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Rhenium

RheniumThe driving force of the Rhenium market over the last 20 years has reflected the commercialization of Rhenium in the aero-engine industry (where it is un-substitutable) and its continued mature use in platinum-rhenium reforming catalysts for the oil industry.

It is an element which may be classed as rare – the 77th least abundant element in the periodic table, nowhere mined for itself, only produced as a by-product of copper (and frequently only as a by-product of by-product Molybdenum Sulphide Concentrates separated from copper porphyry ores and sent for roasting), and with a worldwide primary supply of about 45mt (less than a quarter of the supply of palladium).

Its growing pains have been reflected in price. In 1979-80 prices first peaked at about $3300 per kg Re as European and U.S. laws on cleaner air led to an expansion in demand for high octane lead-free gasolines. Meanwhile the ending of the Soviet Union saw the first flows of Rhenium from East to West, largely from Kazakhstan, forcing prices down to a low of $300 per kg Re in 1996. Just twelve years later, in August 2008, Rhenium reached a peak of $12,000 per kg as a result of a combined demand for units for aerospace and industrial gas turbines and the now presently abandoned prospects of Rhenium’s use in catalyst formulations for gas to liquids technology (GTL).

Rhenium metalLipmann Walton & Co Ltd`s main business in Rhenium consists of sourcing a wide range of Re-containing raw materials which are then converted and upgraded at W.C. Heraeus GmbH in Germany. Both rhenium pellets and very pure catalyst grade ammonium perrhenate are then stocked for customers.

Our rhenium pellets are assayed by GDMS (Glow discharge mass spectrometry) and Heraeus guarantee the maximum impurities for 45 elements, including very low gas levels. Re in pellet is Re 99.9% pure, Re 99.97% typical.

Heraeus Rhenium Metal Pellets have been approved for use as virgin addition in superalloys destined for precision casting into single crystal turbine blades at Rolls-Royce Plc in Derby as well as most other aero engine and gas turbine manufacturers. Second generation alloys contained typically Re 3%, third generation 6% and now the 4th generation, yet to be commercialised, will contain Re 6% and Ru 3%.

These same alloys are also being used in power generation plant which is transforming the way in which the supply of electricity may be made in a world of increasing deregulation in the power industry. The blades here have to withstand the same requirements as in an aero engine, of high operating temperatures, creep resistance and now anti NOx emmissions.

Rhenium metal and APRLooking ahead, the next structural change is the likelihood that the world’s leading producer, Molymet (Chile), will cease fixed-price long-term contracts, and move to objective prices (reported by responsible metals publications such as Metals Week, Metal Bulletin, Metal Pages etc). This will allow Molymet and others to construct long term sales to consumers while advancing a Rhenium credit to miners on the same published basis. As a result it is likely that the existing two-tier market, in which fixed-price long-term sales at a differential to free market published price levels will cease.

Rhenium FACTS

Rhenium is a new and special industrial metal. It is rare in metallurgy, difficult to extract, has a high cost of extraction and is prized by society for the properties it brings to some high-tech products. It has some similar properties to the Platinum Group Metals (PGMs) and shares other properties with refractory metals. When it is in its ‘great’ form it has a white, platinum-like appearance but is a dull grey when in its powder form.

When the Periodic Table was first introduced in 1869, rhenium was one of the unknown elements. It was predicted to exist by D.I. Mendeleeff, who thought it should have similar properties to manganese, but it wasn’t until 1925 that Ida Tacke, Walter Noddack and O. Berg of Germany claimed the first identification by obtaining 1 mg of the element in an Ural native platinum ore. They later went on to process metallic rhenium from a virtually pure sample of molybdenite, (MoS2 58% molybdenum, 39.8% sulphur and 2 ppm Re).

At room temperature, rhenium is inert in air, but when temperatures reach above 400°C it will rapidly oxidise forming a heptoxide which is soluble in both water and alcohol. It has a high volatility in the heptoxide form and the relative solubilities in water and oxygenated solvents are used in rhenium recovery. At high temperatures it corrodes with sulphuric acid. Rhenium can be attacked by hydrochloric acid, but oxidizes with nitric acid.

Rhenium has oxidation states of I-VII and valences of 1, 2, 3, 4, 5, 6 and 7, which can easily change. This makes it a highly desirable component in catalysts. Due to its high susceptibility to oxidation some degradation may take place at high temperatures. As rhenium’s properties rely heavily on its purity, experimental conditions must be carefully maintained.
Rhenium does not occur in nature as a free metal, but can be found in certain copper or molybdenum ores. The occurrence of rhenium in its own ore has recently been reported in the mineral rhenite (ReS2), on the surface of the Kudryavy Volcano in the Kuril Islands of Russia, where it cannot be mined. However, this report has yet to be fully substantiated.

It is usually extracted as a by-product of a by-product from the flue dusts generated by molybdenum roasters associated with copper porphyry mines (in other words, rhenium is produced as a by-product of molybdenum production which is itself a by-product of copper production). Its abundance on the Earth’s crust is therefore relatively low, at 0.4 ppb, and even lower in seawater at 0.004 ppb (compared with molybdenum at 1.5 ppm and copper at 50 ppm). It is usually more commonly found as an isomorphic replacement of molybdenum in molybdenite crystals, because molybdenum and rhenium have almost equal atomic radii (1.39 Å and 1.37 Å, respectively) and identical ionic radii (0.68 Å).

Atomic no.
Relative atomic mass
Melting point
Boiling point
Density
Electrical resistivity
Young’s modulus
Heat capacity
Abundance
Thermal conductivity
75
186.207
3186 °C
5596 °C
21020 kgm-3
190 nΩm
463 Gpa
25.48 J/K/mol
4 x 10-4 ppm
47.9 W /m/K