I believe that you can remove the ethanol from gas by adding water to it. Shake it up, let it settle and siphon the gas off of the top. The ethanol preferentially attaches to the water. At least that's how we test for ethanol in gas for our race cars.
If you do that you'll remove most of the octane rating. The way ethanol fuels are made the ethanol is what gives it a good octane rating after removing it there's no way to know what octane your fuel is.
