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en2oh
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[*] posted on 10-12-2014 at 13:47
100% ethanol


Hi guys,

I've searched around here a little but didn't find the answer to this question.
Anyone care to take a shot at using propylene glycol to distill higher proof alcohol?

I'm looking for a discussion around extractive vs azeotropic distillation.

Thanks
En2oh

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[*] posted on 10-12-2014 at 13:48


Why use propylene glycol instead of a better dessicant?



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en2oh
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[*] posted on 10-12-2014 at 14:01


Regardless of solvent choice, I'm really looking at the principle of extractive vs azeotropic distillation. I found a patent using propylene glycol - ethanol -water mixtures for extraction distillation.

En2of
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[*] posted on 10-12-2014 at 16:45


If you want anyone to comment on the patent or any topic, it would be very helpful to reference it. We are not great at reading your mind as too which patent or source you are talking about.
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Chemosynthesis
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[*] posted on 10-12-2014 at 17:14


I agree with Dr. Bob. Generally, the forum guidelines indicate to post references when making topics outside of the "Beginnings" section.
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[*] posted on 10-12-2014 at 17:40


This goes to "beginnings" until and unless there is some documentation.

FYI, TONS of information on the production of anhydrous ethanol is to be found around here- UTFSE would really be a good idea!

Just off the top of my head: Removal of H2O as water of crystallization by various heat dehydrated salts, or via molecular sieves. Other more esoteric methods are detailed here as well. But use of propylene glycol? You tell us-




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[*] posted on 10-12-2014 at 18:39


Ethylene glycol is usually used instead of propylene glycol.
In the ethylene glycol case ethanol distills over.

http://www.separationprocesses.com/Distillation/DT_Chp06c08....

Benzene is another commonly used substance.
In the benzene case it creates a lower boiling point
Azetrope with 3 components. That allows the water to
Be removed. First the three component azetrope comes over
then a two component mixture of ethanol and benzene.
Finally an almost pure ethanol is distilled. Cyclohexane
provides the same type of azetropic behavior.

https://books.google.com/books?id=gmnWZ1zNON0C&pg=PA262&...

[Edited on 11-12-2014 by macckone]
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en2oh
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[*] posted on 10-12-2014 at 20:08


Thanks for your feedback gents.
This paper examines propylene glycol as an entrainer, specifically as compared to ethylene glycol.

http://www.revistadechimie.ro/pdf/NEAGU%20PETRE%20M.pdf%201%...

It seems to be a more environmentally friendly alternative to benzene or ethylene glycol. I was struggling with my basic thermodynamics (coefficient of activity) as it applies to separating an azeotrope of water/alcohol. I did grad studies in P Chem, but that was many years and at least one career change ago.

I (wrongly ) hoped that this might generate a general discussion of azeotropic vs extractive distillation. I was wrong. My mistake.

En2oh

[Edited on 11-12-2014 by en2oh]
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[*] posted on 10-12-2014 at 20:16


Quote: Originally posted by macckone  
Ethylene glycol is usually used instead of propylene glycol.
In the ethylene glycol case ethanol distills over.

http://www.separationprocesses.com/Distillation/DT_Chp06c08....

Benzene is another commonly used substance.
In the benzene case it creates a lower boiling point
Azetrope with 3 components. That allows the water to
Be removed. First the three component azetrope comes over
then a two component mixture of ethanol and benzene.
Finally an almost pure ethanol is distilled. Cyclohexane
provides the same type of azetropic behavior.

https://books.google.com/books?id=gmnWZ1zNON0C&pg=PA262&...

[Edited on 11-12-2014 by macckone]


Thanks for the link and your general comments. I appreciate your thoughts.
En2oh
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[*] posted on 10-12-2014 at 20:23


Now that you have provided your source document, perhaps you will get some discussion on this.

Especially if you mention why/what about it interests you.


For a small batch, I'll probably stick with the processes mentioned earlier.




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3. Mention anything you have learned from your target.
4. Only then are you permitted to say so much as a word of rebuttal or criticism.

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[*] posted on 10-12-2014 at 20:24


Quote: Originally posted by Bert  
This goes to "beginnings" until and unless there is some documentation.

FYI, TONS of information on the production of anhydrous ethanol is to be found around here- UTFSE would really be a good idea!

Just off the top of my head: Removal of H2O as water of crystallization by various heat dehydrated salts, or via molecular sieves. Other more esoteric methods are detailed here as well. But use of propylene glycol? You tell us-


Thanks for your thoughts. As a point of clarification. Should that not have been U(of)TFSE would really be a good idea! Or more simply put, "UTFSE next time!"? Is that what you were trying to say? Personally, as a TA and ultimately on faculty, I never found the "eF" word, even hidden in an acronym, to be useful. YMMV, of course. :)

Thanks again.
En2oh



[Edited on 11-12-2014 by en2oh]
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[*] posted on 10-12-2014 at 20:27


Quote: Originally posted by DraconicAcid  
Why use propylene glycol instead of a better dessicant?


I really don't think that propylene glycol is acting as a desiccant in extractive distillation. It's acting as an entrainer. It's the thermodynamics behind extractive distillation that I'm struggling with. A bit embarrassing for a guy who did PChem, but I was more of a "constrained motions in glassy states" kind of guy, not a wet bench chemist.

Thanks

En2oh

[Edited on 11-12-2014 by en2oh]
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[*] posted on 10-12-2014 at 20:42


en2oh, download the small program called ChemSep lite, it will allow you to simulate this distillation and all the thermodynamics you could want REALLY easily.

You will need to use the DECHEMA property model and an appropriate activity coefficient model, fortunately the built-in library already has the required data for using the NRTL model for your components. NRTL is one of the more accurate activity coefficient models... just load the constants for this system from the library.

If you don't have chemical engineering training, you will find the design of such distillation columns extremely challenging... but you can do it all on this program and simulate the outcome.

[Edited on 11-12-2014 by deltaH]




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en2oh
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[*] posted on 10-12-2014 at 20:46


Quote: Originally posted by deltaH  
en2oh, download the small program called ChemSep lite, it will allow you to similate this distillation and all the thermodynamics you could want REALLY easily.

You will need to use the DECHEMA property model and an appropriate activity coefficient model, to accurately describe the nonideal solution of this system... very NB!


[Edited on 11-12-2014 by deltaH]


Perfect! Thanks for the lead.
en2oh:D

(To be clear, NB in this case is for nota bene I.e. VeryI Important)

[Edited on 11-12-2014 by en2oh]
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[*] posted on 10-12-2014 at 21:03


You replied before I was completely done with the edit... you can use NRTL model in DECHEMA, see my post above...



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[*] posted on 10-12-2014 at 23:10


Quote: Originally posted by deltaH  
If you don't have chemical engineering training, you will find the design of such distillation columns extremely challenging... but you can do it all on this program and simulate the outcome.

Pff. It's just a glorified tubular heat exchanger. How complicated could it be?

Kidding!
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[*] posted on 11-12-2014 at 03:30


:D:D:D:D



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[*] posted on 11-12-2014 at 05:56


Quote: Originally posted by deltaH  
You replied before I was completely done with the edit... you can use NRTL model in DECHEMA, see my post above...


Thanks again
en2oh
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