[enkay]

Distilling azeotrope of n-Butanol & Water, I'm getting mixture of both in two layers in the receiving flask with following composition :

Upper layer % : n-BA/Water : 79/21

Lower layer % : n-BA/Water : 8/92


Now after separating again these receiving flask layers, how can I remove this 20-21% moisture from the n-Butanol ? 

Can I again recover the remaining 8% n-BA from the lower water layer ?

 

[lavoisier]

May I ask you a silly question?

Why are you doing azeotropic distillation to remove water from your alcohol? Couldn't you just dry the initial wet material that you have (btw, how much water is there in it?) with some standard drying agent (CaO?) and then distill it?

And if for some reason you definitely need to do the azeotropic distillation, why are you collecting both the wet distillate and the dry one in the same flask? Isn't this going against the aim of your process?

Sorry, maybe I'm not entirely getting your point here...

[enkay]

I will clarify this in detail.

I've done reduction of oxime in n-butanol with sodium metal. After the reduction completion, I added water into it to break the butoxide salt separating it into NaOH & n-Butanol.

Now after this addition of water, I'm getting two layers, one of n-Butanol+Amine & lower one of caustic solution. I separated these layers & then start distilling the n-BA layer. This n-BA also contains significant amount of water as its solubility in n-BA is 9% by vol. Hence, the starting of distillation is  azeotrope of both for a long time. (Why long time ?) To understand this, pls click to this link : http://www.chemeng.ed.ac.uk/people/jack/azeotrope/hetero.html    Which shows compositions of lots of solvents with their azeotropes.

I hope, now you will understand my problem.

By the way, For your kind info, this process is being run on my plant scale. Hence, I have to find a commercial solution for this.


 

 

[lavoisier]

No, sorry, I still don't see your point.

You say you reduced an oxime to an amine with Na/BuOH, then you added H2O and you ended with the amine in the organic layer because the aqueous layer was basic. So far OK.

Then you take the organic layer and distill it, and you worry about how much water is in the distillate layers. What does this all have to do with the amine? You seem to forget about your product...
And in fact in your first post you didn't even mention the amine!

I can only guess that you're more interested in getting back dry BuOH from your mixture than getting the product.

If that's the case, I think your method is wrong in the fact that you take a wet solution and distill it straight away. I've always been used to dry my extracts before distilling them.

There are two possible methods I would apply:
1 - after adding H2O, separate, extract the aq. layer with DCM, combine the org. layers, dry them with a suitable drying agent and distill under vacuum (better if you decrease the pressure stepwise). If the amine is not too volatile, you will get little wet BuOH, some reasonably dry BuOH and then your amine (if you care at all about it).
2 - after adding H2O, acidify with conc. HCl to pH 1, extract BuOH several times with DCM or EtOAc. You have then your organic layer of solvent+BuOH. You can dry it with something and distill it, and you'll get your 'dry' BuOH. The aqueous layer, basified with NaOH, will yield your amine, which you can extract with DCM, dry and distill.

[enkay]

Oh friends !

I've got a very good solution for this task & wish to share this with you all. 

One of my friend suggested me to add caustic flakes into the n-BuOH layer containing water. after shaking this for a while, the water layer separated out forming the caustic lye solution at the bottom..!!!!! 

I just separated both these layers & checked moisture of the butanol. It was <2% !

However, this butanol was alkaline & I distilled it to get the neutral n-BA.

Thanks for your comments..! 



kmorendha