The chloride process is used to separate

titanium Titanium is a chemical element; it has symbol Ti and atomic number 22. Found in nature only as an oxide, it can be reduced to produce a lustrous transition metal with a silver color, low density, and high strength, resistant to corrosion in ...

from its ores. The goal of the process is to win high purity

titanium dioxide Titanium dioxide, also known as titanium(IV) oxide or titania , is the inorganic compound derived from titanium with the chemical formula . When used as a pigment, it is called titanium white, Pigment White 6 (PW6), or Colour Index Internationa ...

from ores such as

ilmenite Ilmenite is a titanium-iron oxide mineral with the idealized formula . It is a weakly magnetic black or steel-gray solid. Ilmenite is the most important ore of titanium and the main source of titanium dioxide, which is used in paints, printi ...

(FeTiO₃) and

rutile Rutile is an oxide mineral composed of titanium dioxide (TiO2), the most common natural form of TiO2. Rarer polymorphs of TiO2 are known, including anatase, akaogiite, and brookite. Rutile has one of the highest refractive indices at vis ...

(TiO₂). The strategy exploits the volatility of TiCl₄, which is readily purified and converted to the dioxide. Millions of tons of TiO₂ are produced annually by this process, mainly for use as white pigments. As of 2017, the chloride process is used alongside the older sulfate process, which relies on hot

sulfuric acid Sulfuric acid (American spelling and the preferred IUPAC name) or sulphuric acid (English in the Commonwealth of Nations, Commonwealth spelling), known in antiquity as oil of vitriol, is a mineral acid composed of the elements sulfur, oxygen, ...

to extract iron and other impurities from ores.

Process chemistry

In this process, the feedstock is treated at 1000 °C with

carbon Carbon () is a chemical element; it has chemical symbol, symbol C and atomic number 6. It is nonmetallic and tetravalence, tetravalent—meaning that its atoms are able to form up to four covalent bonds due to its valence shell exhibiting 4 ...

and

chlorine Chlorine is a chemical element; it has Symbol (chemistry), symbol Cl and atomic number 17. The second-lightest of the halogens, it appears between fluorine and bromine in the periodic table and its properties are mostly intermediate between ...

gas, giving

titanium tetrachloride Titanium tetrachloride is the inorganic compound with the formula . It is an important intermediate in the production of titanium metal and the pigment titanium dioxide. is a volatile liquid. Upon contact with humid air, it forms thick clouds o ...

. Typical is the conversion starting from the ore

: :2 FeTiO₃ + 7 Cl₂ + 6 C → 2 TiCl₄ + 2 FeCl₃ + 6 CO The process is a variant of a

carbothermic reaction Carbothermic reactions involve the reduction of substances, often metal oxides (O2-), using carbon (C) as the reducing agent. The reduction is usually conducted in the electric arc furnace or reverberatory furnace, depending on the metal ore. The ...

, which exploits the reducing power of carbon. The titanium tetrachloride is purified by

distillation Distillation, also classical distillation, is the process of separating the component substances of a liquid mixture of two or more chemically discrete substances; the separation process is realized by way of the selective boiling of the mixt ...

. Other impurities are converted to the respective chlorides as well, but most are less volatile than TiCl₄. Vanadium tetrachloride and

vanadium oxytrichloride Vanadium oxytrichloride is the inorganic compound with the chemical formula, formula VOCl3. This yellow distillable liquid hydrolyzes readily in air. It is an oxidizing agent. It is used as a reagent in organic synthesis. Samples often appear r ...

codistill with TiCl₄, but these impurities can be removed by chemical reduction. It can be subsequently oxidized in an

oxygen Oxygen is a chemical element; it has chemical symbol, symbol O and atomic number 8. It is a member of the chalcogen group (periodic table), group in the periodic table, a highly reactivity (chemistry), reactive nonmetal (chemistry), non ...

flame or plasma to give the pure titanium dioxide. :TiCl₄ + O₂ + heat → TiO₂ + 2Cl₂ In this way, chlorine is recovered for recycling.

Process engineering

The standard chloride process for titanium dioxide base material consists of the following main production units: *Oxidation *Chlorination *Condensation *Purification The following auxiliary production units are necessary: *Ore/coke storage *Off-Gas Treatment *Dust treatment Under steady state conditions the chloride process is a continuous cycle in which chlorine changes from the oxidized state to the reduced state and reverse. The oxidized form of the chlorine is molecular chlorine Cl₂, the reduced form is titanium tetrachloride (TiCl₄). The oxidizing agent is molecular oxygen (O₂), the reducing agent is coke. Both must be fed into the process. The titanium is fed into the process in form of ore together with the coke. Titanium ore is a mixture of oxides. The added O₂ leaves the process with the product TiO₂, the added coke leaves the process together with the added oxygen from the titanium ore in form of CO and CO₂. The other fed metals leave the process in form of metal chlorides.

References

External links

* *{{cite web , title= The Chloride Process from Ti-Cons , publisher= Ti-Cons Jendro, Weiland und Partner , url= https://ti-cons.com/technology/ , access-date= 2010-06-16 Chemical processes Chlorine