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Acid water as a fuel

Released protons in aqueous medium get burned by fluorine
(+2, -2)
  [vote for,

Any soft acid medium (even a neutral medium) contains a share of ionized molecules. H20 -> H3(+)O + OH(-)

If, say, H3PO4 is kept in solution it can release 1, 2, or even 3 protons per molecule, which are not 'free', but hydrated as H3(+)O.

Good. Now, say the proton is the reducer agent. This way, we prevent the use of any Carbon molecule as a fuel. And what about the oxydizing agent? Not O2 in the air, that's for sure. The most electronegative element, Fluorine, which is easily kept in plastic containers.

The exothermic reaction:

proton + fluoride -> HF + energy

Admittedly, the developed formula is:

2 H3(+)O + F2 -> 2 HF + 2 ENERGY

HF is not a very strong acid (pKa = 3,5). But, it presents abnormal boiling point (293 K), because of the hydrogen bonds HF molecules can build among them.

This would render dissociation in aqueous medium, so that F2 gets recycled:

2 HF + 2 H2O -> 2 H3(+)O + 1 F2 [gas]

The buffering effect (keeping pH almost constant) would be provided by H2PO4(-) and HPO4(2-) species, the cognate bases for phosphoric acid.

Then, the steam-machine power scheme could be easily adapted so that the energy from the reactor activates a turbine, and that's it!

I know it's halfbaked, but... can anyone see to some references?

mayihave, Aug 10 2007


       Erm, am I right in thinking that if you'd missed out the unnecessary steam/turbine steps, you would have just invented the car battery?
zen_tom, Aug 11 2007

       Hydrofloric acid is not something you want to have anything to do with period. There are much greater issues than just the strength of an acid.   

       "Deaths have been reported from concentrated acid burns to as little as 2.5% BSA."   

       This is not stuff you want to be anywhere near or involved with period. No questions asked.   

       Secondarily how exactly are you getting this solution to boil at 293K. You will not get that much heat out of the formation reaction. I think you just twiddled around in a chemistry book and found some nice sounding formulas that you dont understand.   

       Lets see you put some calculations together showing the number of jouls generated in the formation reaction the number of jouls required to boil the HF acid and seperated the H and F from one another. and exactly how much steam this would generate and then how much power that would represent.   

       I think you will find very quickly that the answer to many of these questions will be "not enough"
jhomrighaus, Aug 11 2007

       Yeah, I guess zet_tom is right.   

       For all other purposes, see below:   

       Enthalpy change per HF formed: -271'1 kJ/mol.   

       Depending on the acid you add at the beginning of the cycle, which is the real proton donor, well, pH DOES matter a lot. If pH drops below HF's dissociation pH, we'll never get F2 back!!   

       As for boiling water, I guess a starter would do, wouldn't it? 373 K (100ºC) is well above HF's boiling temperature, so the real problems are at the beginning and the end of the cycle.   

       (H+ input, for example very low concentration H2SO4, would render around 5,4 MJ/kg; as compared to ethanol combustion's 28 MJ/kg)   

       C'mon, man, I'm not an idiot, if I use chemistry, I understand the concepts behind that.   

       Could you solve, say, SO4(2-) excess? Would Ca(2+) drop as CaF2 or CaSO4???? Would Pb(2+) do better or worse than that? Explain your answer. I can also ask for the explosive mechanism of tri-nitro-toluene, then sit and watch you while you take your exam.   

       The proposal, anyway, is not to exhaust any CO2 at all, and the idea should stick to it were it to be baked. What's the point in trying to bio-fuel every single motor / engine in the globe? Not ecological concern, that much I take for granted.
mayihave, Aug 11 2007

       how exactly were you planning to generate the required materials with which to power your car(assuming your no CO2 discharge goal that is)
jhomrighaus, Aug 11 2007

       It would have saved me some time if you'd said this was intended as a means of energy storage rather than energy production.   

       So, the idea is to make acid and then react it with a fluoride, yes?
MaxwellBuchanan, Aug 11 2007

       [MaxwellBuchanan] got it right, acid + fluoride 'non-combustion'. Sorry I wasn't straightforward before.   

       Made some calculations on efficiency: It seems -540 kJ could be obtained per mol H2SO4. It takes +2260 J to evaporate 1 gram of water.   

       Roughly 4'2 Molar concentrarion H2SO4 (239 grams) would be needed for 1 liter of water to boil.   

       Under those conditions, sulphuric acid would yield 30 MJ/kg, outperforming ethanol combustion's 28 MJ/kg). Gave up on this one, though, because it would take real-world experiments to close the SO4(2-) cycle up -or whatever the anion involved.   

       Thanks for your comments, by the way.
mayihave, Aug 12 2007

       as I said, not enough.
jhomrighaus, Aug 12 2007


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