AndrewOfWallachia
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Separating Toluene from N-Butyl Acetate
Very simple question. Toluene has a boiling point of 110 C, N-Butyl Acetate has a boiling point of 126 C. Is it feasible to separate them through
distillation with a fractionating column?
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walruslover69
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yes
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Fery
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Luckily they seems not to form any azeotrope:
http://www.sciencemadness.org/talk/viewthread.php?tid=14484
How much pure do you need them?
I performed a column distillation of a mixture with similarly narrow b.p. differences (fermented apples) - methanol, 80% ethanol, ethyl acetate,
water. Methanol boiled first, then an azeotrope of ethyl acetate+ethanol+water, then main fraction azeotropic ethanol+water.
I used 1 meter long 30 mm diameter Hempel column packed with Raschig rings (cca 5-10 x 5-10 mm), insulated the column with a lot of turns of newspaper
(vacuum jacket would be better) and variable ratio reflux distillation head with reflux:takeoff ratio cca 5:1.
My friend performed a gas chromatography analysis and concentrations of contaminants (methanol, ethyl acetate, higher alcohols) were all below 0,1%.
But do not expect such good separation when using less efficient column (like Vigreux, or a colum without good efficient packing) and when not using
reflux ratio adjustable distillation head.
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night429
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Quote: Originally posted by Fery  | Luckily they seems not to form any azeotrope:
http://www.sciencemadness.org/talk/viewthread.php?tid=14484
How much pure do you need them?
I performed a column distillation of a mixture with similarly narrow b.p. differences (fermented apples) - methanol, 80% ethanol, ethyl acetate,
water. Methanol boiled first, then an azeotrope of ethyl acetate+ethanol+water, then main fraction azeotropic ethanol+water.
I used 1 meter long 30 mm diameter Hempel column packed with Raschig rings (cca 5-10 x 5-10 mm), insulated the column with a lot of turns of newspaper
(vacuum jacket would be better) and variable ratio reflux distillation head with reflux:takeoff ratio cca 5:1.
My friend performed a gas chromatography analysis and concentrations of contaminants (methanol, ethyl acetate, higher alcohols) were all below 0,1%.
But do not expect such good separation when using less efficient column (like Vigreux, or a colum without good efficient packing) and when not using
reflux ratio adjustable distillation head. |
Even though it's a staple of lab equipment, a Vigreux is pretty poor without packing. I believe it only has 1 theoretical plate per 10cm. Screws over
a lot of chemists expecting a good separation.
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AndrewOfWallachia
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| Quote: Originally posted by Fery | Luckily they seems not to form any azeotrope:
http://www.sciencemadness.org/talk/viewthread.php?tid=14484
How much pure do you need them?
I performed a column distillation of a mixture with similarly narrow b.p. differences (fermented apples) - methanol, 80% ethanol, ethyl acetate,
water. Methanol boiled first, then an azeotrope of ethyl acetate+ethanol+water, then main fraction azeotropic ethanol+water.
I used 1 meter long 30 mm diameter Hempel column packed with Raschig rings (cca 5-10 x 5-10 mm), insulated the column with a lot of turns of newspaper
(vacuum jacket would be better) and variable ratio reflux distillation head with reflux:takeoff ratio cca 5:1.
My friend performed a gas chromatography analysis and concentrations of contaminants (methanol, ethyl acetate, higher alcohols) were all below 0,1%.
But do not expect such good separation when using less efficient column (like Vigreux, or a colum without good efficient packing) and when not using
reflux ratio adjustable distillation head. |
Ok... That's lucky. But... I only have a simple Vigreux...  and I haven't even
heard of a variable reflux ratio distillation head. Could this still work? I saw some videos on Youtube distilling Toluene out of laquer thinner using
only a Vigreux Column but their thinner didn't contain anything that had such a close boiling point to the toluene.
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greenlight
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How long is your column?
You could pack it with broken glass pieces for extra surface area for condensation which should increase the separation of the boiling points.
The only use for an atomic bomb is to keep somebody else from using one.
George Wald
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AndrewOfWallachia
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| Quote: Originally posted by greenlight | How long is your column?
You could pack it with broken glass pieces for extra surface area for condensation which should increase the separation of the boiling points.
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I believe it is 300mm but I haven't checked for sure. If it's not long enough, I also have an Allihn condenser, could it maybe work for to extend the
efficiency a little bit if I connected them vertically, head-to-head?
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greenlight
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You could use the allihn as a column without water circulating through it and pack it with broken glass too.
You want to have decent surface area but ensure that the vapour flow isn't completely restricted resulting in pressure build up.
The problem with long columns is that they can be difficult to get the heat all the way up entire length to the still head especially if the climate
is cold. I used to wrap it in a thin layer or roof insulation "fleece" surrounded by aluminium foil back in the day when doing vacuum distillation
of high boiling oil mixtures. Even sometimes had to use a hair dryer to warm the column on very cold winter days or nights.
The only use for an atomic bomb is to keep somebody else from using one.
George Wald
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AndrewOfWallachia
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| Quote: Originally posted by greenlight | You could use the allihn as a column without water circulating through it and pack it with broken glass too.
You want to have decent surface area but ensure that the vapour flow isn't completely restricted resulting in pressure build up.
The problem with long columns is that they can be difficult to get the heat all the way up entire length to the still head especially if the climate
is cold. I used to wrap it in a thin layer or roof insulation "fleece" surrounded by aluminium foil back in the day when doing vacuum distillation
of high boiling oil mixtures. Even sometimes had to use a hair dryer to warm the column on very cold winter days or nights. |
So, you're saying that just a 300mm Vigreux won't work?
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greenlight
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Its not really a complex mixture, you have a difference in boiling point of 16°C. The 300mm vigreux should be fine on its own.
Just bring the heat up as gradually as you can.
[Edited on 30-6-2024 by greenlight]
The only use for an atomic bomb is to keep somebody else from using one.
George Wald
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AndrewOfWallachia
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| Quote: Originally posted by greenlight | Its not really a complex mixture, you have a difference in boiling point of 16°C. The 300mm vigreux should be fine on its own.
Just bring the heat up as gradually as you can.
[Edited on 30-6-2024 by greenlight] |
Perfect. Thank you I hope it works. I don't have a precise heater in the slightest, but I figured out around where I can set it close to the
temperature of 126 degrees. Once, I get to the distillation, I'll let you know how it went!! 
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DraconicAcid
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If you can't pack your column with broken glass, we use copper ribbon. Copper wire would probably work just as well.
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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Sir_Gawain
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Like this: https://www.amazon.com/Pack-Copper-Coated-Scourers-Scrub/dp/...
“Alchemy is trying to turn things yellow; chemistry is trying to avoid things turning yellow.” -Tom deP.
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