Rameez Ahmad,Pandey
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- Relationship between pack chemistry and growth of silicide coatings on Mo-TZM alloy
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A theoretical model equation has been derived to relate the growth kinetics of silicide coating with the pack chemical composition and other processing conditions for siliconizing of Mo-TZM (Mo-0.5Ti-0.1Zr-0.02C) alloy to improve its oxidation resistance at high temperatures. A series of experiments conducted with varying pack Si (1-10 wt %) and N H4 F (2-20 wt %) content, time (1-25 h), and temperature (800-1200°C) confirmed the validity of the model. MoSi2 was the main coating layer formed during the siliconizing process. Optimum processing conditions were derived for doping of Al in MoSi2 to form Mo (Si,Al)2 in the outer layer of the coating.
- Majumdar, Sanjib,Sharma, Indrakumar,Samajdar, Indradev,Bhargava, Parag
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- Synthesis, structure, and thermoelectric properties of the new antimonide sulfide MoSb2S
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The structure of a new ternary compound, MoSb2S, was identified by single-crystal X-ray diffraction. The title compound was synthesized by heating the elements in stoichiometric ratios in sealed silica tubes at 600-800 °C using small amounts of
- Lee, Chi-Shen,Kleinke, Holger
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- A novel route to nanosized molybdenum boride and carbide and/or metallic molybdenum by thermo-synthesis method from MoO3, KBH4, and CCl4
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Nanosized molybdenum boride and carbide were synthesized from MoO3, KBH4, and CCl4 by thermo-synthesis method at lower temperature. The relative content of Mo, Mo2C, and molybdenum boride in the product was decided by the molar ratio between MoO3, KBH4, and CCl4. Increasing the molar ratio of CCl4 to MoO3 was favorable to the production of Mo2C. Increasing the molar ratio of KBH4 to MoO3 was favorable to the production of molybdenum boride. By carefully adjusting the reaction conditions and annealing in Ar at 900°C, a single phase of MoB could be obtained.
- Li, Yuanzhi,Fan, Yining,Chen, Yi
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- SELECTIVE MOLYBDENUM DEPOSITION BY LPCVD.
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Molybdenum films have been deposited by low pressure chemical vapor deposition (LPCVD) on silicon substrates by the reduction of molybdenum hexafluoride in hydrogen and argon atmospheres. The deposition is extremely selective, with no Mo observed on silic
- Lifshitz,Williams,Capio,Brown
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- The Metathesis of Propylene Catalyzed by Model Oxides Studied Using a High-Pressure Reactor Incorporated into an Ultrahigh Vacuum Chamber
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The olefin metathesis activity of a series of model catalysts consisting of metallic molybdenum, MoO2, or MoO3 is investigated using a combined high-pressure reactor/ultrahigh vacuum apparatus. The model catalysts are analyzed using X-ray and ultraviolet photoelectron, Raman, and Auger spectroscopies and it is shown that MoO2 is the most active above ～650 K. Reaction in this temperature regime proceeds with a high activation energy (～60 kcal/mol). Another, lower-activation-energy (～6 kcal/mol) regime is encountered for reaction below ～650 K and it is suggested that both reactions proceed simultaneously. In addition, the absolute rate and selectivity for the reaction on MoO2 below 650 K are similar to those found for high loadings of supported molybdenum oxide, suggesting that an oxide layer provides a good model catalyst for this reaction. It is also found that reaction proceeds in the presence of a thick carbonaceous layer where the thickness of this layer decreases with increasing oxidation state. A Raman analysis of the surface of the catalyst following reaction indicates that this layer consists predominantly of hydrocarbon species, although a small amount of graphitic carbon is detected.
- Bartlett,Molero,Tysoe
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- On the genesis of molybdenum carbide phases during reduction-carburization reactions
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Molybdenum carbide has been prepared according to the carbothermal reduction method. Carbon black substrate was used as C-source whereas a H 2-flow was the reducing agent. Two different H2 consumption steps were identified during the carburization treatment. The low temperature step is related to the reduction of Mo6-to-Mo 4, the higher temperature process accounts for the deep reduction of Mo4-to-metal Mo0 and its subsequent reaction with C to form the Mo-carbide. The influences of the maximum carburization temperature, carburization time, gas hourly space velocity regarding Mo-loading, heating rate and temperature of Ar pre-treatment were analyzed. All these conditions are interrelated to each other. Thus, the carburization process ends at 700 °C when Mo-loading is 10 wt%, however Mo-loading higher than 10 wt% requires higher temperatures. Carburization temperatures up to 800 °C are needed to fulfill Mo-carbide formation with samples containing 50 wt% Mo. Nevertheless, Ar pre-treatment at 550 °C and slow heating rates favor the carburization, thus requiring lower carburization temperatures to reach the same carburization level.
- Guil-Lopez,Nieto,Botas,Fierro
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- Effect of sulfidation atmosphere on the hydrodesulfurization activity of SiO2-supported Co-Mo sulfide catalysts: Local structure and intrinsic activity of the active sites
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The effects of the sulfidation atmosphere on the local structure and intrinsic activity of the active sites, Co-Mo-S, are studied with SiO2-supported Co-Mo sulfide catalysts prepared by a chemical vapor deposition method using Co(CO)3/sub
- Okamoto, Yasuaki,Hioka, Kazuya,Arakawa, Kenichi,Fujikawa, Takashi,Ebihara, Takeshi,Kubota, Takeshi
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- Effect of hydrogen annealing on the composition and particle size of molybdenum nanopowders
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We have studied the behavior of molybdenum nanopowder consisting of particles with an average size of 23.7 nm. The powder was prepared by hydrogen plasma reduction of molybdenum trioxide and contained considerable amounts of oxygen in the form of amorphou
- Levinsky, Yu. V.,Blagoveshchenskii, Yu. V.,Vol'Dman,Kobzarev
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- Electrodeposition of metallic molybdenum films in ZnCl2-NaCl-KCl-MoCl3 systems at 250 °C
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Molybdenum metal film has been electrodeposited in ZnCl2-NaCl-KCl (0.60:0.20:0.20, in mole fraction) melt containing MoCl3 at 250 °C. In this melt, a dense film was obtained by potentiostatic electrolysis at 0.15 V versus Zn(II)/Zn for 3 h. However, the film had a thickness of smaller than 0.5 μm and was not adhesive. On the other hand, addition of 4 mol% of KF to the melt led to larger cathodic current in cyclic voltammogram, and gave a dense, adhesive and thicker metal film of ca. 3 μm thickness in the same electrolysis condition as above. The present process is promising as a new method for molybdenum coating at low temperatures.
- Nakajima, Hironori,Nohira, Toshiyuki,Hagiwara, Rika
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- Thermal study of chromium and molybdenum complexes with some nitrogen and nitrogen-oxygen donors ligands
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The complexes of chromium and molybdenum with salicylidene-2-aminophenol (shaH2), salicylidene-2-aminoanisole (salanH2), salicylidene-2-aminoaniline (salphenH2) and biquinoline (biq) were studied using the thermogravimetri
- Soliman,El-Medani,Ali
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- The influence of phase and morphology of molybdenum nitrides on ammonia synthesis activity and reduction characteristics
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The reactivities of a series of ternary and binary molybdenum nitrides have been compared. Data have been obtained for the catalytic synthesis of ammonia at 400 °C and ambient pressure using a 3:1 H2:N2 mixture. Amongst the ternary nitrides, the mass normalised activity is in the order Co3Mo3N>Fe3Mo3N?Ni2Mo3N. For the binary molybdenum nitrides, the ammonia synthesis activity is significantly lower than that of Co3Mo3N and Fe3Mo3N and varies in the order γ-Mo2N～β-Mo2N0.78?δ-MoN. Nanorod forms of β-Mo2N0.78 and γ-Mo2N exhibit generally similar activities to conventional polycrystalline samples, demonstrating that the influence of catalyst morphology is limited for these two materials. In order to characterise the reactivity of the lattice nitrogen species of the nitrides, temperature programmed reactions with a 3:1 H2:Ar mixture at temperatures up to 700 °C have been performed. For all materials studied, the predominant form of nitrogen lost was N2, with smaller amounts of NH3 being formed. Post-reaction powder diffraction analyses demonstrated lattice shifts in the case of Co3Mo3N and Ni2Mo3N upon temperature programmed reaction with H2/Ar. Incomplete decomposition yielding mixtures of Mo metal and the original phase were observed for Fe3Mo3N and γ-Mo2N, whilst β-Mo2N0.78 transforms completely to Mo metal and δ-MoN is converted to γ-Mo2N.
- Mckay,Hargreaves,Rico,Rivera,Sun
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- Depletion kinetics of Mo(a7S3,a5S2,a5D J) by N2, SO2, CO2, N2O, and NO
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The gas phase collisional disappearance of Mo(a7S3,a5S2,a5D J) in the presence of N2, SO2, CO2, N2O, and NO over the temperature range 294-621 K and in the total pressure range 10-600 Torr is reported. Mo atoms were produced by the 248 nm photodissociation of Mo(CO)6 and MoCl4 and detected by laser-induced fluorescence. The room temperature depletion rate constant of Mo(a5S2) + N2 is (2.3 ± 0.7) × 10-11 cm3 s-1; the depletion rate constants of the a5DJ are smaller and range from (16 ± 8) × 10-12 for Mo(a5D0) to (0.13 ± 0.04) × 10-12 cm3 s-1 for the other spin-orbit states. The depletion rate of all states of Mo by SO2 are on the order of the collision rate. Mo(a7S3) is found to be unreactive toward CO2, and the rate constant for the reaction of Mo(a7S3) with N2O is expressed as k(T) = (2.0 ± 0.5) × 10-10 exp[-(9.8 ± 0.3) kcal mol-1/RT] cm3 s-1. Termolecular kinetics are observed for Mo(a7S3) + NO with k0 = (2.6 ± 0.3) × 10-29 cm6 s-1, k∞ = (5.8 ± 0.5) × 10-11 cm3 s-1, and Fc = 0.72 ± 0.07 at 296 K; the reaction rates for this reaction decrease with increasing temperature. Depletion rate constants of the reactions of the excited states of Mo with CO2, N2O, and NO are on the order of 10-12-10-10 cm3 s-1; the depletion kinetics are complex and involve significant energy transfers. Results indicate that the electron configuration of Mo plays a role in its depletion kinetics. In all cases, Mo(4d55s1a5S2) depletes faster than Mo(4d45s2a5DJ). The inefficient reactions of Mo(a7S3) with CO2 and N2O are attributed to the production of spin-forbidden states.
- McClean, Roy E.,Campbell, Mark L.,Goodwin, Robert H.
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- Densification behavior of Mo nanopowders prepared by mechanochemical processing
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The sintering behavior of molybdenum (Mo) nanopowder was investigated in comparison to that of commercial Mo powder. At a sintering temperature of 1400 °C, the relative density of Mo nanopowder (94%) was found to be higher than that of commercial powder (
- Kim, Gil-Su,Kim, Hai Gon,Kim, Dae-Gun,Oh, Sung-Tag,Suk, Myung-Jin,Kim, Young Do
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- FLUORESCENCE ANALYSIS OF LASER PRODUCED RADICALS AND ATOMS
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The IR-MPD of C2H4 and C2H5Cl leads to C2-radicals in electronic excited states (d3 ? g) and electronic ground state (a3 ? u).Treating the measured fluorescence of the C2-radicals in the visible range as a measure for the radical concentration, we have found that the radical concentration depends quadratically on the laser fluence and with the power of 2 on the parent gas pressure.The addition of buffer gas Xe leads to an enhancement of the radical concentration due to rotational relaxation. --- By UV-photolysis of Mo(CO)6 neutral Mo-atoms are produced (at 308 nm as well as 248 nm). --- The intensity dependences of the fluorescence of the excited Mo-atoms indicate direct 2-photon absorption at 248 nm and 3- or 4-photon absorption at 308 nm.An upper limit of the dissociation energy is estimated to be Ediss = 5.6 eV.
- Hohmann, H.,Radloff, W.
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- Characteristics of MoO3 reduced with H2 at the different flow rates of H2
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MoO3 was treated with H2 at 623 K for 12 h. The degree of reduction and the specific surface area of H2-reduced MoO3 were dependent on the flow rate of H2 in the reduction process. MoO3 with a surface area of about 5 m2 g-1 was transformed to a porous MoO(x) with a surface area of 180 m2 g-1 after reduction at a flow rate of H2 larger than 600 ml min-1 g-1. The MoO(x) was found to be stable at 623 K, even in the presence of H2O vapor. A study of reduction with a mixture of H2 and H2O showed that the degree of reduction and the surface area decreased with increasing partial pressure of H2O in the reduction process. We conclude from these results that the reduction of MoO3 to porous MoO(x) with a large surface area was prohibited by the action of H2O produced by the reduction.
- Matsuda, Takeshi,Hirata, Yasuyoshi,Uchijima, Fumiko,Itoh, Hidenobu,Takahashi, Nobuo
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- Synthesis of Molybdenum Nitrides
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Abstract—: We have studied the effect of precursors on the synthesis conditions and characteristics of molybdenum nitrides. Mo, MoO3, and MgMoO4 powders were nitrided in flowing ammonia at temperatures in the range 500–800°C. The use of molybdenum nanopowder as a precursor has made it possible to reduce the synthesis temperature and time. We have demonstrated the possibility of direct ammonolysis of the double oxide MgMoO4. Using this molybdate, we have obtained a material with a specific surface area up to 29 m2/g, which is a factor of 2 to 3 larger than that reached by nitriding MoO3. In all cases, the synthesis products consisted of the γ- and β-phases of Mo2N, with cubic and tetragonal lattices, respectively.
- Kuznetsov, V. Ya.,Orlov, V. M.,Osaulenko, R. N.
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p. 1113 - 1121
(2020/11/20)
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- Large-scale synthesis of van der Waals 1-dimensional material Mo6S3I6 by using a MoI2 precursor
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By using a MoI2 precursor, a one-dimensional linear chain material, Mo6S3I6, was synthesized on a centimeter scale. As MoI2 can be used to form Mo6S3I6 through a gas-phase reaction, a larger amount of single crystals can be synthesized; moreover, these crystals are significantly longer than those synthesized by using Mo, S, and I powder. The synthesized Mo6S3I6 exhibited the characteristics of paramagnetic semiconductors with excellent thermal stability and a low bandgap. Furthermore, Mo6S3I6 can be separated into long nanometer-scale chains by a solution dispersion process.
- Oh, Seungbae,Chae, Sudong,Choi, Kyung Hwan,Kim, Bum Jun,Lee, Sang Hoon,Wang, Cong,Liu, Zhixiang,Jeon, Jiho,Lee, Jae-Hyun,Yu, Hak Ki,Choi, Jae-Young
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p. 499 - 504
(2019/07/03)
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- New insights into the effect of nitrogen incorporation in Mo: Catalytic hydrogenation: Vs. hydrogenolysis
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The catalytic effect of nitrogen incorporation into Mo on hydrogenation (of -NO2 to -NH2 in nitrobenzene to aniline) and hydrogenolysis (of -CO in benzaldehyde to toluene) processes has been assessed. Bulk Mo was prepared by temperature programmed reduction of MoO3 (in H2 to 933 K) and β-Mo2N (confirmed by powder XRD) subsequently synthesised by Mo nitridation in N2/H2. Two intermediate samples (MoN-1 and MoN-2) with different Mo/N ratio were prepared by altering the duration (1 and 2 h) of the nitridation step. XPS analysis revealed a nitrogen surface enrichment (Mo/N = 2.2 → 0.9 from MoN-1 to β-Mo2N) relative to the bulk (Mo/N = 5.1 → 2.5). Incorporation of N did not affect morphology and each sample exhibited (by SEM analysis) aggregates (2 g-1). Hydrogen chemisorption and release (by TPD) increased with decreasing Mo/N (Mo 2N). Gas phase hydrogenation of nitrobenzene to aniline exhibited increasing rate from Mo → β-Mo2N, attributed to higher availability of surface heterolytic hydrogen (on Mo-N). In contrast, conversion of benzaldehyde to toluene was favoured by increasing Mo/N (from β-Mo2N → Mo) where hydrogenolytic -CO scission is favoured by homolytic hydrogen chemisorption (on Mo). Our results provide the first evidence that N incorporation in Mo structure can control catalytic hydrogenation vs. hydrogenolysis performance.
- Perret, Noémie,Lamey, Daniel,Kiwi-Minsker, Lioubov,Cárdenas-Lizana, Fernando,Keane, Mark A.
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p. 1891 - 1901
(2019/04/29)
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- Synthesis, characterization and theoretical investigations of molybdenum carbonyl complexes with phosphorus/nitrogen/phosphorus ligand as bidentate and tridentate modes
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Carbonyl complexes of molybdenum with the phosphorus/nitrogen/phosphorus ligand, PNP-Mo(CO)n, where n = 3, 4 and PNP is N,N-bis[2-(diphenylphosphino)ethyl]phenylamine have been synthesized and characterized by 1H, 31P{1H} NMR, IR (ATR and solution state), Raman, X-ray diffraction, MS and elemental analysis. DFT calculations of the complexes were also performed. The PNP-Mo(CO)4 complex in which the binding mode is bidentate cis-phosphine and, facial and meridional isomers of PNP-Mo(CO)3 in which the binding mode is tridentate were obtained. The facial isomer and the tetracarbonyl complexes were successfully synthesized and purified; however, it was not possible to isolate the meridional isomer. Only a few crystals of the meridional isomer were detected and used for X-ray analysis. When the facial isomer was dissolved in CH2Cl2 or in THF, it was found to undergo decomposition thereby generating the tetracarbonyl complex, meridional isomer, Mo(0) as a dark precipitate along with some facial isomer that was left intact in solution. The reason that the facial isomer was the preferred structure with respect to the meridional isomer was also investigated.
- Goren Keskin, Seyma,Stanley, Julie M.,Cowley, Alan H.
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p. 206 - 217
(2017/10/16)
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- Influence of the composition of precursors and reduction conditions on the properties of magnesiothermic molybdenum powders
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We have investigated the preparation of molybdenum powders by reducing the oxide compounds MoO3, MgMoO4, and CaMoO4 with magnesium vapor at residual argon pressures in the range 5–20 kPa and temperatures in the range 700–800°C. Using the MgMoO4 and CaMoO4 compounds as precursors, we have obtained molybdenum powders with specific surface areas of up to 20 m2/g. The powders have a mesoporous structure. The reduction of the molybdenum compounds under such conditions was accompanied by separation of the reaction products due to the removal of magnesium oxide from the reaction zone.
- Kolosov,Miroshnichenko,Orlov
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p. 1058 - 1063
(2017/09/23)
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- Study on the preparation of molybdenum silicides by the silicothermic reduction of MoS2
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In this paper, a novel process about the silicothermic reduction of molybdenum disulfide was proposed to prepare molybdenum silicides. This new method has a short process, which is beneficial for energy saving, environmental protection and cost reduction relative to the traditional methods by using pure molybdenum and silicon as the raw materials. It was found that the phase compositions and microstructures of products were greatly influenced by the molar ratio of Si to MoS2 and temperature. From the experimental results, it was concluded that MoSi2, Mo5Si3 and Mo3Si can be prepared when the temperature was above 1100 °C, 1300 °C and 1500 °C, and the Si/MoS2 molar ratio was 4, 2.6 and 7/3, respectively. When the Si/MoS2 molar ratio was less than 4 and the temperature was below 1100 °C, only one Mo-Si compound (MoSi2) was generated; while above 1200 °C, the excessive MoS2 could react with MoSi2 to generate Mo5Si3, but Mo5Si3 can't react with excessive MoS2 below 1300 °C; until above 1400 °C, Mo5Si3 and MoS2 can react to generate Mo3Si. However, even at 1600 °C, excessive MoS2 couldn't react with Mo3Si but can be decomposed. Besides molybdenum silicides, other products SiS or SiS2 can also be generated. SiS could escape from sample at 1100 °C in the form of gas while SiS2 couldn't. Both the increases of temperature and molar ratio of Si to MoSi2 were beneficial for the decrease of the residual sulfur content in the final products. From the experimental results, it was found that as increasing the temperature or the molar ratio of Si to MoS2 from 7/3 to 4, the grain size of products increased and the sintering phenomenon among grains was more and more obvious.
- Sun, Guo-Dong,Zhang, Guo-Hua
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p. 295 - 306
(2017/09/11)
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- Co-precipitate precursor-based synthesis of new interstitial niobium molybdenum nitrides
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A simple method of preparation of interstitial niobium molybdenum nitride solid solutions in the series Nb1-x Mo x N y (x = 0.0, 0.2, 0.4, 0.5, 0.6, 0.8, 1.0) has been developed. It is based on direct ammonolysis of precursors resulting from co-precipitation of aqueous solutions of the appropriate common metal salts. A study of the effect of method conditions on the outcome of the procedure is presented. Compounds in this series were prepared as single phases by nitridation at 1,173 K followed by rapid cooling of the samples. Similarly to the individual nitrides NbN and Mo2N, all the Nb1-x Mo x N y compounds in this series have the rock-salt crystal structure in which the metal atoms are in an fcc arrangement with N atoms occupying octahedral interstitial positions. The materials were characterized by X-ray powder diffraction, elemental analysis, scanning electron microscopy, and thermogravimetry under oxygen flow.
- El Himri, Abdelouahad,El Himri, Mamoune,Pérez-Coll, Domingo,Nú?ez, Pedro
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p. 6397 - 6407
(2015/08/18)
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- A thermogravimetric study of the reactions of molybdenum disilicide with anhydrous hydrogen fluoride and fluorine
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The results of a thermogravimetric study into the dry fluorination of molybdenum disilicide, MoSi2, using hydrogen fluoride and dilute fluorine gas as fluorinating agents are reported. The reaction between molybdenum disilicide and fluorine follows the thermodynamically preferred route, viz. the formation of the volatile molybdenum hexafluoride along with gaseous silicon tetrafluoride, with the reaction starting just below 200 °C. The reaction with hydrogen fluoride yields solid molybdenum metal and gaseous silicon tetrafluoride, similarly thermodynamically predicted, above 250 °C. No reaction is observed at low temperatures where solid molybdenum trifluoride is expected to form. The results of a kinetic analysis of the data for the reaction with hydrogen fluoride are reported. In the range 250-450 °C the kinetics are chemical reaction controlled. Above this, up to 700 °C, the rate is controlled by diffusion through the stagnant gas films surrounding the solid particles. Evidence for a third, un-quantified, high-temperature mechanism is given.
- Gama,Wagener,Crouse
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- Potassium-modified molybdenum-containing SBA-15 catalysts for highly efficient production of acetaldehyde and ethylene by the selective oxidation of ethane
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Mo-incorporated SBA-15 (Mo-SBA-15) catalysts with different Mo:Si molar ratios were synthesized by a direct hydrothermal method, and SBA-15-supported Mo catalysts (Mo/SBA-15 and K-Mo/SBA-15) were prepared by an incipient-wetness impregnation method. The structures of the catalysts were characterized by means of N2 adsorption-desorption, XRD, TEM, FT-IR, and UV-Raman, and their catalytic performance for the oxidation of ethane was tested. Turnover frequency and product selectivity are strongly dependent on the molybdenum content and catalyst preparation method. Furthermore, the addition of potassium promotes the formation of isolated tetra-coordination molybdenum species and potassium molybdate. The K/Mo-SBA-15 catalysts possess much higher catalytic selectivity to acetaldehyde in the selective oxidation of ethane than the supported molybdenum catalysts (Mo/SBA-15 or K-Mo/SBA-15). The highest selectivity of CH3CHO + C2H4 68.3% is obtained over the K/Mo-SBA-15 catalyst. Analysis of kinetic results supports the conclusion that ethane oxidation is the first-order reaction and ethane activation may be the rate-determining step for the oxidation of ethane. Ethylene is a possible intermediate for acetaldehyde formation.
- Liu, Jian,Yu, Lihong,Zhao, Zhen,Chen, Yongsheng,Zhu, Pengyu,Wang, Chao,Luo, Yan,Xu, Chunming,Duan, Aijun,Jiang, Guiyuan
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p. 134 - 144
(2012/03/10)
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- Influence of nano nutrients on heterocyst-forming cyanobacterium Anabaena ambigua Rao
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The present study is deals with the influence of nanoparticles on the growth of heterocyst-forming cyanobacterium Anabaena ambigua Rao [A100]. The nano molybdenum and iron particles have been synthesized respectively from molybdenum trioxide (MoO3) and iron chloride (FeCl3) employing sodium borohydride (NaBH4) as a reducing agent and characterized comprehensively. BG11 (N-) media containing micronutrients like molybdenum and iron were replaced respectively by different concentrations of nano molybdenum [BG11 (N-Mo- + nano Mo)] (0, 5, 10, 15, 20, 25, 40, 60, 80, and 100%) and nano iron [BG11 (N -Fe- + nano Fe)] (0, 0.1, 0.2, 0.3, 0.4, 0.5, 1, 2, 3, 4, 5, 10, 15, 20, 25, 40, 60, 80, and 100%) particles for the cultivation. The effect of nano nutrients on cyanobacterial growth parameters like heterocyst formation, chlorophyll content, and protein content was analyzed. The obtained results showed that the high concentrations of nano molybdenum induce heterocyst formation, increase protein content, and decrease chlorophyll content when compared to the control, whereas the nano iron suppresses the growth of cyanobacteria Anabaena ambigua Rao [A 100]. Copyright Taylor & Francis Group, LLC.
- Yuvakkumar,Elango,Venkatachalam,Kannan,Prabu
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p. 1234 - 1239
(2012/03/13)
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- Synthesis, spectroscopic characterization, thermal studies, catalytic epoxidation and biological activity of chromium and molybdenum hexacarbonyl bound to a novel N2O2 Schiff base
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Complexes of M(CO)6 (M = Cr and Mo) with novel Schiff base N,N′-bis(salicylidene)4,5-dichloro-1,2-phenylenediamine (H2L) were prepared in benzene in two different conditions: (i) under reduced pressure resulting the dicarbonyl precursors [Cr(CO)2(H2L)] and [Mo(CO)2(L)] and (ii) in air resulting the oxo complex [Cr(O)(L)] and the dioxo complex [Mo(O)2(L)]. The complexes were characterized by elemental analysis, IR, 1H NMR, mass spectrometry, and magnetic measurement. Thermal behaviors of the complexes were also studied by using thermogravimetric analysis (TGA). The catalytic activity of the novel complexes in the epoxidation of cyclooctene, cyclohexene, 1-octene and 1-hexene with tert-butyl-hydroperoxide (TBHP) in methylene chloride was investigated. The antimicrobial activities of the ligand and their complexes have been screened against various strains of bacteria and fungi and the results have been compared with some known antibiotics.
- Abdel Aziz, Ayman A.
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- Studies on the synthesis of a Mo-30 wt% W alloy by non-conventional approaches
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In the present study, alternate routes for the synthesis of a single phase Mo30wt%Walloy were pursued to surmount the limitations experienced in conventional technique. The process essentially consists of preparation of active Mo andWpowders by H2 reduction of the respective oxide intermediates through multiple processing steps and then converting those pure powders into Mo30wt%Walloy by mechanical alloying technique (MA) at RT under Ar atmosphere in a high-energy planetary ball mill. The structural evolution of the alloy from the milled powders at different interval of time was studied by X-ray diffraction (XRD) and phase corresponding to Mo30W alloy was confirmed. The broadening of peaks in XRD pattern was due to crystallite refinement during milling towards the formation of the designated alloy. A high rate of densification for MA powder was achieved during sintering between 900 °C and 1200 °C and density close to theoretical density was attained. The microstructure of sintered alloy exhibited uniform, polyhedral grains with average grain size of about 3μm. The morphological evolution of as-milled powder was studied by Scanning electron microscopy (SEM) which revealed the formation of nano sized crystallites with polyhedral shapes. The crystallites were initially arranged in clusters which later on got distributed uniformly with the progress in milling time. The average crystallite size of MA powder was found to be 7.3nm after 25 h of milling.
- Chakraborty,Banerjee,Sanyal, Gopal,Bhave,Paul, Bhaskar,Sharma,Suri
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p. 211 - 217
(2010/10/01)
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- Hydrogenation catalyst and use thereof
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The present invention provides a hydrogenation catalyst, containing a carrier, metal components of nickel, molybdenum and tungsten supported thereon, and an adjuvant component selected from the group consisting of fluorine and phosphor and combination thereof. In another embodiment, the present invention provides a hydrogenation catalyst, containing a carrier and metal components of nickel, molybdenum and tungsten supported thereon, wherein said carrier contains a molecular sieve. The present invention provides further use of said catalyst in the process for hydrogenating hydrocarbon oil. In comparison with a hydrogenation catalyst according to the prior art, the catalyst according to the present invention has a much higher activity.
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- ORGANIC MOLYBDENUM ADDITIVE, ITS PREPARATION METHOD, A LUBRICATING COMPOSITION CONTAINING SAID ADDITIVE, AND USE OF THE SAME
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The present invention relates to an organic molybdenum additive and its preparation method, and a lubricating composition comprising said additive, and use of said additive and its lubricating composition in the aspect of improving antiwear and antifriction property of oil products. The organic molybdenum additive according to the present invention is characterized in that it is prepared by reacting several kinds of feedstock as follows: a polylol ester of p-hydroxybenzene alkyl acid, an inorganic molybdenum compound and an aliphatic amine and/or an aromatic amine and/or an amide. The organic molybdenum additive of the present invention has excellent antiwear and/or antifriction property.
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- PHOSPHORUS-MOLYBDENUM COMPOUND, METHOD FOR PRODUCING THE SAME, LUBRICANT ADDITIVE CONTAINING THE COMPOUND, AND LUBRICANT COMPOSITION
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A lubricating oil additive capable of providing an antioxidant which enables a lubricating oil composition to have long drain intervals, while reducing specific components such as metals and phosphorus atoms, and a lubricating oil composition containing the lubricating oil additive are provided. A phosphorus molybdenum compound represented by the following general formula (1) where R1, R2, and R3 each independently represent a hydrocarbon group having 1 to 20 carbon atoms is also provided.
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- Preparation and characterization of molybdenum particles by reducing MoO3 nano-fibers
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One-dimensional nanostructures of orthorhombic molybdenum trioxide have been synthesized in the forms of fibers under hydrothermal conditions at 170-180°C. It has been found that the dimensions of the fibers are about 50 nm in thickness, 100-200 nm in width and a few tens of micrometers in length under our experimental settings. Using H2 stream, the MoO3 fibers prepared can be converted completely to Mo metal powders at 600°C. The original fiber-like morphology is not well-retained, but in some special cases, fiber-like morphology can be partial retained, although the aspect ratio of the oxide template is reduced upon the reduction treatment. Copyright
- Peng, Zhao,Jing, Li,Lin, Wang,Baohua, Zhao,Liuxiao, Yang,Huiqing, Fan
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p. 318 - 321
(2009/02/04)
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- Consolidation behavior of Mo powder fabricated from milled Mo oxide by hydrogen-reduction
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Nano-sized Mo powder was synthesized by ball-milling and subsequent hydrogen-reduction of MoO3 powder. The crystalline size of the MoO3 powder was decreased to below 10 nm by a 20 h ball-milling process. Hygrometric measurement was performed to understand hydrogen-reduction behavior of MoO3 with different milling time. The peak temperature for the reduction was shifted to lower temperatures by increasing the milling time. The peak for the reaction of MoO3 → MoO2 was more effective than that for the reaction of MoO2 → Mo. This result is due to the transformation steps for the reaction of MoO3 → MoO2 take place via chemical vapor transport (CVT) by generation of a gaseous transport phase. After hydrogen-reduction at 800 °C, the crystalline size of the Mo powder was about 60 nm. The sinterability of the nano-sized Mo powder was considerably enhanced compared with that of a commercial Mo power.
- Kim, Gil-Su,Lee, Young Jung,Kim, Dae-Gun,Kim, Young Do
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p. 327 - 330
(2009/02/03)
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- Synthesis, Mo-valence state, thermal stability and thermoelectric properties of SrMoO3-xNx (x>1) oxynitride perovskites
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Oxynitrides of the general composition SrMoO3-xNx (x>1) were synthesized by thermal ammonolysis of crystalline SrMoO4. According to neutron and X-ray diffraction experiments, the materials crystallize in the cubic perovski
- Logvinovich,Aguiar,Robert,Trottmann,Ebbinghaus,Reller,Weidenkaff
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p. 2649 - 2654
(2008/10/09)
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- Dilithiation of bis(benzene)molybdenum and subsequent isolation of a molybdenum-containing paracyclophane
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The homoleptic sandwich complex bis(benzene)molybdenum, [Mo(η6-C6H6)2], was successfully dilithiated by employing an excess of BuLi in the presence of N,N,N,′,N′-tetramethylethylenediamine (up to 6 equiv each) at slightly elevated temperatures furnishing the highly reactive, ring metalated species [Mo-(η6-C6H5Li)2] ·tmeda in high yields. Alternatively, this compound was synthesized upon prolonged sonication with 5 equiv of tBuLi/tmeda without heating. An X-ray crystal structure determination revealed a symmetrical, dimeric composition in the solid state, i.e., a formula of [Mo(η6-C 6H5Li)2]2·(thf)6, where the six-membered rings are connected by two pairs of bridging lithium atoms. The synthesis of an elusive ansa-bridged complex failed in the case of a [1]bora and a [1]sila bridge due to the thermal lability of the resulting compounds. Instead, reverse addition of the dilithio precursor to an excess of the appropriate element dihalide facilitated the isolation of several unstrained, 1,1′-disubstituted derivatives, namely, [Mo{η6- C6H5(BN(SiMe3)2X)}2] (X = Cl, Br) and [Mo{η6-C6H5(Si iPr2Cl)}2], respectively. However, the incorporation of a less congesting [2]-sila bridge was accomplished. In addition to the formation of [Mo{ (η6-C6H5) 2Si2Me4}], a molybdenum-containing paracylophane complex was isolated and characterized by means of crystal structure analysis. The ancillary formation of 1 equiv of bis(benzene)molybdenum strongly suggests that this species is generated by deprotonation of the ansa-bridged complex by the dilithiated precursor and subsequent reaction with a second equivalent of the disilane.
- Braunschweig, Holger,Buggisch, Nele,Englert, Ulli,Homberger, Melanie,Kupfer, Thomas,Leusser, Dirk,Lutz, Matthias,Radacki, Krzysztof
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p. 4840 - 4846
(2008/01/27)
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- A photoemission study of molybdenum hexacarbonyl adsorption and decomposition on TiO2(1 1 0) surface
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The adsorption and decomposition of molybdenum hexacarbonyl on (1 1 0) TiO2 surfaces were studied using both core levels and valence band photoemission spectroscopies. It was found that after an adsorption at 140 K, when going back to room temperature, only a small part of molybdenum compounds, previously present at low temperature, remained on the TiO2 surface. This indicates that the desorption temperature on such a surface is lower than the decomposition one. The use of photon irradiation to decompose the hexacarbonyl molecule was also studied. It was shown that during such a decomposition molecular fragments were chemisorbed on the surface allowing a higher amount of metal to remain on the surface. It was also shown that it was possible to get rid of adsorbed subcarbonyl groups and to organize the metal atoms by thermal treatments at temperatures as low as 400 K, i.e. much lower than the one needed to obtain the same structures using physical vapour deposition (PVD). Moreover, due to lower used temperatures, this chemical way of deposition allows a better control of the interface than during PVD growth.
- Prunier,Domenichini,Li,M?ller,Bourgeois
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p. 1144 - 1152
(2008/10/09)
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- Synthesis of MWNTs using Fe-Mo bimetallic catalyst by CVD method for field emission application
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Multiwalled carbon nanotubes (MWNTs) were synthesized by chemical vapor deposition technique using MgO supported bimetallic Fe-Mo catalyst. The role of Mo on the quality of as-synthesized CNTs and their application in field emission has been investigated. The field emission properties of the device fabricated from the CNTs synthesized with Fe-Mo catalyst was found to be better than the similar device prepared with CNTs synthesized with Fe catalyst alone.
- Singh,Cho, Sung-Wook,Bartwal,Hoa, Nguyen Duc,Ryu, Hojin
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p. 498 - 502
(2008/10/09)
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- Synthesis and structures of metallocene complexes of iron(II) and ruthenium(II) derived from 9,9′-spirobifluorene
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Reaction between 9,9′-spirobifluorene and [CpM]+ (where M = Fe and Ru) equivalents gives the complexes [CpRu(η 6-SBF)][PF6] (1), [(CpRu)2(η 6,η6-SBF)][PF6]2 (2) and [(CpFe)2(η6,η6-SBF)][PF 6]2 (3), respectively. Single crystal X-ray structures of 1 and 3 show that the metal atoms exhibit distorted η 6-coordination to SBF phenyl moieties primarily as a consequence of steric interactions between Cp and SBF. The structure of 3 contains each of the possible C2 enantiomers whereas NMR spectroscopy shows signals consistent with a 1:1 mixture of C2 and C1 stereoisomers for both 2 and 3. In conjunction with electrochemical data the observations are consistent with SBF acting as a molecule containing two independent biphenyl moieties.
- Douthwaite, Richard E.,Guillaume, Neil,Whitwood, Adrian C.
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p. 711 - 716
(2007/10/03)
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- The role of Rh on a substituted Al Anderson heteropolymolybdate: Thermal and hydrotreating catalytic behavior
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The influence of Rh heteroatom on the molybdenum reducibility in the Anderson-type heteropolyoxomolybdate structure of formula (NH4)3[RhMo6O24H6]·7H2O was investigated by means of TPR technique. With comparative purposes, the thermal behavior in non-reducing conditions was also carried out by means of TGA-DTA studies. The study was performed by XRD, SEM, EDAX and FTIR-Raman techniques. Results were related to those preliminary measurements over other XMo6 Anderson phases. Likewise, Rh(III)-Al(III) formal replacement in the RhMo6 structural arrangement was proved. The formation of a solid solution in a limited range of composition (up to 0.25 Rh) was established in order to explore the catalytic performance of γ-Al2O3 supported planar heteropolyoxomolybdate, aiming at optimizing the noble metal content in the catalytic system. Preliminary measurements of RhMo6/γ-Al2O3 and (Rh, Al)Mo6/γ-Al2O3 activity for HDS and HYD processes were also performed. These results were compared to those obtained for CoMo6/γ-Al2O3 system in similar operating conditions and other conventional catalytic systems. The potentiality and scope of RhMo6 catalytic system for the HDS and HYD processes were analyzed.
- Cabello, Carmen I.,Mu?oz, Mercedes,Botto, Irma L.,Payen, Edmond
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- Dependence of size and size distribution on reactivity of aluminum nanoparticles in reactions with oxygen and MoO3
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The oxidation reaction of aluminum nanoparticles with oxygen gas and the thermal behavior of a metastable intermolecular composite (MIC) composed of the aluminum nanoparticles and molybdenum trioxide are studied with differential scanning calorimetry (DSC) as a function of the size and size distribution of the aluminum particles. Both broad and narrow size distributions have been investigated with aluminum particle sizes ranging from 30 to 160 nm; comparisons are also made to the behavior of micrometer-size particles. Several parameters have been used to characterize the reactivity of aluminum nanoparticles, including the fraction of aluminum that reacts prior to aluminum melting, heat of reaction, onset and peak temperatures, and maximum reaction rates. The results indicate that the reactivity of aluminum nanoparticles is significantly higher than that of the micrometer-size samples, but depending on the measure of reactivity, it may also depend strongly on the size distribution. The isoconversional method was used to calculate the apparent activation energy, and the values obtained for both the Al/O2 and Al/MoO3 reaction are in the range of 200-300 kJ/mol.
- Sun, Juan,Pantoya, Michelle L.,Simon, Sindee L.
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p. 117 - 127
(2008/10/09)
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- Mesoporous material with active metals
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A process for treating organic compounds includes providing a composition which includes a substantially mesoporous structure of silica containing at least 97% by volume of pores having a pore size ranging from about 15 ? to about 30 ? and having a micropore volume of at least about 0.01 cc/g, wherein the mesoporous structure has incorporated therewith at least about 0.02% by weight of at least one catalytically and/or chemically active heteroatom selected from the group consisting of Al, Ti, V, Cr, Zn, Fe, Sn, Mo, Ga, Ni, Co, In, Zr, Mn, Cu, Mg, Pd, Pt and W, and the catalyst has an X-ray diffraction pattern with one peak at 0.3° to about 3.5° at 2θ. The catalyst is contacted with an organic feed under reaction conditions wherein the treating process is selected from alkylation, acylation, oligomerization, selective oxidation, hydrotreating, isomerization, demetalation, catalytic dewaxing, hydroxylation, hydrogenation, ammoximation, isomerization, dehydrogenation, cracking and adsorption.
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- Reactivity studies with gold-supported molybdenum nanoparticles
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The reconstructed (22 × √3)-Au(1 1 1) surface was used as a template and inert support for depositing Mo nanoparticles for reactivity studies of desulfurization and the formation of MoSx nanoparticles. Nanoparticles of Mo were prepared on the Au(1 1 1) substrate by two methods: physical vapor deposition (PVD) of Mo and UV-assisted chemical vapor deposition (UV-CVD) through a molybdenum hexacarbonyl precursor. STM studies have shown that the Mo nanoparticles are thermodynamically unstable on the Au(1 1 1) surface, and that gold encapsulates Mo at temperatures above 300 K. Reactivity studies using Auger electron spectroscopy (AES) and temperature programmed desorption (TPD) show that bare Mo nanoparticles are very reactive and can cause complete dissociation of hydrogen sulfide, methyl mercaptan, and thiophene. The presence of gold atoms on the Mo nanoparticles modifies their reactivity. In the case of H2S and CH3SH, the overall activity for desufurization is unaffected by gold encapsulation; however, the selectivity to form methane from CH3SH increased from 20% on bare Mo particles to 60% on gold-covered Mo particles. In contrast, gold-encapsulated Mo nanoparticles are relatively inert towards dissociation of thiophene. We believe that the interaction of R-SH compounds with Au-encapsulated Mo nanoparticles proceeds through intermediacy of surface gold thiolates.
- Potapenko, Denis V.,Horn, Jillian M.,Beuhler, Robert J.,Song, Zhen,White, Michael G.
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p. 244 - 258
(2008/10/09)
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- Photon-induced chemical vapor deposition of molybdenum on Pt(1 1 1)
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Temperature-programmed desorption (TPD) and X-ray photoelectron spectroscopy (XPS) have been employed to study the adsorption and photon-induced decomposition of Mo(CO)6. Mo(CO)6 adsorbs molecularly on a Pt(111) surface with weak interaction at 100 K and desorbs intact at 210 K without undergoing thermal decomposition. Adsorbed Mo(CO)6 undergoes decarbonylation to form surface Mo(CO)x (x ≤ 5) under irradiation of ultraviolet light. The Mo(CO)x species can release further CO ligands to form Mo adatoms with CO desorption at 285 K. In addition, a fraction of the released CO ligands transfers onto the Pt surface and subsequently desorbs at 350-550 K. The resulting Mo layer deposited on the Pt surface is nearly free of contamination by C and O. The deposited Mo adatoms can diffuse into the bulk Pt at temperatures above 1070 K.
- Yeh, Chun-Chuan,Lai, Yine-Huang,Chu, Wen-Yi,Yeh, Chuin-Tih,Hung, Wei-Hsiu
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- Heteroepitaxial growth of novel MoO3 nanostructures on Au(1 1 1)
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We have developed a synthetic procedure that yields novel nanocrystalline, islands of MoO3 on Au(1 1 1). Careful control of the growth conditions yields monolayer islands with a rectangular unit cell that is aligned with the Au substrate. These structures are distinctly different than either bulk MoO3 or than ramified, two-dimensional MoO3 islands formed on Au(1 1 1) which were recently reported [J. Am. Chem. Soc. 125 (2003) 8059, Surf. Sci. 512 (2002) L353]. The atomic structure of these single-layer MoO3 islands has been characterized by scanning tunnelling microscopy (STM), low energy electron diffraction (LEED), X-ray photoelectron spectroscopy (XPS), and Auger electron spectroscopy (AES). We discuss our synthetic method and important characteristics of the MoO3 islands.
- Biener, Monika M.,Friend, Cynthia M.
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p. L173-L179
(2008/10/09)
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- Process for the preparation of 3-methyltetrahydrofuran
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Disclosed is a process for the preparation of 3-methyltetrahydrofuran (MeTHF) from 3-(hydroxymethyl)tetrahydrofuran (HOMeTHF) by contacting HOMeTHF with hydrogen in the presence of an acidic, supported catalyst comprising a Group VIII metal.
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