runlabrun
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Butane isomers from refills
Hi all,
Just wondering about the isomer content of butane gas refills.... i am trying to get n-butane.
I found this site:
http://home.comcast.net/~agmann/stove/Canister.htm
This lists the canisters as having mostly n-butane and some iso-butane so that they can be used at sub-freezing levels.
What im TRYING to do.... is to get n-butane oxidised to n-butanol, with the mixture of isomers of butane there would be 4 products of oxidation,
n-butanol, sec-butanol, tert-butanol and iso-butanol.
Could this oxidation be completed by heating an aqueous solution of potassium dichromate to ~125oC and venting into the solution the butane?
Care would be required as the immediate distillation of all butanol isomers would occur, hopefully overoxidation to butanal isomers does not occur....
The isomers can then be seperated easily enough, the bp's are atleast a few degrees apart.
n-butanol - 117.7oC
s-butanol - 99.5oC
t-butanol - 82.6oC
iso-butanol - 107.9oC
source: SI chemical data.
What do you think? will i blow myself up before i get my butanol?
The reason i dont want to just purchase butanol (which is easy enough) is because i just want to see if it can be done with the common off the shelf
refills....
-rlr
EDIT: Figured out dumb mistake #1 here.... aqueous solutions wont be that way when heated to 125oC.... swap another solvent for the dichromate....
what could be used that has a bp > 125oC??
-rlr
[Edited on 3-2-2005 by runlabrun]
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BromicAcid
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Photochemical chlorination of n-butane:
CH3CHClCH2CH3 (75%) @ 30C
CH3CH2CH2CH2Cl (25%) @ 30C
Seperation of the two is very difficult though so go to the next step:
CH3CH2CH2CH2Cl --(NaOH aq)--> CH3CH2CH2CH2OH
The different alchols having a slightly greater difference in boiling point, but fractional distillation would still take several fractions. I was
going over this in my mind the other day just as a method to make chlorinated hydrocarbons, and n-butane was one of the ones that I found the mixture
ratio for, but there has to be a better way. Maybe haloform propylmethylketone and reduce the butanoic acid formed (again, very difficult). Hummm...
can't seem to think of any easy ways, there has to be something simple I am over looking.
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mick
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I think the different butanols have different solubilities in water. Maybe the equivalent of fractional extraction could work. Something like ester
plus water. Extract, re-extract each layer and combine the aqueous extracts and re-extract. Combine the organics and re-extract. A bit tedious.
mick
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runlabrun
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tedious maybe but i only want a small amount, 50mL or so? for a project im working on so the small amount of stress it may cause is not really that
bad....
Thanks, so i could possibly extract all of the butanol isomers into formic or acetic acid add some H2SO4 and heat to form the esters and seperate
based on the solubility of the ester.... or distillation of the ester would be easier than the alcohols on their own probably....
-rlr
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mick
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Thats not what I meant.
Sorry I have not realy thought this right through.
I was thinking you might be able to partition them between an organic solvent and water but the solubilities of iso- and n-butanol are too close.
t-butanol could be frozen out, it is a solid a 25oC, the others freeze at -80oC or below. sec-butanol is more soluble in water than n- and iso-. n-
and iso- butanols would be the hardest to separate.
mick
I love the smell of iso-butanol
mick
[Edited on 17-2-2005 by mick]
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