Fluorine Reaction

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Fluorine reaction refers to a series of chemical reactions intended to produce oxygen (and possibly other materials) by the reduction of lunar regolith. It is a form of In Situ Resource Utilization.

In the basis process, fluorine is reacted with the lunar material at elevated temperature. The fluorine attacks the oxides, liberating oxygen and producing fluoride salts. The fluoride salts are then separated into fluorine and reduced metals by electrolysis.

In a variant version of the process, hydrofluoric acid, rather than gasseous fluorine, is used to attack the lunar material.

The fluorine reaction has the advantage that, since fluorine is more electronegative than oxygen, fluorine will displace oxygen from any composition of lunar rock. Hence, in principle, the process chemistry does not require finding any particular mineral source, or beneficiation of the soil to enhance the content of a particular mineral.

Recently Geoffrey A. Landis of NASA's John Glenn Research Center has proposed that the use of the fluoride reaction sequence could be a method by which processing lunar materials could be done to produce silicon as well as iron, aluminum, and the basic oxide components of glass, which could be used in manufacturing, as well as producing oxygen. In his proposal the fluorine is brought to the moon in the form of potassium fluoride, and is liberated from the salt by electrolysis in a eutectic salt melt. Tetrafluorosilane produced by this process is reduced to silicon by a plasma reduction stage; and the fluorine salts are reduced to metals by reaction with metallic potassium to form potassium fluoride, K F, the original starting material). Fluorine is recovered from residual Mg F and Ca F₂ by reaction with K₂O.

Reaction Materials

The system used to carry out any reaction must be well suited and as inert as possible towards the reactants.

When the fluoride salt is put through electrolysis, the neutral charge of the ions is restored and fluorine gas is produced. Fluorine, like other elements, is more reactive in its unionized state. The gas is highly reactive and tends to cause stress crack corrosion in many kinds of metal piping. This issue can be mitigated at lower temperatures by coating the inside of metal pipes with Teflon. Teflon is also a excellent material for low temperature gaskets.

The eutectic melt and electrolysis will need to be carried out in a suitable container. Nickel and Monel crucibles, using copper gaskets, are compatible with the fluorine gas. At higher temperatures platinum crucibles would be needed, but the eutectic electrolysis should have a temperature low enough that platinum isn't required.

Attention:

If you are aware of any metals or materials which are inert towards fluorine gas at high temperature and can be used as/in durable piping/tubing, please add your suggestions to the discussion page of this article.