Chemistry:Molybdenum trioxide
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| Names | |||
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| IUPAC name
Molybdenum trioxide
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| Other names | |||
| Identifiers | |||
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3D model (JSmol)
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PubChem CID
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| UNII | |||
| UN number | 3288 | ||
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| Properties | |||
| MoO3 | |||
| Molar mass | 143.95 g·mol−1 | ||
| Appearance | yellow solid | ||
| Odor | odorless | ||
| Density | 4.70 g/cm3[1] | ||
| Melting point | 802 °C (1,476 °F; 1,075 K)[1] | ||
| Boiling point | 1,155 °C (2,111 °F; 1,428 K)(sublimes)[1] | ||
| 1.066 g/L (18 °C) 4.90 g/L (28 °C) 20.55 g/L (70 °C) | |||
| Band gap | >3 eV (direct)[2] | ||
| +3.0·10−6 cm3/mol[3] | |||
| Structure[4] | |||
| Orthorhombic, oP16 | |||
| Pnma, No. 62 | |||
a = 1.402 nm, b = 0.37028 nm, c = 0.39663 nm
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Formula units (Z)
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4 | ||
| see text | |||
| Thermochemistry[5] | |||
Heat capacity (C)
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75.0 J K−1 mol−1 | ||
Std molar
entropy (S |
77.7 J K−1 mol−1 | ||
Std enthalpy of
formation (ΔfH⦵298) |
−745.1 kJ/mol | ||
Gibbs free energy (ΔfG˚)
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-668.0 kJ/mol | ||
| Hazards[7] | |||
| GHS pictograms |  
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| GHS Signal word | Warning | ||
| H319, H335, H351 | |||
| P201, P202, P261, P264, P271, P280, P281, P304+340, P305+351+338, P308+313, P312, P337+313, P403+233, P405, P501 | |||
| NFPA 704 (fire diamond) | |||
| Flash point | Non-flammable | ||
| Lethal dose or concentration (LD, LC): | |||
LD50 (median dose)
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125 mg.kg (rat, oral)[citation needed] 2689 mg/kg (rat, oral)[6] | ||
LDLo (lowest published)
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120 mg Mo/kg (rat, oral) 120 mg Mo/kg (guinea pig, oral)[6] | ||
LC50 (median concentration)
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>5840 mg/m3 (rat, 4 hr)[6] | ||
| Related compounds | |||
Other cations
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Chromium trioxide Tungsten trioxide | ||
Related molybdenum oxides
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Molybdenum dioxide "Molybdenum blue" | ||
Related compounds
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Molybdic acid Sodium molybdate | ||
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa). | |||
 verify (what is   ?)
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| Infobox references | |||
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Molybdenum trioxide describes a family of inorganic compounds with the formula MoO3(H2O)n where n = 0, 1, 2. The anhydrous compound is produced on the largest scale of any molybdenum compound since it is the main intermediate produced when molybdenum ores are purified. The anhydrous oxide is a precursor to molybdenum metal, an important alloying agent. It is also an important industrial catalyst.[8] It is a yellow solid, although impure samples can appear blue or green.
Molybdenum trioxide occurs as the rare mineral molybdite.
Structure
In the gas phase, three oxygen atoms are bonded to the central molybdenum atom. In the solid state, anhydrous MoO3 is composed of layers of distorted MoO6 octahedra in an orthorhombic crystal. The octahedra share edges and form chains which are cross-linked by oxygen atoms to form layers. The octahedra have one short molybdenum-oxygen bond to a non-bridging oxygen.[9][10] Also known is a metastable (β) form of MoO3 with a WO3-like structure.[11][2]
Preparation and principal reactions
MoO3 is produced industrially by roasting the compound molybdenum disulfide, the chief ore of molybdenum:[8]
- 2 MoS
2 + 7 O
2 → 2 MoO
3 + 4 SO
2
Similar procedures apply to the recovery of molybdenum from spent catalysts. The resulting trioxide can be purified by sublimation. The laboratory synthesis of the dihydrate entails acidification of aqueous solutions of sodium molybdate with perchloric acid:[12]
- Na
2MoO
4 + H
2O + 2 HClO
4 → MoO
3 · 2H2O + 2 NaClO
4
The dihydrate loses water readily to give the monohydrate. Both are bright yellow in color. Molybdenum trioxide dissolves slightly in water to give "molybdic acid". In base, it dissolves to afford the molybdate anion.
Uses
Molybdenum trioxide is used to manufacture molybdenum metal:
- MoO3 + 3 H2 → Mo + 3 H2O
Molybdenum trioxide is also a component of the co-catalyst used in the industrial production of acrylonitrile by the oxidation of propene and ammonia.
Because of its layered structure and the ease of the Mo(VI)/Mo(V) coupling, MoO3 is of interest in electrochemical devices and displays. It has been described as "the most commonly used TMO [transition metal oxide] in organic electronics applications ... it is evaporated at relatively low temperature (~400 °C)."[13] It has favourable electronic and chemical properties for use as interfacing layers, p-type dopants and hole transport materials in OLEDs, organic solar cells and perovskite solar cells,[14] especially when forming an ohmic contact to organic semiconductors.[15]
References
- ↑ 1.0 1.1 1.2 Haynes, p. 4.77
- ↑ 2.0 2.1 Balendhran, Sivacarendran; Walia, Sumeet; Nili, Hussein; Ou, Jian Zhen; Zhuiykov, Serge; Kaner, Richard B.; Sriram, Sharath; Bhaskaran, Madhu et al. (2013-08-26). "Two-Dimensional Molybdenum Trioxide and Dichalcogenides". Advanced Functional Materials 23 (32): 3952–3970. doi:10.1002/adfm.201300125.
- ↑ Haynes, p. 4.134
- ↑ Åsbrink, S.; Kihlborg, L.; Malinowski, M. (1988). "High-pressure single-crystal X-ray diffraction studies of MoO3. I. Lattice parameters up to 7.4 GPa". J. Appl. Crystallogr. 21 (6): 960–962. doi:10.1107/S0021889888008271.
- ↑ Haynes, p. 5.15
- ↑ 6.0 6.1 6.2 "Molybdenum (soluble compounds, as Mo)". Immediately Dangerous to Life and Health Concentrations (IDLH). National Institute for Occupational Safety and Health (NIOSH). https://www.cdc.gov/niosh/idlh/moly-mo.html.
- ↑ "Molybdenum trioxide" (in en). https://pubchem.ncbi.nlm.nih.gov/compound/14802#section=Safety-and-Hazards.
- ↑ 8.0 8.1 Roger F. Sebenik (2005). "Ullmann's Encyclopedia of Industrial Chemistry". Ullmann's Encyclopedia of Industrial Chemistry. Weinheim: Wiley-VCH. doi:10.1002/14356007.a16_655.
- ↑ 9.0 9.1 "Molybdite Mineral Data". http://www.webmineral.com/data/Molybdite.shtml.
- ↑ Wells, A.F. (1984) Structural Inorganic Chemistry, Oxford: Clarendon Press. ISBN:0-19-855370-6.
- ↑ McCarron, E. M. (1986). "β-MoO3: A Metastable Analogue of WO3". J. Chem. Soc., Chem. Commun. (4): 336–338. doi:10.1039/C39860000336.
- ↑ Heynes, J. B. B.; Cruywagen, J. J. (1986). "Yellow Molybdenum(VI) Oxide Dihydrate". Inorganic Syntheses. 24. pp. 191–2. doi:10.1002/9780470132555.ch56. ISBN 9780470132555.
- ↑ Meyer, Jens; Hamwi, Sami; Kröger, Michael; Kowalsky, Wolfgang; Riedl, Thomas; Kahn, Antoine (2012). "Transition Metal Oxides for Organic Electronics: Energetics, Device Physics and Applications". Advanced Materials 24 (40): 5408–5427. doi:10.1002/adma.201201630. PMID 22945550. Bibcode: 2012AdM....24.5408M.
- ↑ White, Robin T.; Thibau, Emmanuel S.; Lu, Zheng-Hong (2016-02-16). "Interface Structure of MoO3 on Organic Semiconductors" (in en). Scientific Reports 6 (1): 21109. doi:10.1038/srep21109. ISSN 2045-2322. PMID 26880185. Bibcode: 2016NatSR...621109W.
- ↑ Gong, Yongshuai; Dong, Yiman; Zhao, Biao; Yu, Runnan; Hu, Siqian; Tan, Zhan'ao (2020). "Diverse applications of MoO 3 for high performance organic photovoltaics: fundamentals, processes and optimization strategies" (in en). Journal of Materials Chemistry A 8 (3): 978–1009. doi:10.1039/C9TA12005J. ISSN 2050-7488. http://xlink.rsc.org/?DOI=C9TA12005J.
Cited sources
- Haynes, William M., ed (2011). CRC Handbook of Chemistry and Physics (92nd ed.). CRC Press. ISBN 978-1439855119.
External links
- U.S. Department of Health and Human Services National Toxicology Program
- International Molybdenum Association
- Los Alamos National Laboratory – Molybdenum
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