separating Acetone from ethanol

[JMiller]

Hello!

 

Does anyone know if Acetone and Ethanol form an azeotrope?

I have a 60/40% Acetone/Ethanol solution that I am trying to separate through fractional distillation.

However, the first product comes over at 60-61C, even though Acetone's BP is 56.53, and Ethanol's is 78.4.

Tried it a couple of times, making sure everything was 100% on each run, with same result, worried that I am NOT getting very clean acetone.

Having said that, I have found NO info about whether the two form an azeotrope on any charts.

Any advice?

 

thanks for your help!

 

Jeff

[Horza2002]

Well acetone will also contain a lot of water...as will the ethanol. So you might have to try drying them with MgSO4 before distiliing it. With regards to the azeotrope...I'm reasonably sure it does form one but not sure at what ratio it occurs..have your looked in Atkins Phys chem?

[UC]

Are you sure that this is not a thermometer issue? Is the thermometer of the correct partial immersion and placed appropriately with regards to the still head?

[John Cuthber]

Well acetone will also contain a lot of water...as will the ethanol. ..have your looked in Atkins Phys chem?

 

Why and why?

 

Anyway the CRC handbook lists acetone/ethanol as zeotropic.

 

Unless you use a good fractionating column what will distill over will be a mixture and will have a boiling point somewhere between the boiling points of the two components.

That seems to be what you have found.

[Horza2002]

Well unless yo were using HPLC grade acetone and ethanol, theu naturally contain water. Even exposure to air for a few seconds is enough to make ethanol too wet for use as an NMR solvent (as I've found many a time).

 

You hamy also need to take into account the pH of the solution as acteone will exist as a mixture of the ketone and the enol...although I doubt the enol will have any baring on the results at all

[John Cuthber]

There's a difference between enough water to upset an NMR and "lot of water", in particular, enough water to upset the boiling point markedly.

 

Unless you add a lot of base the amount of the enol form will be too small to matter.

If you do add a lot of base then the formation of the hemiketal will bugger things up.

 

BTW, do you realise that a data book like the CRC handbook is much more likely to help than a textbook like Atkins'?

[JMiller]

thank you all very much for your replies, they helped a lot. this is a great forum btw, love it!

[Sedit]

As already stated you will have a rough time getting a decent seperation of this mixture. As long as you are not hell bent on using distillation as the means of seperation then it will be a walk in the park.

 

Sodium Hydrosulfite(Sodium Bisulfite) will form the sulfonate adduct with the acetone forming a solid precipitate allowing you to filter and redistill the resulting acetone free Ethanol. Keep in mind I said Bisulfite and not Bisulfate.

[UC]

As already stated you will have a rough time getting a decent seperation of this mixture. As long as you are not hell bent on using distillation as the means of seperation then it will be a walk in the park.

 

Sodium Hydrosulfite(Sodium Bisulfite) will form the sulfonate adduct with the acetone forming a solid precipitate allowing you to filter and redistill the resulting acetone free Ethanol. Keep in mind I said Bisulfite and not Bisulfate.

 

Hydrosulfite (dithionite) is not the same as bisulfite. Perhaps you are thinking of metabisulfite, which is a dehydrated form of bisulfite.

 

The problem is that we're dealing with 60% acetone in solution, and producing the bisulfite adduct requires adding water. If you use enough water that the complex is filterable, you are going to be left with very dilute ethanol solution, and the distillation thereof will leave you with the azeotrope at best.

 

http://www.chemeng.ed.ac.uk/~jwp/procalcs/procalcs/mixtures/nonideal/slides/data/acet-eth.gif

 

That chart shows no azeotrope or funny business of any kind. Plain old fractionation should yield pure ethanol and pure acetone. Consider using a better column (is yours insulated and is it packed or a vigreux?) or making sure your thermometer is properly calibrated.