Occurrence, Extraction, Production and uses of Molybdenum
About: This article is published in Studies in Inorganic Chemistry.The article was published on 1994-01-01. It has received 10 citations till now. The article focuses on the topics: Extraction (chemistry) & Molybdenum.
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TL;DR: In this article, a density functional theory (DFT) analysis of the O 2sp dominated valence band region of MoO 3 was carried out to examine the electronic structure of the oxide systems.
156 citations
TL;DR: In this paper, the structure and electronic properties of the α-MoO3 were studied with periodic LAPW calculations with the results in excellent agreement with the reported experimental pseudo-cubic results.
41 citations
TL;DR: In this paper, the authors performed cluster model studies by means of ab initio DFT method to examine electronic properties of different surface O atoms in several V2O5 and MoO3 systems and correlate them with catalytic behavior.
27 citations
TL;DR: In this paper, the electronic properties of MoO 2 bulk and (0, 1, 1) surface are discussed. But the surface retains the metallic character of the bulk, and it is found that Fermi level is located within the band dominated by d molybdenum orbitals.
Abstract: Electronic properties of MoO 2 bulk and (0 1 1) surface are discussed. It is found that Fermi level is located within the band dominated by d molybdenum orbitals, thereby reflecting the metallic character of the system. Results for (0 1 1)MoO 2 surface indicate that the surface retains the metallic character of the bulk. Depending on the thickness of the slab used to model the surface (1-layer or 2-layers) the electronic structure and properties change. In the 2-layer slab, bands close to the Fermi level originate both from regular six-fold coordinated Mo(6) centers as well as from five-fold coordinated Mo(5) centers occurring due to surface formation. In the 1-layer slab, peaks right below the Fermi level are dominated by the surface centers that are six-fold coordinated Mo(6) but also centers which are effectively four-fold coordinated Mo(4). This has a profound effect on the reactivity as was tested by a probe reaction of H 2 adsorption, which did not interact with the surface described by the 2-layer slab, but underwent dissociation on the 1-layer slab. The Mo–Mo pairs with bonds of approximately single character, characteristic for the bulk structure, are also present on the surface, both on 1-layer and 2-layer slabs. The local properties of (0 1 1)MoO 2 surface are very similar to other transition metal oxides. Metal–oxygen bonds are of a mixed ionic and covalent nature and the nucleophilicity of oxygen increases with the increase of coordination numbers of the corresponding oxygen atoms.
26 citations
TL;DR: In this article, the atomic structure of a reconstructed Mo(1/1/2)-O(2/2/3) surface has been revisited using photoelectron spectroscopy with synchrotron radiation, scanning tunneling microscopy, infrared reflection absorption spectrography and density functional theory.
22 citations
References
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TL;DR: In this article, a molybdenum subcarbonyl species encaged in a zeolite, particularly in LiY, showed a high activity for the selective hydrogenation of buta-1,3-diene to cis-but-2-ene.
Abstract: Molybdenum subcarbonyl species encaged in a zeolite, particularly in LiY, showed a high activity for the selective hydrogenation of buta-1,3-diene to cis-but-2-ene (>96%), providing the first example of hydrogenation activity of molybdenum subcarbonyl species immobilized on inorganic matrices.
10 citations
TL;DR: In this paper, the dry sliding wear behavior of filled ultrahigh molecular weight high density polyethene (Uhmwhdpe) as influenced by different filler concentrations (3-10wt%) was investigated.
10 citations
TL;DR: In this article, a stereo-selective hydrogenation of trans-1,3-pentadiene to cis-2-pentene and isomerization of 1,4- pentadiene isomerized to cis 1,3,1, 3-pentadene was found to take place at 423 K over Mo(CO)6/NaY.
Abstract: Highly stereo-selective hydrogenation of trans-1,3-pentadiene to cis-2-pentene and isomerization of 1,4-pentadiene to cis-1,3-pentadiene were found to take place thermally at 423 K over Mo(CO)6/NaY. Relative hydrogenation rates of pentadiene isomers indicated that s-cis conformation of diene was crucial for the selective hydrogenation to occur. This was substantiated by an IR study.
9 citations
TL;DR: In this article, a group VIB metal carbonyls supported on titania which had been partially dehydroxylated at 250 and 500 °C were characterized by temperature-programmed decomposition, chemisorption of carbon monoxide, and activity for ethylene hydrogenation.
9 citations
TL;DR: The role of polyatomic groups in refractory borides is examined in this article, where various arrangements of icosahedral boron groups are reviewed with emphasis on the crystal chemistry of these structures.
Abstract: The role of polyatomic groups in refractory borides is examined. Various arrangements of icosahedral boron groups are reviewed with emphasis on the crystal chemistry of these structures. It is demonstrated that formal presentation of lower borides in terms of tetrahedra (four metal atoms or two metal and two boron atoms) can be utilized to simplify understanding of these structures and to show relationship among structures that otherwise appear unrelated. It is shown that the M2B2 configuration appears in a great majority of lower borides. Some principles on which these structures are built are described for the first time. INTRODUCTiON Many problems in identification of phases and variations in compositions of refractory borides can be traced to the lack of understanding of the role of polyatomic structural units in boron and related compounds. Thus, though a good quality boron was prepared at the beginning of the century1 and even such complex compounds as C2A13B43 have been identified2 difficulties in distinguishing between boron, aluminium borides, aluminium boro-carbides etc.3 , still seem to persist. Similarly, considerable amounts of work have been done since Moissan reported the existence of a boron carbide with the composition of B6C5, yet our recent work (unreported) indicates that the homogeneity range in the boron—carbon system has not yet been resolved. The consideration of stoichiometries, coordinations, electronic structure, nature of bonding, etc. have been applied to refractory borides with considerable difficulties and generally with less than satisfactory results. The difficulty arises from the facts that: (a) chemically different compounds are structurally closely related and produce similar x-ray patterns, (b) many structures may be stable only in the presence of impurities, and (c) many atomic positions show a tendency to partial occupancy6. A helpful concept in the understanding of borides is based on the observation that boride structures can be described in terms of three-dimensional networks of polyatomic units with additional atoms being accommodated in the interstices among these groups. The variations in compositions and compounds can, thus, often be interpreted by either multiple or partial 525
9 citations