Rhenium

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75 tungsten ← rhenium → osmium
Tc
↑
Re
↓
Bh
General
Name, Symbol, Number rhenium, Re, 75
Element category transition metals
Group, Period, Block 7, 6, d
Appearance grayish white
Standard atomic weight 186.207(1)  g·mol−1
Electron configuration [Xe] 4f14 5d5 6s2
Electrons per shell 2, 8, 18, 32, 13, 2
Physical properties
Phase solid
Density (near r.t.) 21.02  g·cm−3
Liquid density at m.p. 18.9  g·cm−3
Melting point 3459 K
(3186 °C, 5767 °F)
Boiling point 5869 K
(5596 °C, 10105 °F)
Heat of fusion 60.43  kJ·mol−1
Heat of vaporization 704  kJ·mol−1
Specific heat capacity (25 °C) 25.48  J·mol−1·K−1
Vapor pressure
P(Pa) 1 10 100 1 k 10 k 100 k
at T(K) 3303 3614 4009 4500 5127 5954
Atomic properties
Crystal structure hexagonal
Oxidation states 7, 6, 5, 4, 3, 2, 1, −1, −2, −3
(mildly acidic oxide)
Electronegativity 1.9 (Pauling scale)
Ionization energies
(more)		 1st:  760  kJ·mol−1
2nd:  1260  kJ·mol−1
3rd:  2510  kJ·mol−1
Atomic radius 135  pm
Atomic radius (calc.) 188  pm
Covalent radius 159  pm
Miscellaneous
Magnetic ordering  ?
Electrical resistivity (20 °C) 193 n Ω·m
Thermal conductivity (300 K) 48.0  W·m−1·K−1
Thermal expansion (25 °C) 6.2  µm·m−1·K−1
Speed of sound (thin rod) (20 °C) 4700 m/s
Young's modulus 463  GPa
Shear modulus 178  GPa
Bulk modulus 370  GPa
Poisson ratio 0.30
Mohs hardness 7.0
Vickers hardness 2450  MPa
Brinell hardness 1320  MPa
CAS registry number 7440-15-5
Most-stable isotopes
Main article: Isotopes of rhenium
iso NA half-life DM DE (MeV) DP
185Re 37.4% 185Re is stable with 110 neutrons
187Re 62.6% 4.35×1010 y α (not observed) 1.653 183Ta
β- 0.0026 187Os
References

Rhenium (pronounced /ˈriːniəm/) is a chemical element with the symbol Re and atomic number 75. A rare silvery-white, heavy, polyvalent transition metal, rhenium resembles manganese chemically, and is used in some alloys. Rhenium is obtained as a by-product of molybdenum refinement, and rhenium-molybdenum alloys are superconducting.[1] It was the last naturally occurring stable element to be discovered[2] and is among the ten most expensive metals on Earth, at times exceeding US$ 12,000 per kilogram).

Contents

Characteristics

Rhenium is a silvery white metal, lustrous, and has one of the highest melting points of all elements, exceeded by only tungsten and carbon. It is also one of the densest, exceeded only by platinum, iridium and osmium. Rhenium has the widest range of oxidation states of any known element: -3, -1, 0, +1, +2, +3, +4, +5, +6 and +7. The oxidation states +7, +6, +4, +2 and -1 are the most common.

Its usual commercial form is a powder, but this element can be consolidated by pressing and resistance-sintering in a vacuum or hydrogen atmosphere. This procedure yields a compact shape that is in excess of 90 percent of the density of the metal. When annealed this metal is very ductile and can be bent, coiled, or rolled. Rhenium-molybdenum alloys are superconductive at 10 K; tungsten-rhenium alloys are also superconductive,[3] around 4-8 K depending on the alloy. Rhenium metal superconducts at 2.4 K.[4]

Applications

The F-15 engine uses rhenium containing second generation superalloys

This element is used in high-temperature superalloys that are used to make jet engine parts, making 70% of the world wide production,[5] and in platinum-rhenium catalysts which in turn are primarily used in making lead-free, high-octane gasoline.[6][7]

Superalloys

The F-22 engine uses rhenium containing third generation superalloys

The nickel-based superalloys are improved in their creep strength if rhenium is added to the alloy. The alloys normally contain 3% or 6% of rhenium.[8] The second generation alloys contain 3%, these alloys were used in the engine of the F-16 and F-15, while the new single crystal third generation alloys contain 6% of rhenium, they are used in the F-22 and F-35 engines.[7][9] For 2006 the consumption is given as 28% for General Electric 28% Rolls-Royce plc and 12% Pratt & Whitney all for superalloys, while the use for catalysts only accounts for 14% and the remaining applications use 18%.[5]

In 2006 77% of the rhenium consumption in the United States was due to the use in alloys.[7]

Catalysts

Rhenium is used as rhenium platinum alloy as catalyst for catalytic reforming, which is a chemical process used to convert petroleum refinery naphthas, with low octane ratings, into high-octane liquid products. World wide 30% of catalysts used for this process contain rhenium.[10]

The olefin metathesis is the other reaction for which rhenium is used as catalyst. Normally Re2O7 on alumina is used for this process.[11]

Other uses

  • Widely used as filaments in mass spectrographs and in ion gauges.[12]
  • An additive to tungsten and molybdenum-based alloys to increase ductility in these alloys.
  • An additive to tungsten in some x-ray sources.
  • Rhenium catalysts are very resistant to chemical poisoning, and so are used in certain kinds of hydrogenation reactions.[13][14]
  • Electrical contact material due to its good wear resistance and ability to withstand arc corrosion.
  • Thermocouples containing alloys of rhenium and tungsten are used to measure temperatures up to 2200 °C.[15]
  • Rhenium wire is used in photoflash lamps in photography.
  • Rhenium forms rhenium diboride with boron. It is a compound noted for its extreme hardness.[16][17]
  • Isotopes of rhenium are radioactive. The 188 isotope, with a half-life of 69 days, has been tested for treatment of liver cancer. The 188 isotope may be obtained in the form of a generator.[18]
  • Related by periodic trends, rhenium has a similar chemistry with technetium; work done to label rhenium onto target compounds can often be translated to technetium. This is useful for radiopharmacy, where it is difficult to work with technetium - especially the 99m isotope used in medicine - due to its expense and short half-life.

History

Rhenium (Latin Rhenus meaning "Rhine")[19] was the next-to-last naturally occurring element to be discovered and the last element to be discovered having a stable isotope. The existence of a yet undiscovered element at this position in the periodic table had been predicted by Henry Moseley in 1914. It is generally considered to have been discovered by Walter Noddack, Ida Tacke, and Otto Berg in Germany. In 1925 they reported that they detected the element in platinum ore and in the mineral columbite. They also found rhenium in gadolinite and molybdenite.[20] In 1928 they were able to extract 1 g of the element by processing 660 kg of molybdenite.[21]

The process was so complicated and the cost so high that production was discontinued until early 1950 when tungsten-rhenium and molybdenum-rhenium alloys were prepared. These alloys found important applications in industry that resulted in a great demand for the rhenium produced from the molybdenite fraction of porphyry copper ores.

In 1908, Japanese chemist Masataka Ogawa announced that he discovered the 43rd element, and named it nipponium (Np) after Japan (which is Nippon in Japanese). However, later analysis indicated the presence of rhenium (element 75), not element 43. The symbol Np was later used for the element neptunium.

Occurrence

Molybdenite

Rhenium is probably not found free in nature (its possible natural occurrence is uncertain), but occurs in amounts up to 0.2% in the mineral molybdenite, the major commercial source. It was only recently that the first rhenium mineral was found and described (in 1994), a rhenium sulfide mineral (ReS2) condensing from a fumarole on Russia's Kudriavy volcano, in the Kurile Islands.[22] Named rheniite, this rare mineral commands high prices among collectors,[23] but is not an economically viable source of the element. Rhenium is widely spread through the Earth's crust at approximately 1 ppb.

Chile has the world's largest reserves, part of the copper ore deposits, and was the leading producer as of 2005.[24]

Production

Ammonium perrhenate

Commercial rhenium is extracted from molybdenum roaster-flue gas obtained from copper-sulfide ores. Some molybdenum ores contain 0.002% to 0.2% rhenium. Rhenium(VII) oxide and perrhenic acid readily dissolve in water; they are leached from flue dusts and gasses and extracted by precipitating with potassium or ammonium chloride as the perrhenate salts, and purified by recrystallization.[25] Total world production is between 40 and 50 tons/year; the main producers are in Chile, USA and Kazakhstan.[6] Recycling of used Pt-Re catalyst and special alloys allow the recovery of another 10 tons/year. Prices for the metal rose rapidly in early 2008, from a price of $1000-$2000 per kg in 2003-2006 to over $10,000 in February 2008.[26][27]

The metal form is prepared by reducing ammonium perrhenate with hydrogen at high temperatures:[25]

2 NH4ReO4 + 7 H2 → 2 Re + 8 H2O + 2 NH3

Isotopes

Main article: Isotopes of rhenium

Naturally occurring rhenium is 37.4% 185Re, which is stable, and 62.6% 187Re, which is unstable but has a very long half-life which can be affected by its electron density[28][29]. The beta decay of 187Re is used for rhenium-osmium dating of ores. The available energy for this beta decay (2.6 keV) is the lowest known among all radionuclides. There are twenty-six other radioactive isotopes of rhenium recognized.[30]

Compounds

For more details on this topic, see Category:Rhenium compounds.

The most common rhenium compounds are the oxides and the halogenides. The broad oxidation number spectrum is also visible in this compounds. Re2O7 ReO3, Re2O5, ReO2, and Re2O3 are the known oxides. ReF7, ReCl6, ReCl5, ReCl4 and ReCl3 are a few of the known halogen derivates.[31]

Rhenium is most available commercially as the sodium and ammonium perrhenates. It is also readily available as dirhenium decacarbonyl; these three compounds are common entry points to rhenium chemistry.

Various perrhenate salts may be easily converted to tetrathioperrhenate by the action of ammonium hydrosulfide.[32]

Rhenium diboride (ReB2) is an extremely hard compound. It can actually scratch diamond, giving it a higher than 10 rank in the Mohs scale of mineral hardness and making it one of the three hardest substances known to man - the other two being ultrahard fullerite and aggregated diamond nanorods.

References

  1. ^ Daunt, J. G.; Lerner, E.. "The Properties of Superconducting Mo-Re Alloys". Defense Technical Information Center.
  2. ^ "Rhenium: Statistics and Information". Minerals Information. United States Geological Survey (2008). Retrieved on 2008-02-03.
  3. ^ Neshpor, V. S.; Novikov, V. I.; Noskin, V. A.; Shalyt, S. S. (1968). "Superconductivity of Some Alloys of the Tungsten-rhenium-carbon System". Soviet Physics JETP 27: 13. Bibcode: 1968JETP...27...13N. 
  4. ^ J. G. Daunt and T. S. Smith (1952). "Superconductivity of Rhenium". Physical Review 88 (2): 309. doi:10.1103/PhysRev.88.309. 
  5. ^ a b Naumov, A. V. (2007). "Rhythms of rhenium". Russian Journal of Non-Ferrous Metals 48 (6): 418–423. doi:10.3103/S1067821207060089. 
  6. ^ a b "Rhenium" (PDF). Mineral Commodity Summaries. U.S. Geological Survey (January 2008). Retrieved on 2008-02-17.
  7. ^ a b c Magyar, Michael J.. "Mineral Yearbook: Rhenium".
  8. ^ Bhadeshia, H. K. D. H.. "Nickel Based Superalloys". University of Cambridge. Retrieved on 2008-10-17.
  9. ^ Cantor, B.; Grant, Patrick Assender Hazel (2001). Aerospace Materials: An Oxford-Kobe Materials Text. CRC Press. ISBN 9780750307420. 
  10. ^ Ryashentseva, Margarita A. (1998). "Rhenium-containing catalysts in reactions of organic compounds". Russian Chemical Reviews 67: 157–177. doi:10.1070/RC1998v067n02ABEH000390. 
  11. ^ Mol, Johannes C. (1999). "Olefin metathesis over supported rhenium oxide catalysts". Catalysis Today 51 (2): 289–299. 
  12. ^ Earle, G. D.; Medikonduri, R.; Rajagopal, N.; Narayanan, V.; Roddy, P. A.. "Tungsten-Rhenium Filament Lifetime Variability in Low Pressure Oxygen Environments". IEEE Transactions on Plasma Science 33 (5): 1736-1737. doi:10.1109/TPS.2005.856413. 
  13. ^ Angelidis, T. N.; Rosopoulou, D. Tzitzios V. (1999). "Selective Rhenium Recovery from Spent Reforming Catalysts". Ind. Eng. Chem. Res. 38 (5): 1830 -1836. doi:10.1021/ie9806242. 
  14. ^ Burch, Robert (1978). "The Oxidation State of Rhenium and Its Role in Platinum-Rhenium". Platinum Metals Review 22 (2), http://www.platinummetalsreview.com/pdf/pmr-v22-i2-057-060.pdf. 
  15. ^ Asamoto, R.; Novak, P. E. (1968). "Tungsten-Rhenium Thermocouples for Use at High Temperatures". Review of Scientific Instruments 39: 1233. doi:10.1063/1.1683642, http://link.aip.org/link/?RSINAK/39/1233/1. 
  16. ^ Inman, M. (20 April 2007). "Super-tough material mimics metal and crystal", New Scientist Tech. 
  17. ^ H.-Y. Chung, M. B. Weinberger, J. B. Levine, A. Kavner, J.-M. Yang, S. H. Tolbert and R. B. Kaner (2007). "Synthesis of Ultra-Incompressible Superhard Rhenium Diboride at Ambient Pressure". Science 316 (5823): 436–439. doi:10.1126/science.1139322. PMID 17446399. 
  18. ^ "The Tungsten-188 and Rhenium-188 Generator Information". Oak Ridge National Laboratory (2005). Retrieved on 2008-02-03.
  19. ^ Tilgner, Hans Georg (2000). Forschen Suche und Sucht (in Geraman). Books on Demand. ISBN 9783898112727. 
  20. ^ Noddack, W.; Tacke, I.; Berg, O (1925). "Die Ekamangane". Naturwissenschaften 13 (26): 567–574. doi:10.1007/BF01558746. 
  21. ^ J. Noddack, W. (1929). "Die Herstellung von einem Gram Rhenium" (in German). Zeitschrift für anorganische und allgemeine Chemie 183 (1): 353–375. doi:10.1002/zaac.19291830126. 
  22. ^ Korzhinsky, M.A.; S. I. Tkachenko, K. I. Shmulovich, Y. A. Taran & G. S. Steinberg (2004-05-05). "Discovery of a pure rhenium mineral at Kudriavy volcano". Nature 369: 51–­­­52. doi:10.1038/369051a0. 
  23. ^ "The Mineral Rheniite". Amethyst Galleries,Inc..
  24. ^ "2005 Minerals Yearbook: Chile". United States Geological Survey. Retrieved on 2008-10-26.
  25. ^ a b Pradyot Patnaik (2003). Handbook of Inorganic Chemicals. McGraw-Hill, 790. ISBN 0070494398. OCLC 47726843. 
  26. ^ "MinorMetal prices". minormetals.com. Retrieved on 2008-02-17.
  27. ^ Harvey, Jan (2008-07-10). "Analysis: Super hot metal rhenium may reach "platinum prices"". Reuters India. Retrieved on 2008-10-26.
  28. ^ http://math.ucr.edu/home/baez/physics/ParticleAndNuclear/decay_rates.html How to Change Nuclear Decay Rates
  29. ^ Bosch (1996). "Observation of bound-state β– decay of fully ionized 187Re:187Re-187Os Cosmochronometry". Physical Review Letters 77 (26): 5190–5193. doi:10.1103/PhysRevLett.77.5190. 
  30. ^ Georges, Audi (2003). "The NUBASE Evaluation of Nuclear and Decay Properties". Nuclear Physics A (Atomic Mass Data Center) 729: 3–128. doi:10.1016/j.nuclphysa.2003.11.001. 
  31. ^ Woolf, A. A. (1961). "An outline of rhenium chemistry". Quarterly Review of the Chemical Society 15: 372. doi:10.1039/QR9611500372. 
  32. ^ Goodman, J. T.; Rauchfuss, T. B., (2002). "Tetraethylammonium-tetrathioperrhenate [Et4N][ReS4]". Inorganic Syntheses 33: 107–110. 

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