i stole this from the Link forums but since not everyone has access i thought i would post it here
http://codsm.org/forums/showthread.php?t=3965and for those who will not follow the link:
So I got a proton NMR of the E85 that I'm using, and man, it looks like it is almost all ethanol. It looks like E90+ to me (which is bizarre considering that this is supposed to be E70 right now). There is gasoline in it which is the next biggest part, then maybe 1-2% water, and a few unknown trace compounds. It will be the trace compounds that I will look for in the sludge.
The machine integrates the peaks so that you get a relative quantity measurement between them. The calculation is a little tricky because a molecule of ethanol is much lighter than a molecule of gasoline (octane) but it also has fewer hydrogens. Ethanol has a molecular weight of about 46 and has 6 hydrogens and octane has a molecular weight of about 114 and has 18 hydrogens. If I ignore everything else, the machine is showing that the 6 hydrogens of ethanol account for about 93.5% of the area and the 18 hydrogens of gasoline account for 6.5% of the area. So from there is is easy to calculate the mole %. First of all, since there are 3X as many protons in gasoline, the 6.5 area % is 3X its mole %, so that would be only 2.17 mole %. But, since gasoline weighs 2.48X more than ethanol, that pushes it up to 5.4 weight %, or about E95.
There is an obvious problem with that, though, and that is that I don't know what all the mystery peaks are. They aren't calling it E85 because it is 85% ethanol and 15% gasoline necessarily. Perhaps it is 85% ethanol, 5% gasoline, and a 10% mixture of other crap. Or, some of the gasoline protons could be buried underneath ethanol peak C and I'm counting them as ethanol when they are really gasoline. Anyway, here is a higher resolution picture of the NMR:
So I let the goo sit out in the open overnight to let the E85 evaporate, and interestingly it still reeks of E85. That implies that this material might be hydrogen bonding or something similar and not allowing the ethanol to evaporate. This is consistent with my hypothesis. I'll put it under high vacuum to pull the volatiles out before I analyze it.
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Alright, I finished my analysis of this stuff, and my finding is very unexpected. I think it will probably surprise everyone else as well. This doesn't appear to be forming because ethanol is "such a good solvent" but because ethanol is a poor solvent. I suppose it should have been obvious when others said that it "washes right off with gasoline". Why would something that ethanol is selectively dissolving wash off with gasoline? If this were something in rubber or from our fuel tanks, wouldn't that imply that gasoline would dissolve it even more readily than E85?
Alright, so what is this stuff? It is a appears to be a very large petroleum based hydrocarbon, similar to Vaseline. There isn't a single hetero-atom in the molecule (ie, the entire molecule is comprised of hydrogens and carbons), but the molecule is very large. It is also completely aliphatic (ie, only single bonds in the structure - no double or triple bonds). Where did it come from? I can only think of two different sources it could be coming from. It is either something that is mixed in with the rubber hoses that is meant to dissolve away in the gasoline, or it is a trace impurity in the 15% gasoline that is in E85 that wasn't separated during the fractional distillation process. Because it is such a large molecule, it wouldn't be very soluble in ethanol and could easily crash out of solution at the injector.
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Well, here is what I did just so everyone is clear. I filled a 40mL vial with E85 and blew it dry with nitrogen gas and mild heating (about 150*F). After there was no fuel left, I placed it under high vacuum to remove any remaining volatiles for about an hour. I was left with a clear sticky residue that smelled bad - like nasty frying oil. I dissolved this sample in the NMR solvent and analyzed it and it IS the same goo that was on the injector. There was smaller amounts of some other stuff in it as well, but the same peaks I saw in the black goo were in this residue. The black goo IS coming from the E85. It isn't naturally black, though. I suspect it just has soot mixed in with it that is giving it the color.
So the next challenge is figuring out why is this crap in our fuel, and if it is in everyone's fuel (particularly people who aren't having this problem).
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