tetraiodide
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LiAlH4 via electrolysis
Had this idea for a while to create lithium aluminium hydride via non aqueous electrolysis in triethylamine. The set up would be two aluminum
electrodes in a solution of lithium chloride and triethylamine with dry hydrogen bubbling through the solution. As far as i can tell the reactions
that would occur would be:
1) electrolysis of LiCl with Al > AlCl3+3Li metal
2) 2Li + h2 > 2LiH
3) 4LiH + AlCl3 > LiAlH4+ 3 LiCl
The LiCl produced at the end can of course be electrolysed again to repeat the cycle until mostly expended. My reasioning for using triethylamine as
the solvent is that it is non reactive with the strong reducing agents here and the majority of reactants are soluble in it, the only ones im not sure
about are LiH and LiAlH4.
Still a hypothetical but i wondered if anyone had any thoughts?
[Edited on 10-4-2019 by tetraiodide]
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12thealchemist
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I'm not sure at what temperature lithium metal will react with hydrogen, but I don't think it's at any temperature at which triethylamine is a liquid
(bp 89°C). Also, according to wikipedia LiH is slightly soluble in DMF - would this be an alternative solvent worth considering? It's an amide, so
unsusceptible to reduction.
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Jackson
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Maybe something like lithium aluminate would work better? Its chemical formula is LiAl(OH)4 so it seems like a good starting place. I think the
triethylamine would work as a solvent, or maybe an ionic liquid. Im not sure about conductivity of triethylamine though so it might not work. This
would be why an ionic liquid would work better. Also, If everything but LiAlH4 is soluble, that could drive the reaction forward.
Edit: if sodium aluminate would be esaier to get, you could use that instead.
[Edited on 4/10/2019 by Jackson]
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tetraiodide
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In the reading that I did it seams that lithium metal will react with hydrogen even at moderate temperatures just not as quickly, since the lithium
metal is soluble in triethylamine (did a ton of digging to figure that out but theres a patant that mentions using it to extract Li from Hg and a few
other papers) I was hoping that it would occur at a reasonable rate. It's been a while since i did this research so i can't recall if i looked at dmf
as a solvent but I'm looking if it is viable operating at a higher temperature should greatly increase the reaction rate.
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tetraiodide
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From wikipedia as to the synthesis of LiH from Li and H2 gas: "However, the reaction proceeds at temperatures as low as 29 °C. The yield is 60% at
99 °C and 85% at 125 °C, and the rate depends significantly on the surface condition of LiH"
[Edited on 10-4-2019 by tetraiodide]
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