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Other Uses

01Other Uses

Titanium extraction

This section covers the conversion of titanium dioxide to titanium(IV) chloride and its reduction with magnesium to produce titanium.

Why magnesium is used

The extraction route uses a metal that is more reactive than titanium. Magnesium can therefore reduce a titanium compound to the metal.

Carbon is unsuitable for this reduction because it can form titanium carbide, TiC\ce{TiC}, instead of producing titanium. Titanium dioxide is first converted into titanium(IV) chloride so that the material can be purified before the reduction stage.

From titanium dioxide to titanium

1

Form TiClX4\ce{TiCl4}

At about 900 °C, chlorine is passed over titanium dioxide with carbon present, converting the oxide into titanium(IV) chloride.

TiOX2(s)+2 C(s)+2 ClX2(g)→TiClX4(g)+2 CO(g)\ce{TiO2(s) + 2C(s) + 2Cl2(g) -> TiCl4(g) + 2CO(g)}
2

Purify TiClX4\ce{TiCl4}

Impurities are removed from the titanium(IV) chloride by fractional distillation, with argon providing an inert atmosphere.

TiClX4\ce{TiCl4} is molecular and liquid at room temperature, whereas TiOX2\ce{TiO2} is an ionic solid. Converting the oxide to the chloride therefore allows purification by distillation.

3

Reduce with Mg

At about 500 °C, magnesium reduces the purified titanium(IV) chloride while an argon atmosphere is maintained.

TiClX4(g)+2 Mg(l)→Ti(s)+2 MgClX2(l)\ce{TiCl4(g) + 2Mg(l) -> Ti(s) + 2MgCl2(l)}

Magnesium is oxidised as it supplies electrons to titanium, so magnesium acts as the reducing agent.

Why the process is expensive

  • The magnesium required for the reduction adds to the cost.
  • The extraction operates in batches, so charging and emptying the reactor takes time and additional labour.
  • Cooling between batches wastes energy.
  • Argon and dry conditions are required; moisture must be excluded because TiClX4\ce{TiCl4} can undergo hydrolysis.
  • The high operating temperatures increase the energy demand.

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