[hvymetalalchmst]

hi, (i think this is inorganic...)

im into nitro rc cars, and a major problem that comes up again and again is the way methanol absorbs moisture from the air, hence making the fuel stale and difficult to use.

i have done a lot of googling in hope to find a way to find a dessicant that can dry moisture from the air AND draw out the moisture (and ONLY the moisture) from the methanol-based fuel.

the fuel we use is approximately 20% nitromethane (CH3NO2), ~15% oil (mix of synthetic and castor) and the rest of the 65% methanol. these % are v/v.

i have a pretty sound knowledge of the basic and moderately-advanced chem, just in case you all wanted to know

Ultimately, what i want, is a solid that removes water, not methanol from the methanol-based fuel without dissolving into the fuel/water nor adversely reacting (pH or redox) with the fuel/water.

note that the fuel is ignited in an engine that has chrome, brass, aluminium, and cast iron.

i want this substance to be relatively readily available, for obvious reasons. ive looked up magnesium sulfate which dissolves in methanol. and right now, im currently trialling calcium sulfate.

ive wikied desiccators, but info on which chemicals will NOT dissolve in methanol is rare... so im hoping the experts here will know .

thanks, any help will be greatly appreciated.

[hvymetalalchmst]

edit: but cant find it yet... dont bother with cuso4 namely cos there will be a redox reaction

[Borek]

molecular sieves?

[hvymetalalchmst]

yeah, but i need to know what size pores, since water, methanol, nitromethane are both really small molecules.

also, i need to know WHERE i can get this. if its at a chemical supplier, im more than happy (since its reusable).

thanks for the input tho.

[hvymetalalchmst]

wait.. but the oil! the oil wont come through... i want to, if possible, to be able to filter the water and only the water from fuel.

[Arkcon]

I think this topic has come up on this board before, you may be able to search for it.  As I recall, if you need small amounts of methanol or isopropanol, and I think RC cars don't really need much fuel -- no matter how many you have or want to supply fuel for, the easiest way to get it is to purchase the small bottles of automotive fuel line antifreeze.  They are sealed bottles of anhydrous alcohol. 

This may not sound as cheap as making your own, but maybe it is -- molecular sieves, sized for water and not methanol, purchased from a chemical supplier, aren't necessarily inexpensive.  Research laboratories aren't known for searching for discounts, they are willing to pay a premium price for convenience, and suppliers tend to follow the money, as it were.

[renge ishyo]

I take it distillation is not an option because of the nitromethane?

[hvymetalalchmst]

i presume so. but i know that water and methanol make a... uhh.... cant think of the word right now...

they become one solution, hence cannot be distilled.

will molecular sieves pass allow (castor) oil through?

there has been some debate in rc forums on the actual effect of water in fuel, but its always nice to play it safe. if there is no easy and straightforward way about it, i guess i will just have to live with it.

[Arkcon]

Azeotrope.  It comes up often, on these boards, so it's on the top of my head.   At any rate, if you used a bulk drying agent, on a large volume of solvent, you'd get all the water absorbed, and a fair bit of drying agent dissolved in the solvent.  Then you'd distill that, to get dry solvent.  That's probably where renge ishyo: was going with that.  Even for methanol, that is a little risky for the home user.  In organic labs, whenever possible, we distill anything over a steam bath, not a flame, to avoid igniting vapors.  It's not likely you have a high pressure steam boiler around.

[DrCMS]

i presume so. but i know that water and methanol make a... uhh.... cant think of the word right now...

As Arkcon said the word is azeotrope but methanol/water dosen't form one and methanol can be can be distilled out of water. 

As you want to do the opposite and get a small amount of water out of a methanol/nitromethane/oil mixture then distillation is not what you need.

I'd use molecular sieves.  They come as pellets that you dry in an oven and they add to the liquid to be dried.  They may remove some of the methanol & nitromethane aswell as water but you have much more of them than water so losing a bit of them will not effect the fuel much.

[hvymetalalchmst]

thanks everyone for your input. ill do some research on molecular sieves and see how it works.

once again, i appreciate all the help offered.