photosyn
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recovering ethanol from gasoline
If gasoline contains 10% ethanol, then has anyone tried recovering the ethanol as a source? If gasoline is 90 cents a litre then a litre of ethanol
for $9 isn't too bad.
How about solvent extraction with water followed by frational distillation and drying with calcium oxide?
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photosyn
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Oh - and you can mix the non-aqueous fraction into your car gas tank so your investment is closer to 90 cents per litre of ethanol.
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j_sum1
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Damn. I wish it was only 90 cents per litre. (USD0.90=AUD1.32) Here in my corner of Oz it has recently drifted down from $2. I managed to score a
bargain today at $1.57. I expect the price will spike again soon.
Back to your question, I believe extraction with water does a reasonable job of removing the ethanol. It will leave you with wet hydrocarbons which
you would want to dry before putting in your car.
You are also going to carry over a reasonable quantity of hydrocarbons into your ethanol-water fraction. You are then left with the age-old problem
of removing the water and removing other organics from your ethanol. (And that includes the dyes and detergents that may be added.) I am not seeing a
big advantage over other sources.
Adding to the calculus... your gasoline is not likely to be 10% ethanol. It is usually stipulated as "up to 10% ethanol". IOW, the composition
varies according to what is economic on the day.
If you don't have other sources, then sure. But I would probably be distilling cheap vodka or doing my own fermenting before I went for automotive
fuel.
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photosyn
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There's no such thing as cheap vodka where I live - the taxes work out on average at about $100 per litre of ethanol content. And you still have to
remove the water.
Any detergent or dye components that transfer to the aqueous layer should be easy to remove in distillation, but I do wonder what the light
hydrocarbon content of the water fraction will be.
Do you think the water content of the hydrocarbon layer will be significant? If not then the non-aqueous layer can go straight back in your gas tank.
Assuming you were going to buy some gas at some future time, the cost of the ethanol is just the volume removed from the fuel, it doesn't matter if
it's 3%, 5% or 10%. It's all priced at the same as the road fuel, per litre extracted.
[Edited on 7-10-2024 by photosyn]
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paulll
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Quote: Originally posted by photosyn  | | Oh - and you can mix the non-aqueous fraction into your car gas tank so your investment is closer to 90 cents per litre of ethanol.
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I wouldn't do that to my car. For one, you're going to be feeding the engine a denser fuel that the ECU may, or may not be able to compensate for and
fully burn. More importantly, in the post-ethyl world detergents are an essential part of petrol and you will surely rinse them right out.
Might be time to check out your local homebrew supplier, if you're that hard-up.
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Keras
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I've tried to recover ethanol from E85 I feed into my car. It works, but it involves adding enough water so that the ethanol + water phase separates
from the hydrocarbons (the 15 rest) and then distilling. You get only azeotropic ethanol and not the anhydrous one E85 is made from. E85 is mixed with
additives that enhance the capacity of the ethanol to absorb atmospheric water without diphasing, which would be catastrophic for the engine.
Distilling E85 does not work, because some branched alcanes are always collected with the ethanol.
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photosyn
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Today I took 500ml of clear, yellow 87 octane road gasoline. I washed it twice with 15ml of water and each time separated the aqueous layer in a
separating funnel, giving a total of 75ml of wet product and leaving a cloudy yellow hydrocarbon layer. This layer - slightly short of the original
500ml - was dried over 20g of 3A molecular sieves and within 2hours had regained it's clear aspect. I will be "disposing" of it into the gas tank of
my car to mix with the 40-50 litres of fuel there.
To the aq. fraction I added a small spatula of activated carbon (to try to hold back some of any aromatics) and conducted a fractional distillation. I
used a 30cm distillation column packed with about half a "ball" of stainless steel pot scrubber. The first distillate came over at 67°C for only
several drops, which surprised me such that I didn't exchange the receiver vessel in time to separate it from a much larger fraction distilled at a
head temperature of 78-79°C.
Overall I collected 34.0ml of clear colourless distillate before the head temperature rose above 80°C and I shut down the heating. The mass of the
distillate was 27.66g for a density of 0.814g/ml. I believe this to be mostly an ethanol/water mix with a small amount of other light hydrocarbon
contents. Such a density of a solely ethanol/water mixture would correspond with 91% ethanol w/w. The distillate has a distinctive but very unpleasant
petroleum/chemical smell that I don't recognize.
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Dr.Bob
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If you can get ethyl acetate easily, then you can simply hydrolyze some with NaOH and some water, and then distill off the ethanol and get fairly pure
ethanol.
Or if someone wants to set up a still, I have some lab grade sucrose you can treat with yeast to make your own brew.
But I also think that you could get mostly ethanol from E85 with a little work, it might have traces of hydrocarbons, but that should not interfere
with most chemistry. Might make it hard to drink, however. That is likely done on purpose.
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Rainwater
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As an experiment I tried using e85 to replace absolute ethanol in a few refining projects with an unwanted oily residue.
great success was achieved by first performing a simple distillation on the e85 to remove tye non-volatile stuff, then using in place of absolute
ethanol.
"You can't do that" - challenge accepted
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j_sum1
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If I was attempting to use E85 as a source, I would distill as a first step.
Separation is not going to be good. But you are going to get a more concentrated fraction for the extraction.
And if I was planning on feeding the waste to my car, I would have heads and tails that I would not need to dry first.
I still don't think this is the best way to go.
(Edit, typo.)
[Edited on 11-10-2024 by j_sum1]
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BromicAcid
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I think there have been other threads on this - it's tickling my brain stem.
If you do wash out the ethanol with water poke around on the site, potassium carbonate can be used to crash out a ethanol rich phase from
ethanol/water mixture. This can get you beyond azeotrope.
It might be worth investigating one of the salts that dissolve well in ethanol and then adding that to the gasoline, the EtOH may well solvate that
salt and crash out of the gasoline without the need for water, then that phase could be separately distilled. Unfortunately, KOH is the only thing
that comes to mind off the top of my head but there are other salts out there that dissolve well in anhydrous EtOH.
@paull - Around here they sell 30% EtOH gasoline, 15% EtOH gasoline, 10% EtOH gasoline, and 0% EtOH gasoline, there is no switch to tell the engine
which it will be fed after a filling, the fuel injectors, oxygen sensors, etc help with the fuel mix going into the engine. There isn't a big
difference in fuel economy between 15% and 10% ethanol but going from 10% to 0% does give a noticeable boost in MPG or kilometers per liter. So long
as you're not introducing something into the gas stream recycling it into the tank wouldn't be a bad idea but even a percent or two water I wouldn't
want to risk a $10,000 car for the sake of saving a few bucks.
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Dr.Bob
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Actually cars that are rated for E85 do have sensors of some sort to determine the ethanol levels, according to my readings. I think as long as
processed fuel is dry, it should burn fine, best as a dilute amount in "real" gasoline. My old friend Ed used to burn lots of recovered alcohols,
isooctane, benzene and related aromatics, and more in his company truck, which ran fine for many years. I would not do it in a fancy car, but for
normal ones, small amounts should be fine.
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Rainwater
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The major problem with trying to purify ethanol from gasoline via distillation is the number of azeotropes other compounds within the fuel form with
ethanol
| Code: |
2nd Component|b.p. of comp.(˚C)|b.p. of mixture (˚C)| % by
weight|spef grav
cyclohexane 80.7 64.9 69.5
toluene 110.8 76.7 32 0.815
n-pentane 36.2 34.3 95
n-hexane 68.9 58.7 79 0.687
n-heptane 98.5 70.9 51 0.729
n-octane 125.6 77.0 22
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table from Wikipedia
Multiple procedures will be needed to separate the mixture.
Perhaps salting out the ethanol with KOH
[Edited on 13-10-2024 by Rainwater]
"You can't do that" - challenge accepted
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Dr.Bob
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None of the hydrocarbons listed there are reactive in most chemistry. So if you want ethanol for making an ester or a similar use, they won't create
any real issues. For drinking, it would be bad, but for most chemistry, traces of hydrocarbons are not a big issue. If you really want good ethanol,
you can buy it, just hard to do without either paying taxes or getting an ATF permit.
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