I have distilled nitromethane many times. I am going to presume your fuel is methanol based. You can get away with a simple distillation but your yield will be lower/have more methanol in it. I would recommend fractional distillation as it takes longer but can completely separate the fractions. I use a 40cm column and it does the trick perfectly. Start the temperature low so that methanol will just start to make it over. Go till no more methanol comes over. Than turn up the heat. Discard the first bit that comes over as it contains some methanol still. The fuels don't usually contain water but ensure your equipment is dried as to not introduce water as it can't be removed by distillation. Do not over heat it will decomposes if you go to hot. It will produce a bunch of nitric oxide and other bs. Overall pretty simple and well behaved, and the azeotrope is easy to separate.
