THE VAPOR PRESSURE OF LITHIUM IN THE REDUCTION OF LITHIUM OXIDE BY SILICON

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At elevated temperatures Li2O will react with elemental silicon according to the equation     Li2O + Si  -->  Li + SiO2

However, the reaction will need higher temperatures, several hundred degrees to proceed substantially. There is a demand for activation energy. The driving force of the reaction is 1.) the vapor pressure of Li, which at high temperatures will leave the reaction system as a gas and thus shifting the equilibrium to the right and 2.) the higher heat of formation of SiO2 (-910 kJ/mol) with respect to Li2O (-600 kJ/mol). The reaction is therefor exothermic.

The reaction depends on the conditions: closed system or open system? Open system with evaporation of Li is favorable for the formation of SiO2. In a closed system without leaving the Li vapour, the reaction will come to an intermediate equilibrium.

Sorry, forgot the stochiometric indices in the reaction equation

2 Li2O  +  Si  -->  4 Li + SiO2

Great answer, exactly what I needed. Would there be anyway to recover the Lithium after it has evaporated? In other word would you be able collect the Lithium gas and change it's state to solid?

In principle, heating Li2O and Si produces liquid Li, since you will have to apply elevated temperatures. Lithium has a very high boiling point ( 1330 oC). The distillation of Li out of the reaction system is thus hampered. And, of course, you will have to exclude strictly any air.

But you have to keep in mind the side reaction that will occur. The Li metal, frehly formed, will react with the not yet consumed Si under formation of lithium silicides.There are several Li-rich phases, all with melting points above 700oC. Once formed, the Li with be nearly untraceable within these compounds.

Nobody tries to make Li metal this way. The electrolysis of molten LiCl/KCl mixtures is the common industrial way.

My aim is to take an excess amount of LiOH(aq) and produce Li metal. In order for my concept to work through the common industrial process for producing Li metal, the excess LiOH would have to react with HCl. Could that be a viable process for creating Li metal?

If you have LiOH at your hands, the straightforward process to obtain Li metal is the neutralisation with HCl to obtain LiCl. Second step is crystallization of LiCl. Third step is grinding of the solid, dry LiCl with KCl (mass ratio 52:48) to obtain an eutectic melt (m.p. slightly above 300 oC). This melt of the two salts is then electrolyzed. At the cathode one obtains  liquid Li as a layer on top of the melt, which can be decanted. Since KCl is not consumed in the process, one has to add solid LiCl in the same amount as Li metall is formed, to maintain the low melting point.