Sciencemadness Discussion Board

Help separating HCl from n-butanol

Mabus - 27-12-2014 at 04:51

I found at a hardware store a paint drying accelerator, with the label indicating the following:
-n-butanol
-7%HCl

Unfortunately I can't find any data about the properties or stability of the n-BuOH-HCl mixture. Since n-butanol has a slightly higher boiling point than water (117.7 °C) would the two-container technique be enough to remove the HCl from the mixture?

HgDinis25 - 27-12-2014 at 05:10

Does that 7%HCl mean a 7%HCl solution in water, added to n-butanol? Or is the HCl actualy dissolved in the n-butanol?

Anyway, if you use the two container technique there will still be water in your butanol (if the HCl is in aquous solution). And you can't simply distill the water because water and Butanol form an azeotrope. Perhaps it would be easier and faster just to neutralize it with NaOH (or another neutralizing agent of your choice). You would end up with just water, butanol, and the chloride salt.

I don't know if you would see a salting out effect here or not. Butanol as limited solubility in water (7,3g per 100mL). The Sodium Chloride formed would increase the ionic strenght of water, forcing the Butanol out. You should end up with two layers, one with the Sodium Chloride solution, the other with the Butanol. Seperation would be quite easy.

Of course this is mostly speculation. Try it out on a test tube, in small quantities, and see if you get two layers.

Mabus - 27-12-2014 at 05:19

The label doesn't specify if it contains water or not (since is consumer product, I'll assume it does).
Well, I wanted to also recover the HCl, but if it's too complicated to do that, I might just neutralize it.

HgDinis25 - 27-12-2014 at 06:24

I really don't understand the HCl content, though. It will acelerate the corrosion of metals, if you use it when painting metals. And if the purpose is to accelerate drying, why containing water?

You could test for the presence of water using anhydrous Copper Sulfate...

CuReUS - 27-12-2014 at 07:18

if you use NaOH to neutralize the HCl,you would have to use a stoichiometric amount or you will end up with excess NaOH with the tert butanol

you could try freezing the tert-butanol/HCl mixture,I have read about products being separated from one another by freezing.

dermolotov - 27-12-2014 at 11:55

What I would do is 2 or 3 things:
1. Reflux with an efficient column. HCl doesn't reflux so that should drive off most of the vapours.
2. Add copious amounts of Sodium Carbonate until it doesn't JUST stop bubbling but until it stops clumping as well. This means it's neutralised AND dehydrated.
3. Distil off the alcohol.

If you don't have a reflux setup, you can just forgo it and add copious amounts of sodium carbonate.
If you dont' have sodium carbonate, just bake sodium bicarbonate at 300deg for an hour or so. Until it stops steaming.

dermolotov - 27-12-2014 at 11:58

Quote: Originally posted by Mabus  
The label doesn't specify if it contains water or not (since is consumer product, I'll assume it does).

Well, I wanted to also recover the HCl, but if it's too complicated to do that, I might just neutralize it.

1. Yupp. Virtually all consumer products contain water. It's too expensive and unecessary to dehydrate things like this.

2. It's too complicated collecting that stuff. 7% HCL is really not worth the hassle in the end...

HgDinis25 - 27-12-2014 at 12:35

@CuReUS
It's not tert butanol, it's n-butanol. And I don't see the problem on having excess NaOH, after all he's after the butanol. Anyway, a simple ph indicator would tell you when to stop.

@dermolotov
I was not refering to regular humidity mostly every product has. I was refering to the 7% HCl. I'm assuming it is a 7% HCl solution (93% water, 7% HCl), so there is a lot more water in there than just regular humidity. Of course it could also mean that the HCl makes 7% of the product, perhaps dissolved in the butanol. An anhydrous Copper Sulfate test would clear this out.

I agree with you, 7% HCl is just not worth it. Refluxing is not such a good idea though. If there's a lot of water in it you'll just keep refluxing the azeotrope (~20% Hydrochloric Acid).

dermolotov - 27-12-2014 at 13:09

Quote: Originally posted by HgDinis25  
@dermolotov
I was not refering to regular humidity mostly every product has. I was refering to the 7% HCl. I'm assuming it is a 7% HCl solution (93% water, 7% HCl), so there is a lot more water in there than just regular humidity. Of course it could also mean that the HCl makes 7% of the product, perhaps dissolved in the butanol. An anhydrous Copper Sulfate test would clear this out.

I agree with you, 7% HCl is just not worth it. Refluxing is not such a good idea though. If there's a lot of water in it you'll just keep refluxing the azeotrope (~20% Hydrochloric Acid).

7% seems very ambiguous. Best case scenario is to weigh out 100cc and see what it approximates. You can make a moderately certain guess with that information.

IF it is 93% alcohol and 7% acid solution, I think you can just get it out the way I mentioned.
However, if it's something silly like 7% acid with 50:50 solvent, a neutralisation (or even basification) followed by a simple distillation should take care of that?

I thought HCl does a 36% (12M) Azeotrope?

HgDinis25 - 27-12-2014 at 13:17

@ dermolotov

The azeotrope of HCl with water boils at 110ºC and it's 20,24% HCl. If it is indeed 93% alcohol and 7% acid the way you mentioned is the best way to procede. If it's not, the method I mentioned seems to be the way to go. I didn't understand what you said by "7% acid with 50:50 solvent". And, in this case, the neutralization will be a basification.

Simple distillation won't cut it. Water and Butanol form an azeotrope. That's why I mentioned the salting out effect. Then, if needed, just drying the solvent and distilling it would get reasonable pure Butanol.

dermolotov - 27-12-2014 at 14:20

Quote: Originally posted by HgDinis25  
@ dermolotov

The azeotrope of HCl with water boils at 110ºC and it's 20,24% HCl.


Hmmmmm... Not sure where I got the 36% idea from. Would that be the highest stable percentage of HCl in water?
Quote: Originally posted by HgDinis25  
If it is indeed 93% alcohol and 7% acid the way you mentioned is the best way to procede. If it's not, the method I mentioned seems to be the way to go. I didn't understand what you said by "7% acid with 50:50 solvent". And, in this case, the neutralization will be a basification.

I guess this discussion is useless without OP seeing what the mixture is. I still go with weighing it.
HCl has a density of 1.1 where n-Butanol has a density of 0.8. Should be able to figure it out with a simple weighing of 100cc.
Quote: Originally posted by HgDinis25  
Simple distillation won't cut it. Water and Butanol form an azeotrope. That's why I mentioned the salting out effect. Then, if needed, just drying the solvent and distilling it would get reasonable pure Butanol.

The latter thing is what I would do. Was thinking of just dumping a lot of calcium chloride/magnesium sulphate into the already distilled azeotrope and then re-distil.
Salting out is an interesting and perhaps more efficient method, though :)

Templar - 27-12-2014 at 16:13

wash with sodium hydroxide soln.

CuReUS - 27-12-2014 at 18:32

Quote: Originally posted by HgDinis25  
@CuReUS
It's not tert butanol, it's n-butanol. And I don't see the problem on having excess NaOH, after all he's after the butanol. Anyway, a simple ph indicator would tell you when to stop.


what I meant was that if excess NaOH is used,he would have a new problem of separating the n-butanol from the NaOH

Pomzazed - 28-12-2014 at 00:21

Add excess base cautiously (NaOH, CaO, or so on) and frac dist?
Unlike HCl they arent volatile thus not contaminate your pdt.

Mabus - 28-12-2014 at 04:24

@HgDinis25 The paint drying accelerator is for wood, more exactly parquet. So it's not meant for painting metals.

The solution is viscous and clear and it does smell like butanol, but I haven't sensed any acidic smell.
I added some bicarbonate to test for acid and there was little fizzling, I guess I can just go for neutralization, there's very little to worth the effort.
To test for water, I added a few crystals of anhydrous copper sulfate (I heated CuSO4 crystals until they turned white). The solution turned green-yellow:

HgDinis25 - 28-12-2014 at 04:28

Interesting. The yellow may be the Copper complex with Chloride dissolved in water. Anyway, go ahead with the neutralization and see if you get the salting out effect. With all the information in this topic you have enough for a successful experiment. Good Luck!

blogfast25 - 28-12-2014 at 07:12

By far the easiest here is to carefully neutralise the HCl then fractionate that mixture. Then deal with the azeotrope (n-BuOH/H2O).

'Virgin' n-BuOH is cheap though...

gsd - 28-12-2014 at 07:29

I have some experience of dealing with n-Butanol (NBA) and Hydrochloric Acid (HCl) mixtures.

1) NBA + commercial HCl (i.e. 30% HCl in water) are miscible in all proportions, no phase separation occurs.

2) If you reflux the mixture you will get N-Butyl Chloride (NBC) - yes this reaction does occur without using ZnCl2 or any other catalyst.

The Over Head product separates into 2 phases top layer NBC + NBA and bottom layer NBA + Water (+ unreacted HCl)

Best way to remove 7% HCl is by alkali treatment - NaOH or Na2CO3 and then "Salt-out" the water by addition of excess NaCl.

gsd

CuReUS - 1-1-2015 at 21:45

Quote: Originally posted by HgDinis25  
Interesting. The yellow may be the Copper complex with Chloride dissolved in water.


copper chloride is greenish yellow in colour upon absorbtion of moisture,how is this related to complex formation ?
http://en.wikipedia.org/wiki/Copper%28II%29_chloride

[Edited on 2-1-2015 by CuReUS]