Chloride process

The chloride process is used to separate titanium from its ores. In this process, the feedstock is treated at 1000 °C with carbon and chlorine gas, giving titanium tetrachloride. Typical is the conversion starting from the ore ilmenite:[1]

2 FeTiO3 + 7 Cl2 + 6 C → 2 TiCl4 + 2 FeCl3 + 6 CO

The process is a variant of a carbothermic reaction, which exploits the reducing power of carbon.

Other impurities are converted to the respective chlorides as well but they are less volatile than TiCl4. The titanium tetrachloride is purified by distillation. It can be subsequently oxidized in an oxygen flame or plasma to give the pure titanium dioxide.[2][3]

TiCl₄ + O₂ + heat → TiO₂ + 2Cl₂

In this way, chlorine is recovered for recycling.

The standard process
The Chloride Process

The standard chloride process for titanium dioxide base material consists of the following main production units:[4]

  • 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.[5]

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References
  1. Greenwood, Norman N.; Earnshaw, Alan (1997). Chemistry of the Elements (2nd ed.). Butterworth-Heinemann. ISBN 978-0-08-037941-8.
  2. "The TiO2 Process". Ti-Cons. Retrieved 2016-12-17.
  3. Jones, Tony; Egerton, Terry A. (2000). "Titanium Compounds, Inorganic". Kirk-Othmer Encyclopedia of Chemical Technology. John Wiley & Sons, Inc. doi:10.1002/0471238961.0914151805070518.a01.pub3. ISBN 9780471238966.
  4. "Manufacture and General Properties of Titanium Dioxide Pigments" (PDF). Ti-Cons. Archived from the original (PDF) on 2011-01-24. Retrieved 2012-04-11.
  5. "The Details of the TiO2 Process" (PDF). Ti-Cons. Retrieved 2012-04-11.
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