Chloride process

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The chloride process is used to separate titanium from its ores. The goal of the process is to win high purity titanium dioxide from ores such as ilmenite (FeTiO3) and rutile (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. The chloride process has largely displaced the older sulfate process, which relies on hot sulfuric acid to extract iron and other impurities from ores. [1]

Contents

Process chemistry

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: [2]

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 most are less volatile than TiCl4. Vanadium tetrachloride and vanadium oxytrichloride codistill with TiCl4, but these impurities can be removed by chemical reduction. [1] The titanium tetrachloride is purified by distillation. It can be subsequently oxidized in an oxygen flame or plasma to give the pure titanium dioxide. [3] [4]

TiCl4 + O2 + heat → TiO2 + 2 Cl2

In this way, chlorine is recovered for recycling.

Process engineering

The Chloride Process Chloride Process By Ti-Cons.jpg
The Chloride Process

The standard chloride process for titanium dioxide base material consists of the following main production units: [5]

The following auxiliary production units are necessary:

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. [6]

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Ilmenite is a titanium-iron oxide mineral with the idealized formula FeTiO
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<span class="mw-page-title-main">Titanium dioxide</span> Chemical compound

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Titanium tetrachloride is the inorganic compound with the formula TiCl4. It is an important intermediate in the production of titanium metal and the pigment titanium dioxide. TiCl4 is a volatile liquid. Upon contact with humid air, it forms thick clouds of titanium dioxide and hydrochloric acid, a reaction that was formerly exploited for use in smoke machines. It is sometimes referred to as “tickle” or “tickle 4”, as a phonetic representation of the symbols of its molecular formula.

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Lead(II) chloride (PbCl2) is an inorganic compound which is a white solid under ambient conditions. It is poorly soluble in water. Lead(II) chloride is one of the most important lead-based reagents. It also occurs naturally in the form of the mineral cotunnite.

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<span class="mw-page-title-main">Zirconium(IV) chloride</span> Chemical compound

Zirconium(IV) chloride, also known as zirconium tetrachloride, is an inorganic compound frequently used as a precursor to other compounds of zirconium. This white high-melting solid hydrolyzes rapidly in humid air.

The Becher process is an industrial process used to produce rutile, a form of titanium dioxide, from the ore ilmenite. It is competitive with the chloride process and the sulfate process, which achieve similar net conversions.

<span class="mw-page-title-main">Selenium tetrachloride</span> Chemical compound

Selenium tetrachloride is the inorganic compound composed with the formula SeCl4. This compound exists as yellow to white volatile solid. It is one of two commonly available selenium chlorides, the other example being selenium monochloride, Se2Cl2. SeCl4 is used in the synthesis of other selenium compounds.

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<span class="mw-page-title-main">Chlorine perchlorate</span> Chemical compound

Chlorine perchlorate is a chemical compound with the formula Cl2O4. This chlorine oxide is an asymmetric oxide, with one chlorine atom in +1 oxidation state and the other +7, with proper formula ClOClO3. It is produced by the photodimerization of chlorine dioxide (ClO2) at room temperature by 436 nm ultraviolet light:

<span class="mw-page-title-main">Ammonium hexafluorotitanate</span> Chemical compound

Ammonium hexafluorotitanate is the inorganic compound with the chemical formula (NH4)2[TiF6]. A colorless salt, the compound consists of ammonium ions and the hexafluorotitanate dianion. It is encountered in the extraction of titanium from its principal ore ilmenite: the ore is treated with excess ammonium fluoride:

The hydrogen assisted magnesiothermic reduction ("HAMR") process is a thermochemical process to obtain titanium metal from titanium oxides.

The +4 oxidation state dominates titanium chemistry, but compounds in the +3 oxidation state are also numerous. Commonly, titanium adopts an octahedral coordination geometry in its complexes, but tetrahedral TiCl4 is a notable exception. Because of its high oxidation state, titanium(IV) compounds exhibit a high degree of covalent bonding.

References

  1. 1 2 Völz, Hans G.; et al. (2006). "Pigments, Inorganic". Ullmann's Encyclopedia of Industrial Chemistry . Weinheim: Wiley-VCH. doi:10.1002/14356007.a20_243.pub2. ISBN   978-3527306732.
  2. ↑ Greenwood, Norman N.; Earnshaw, Alan (1997). Chemistry of the Elements (2nd ed.). Butterworth-Heinemann. ISBN   978-0-08-037941-8.
  3. ↑ "The TiO2 Process". Ti-Cons. Retrieved 2016-12-17.
  4. ↑ 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.
  5. ↑ "Manufacture and General Properties of Titanium Dioxide Pigments" (PDF). Ti-Cons. Archived from the original (PDF) on 2011-01-24. Retrieved 2012-04-11.
  6. ↑ "The Details of the TiO2 Process" (PDF). Ti-Cons. Retrieved 2012-04-11.
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