by U.S. Geological Survey Wednesday, June 13, 2018
Désirée E. Polyak, a mineral commodity specialist for the U.S. Geological Survey, compiled the following information on rhenium, the last naturally occurring element to be discovered. Rhenium is used primarily in producing high-octane, lead-free gasoline and high-temperature superalloys.
Rhenium, a silvery-white, heat-resistant metal, has increased significantly in importance since its discovery in 1925. First isolated by a team of German chemists studying platinum ore, the mineral was named for the Rhine River. From 1925 until the 1960s, only two metric tons of rhenium were produced worldwide. Since then, its uses have steadily increased, including everything from unleaded gasoline to jet engines, and worldwide annual production now tops 45 metric tons.
Rhenium is one of the rarest and most dispersed metallic elements in Earth’s crust, with abundance estimated to be about 1 part per billion. Although traces of rhenium occur in some minerals, molybdenite is the only significant host mineral. Most of the world’s reserves of rhenium are found in the Western Cordillera of North America and South America, extending from Alaska and British Columbia through the United States and Central America to the Andes Mountains of Peru and Chile. Some rhenium-bearing sedimentary deposits are located in Kazakhstan and neighboring countries.
Rhenium’s high melting point (3,180 degrees Celsius) and heat-stable crystalline structure make it an excellent refractory metal. Since the late 1980s, rhenium’s two most important uses have been in high-temperature superalloys and platinum-rhenium catalysts. In fact, in 2010, superalloys accounted for 70 percent of total use of rhenium, whereas petroleum-reforming catalysts accounted for another 20 percent, leaving just 10 percent for all other uses.
Rhenium is used in jet engine components, specifically in single-crystal, high-temperature superalloy turbine blades for aircraft engines. Rhenium is also used in land-based turbine applications. Because the life cycle of turbine blades in jet engines is approximately 10 years, significant quantities of second-generation blades (containing 3 percent rhenium) are accumulating. Technology is being developed to allow recycling of second-generation blades for recovery of rhenium that can be used in the manufacture of new third-generation blades, potentially reducing requirements for primary rhenium by half.
Platinum-rhenium catalysts are used to produce high-octane, unleaded gasoline. In the early 1970s, Chevron Corp. developed a series of platinum-rhenium catalysts that would not react with sulfur. As a response to the oil crisis in the 1970s and early 1980s, a second generation of more efficient catalysts was developed with double the platinum-rhenium content, boosting refinery efficiency and octane levels. Other applications of rhenium, primarily as tungsten-rhenium and molybdenum-rhenium alloys, are more diverse, including electrical contact points, flashbulbs, heating elements, vacuum tubes, and X-ray tubes and targets.
For more information on rhenium and other mineral resources, visit http://minerals.usgs.gov/minerals.
Rhenium production and consumption
In 2010, the United States produced an estimated 6,000 kilograms of rhenium, 13 percent of the world’s production.
In 2010, worldwide production was estimated to be more than 46 metric tons.
In 2010, Chile, the United States, Poland and Kazakhstan provided most of the world’s production of rhenium.
Molibdenos y Metales (Molymet), a private company in Santiago, Chile, produces more than half of worldwide production.
The cost for producing the first gram of rhenium in 1928 was estimated to be $15,000. Today it is estimated to be less than $4.70 per gram.
Between 1930 and 1950, before rhenium’s critical applications were discovered, rhenium was used in pen tips and jewelry.
In the late 1960s and early 1970s, rhenium was used in rocket thrusters, which reach temperatures of up to 2,230 degrees Celsius.
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