Isolation


Isolation

Because the metal reacts with air at high temperatures it cannot be produced by reduction of its dioxide. Titanium metal is therefore produced commercially by the Kroll process, a complex and expensive batch process developed in 1946 by William Justin Kroll. In the Kroll process, the oxide is first converted to chloride through carbochlorination, whereby chlorine gas is passed over red-hot rutile or ilmenite in the presence of carbon to make TiCl4. This is condensed and purified by fractional distillation and then reduced with 800 °C molten magnesium in an argon atmosphere.

A newer process, the FFC Cambridge Process, may replace the older Kroll process. This method uses the feedstock titanium dioxide powder (which is a refined form of rutile) to make the end product which is either a powder or sponge. If mixed oxide powders are used, the product is an alloy at a much lower cost than the conventional multi-step melting process. It is hoped that the FFC Cambridge Process will render titanium a less rare and expensive material for the aerospace industry and the luxury goods market, and will be seen in many products currently manufactured using aluminium and specialist grades of steel.

Titanium was purified to ultra high purity in small quantities when Anton Eduard van Arkel and Jan Hendrik de Boer discovered the iodide, or crystal bar, process in 1925, by reacting with iodine and decomposing the formed vapors over a hot filament to pure metal.

Titanium oxide is produced commercially by grinding its mineral ore and mixing it with potassium carbonate and aqueous hydrofluoric acid. This yields potassium fluorotitanate (K2TiF6) which is extracted with hot water and decomposed with ammonia, producing an ammoniacal hydrated oxide. This in turn is ignited in a platinum vessel, which creates pure titanium dioxide.

Common titanium alloys are made by reduction. For example; cuprotitanium (rutile with copper added is reduced), ferrocarbon titanium (ilmenite reduced with coke in an electric furnace), and manganotitanium (rutile with manganese or manganese oxides) are reduced.