clearly_not_atara - 9-6-2017 at 13:12
http://en.wikipedia.org/wiki/Butanol_fuel
Despite the general consensus that the future is in electric cars, there are still cases where you need fuel: very cold places, where ionic conduction
doesn't work as well; airplanes, where weight is more important than volume or cost; portable motors and heaters, same thing; boats, ditto; any time
that waste heat is actually good; and so forth.
Butanol's great (less corrosive/higher energy density than ethanol), but the standard method of making it by fermentation produces about 30% acetone.
It would be cool for this not to be wasted, right?
There is a patent which discloses 2,2-dimethoxypropane as a gasoline oxygenation additive, but only in tiny (0.1%) amounts:
https://www.google.com/patents/US2878109
It appears to be a good candidate from its molecular structure: it should not form radicals or peroxides easily, although it is an ether, because it
lacks a tertiary or secondary carbon attached to oxygen. The patent suggests that the RON of 2,2-dimethoxypropane is above 100, which would certainly
be convenient if true. Plus the instability of ethers is usually suppressed by alcohols.
The resulting fuel would be about half butanol and half dimethoxypropane. ABE fermentation produces 60% butanol, 30% acetone and 10% ethanol. If the
acetone can be burned the yield of fuel is increased from 60% to 90%. If the resulting mixture remains usable with the addition of 10% ethanol, the
yield is 100%!
Metacelsus - 10-6-2017 at 03:53
Acetone would form ketals, not acetals. Still, this is a good idea.
In any case, there needs to be a cheap, high-yielding, and scale-able way to convert the acetone into the ketal.
[Edited on 6-10-2017 by Metacelsus]
Dr.Bob - 12-6-2017 at 11:39
That is a good idea, n-butanol appears to be a much better fuel than ethanol, and the waste acetone is not ideal as a fuel directly, it has a low
octane rating, I believe. But the methoxy ketal might be much better. It should have properties much like other low MW ethers/ketals.
A sad part of the whole fuels mess is that MTBE is now almost completely gone, when it had many good properties, it has a good octane rating, was
cheap to make from cheap commodity chemicals, has low toxicity (compared to most fuel additives), and is storage stable, non-hydrophillic, and does
not freeze too easily in winter. The only real problem is that it is slightly more water soluble than straight hydrocarbons and tastes bad, so it
was easily detected in water wells when it leaked. This seems like a good, canary-in-the-mine, type of feature, but many people did not like being
able to detect leaking fuel tanks easily, so they just got rid of it. Even methanol makes a better fuel additive than ethanol (in amounts over a few
percent), and it is very cheap to make from natural gas. They are also looking at Dimethyl ether as a fuel replacement/additive in some cases.
tsathoggua1 - 14-6-2017 at 06:37
Can anybody else picture the scummier elements of the 'cook' type clandestine chemist element, the ones who go round nicking anhydrous off farmers in
the US raiding fuel tanks for cryogens if DME became widespread as a fuel? 