deltaH
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Method for preparing anhydrous aluminium chloride
This is a hypothetical idea of mine for making anhydrous aluminium chloride with low cost OTC chemicals that avoids strong acids (in part)?
Potassium alum dodecahydrate, KAl(SO4)2.12H2O, can be easily and cheaply bought in most parts of the world and it's not hazardous.
It melts at 92°C and continued heating dehydrates it fully.
METHOD A
Mixing the anhydrous alum with anhydrous calcium chloride and fusing those two in a furnace (calcium chloride melts at 772°C) should fume off
aluminium chloride due to the latter's volatility.
2KAl(SO4)2(l) + 3CaCl2(l) => 2AlCl3(g) + K2SO4(s) + 2CaSO4(s)
The apparatus would have to be constructed in such a way as to condense the AlCl3 evolved downstream in a cold trap of sorts.
METHOD B
Alternatively, if one has access to conc. H2SO4, moistening an intimate grind of anhydrous alum and anhydrous CaCl2 with a few drops of conc.
sulphuric acid as solvent and heating in an apparatus as for the reaction of aluminium powder and ZnCl2?
That may allow for the reaction to be done with a simple burner and unlike the aluminium powder version, this one should be endothermic and so very
manageable and possibly better yielding?
Beware HCl fumes given off when conc. H2SO4 contacts CaCl2!
[Edited on 2-4-2016 by deltaH]
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blogfast25
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@deltaH:
Method A would be worth a shot. I think you'll need at least red heat for any appreciable yield.
Re. Method B, what will happen is that briefly the reagent mix will act as a HCl generator, until all the H2SO4 has been used
up.
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deltaH
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Quote: Originally posted by blogfast25  | @deltaH:
Method A would be worth a shot. I think you'll need at least red heat for any appreciable yield.
Re. Method B, what will happen is that briefly the reagent mix will act as a HCl generator, until all the H2SO4 has been used
up. |
Yes method B is less likely to work for that reason, plus what makes method A attractive is that it avoids the need for strong acids that also might
not be easy to obtain for some.
I think the melting point of CaCl2 is within the realm of what can easily be done with crude homemade gas furnaces or simply charcoal and a blower
with bricks.
[Edited on 2-4-2016 by deltaH]
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aga
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This may be a really silly question, but what would be so badly wrong with bashing elemental Al with chlorine gas ?
Much more easily do-able in the amateur scenario.
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blogfast25
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| Quote: Originally posted by aga | This may be a really silly question, but what would be so badly wrong with bashing elemental Al with chlorine gas ?
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That works but not many are keen on handling Cl2. And the reaction only proceeds at a few hundred C.
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aga
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Why are people so Cl2 averse ?
OK, it can kill you, but so can a moving Car, or an irked Camel or a particularly determined and intrepid Badger.
With probably less than ideal precautions (home-made fume hood, A1 filters in an ebay gas mask, a rubber glove on one occasion) Cl2 use
has usually gone adequately well, and i appear to remain alive, as do the people nearby (~400m).
If the Al turnings were heated electrically, there seem to be no unsurmountable difficulties in an amateur setting.
Not knowing, i got to ask if the Al+Cl2 reaction is massively exothermic or something, making it very dangerous.
[Edited on 2-4-2016 by aga]
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blogfast25
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| Quote: Originally posted by aga |
Not knowing, i got to ask if the Al+Cl2 reaction is massively exothermic or something, making it very dangerous.
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Exothermic but not particularly dangerous, if you know how to handle Cl2.
ΔH0Rxn = - 706 kJ/mol AlCl3.
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Darkstar
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Chlorine doesn't like to cooperate. Need I remind you of the TCA synth?
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DraconicAcid
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| Quote: Originally posted by blogfast25 | | Quote: Originally posted by aga | This may be a really silly question, but what would be so badly wrong with bashing elemental Al with chlorine gas ?
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That works but not many are keen on handling Cl2. And the reaction only proceeds at a few hundred C. |
Really? Could it not be speeded up by doing it in a solvent such as carbon tetrachloride, or adding a bit of gallium to aluminum?
Please remember: "Filtrate" is not a verb.
Write up your lab reports the way your instructor wants them, not the way your ex-instructor wants them.
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blogfast25
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| Quote: Originally posted by DraconicAcid |
Really? Could it not be speeded up by doing it in a solvent such as carbon tetrachloride, or adding a bit of gallium to aluminum?
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Some years ago 'peach' tried HCl + Al in DCM, at RT. Despite many attempts nothing came of it. I always attributed that to activation energy.
With Cl2 it's likely to be the same as you have at least the dissociation energy of Cl2 === > 2 Cl* to overcome.
Remember how Al unites easily with I2 at RT but not with Cl2.
My prediction for that reason is that it wouldn't work. I could be totally wrong on that, of course...
And if it does work you really have that exotherm to cope with, in a low BP solvent.
[Edited on 2-4-2016 by blogfast25]
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macckone
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You can react HCl with Al in situ in benzene but a small amount of aluminum chloride is required to catalyze the reaction.
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