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I'm laying the foundation for a project called 21st Century steampunk, where I figure out what the world would look like if electricity was never discovered.

I'm wondering if it's possible to derive usable metallic aluminum from naturally occurring substances without using the Hall–Héroult process.

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    $\begingroup$ Recycling, maybe? $\endgroup$ Aug 8 at 20:36

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One method, which would also require a non-electrical heating source, involves reduction with carbon. Given a high enough temperature -- meaning over 2000°C -- carbon carries off the oxygen as carbon monoxide and leaves the aluminum behind. See Ref. [1](https://doi.org/10.1016/j.energy.2007.06.002), which includes the equilibrium composition calculation below.

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Reference

  1. M.Halmann, A.Frei, A.Steinfeld (2007)."Carbothermal reduction of alumina: Thermochemical equilibrium calculations and experimental investigation". Energy 32, Issue 12, December 2007, Pages 2420-2427. https://doi.org/10.1016/j.energy.2007.06.002
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    $\begingroup$ Thank you so much. After searching around for more than a week, this is finally the solution I needed. $\endgroup$ Aug 9 at 1:47
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    $\begingroup$ This aluminium would be gaseous, and spontaneously react with oxygen should it ever encounter any... $\endgroup$ Aug 9 at 9:38
  • $\begingroup$ @StianYttervik that depends on conditions. Wikipedia reports a normal boiling point of 2470°C, which is in the range where aluminum can be produced. $\endgroup$ Aug 10 at 1:16
  • $\begingroup$ @Oscar the partial pressure is higher than comfortable above 1800 though. It doesn't have to boil to vanish well before it can be solidified. $\endgroup$ Aug 10 at 7:06
  • $\begingroup$ @StianYttervik Most likely, a cooling chamber that allows condensation before the aluminum can re-react with the CO would be involved in the process. $\endgroup$ Aug 10 at 14:05
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Prior to the electrolysis (Hall–Héroult) process, elemental aluminium was made by reducing aluminium chloride (AlCl3) with elemental sodium or potassium in a vacuum.

See the wikipedia article on "History of aluminium"

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    $\begingroup$ Which prompts the question: how do you get elemental sodium or potassium without electricity? $\endgroup$ Aug 9 at 8:31
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    $\begingroup$ For the potassium case from the azide by heating or exposing it to ultraviolet light (en.wikipedia.org/wiki/Potassium_azide). The azide can be made from potassium carbonate and hydrazoic acid. I am not saying this is a good method, but you did ask! Sodium azide I assume can be made analogously, and is actually made on a n industrial scale (en.wikipedia.org/wiki/Sodium_azide), but that process seems ultimately to use sodium metal as an input. $\endgroup$
    – Ian Bush
    Aug 9 at 10:08
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    $\begingroup$ @GuntramBlohm, if you prefer sodium, you can get it by heating sodium carbonate to 1100 ˚C in the presence of pure carbon. $\endgroup$
    – Mark
    Aug 9 at 23:46

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