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Author: Subject: Moisture removal in n-Butanol
enkay
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wink.gif posted on 18-6-2006 at 00:01
Moisture removal in n-Butanol


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 ?
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unionised
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[*] posted on 18-6-2006 at 00:41


I'd try adding common salt to the aqueous layer and seeing if any of the n-BA is salted out.

What do you get if you redistill each of the 2 fractions separately?
Anyway, I'm pretty sure that MgSO4 would dry the stuff nicely.
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enkay
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[*] posted on 18-6-2006 at 01:39
Moisture removal in n-Butanol


MgSO4 can not be a solution for me to remove this huge amount (>20%) of water, as I want to perform this task on my plant scale.

Whenever I distill them separately, first the azeotrope will come......

For aq. layer I will try this.
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gsd
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[*] posted on 18-6-2006 at 05:34


n Butanol - Water is a classic case of Azeotrope with limited solubilities. The components can be completely separated by conducting azeotropic distillation with 2 separated distillation columns and an overhead phase separator; withour addition of any other compound.

You can find a the relevent reference in chemical engineering distillation books. ECT - kirk Othmur has given detailed description along with phase equilibrium data and block diagram of distillation system.

If you can't find it then let me know, I will try to upload it.
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[*] posted on 18-6-2006 at 07:21


"Whenever I distill them separately, first the azeotrope will come......"
Precisely my point. After the azeotrope has come off, change the receiver and carry on distiling to get one of the pure components.
I'm pretty sure that the continuous version of this idea is what GSD is on about.
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Magpie
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[*] posted on 18-6-2006 at 10:01


enkay: how are you getting "plant scale" quantities of n-butanol, if I might ask?



The single most important condition for a successful synthesis is good mixing - Nicodem
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neutrino
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[*] posted on 18-6-2006 at 16:26


My guess is that he's a chemical engineer working on a project.

Could salting out be practical here?




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daeron
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[*] posted on 19-6-2006 at 13:56


^not on a plant scale.

the full list of your options is as follows( if you want to recover most of the n butane):
-reactive or extractive distillation, but you must find a suitable 3rd component.
-retention of water in suitable solid packings(that means youll need a packed column, ie money). consider molecular sieves
-membrane separation, you also have distillation columns with membranes in them
-last option, a suitable stripping system, but that will not work as well im afraid

if youre trying to recycle all of C4 frac from some process you must have in mind that not all is recyclable(is that a word?) and might consider to use purge for a sufficient part of the lower fraction, to lower the levels of C4 and make the water reusable. that or the waterprocessing unit( more cash).




Humans with their brains are like a caveman with a supercomputer. Yes there is a chance that the caveman will use it to calculate the trajectories and the momentums of the celestial bodies, but the chances are that he will just crack open a coconut with it.
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Dr. Beaker
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[*] posted on 20-6-2006 at 00:03


n-BuOH freezes at about -90 deg. C.
you can cool the organic phase to, say, -80 and filter off the ice. the remaining moisture can be removed by chemucal means (drying agents like CaCl2 etc.)
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enkay
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[*] posted on 20-6-2006 at 04:47


Sorry friends for the delayed reply.

Yes, I'm a chemical engineer & manufacturing organic intermediates in my small plant. In one of my reaction, I'm getting recovered n-BuOH containing aprx. 8% water.

My aim is not to completely dry this butanol but most of the water removal is desirable (upto 1-2% water remaining).

Once I read somewhere that caustic flakes can be used for this purpose. Do anyone have idea for this ?
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Swany
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[*] posted on 20-6-2006 at 13:45


Perhaps CaO could be used and then the n-BuOH distilled off? I thought this was used to dry EtOH, though I may be delusional.



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Magpie
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[*] posted on 20-6-2006 at 14:06


I don't know what the economics would be but I believe that 3A (or 4A) molecular sieves would work beautifully. You can recover the sieves and reactivate them by heating them to around 250-300C, IIRC.

Molecular sieves could be overkill as they can dry that alcohol right out. You might be able to control the residual water, however, by controlling the exposure time of the alcohol to the sieves.

Again, if you don't mind me asking, how are you producing your n-butanol?

[Edited on 20-6-2006 by Magpie]




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daeron
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[*] posted on 21-6-2006 at 02:29


Quote:
Originally posted by Magpie
I don't know what the economics would be but I believe that 3A (or 4A) molecular sieves would work beautifully. You can recover the sieves and reactivate them by heating them to around 250-300C, IIRC.

yup that would be the most feasible solution, you just need a packed column, with a heat jacket and a pump to recycle the feedstock. you can later dry the sieves w the heating jacket.
the costs shouldnt go over 4500 eur for the 20ish meter column if im not mistaking
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[*] posted on 21-6-2006 at 07:28


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 sufficient caustic flakes into the n-BuOH layer containing water. after shaking/stirring this for sometime, the water layer separated out forming the caustic lye solution at the bottom.....!!!!! :o

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.

Magpie, I'm not producing n-BuOH but purchasing it easily from the market in commercial quantities.

Thank you all for your comments friends.....! ;)
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daeron
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[*] posted on 21-6-2006 at 08:15


great! whats your capacity? did you try it at a larger scale?



Humans with their brains are like a caveman with a supercomputer. Yes there is a chance that the caveman will use it to calculate the trajectories and the momentums of the celestial bodies, but the chances are that he will just crack open a coconut with it.
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neutrino
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[*] posted on 21-6-2006 at 10:27


Quote:
Originally posted by enkay
One of my friend suggested me to add sufficient caustic flakes into the n-BuOH layer containing water. after shaking/stirring this for sometime, the water layer separated out forming the caustic lye solution at the bottom.....!!!!! :o


Classic salting out. Why not use another salt instead of lye / NaOH? For example, simple NaCl (table salt) should work about as well and leave you with neutral butanol.

Using other salts also eliminates the problem of working with large amounts of highly corrosive lye solutions.

[Edited on 22-6-2006 by neutrino]




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[*] posted on 21-6-2006 at 16:25


How do you determine the approximate (down to a whole number precentile) water levels in something? Could strips of paper impregnated with cobalt chloride or a similar salt work? Or would it turn pink regardless (like litmus paper).



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[*] posted on 21-6-2006 at 17:13


One can learn the mass of the water content by simply weighing the drying agent before and after the procedure :D



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enkay
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[*] posted on 21-6-2006 at 19:48


Quote:
Originally posted by daeron
great! whats your capacity? did you try it at a larger scale?


I had tried this in my lab & by next 2-3 days I'm going to perform it on my plant with 1000 liters of n-BA. I will inform my experience of that also.


Regarding calculating moisture, I simply got it from the Karl-Fischer apparatus.
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[*] posted on 22-6-2006 at 00:50


With that large amounts remember the rather large heat evolution when solid NaOH dissolves in water. For that reason NaCl would be better as it doesn't generate heat when it dissolves and it would be easier to reuse by simply evaporating the water.
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enkay
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[*] posted on 22-6-2006 at 21:47
Salt is working !!!!


Quote:
Originally posted by unionised
I'd try adding common salt to the aqueous layer and seeing if any of the n-BA is salted out.



Yes, salt is also working so nicely !!!! :o

Thank you all again..........;)
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[*] posted on 23-6-2006 at 00:16


This still leaves you with a waste disposal problem (polluted salty water). You might recover the salt by evaporating the water but you will lose butanol to the atmosphere that way. It's a waste as well as pollution.

If you are planning to do this process often or for a long time you really ought to think about distillation, separating the layers and redistilling them. This can (as has been mentioned) be set up as a continuous process. The capital cost will be higher but the running costs won't and, since you already have a still, you have most of the kit.

Lots of salty water is less of a problem than lots of caustic waste so I'm surprised you didn't try salt first (it's cheap too)
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enkay
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thumbdown.gif posted on 23-6-2006 at 02:36
Waste problem


No dear !

In india, it's absolutely not a problem industrially because in our factory area there is a common effluent treatment plant (CETP) situated where over 200 chemical related factories are there & all are members of this CETP.

This CETP accepts aqueous effluents generated from any member factory with any TDS content & upto 2000 COD !!! :o

Isn't it great ?

So, I'm absolutely not worried about this point.:D

Regarding using salt instead of caustic first, I'm feeling really stupid for that....:(

[Edited on 23-6-2006 by enkay]
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kalpakchhajed
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[*] posted on 29-6-2006 at 01:47


I am also working on the same project in a chemical plant n my problem is to increase, the efficiency of the distillation column, it is right now working with very low efficiency, n i want the purity 99.9% butanol n my input is 95 %butanol n 30 % butanol, we have both the feed.. i would be thankful if u can suggest something effective.
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enkay
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[*] posted on 5-7-2006 at 00:51


Sorry Kalpa,

I'm not in position to give you advice at this stage as I'm not an egineer.....

I posted all the experience & solutions for this task on this forum.

I hope, you will get suggetions from other members.

[Edited on 5-7-2006 by enkay]
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