Sciencemadness Discussion Board

Has anyone ever tried seperating the ethanol from gasoline with water?

RogueRose - 18-9-2020 at 07:23

I've seen a number of threads about this and some video's (none of which were really any good) so I thought I would try with a small batch just to see how easy it is and my results are less than satisfying. The gas states it has a 10% minimum of ethanol. I filled a 2L bottle then put 800ml in a different bottle along with 100ml of dH2O & shook it 15-20x for 2-3 mins & allowed to settle for a week. Then I decanted off about 600ml of gas & poured the remaning gas/ethanol/water into the original 2L bottle & repeated the process.

I was expecting to get about 300ml of water/ethanol mix but I'm guessing I don't even have 1/2 of that. It wouldn't surprise me if I only has 20-40ml more in the 100ml of water than I began with.

I figure there are a couple options, one is there is less ethanol than stated, possibly b/c of all the hand sanitizer being made, but I think this gas was from a can that was filled near the middle/end of winter. The other options are it takes a lot more energy to seperate the ethanol/gas than violent shaking (it turned into a froth while shaking, so it was thouroughly mixed.) or there is some kind of homogenizer or emulsifier like substance that is binding the ethanol & gasoline, though I would think this might effect the water as well.

I wouldn't think there is any homogenizer b/c the Heet products (methanol or isopropanol) are made to "remove water" from fuel systems which I'm kind of questioning now. If the water was in the tank, wouldn't the alcohol mix with the gasoline before getting to the water? It's not like you can shake the gas tank or anything - this is kind of the same principle but opposite.

So has anyone tried this method of seperating the ethanol & gasoline and if you have, how did it work for you?

njl - 18-9-2020 at 08:47

If you want to accurately gauge how much ethanol is in the gas you probably want to do more than one extraction

macckone - 18-9-2020 at 11:03

The 10% ethanol listed on the pump is the maximum not the minimum, assuming the USA.
Further, ethanol content is decreased in warmer months as it contributes to ozone and poor air quality.
The final factor is ethanol and methanol entrain water in the gasoline (that is how methanol removes it).
So some water winds up in the gasoline and as njl mentioned you need to do more than one extraction.
I would expect at least four as necessary.

Given that your gasoline is 'old', you may also be running into the problem of ethanol being sequested by condensation with unsaturated hydrocarbons.
And of course some of the ethanol evaporating.

AgCollector - 18-9-2020 at 17:20

It seems weird that you've added 200 mL of water but only recovered 150 mL of it back- or am I misunderstanding something?

RogueRose - 18-9-2020 at 22:29

Quote: Originally posted by AgCollector  
It seems weird that you've added 200 mL of water but only recovered 150 mL of it back- or am I misunderstanding something?


I added 100ml to the 800ml bottle which left ~100ml of space for good shaking.

I did a final separation with my sep funnel and it came out to 148g of water/ethanol, so 48g of ethanol in the total of 2L of gasoline.


I was planning on getting 200ml from this. The video's I saw they all used 10% to do a 1:1 water/ethanol ratio but I figured that since water/ethanol forms a ~95% azeotrope that the 100ml would be fine giving me a 66% ethanol mix in the end.

I think I'll try adding another 100ml to the bottle that had the 1200ml (which was the second bottle I extracted) so maybe since the water had already absorbed a fair amount of ethanol, maybe it didn't work well in the larger volume bottle.

RogueRose - 18-9-2020 at 22:35

Quote: Originally posted by macckone  
The 10% ethanol listed on the pump is the maximum not the minimum, assuming the USA.
Further, ethanol content is decreased in warmer months as it contributes to ozone and poor air quality.
The final factor is ethanol and methanol entrain water in the gasoline (that is how methanol removes it).
So some water winds up in the gasoline and as njl mentioned you need to do more than one extraction.
I would expect at least four as necessary.

Given that your gasoline is 'old', you may also be running into the problem of ethanol being sequested by condensation with unsaturated hydrocarbons.
And of course some of the ethanol evaporating.


Do you think that gas or ethanol can escape from a very well sealed gas can (HDPE I think - but has very good seals)? I had a 2L bottle (soda bottle) of gas that was well over 10 years old and it was just as full as it was when I filled it. Also, I'm not sure gas really goes bad as quickly as some people think. We just fired up a car that had been sitting for 5 years and it ran fine on the gas that was 5+ (could have been many more years than this) old. & as you said the mixtures change over the seasons and I think they may add stabilizers in winter or something.

I really thought I had seen "Min" next to the 10% on some of these pumps, but I go to a station that is a "boutique" gas station that also sells E85, biodiesel, kerosene and maybe E40 and some super octane gasoline (94 or 95). I don't think I read it wrong b/c I always wondered just what % of ethanol was in the gas but figured it wasn't very much above 10%, if any, b/c I think ethanol is much more expensive than gas, especially regular 87 octane - but it is farm country here which is why we have the biofuels available.

[Edited on 9-19-2020 by RogueRose]

Deathunter88 - 18-9-2020 at 23:09

Quote: Originally posted by RogueRose  
Quote: Originally posted by macckone  
The 10% ethanol listed on the pump is the maximum not the minimum, assuming the USA.
Further, ethanol content is decreased in warmer months as it contributes to ozone and poor air quality.
The final factor is ethanol and methanol entrain water in the gasoline (that is how methanol removes it).
So some water winds up in the gasoline and as njl mentioned you need to do more than one extraction.
I would expect at least four as necessary.

Given that your gasoline is 'old', you may also be running into the problem of ethanol being sequested by condensation with unsaturated hydrocarbons.
And of course some of the ethanol evaporating.


Do you think that gas or ethanol can escape from a very well sealed gas can (HDPE I think - but has very good seals)? I had a 2L bottle (soda bottle) of gas that was well over 10 years old and it was just as full as it was when I filled it. Also, I'm not sure gas really goes bad as quickly as some people think. We just fired up a car that had been sitting for 5 years and it ran fine on the gas that was 5+ (could have been many more years than this) old. & as you said the mixtures change over the seasons and I think they may add stabilizers in winter or something.

I really thought I had seen "Min" next to the 10% on some of these pumps, but I go to a station that is a "boutique" gas station that also sells E85, biodiesel, kerosene and maybe E40 and some super octane gasoline (94 or 95). I don't think I read it wrong b/c I always wondered just what % of ethanol was in the gas but figured it wasn't very much above 10%, if any, b/c I think ethanol is much more expensive than gas, especially regular 87 octane - but it is farm country here which is why we have the biofuels available.

[Edited on 9-19-2020 by RogueRose]


Why don't you buy E85 for the ethanol?

macckone - 19-9-2020 at 00:57

HDPE gas cans will 'leak' lower boiling point compounds, including ethanol.
Actual gas cans usually have a vent that is practically impossible to disable as well.
Metal or Glass containers are going to retain the lower boiling compounds much better.

And yes gas goes bad. It isn't going to do it in a month but it does form some pretty radical varnish in a carb.
Lawn mower gas kept over winter killed more than one mower. Sometimes you can clean it up but other times not so much.


https://www.eia.gov/tools/faqs/faq.php?id=27&t=10
Quoting the above site:
The ethanol content of most of the motor gasoline sold in the United States does not exceed 10% by volume.

E10 cannot exceed 10% because it can damage seals in vehicles older than 2001.
Light duty vehicles newer than 2001 are required to handle E15.
It is usually just changing to viton seals.

AgCollector - 19-9-2020 at 04:10

Well the theory behind it is sound - E10 gas (10% ethanol) will only hold 0.5% water by volume before it phase separates

https://www.epa.gov/sites/production/files/2015-09/documents...

and at the same time the fuel-water partition coefficient for ethanol is only 0.01 according to

https://pubs.acs.org/doi/10.1021/es048901l

(meaning only 1% will stay dissolved in the fuel if given the choice of solvents)

you could try a second extraction as previously suggested, but I would also test out a few different sources of E10 gas to see how different the results are.