Ever since its discovery in 1907 does chemical element lutetium truly deserve the title as an underutilized member of the rare earth family?
By: Ringo Bones
Lutetium, chemical symbol Lu, is named after Lutetia, the ancient name for Paris. The element was discovered back in 1907 by Georges Urbain of France and by Carl Auer von Welsbach of Austria. And it is the heaviest of the rare earth metals.
Although rare earth alloys intended for commercial use – such as misch metal – costs as low as US$3.15 a pound, a pound of chemically pure lutetium costs US$1,300 – or about US$108 an ounce, which is more expensive than gold at the time when gold prices hovers at around US$38 an ounce for much of the 1960s.
Back in the 1960s – when America was at the height of the Space Age – many of lutetium’s chemical and physical properties were yet to be studied – i.e. lutetium’s practical value has yet to be discovered. Currently, as the heaviest and most expensive member of the rare earth elements, a naturally occurring radioactive isotope of lutetium is used in determining the age of recovered meteorites in relation to the age of the planet Earth. In the petrochemical industry, lutetium is now often used as a super-efficient catalyst for polymerization, alkylation and hydrogenation.
Alkylation is a petrochemical refining process in which light gaseous hydrocarbons are combined to produce high-octane components in gasoline. The light hydrocarbons consist of olefins such as propylene and butylenes and isoparaffins such as isobutene. These compounds are fed into a reactor where under the influence of a sulfuric acid or hydrofluoric acid catalyst combine to form a mixture of heavier hydrocarbons. The liquid fraction of this mixture, known as alkylate, consists mainly of isooctane, a compound that lends excellent antiknock characteristics to unleaded gasoline.
Alkylation units were installed in petroleum refineries in the 1930s, but the petrochemical process became especially important during World War II, where there was a great demand for reasonably-priced aviation gasoline. Since then, alkylation is used in combination with fractional distillation, catalytic cracking and isomerization to increase a petroleum refineries’ yield of automotive gasoline. Although other rare earth based catalysts – like cerium - are used in alkylation. But lutetium based catalysts require way much less energy to keep the chemical reaction going in comparison to other petrochemical alkylation catalysts.