Rhenium is a transition metal that is produced as a byproduct when refining molybdenum. It was the last discovered of all naturally-occurring elements and is one of the ten most expensive metals on Earth.
Domestic Production and Use: During 2009, ores containing rhenium were mined at five operations (three in Arizona, and one each in Montana and Utah). Rhenium compounds are included in molybdenum concentrates derived from porphyry copper deposits, and rhenium is recovered as a byproduct from roasting such molybdenum concentrates. Rhenium-containing products included ammonium perrhenate (APR), metal powder, and perrhenic acid. The major uses of rhenium were in petroleum-reforming catalysts and in superalloys used in high-temperature, turbine engine components, representing an estimated 20% and 70%, respectively, of the end use. Bimetallic platinum-rhenium catalysts were used in petroleum-reforming for the production of high-octane hydrocarbons, which are used in the production of lead-free gasoline. Rhenium improves the high-temperature (1,000° C) strength properties of some nickel-based superalloys. Rhenium alloys were used in crucibles, electrical contacts, electromagnets, electron tubes and targets, heating elements, ionization gauges, mass spectrographs, metallic coatings, semiconductors, temperature controls, thermocouples, vacuum tubes, and other applications. The estimated value of rhenium consumed in 2009 was about $72 million.
Recycling: Small amounts of molybdenum-rhenium and tungsten-rhenium scrap have been processed by several companies during the past few years. All spent platinum-rhenium catalysts were recycled.
Import Sources (2005-08): Rhenium metal powder: Chile, 93%; Netherlands, 3%; and other, 4%. Ammonium perrhenate: Kazakhstan, 68%; China, 8%; Germany, 7%; Chile, 5%; and other, 12%.
Depletion Allowance: 14% (Domestic and foreign).
Government Stockpile: None.
Events, Trends, and Issues: During 2009, average rhenium metal price, based on U.S. Census Bureau customs value, was about $2,400 per kilogram, about 17% more than that of 2008. Rhenium imports for consumption decreased by about 41% owing to the increase in price as well as the downturn in the financial markets. Rhenium production in the United States decreased by about 6% owing to decreased production of byproduct molybdenum concentrates in the United States. The four larger working copper-molybdenum mines decreased byproduct molybdenum production levels in 2009, while the one remaining smaller operation made incremental decreases in production in 2009. Three smaller operations ceased byproduct molybdenum production in 2009.
The United States continued to rely on imports for much of its supply of rhenium, and Chile and Kazakhstan supplied the majority of the imported rhenium. Owing to strong demand, both APR and metal powder spot prices rose sharply at the end of 2008. However, in 2009, catalytic-grade APR price decreased from about $10,000 per kilogram in January to about $7,500 per kilogram in April to about $6,200 per kilogram in November. Metal powder price decreased from about $9,700 per kilogram in January to about $6,900 per kilogram in April to about $4,900 in November.
Demand for catalyst-grade APR, supported by the petroleum industry, was expected to continue to remain strong. Demand for rhenium in the aerospace industry, although more unpredictable, was also expected to remain strong. However, the major aerospace companies were expected to continue testing superalloys that contain half the current rhenium content for engine blades, as well as rhenium-free alloys for other engine components.
Owing to the scarcity and minor output of rhenium, its production and processing pose no known threat to the environment. In areas where it is recovered, pollution-control equipment for sulfur dioxide removal also prevents most of the rhenium from escaping into the atmosphere.
World Resources: Most rhenium occurs with molybdenum in porphyry copper deposits. Identified U.S. resources are estimated to be about 5 million kilograms, and the identified resources of the rest of the world are approximately 6 million kilograms. In Kazakhstan, rhenium also exists in sedimentary copper deposits.
Substitutes: Substitutes for rhenium in platinum-rhenium catalysts are being evaluated continually. Iridium and tin have achieved commercial success in one such application. Other metals being evaluated for catalytic use include gallium, germanium, indium, selenium, silicon, tungsten, and vanadium. The use of these and other metals in bimetallic catalysts might decrease rhenium’s share of the existing catalyst market; however, this would likely be offset by rhenium-bearing catalysts being considered for use in several proposed gas-to-liquid projects. Materials that can substitute for rhenium in various end uses are as follows: cobalt and tungsten for coatings on copper x-ray targets, rhodium and rhodium-iridium for high-temperature thermocouples, tungsten and platinum-ruthenium for coatings on electrical contacts, and tungsten and tantalum for electron emitters.
(usgs) - Rhenium statistics and information from the US Geological Survey
(wiki) - Rhenium on Wikipedia
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