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[*] posted on 22-9-2023 at 12:22
(Anhydrous?) Ethanol from car E85


Folks,

over here in France we are one of the rare European countries (with Sweden) to have wide access to E85 (my car runs on it). At less than 1 € per litre, it seems a cheap source of (anhydrous) ethanol.

I tried a quick distillation of ~ 100 ml of E85 today. It’s not as promising as it’s cracked up to be. The first fractions passed around 40 °C and then the temperature slowly rose up to ~ 76 with a definite plateau at 78 °C which was nice. But then I was surprised to see that the thermometer rose again, and when I stopped at 80 °C I was left with quite a quantity of a clear liquid not really smelling of anything, and not boiling either. Just like… water? But it can’t be, since the amount is way too big, E85 is (supposedly) anhydrous and, overall, that residue doesn’t mix with water.

E85 is supposed to be 85% ethanol, 15% lead-free petrol. I was expected the 15% to pass around 40 °C and the 85% to pass at 78 °C. Can the petrol portion contain high boiling alcanes and/or aromatic compounds? Seems weird to me.

Did anyone in the US ever try to get ethanol from E85?
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unionised
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[*] posted on 22-9-2023 at 14:46


Good luck.
Ethanol forms azeotropes with octane and with toluene.
I would assume it also does so with other components of gasoline.
"Isooctane" boils at about 99C if I remember rightly.

Why would you expect gasoline to boil around 40C?
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[*] posted on 22-9-2023 at 15:33


You'd probably have much better luck trying to salt it out.



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[*] posted on 22-9-2023 at 22:11


Quote: Originally posted by unionised  
Good luck.
Ethanol forms azeotropes with octane and with toluene.
I would assume it also does so with other components of gasoline.
"Isooctane" boils at about 99C if I remember rightly.
Why would you expect gasoline to boil around 40C?


I don’t really care about azeotropes. There is so much more ethanol than petrol that most azeotropes could be dealt with just by distilling away all the azeotrope itself. My goal is not to get pure alcane products.

TBH, I probably can handle the presence of traces of alcanes in the ethanol, given that they are mostly unreactive.

The official reason why petrol is mixed to pure ethanol to form E85 is that petrol kick-starts the engine at low temps because ethanol vapour pressure is too low. So I'd naturally expect the additive to have a much lower boiling point than the ethanol's (which I observed, since the first drop began to pass at 40 °C). I wonder, by the way, why they don’t add some ether (MTBE, for example) instead of unleaded petrol. I suppose the answer is price.

My goal wasn't to obtain super-high purity ethanol either. For ether synthesis, for example, I can probably start from water-ethanol azeotrope, and so can I for ester synthesis. I didn't try that yet, but it seems separating alcohol from E85 is easy if you tolerate water, because adding water to E85 will cause the mixture to separate into two phases, hydrocarbons and alcohol/water. That is why, apparently, it is not recommended to let an E85 car unused for several months with its tank full.
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clearly_not_atara
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[*] posted on 23-9-2023 at 11:10


I'm going to guess that there's a denaturant or something designed to make it harder to distill any usable ethanol. The government doesn't like letting anyone get their hands on untaxed alcohol however unlikely it seems.

[Edited on 23-9-2023 by clearly_not_atara]




[Edited on 04-20-1969 by clearly_not_atara]
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Dr.Bob
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[*] posted on 23-9-2023 at 16:21


Some alkanes like heptanes will boil above ethanol and likely a trace of aromatics. Remember gasoline is a mixture of about 100 or more various hydrocarbons. The old "pure" gasoline commercials are a bad joke.
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[*] posted on 23-9-2023 at 18:03


I thought I would share my experience with trying to do what you are and I'm still extremely confused as to my results. I bought some fresh E85. I put 100ml of water into a 2L bottle and marked the level. I then added about 1800ml of E85 and shook it up about 25-30 times, shaking for a couple minutes each time. Every single time it seperated back out! The level of the water never changed from what I could tell (I guess it might have lost 5% but it's hard to tell for sure). I even tried a hot water bath and nothing worked.

IDK if this matters but I bought the E85 in June at an extremely busy gas station in SE Pennsylvania, so it should have been fresh & non-winterized.
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[*] posted on 24-9-2023 at 02:43


Interesting.
Summer E85 actually contains more ethanol, so it’s likely to give higher yields.
Did you try and increase the amount of water? At the end of this article the guy adds .3 l of water for circa 1 l of E85. Apparently, E85 is mixed with cosolvents that increase the capacity of the ethanol to keep petrol dissolved while absorbing moisture. It takes quite a lot of water to overcome that extra capacity.
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[*] posted on 24-9-2023 at 10:35


There are almost totally inseparable denaturants in use that make it impractical to get potable ethanol from such sources ;) Perhaps there will be time to explain this arcane art more thoroughly eventually :cool:
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[*] posted on 25-9-2023 at 00:24


Quote: Originally posted by leau  
There are almost totally inseparable denaturants in use that make it impractical to get potable ethanol from such sources ;) Perhaps there will be time to explain this arcane art more thoroughly eventually :cool:


I mean, fair enough, still it’s not really costly either in time or money to try and find out.
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[*] posted on 25-9-2023 at 18:25


the lighter components are isopentanes which boil around 40C. winter mix is going to contain some butane in it as well as ethyl ether and other low temperature boosters. The heavier components are going to be detergents and lubricants as well as toluene and xylene as octane boosters. There are going to be branched chain alkanes and alkenes as well. Specifically Hexane, Heptane, Octane as branched chain molecules. There is also going to be methanol in there as a denaturant. E85 is a simpler mixture than regular gasoline because not everything will stay in a single phase when exposed to moisture.

The biggest difference is going to be lack of heavier compounds in E85.

One patent I was able to find calls for 85% ethanol, 6% isopentane and 9% regular gasoline.
What is in the regular gasoline of course will vary and the isopentane content will vary by season.
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[*] posted on 25-9-2023 at 21:44


Quote: Originally posted by macckone  
The heavier components are going to be detergents and lubricants as well as toluene and xylene as octane boosters.
What is in the regular gasoline of course will vary and the isopentane content will vary by season.


I don’t see why they would add octane boosters since ethanol has already a RON of 120 or so. Besides, toluene and xylene combustion generates much soot, while E85 is boasted to be a particulate free fuel.

Frankly, I was expecting a much purer mixture. I suppose the fraction collected between 76 and 80°C is pure enough to be used as solvent and/or reactant for ether/ester syntheses.
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[*] posted on 26-9-2023 at 17:32


Almost all gasoline contains some amount of benzene, toluene, xylene and ethylbenzene, as those are formed in hydropcarbon crackers and reformers, which try to take the naturally occuring straight chain hydrocarbons into more branched alkanes, which have much higher octane numbers. While ethanol has a high octane, there are very few refineries that have been built since over 40 years ago, when boosting octane was critical. So while they could use a differert mix of hydrocxarbons in E85, it is not likely that they would bother when they already have gasoline available with many hydrocarb in it. Remember they want to use everything they can of the crude oil fractions and outputs. But none of those should bother most ethanol chemistry, you will just need more of it, since it will not be pure ethanol.
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[*] posted on 26-9-2023 at 22:28


Yeah, fair enough. I suppose a crude distillation such as what I did would give a decent ethanol for anything from diethyl ether to solvating.
Still, I’ll try to shake it with, say, 25% w/w water and see what comes out of it.
Thanks for your input!
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[*] posted on 28-9-2023 at 21:15


Quote: Originally posted by unionised  
Good luck.
Ethanol forms azeotropes with octane and with toluene.
I would assume it also does so with other components of gasoline.
"Isooctane" boils at about 99C if I remember rightly.

Why would you expect gasoline to boil around 40C?


Gasoline has butane+pentane,hexane
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[*] posted on 29-9-2023 at 04:31


So I have poured round 350 ml of E85 in a bottle and shaken with 100 ml of water (circa). The result is a biphasic mixture. The upper layer burns with a very sooty flame, typical of what is expected from aromatics or branched alkanes. The lower layer burns with the typical blue flame of ethanol. It doesn’t smell of ethanol, probably because there are still a small amount of hydrocarbons dissolved in it. I’m going to try and distill it later, and see what comes of it.

[EDIT]
I distilled around 15 ml of what I assume is azeotropic ethanol from a bit less than 25 ml of the lower layer. The first few ml passed at less than 75 °C so I discarded them (they smelled foul anyway) and began collecting at 76 °C, stopping at 80 °C.

So it’s definitely possible to extract azeotropic alcohol from E85, provided you’re willing to go the extra mile :p, i.e. shake it with water, wait one day for the mixture to separate cleanly, then distill it.

Getting almost pure anhydrous ethanol from it is probably much more involved.


[Edited on 29-9-2023 by Keras]
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