[hecilopter]

Not being a chemical engineer, just thought I would ask a question that an engineer could answer.

1) If I had 10 gallons of 93 octane mogas with 10% ethanol would I have 9 gallons of gasoline and 1 gallon of ethanol?

2) If ethanol absorbs water, and I added 1 gallon of water to the 10 gallons of ethanol enhanced mogas above, would I get 9 gallons of gasoline floating on 2 gallons of an ethanol/water mixture?

3) If so, could I now drain the 2 gallons (should be visible as clear) from the bottom of the resulting mixture and have 9 gallons of "pure" (ethanol and water free) gasoline?

4) And finally, if somehow miraculously this all worked, would I still have a 93 octane rated gasoline leftover?

Sounds too simple but just wanted to ask.

 

[pierre smith]

Good ol' down home common sense..

...is what you have!

I taught an English teacher how to test for ethanol and it went down exactly as you suggested. The students used a tall, glass container, marked in ten one inch increments and put in an inch of water. They then added 9 inches of 10% ethanol gas, (at a gas station), shook up the mixture and watched the water 'suck' the ethanol out of the fuel, increasing to 2 inches of clear water/ethanol.

Best,

 

[hecilopter]

Really???

Thanks Pierre. I wouldn't have believed it, sounds too simple.

I just looked it up and Ethanol has an octane rating of 113. If I remember my high school math, the resulting octane after the Ethanol is removed, assuming starting with 10 gallons of 93 octane gas/ethanol blend:

R = gasoline only octane rating

(1 gal ETOH * 113 octane) + (9 gal gasoline * R) = 10 gal * 93 octane

113 + 9R = 930

9R = 817

R = 90.77 octane rating.

My Superior XP-360 is approved for 91 octane or higher. Hmmmmmmmmm....

 

[Greg Arehart]

Rusty,

What Pierre said is correct and you have the calculated octane correct. Actually, there is a slight difference in density and a few other little corrections, but they are so minor as to not make any difference. Make sure you give your mixture time to separate completely. And note that even if the pump says 10%, it may be less so you might not ever get two gallons of ethanol-water mix. Usually by law the ethanol content is 10% maximum, but may be less.

Cheers,
greg

 

[nomocom]

BAD IDEA

Not being a chemical engineer, just thought I would ask a question that an engineer could answer.

1) If I had 10 gallons of 93 octane mogas with 10% ethanol would I have 9 gallons of gasoline and 1 gallon of ethanol?

2) If ethanol absorbs water, and I added 1 gallon of water to the 10 gallons of ethanol enhanced mogas above, would I get 9 gallons of gasoline floating on 2 gallons of an ethanol/water mixture?

3) If so, could I now drain the 2 gallons (should be visible as clear) from the bottom of the resulting mixture and have 9 gallons of "pure" (ethanol and water free) gasoline?

4) And finally, if somehow miraculously this all worked, would I still have a 93 octane rated gasoline leftover?

Sounds too simple but just wanted to ask.

Not chem E, but very familiar with ethanol and gasoline.
1)yes
2) mmm, pretty much, but the separation will not be perfect or complete
3) you will have "wet gasoline" and an ethanol/water mixture that has gasoline components in it as well. Think about why the BATF was OK the use of gasoline as a denaturant. It's darn hard to completely separate. Once the fuel ethanol goes out of the factory with gasoline on board... it's effectively denatured, undrinkable, very difficult separation, which protects our governments liquir tax income.
4) you'd have a big question mark and probably some haz waste (can't drink it, can't burn it in an engine, so what will you do with it?)

 

[airguy]

....except that the "base stock" fuel to be blended with the ethanol IS NOT the same as standard gasoline. The blend is different, to account for the higher octane of the ethanol, such that the base blend is actually considerably lower. When you remove the ethanol, you are not left with "gasoline" as you know it - you have base blend stock for E10 (and water saturated, at that) - different stuff entirely.

 

[Danny7]

....except that the "base stock" fuel to be blended with the ethanol IS NOT the same as standard gasoline. The blend is different, to account for the higher octane of the ethanol, such that the base blend is actually considerably lower. When you remove the ethanol, you are not left with "gasoline" as you know it - you have base blend stock for E10 (and water saturated, at that) - different stuff entirely.

yes. ni