Hydrogen Peroxide, Ethanol and Water 1

[seanbouk]

I'm designing an internal combustion engine for use under water. The fuel will need to contain it's own oxygen, so I'm looking for a monopropelant rocket fuel. I'm toying with Hydrogen Peroxide and Ethanol, with some water for stability and for better expansion.

I'm not great with the chemistry side. Can somebody here check my numbers? I'm ignoring the water for now until I get this bit right.

_____________________

C2H60 + 6H2O2 --> 9H2O + 2CO2

Ethanol: 46g/mol; 0.789 g/ml
Hydrogen Peroxide: 34g/mol; 1.4425 g/ml

46 / 0.789 = 58.3 --- 6 * 34 / 1.4425 = 141.42

The mixture should be 29.2% Ethanol, 70.8% Hydrogen Peroxide.

_____________________

Cheers.

 

[Chance17]

The number crunching looks OK. The equations are for "neat" solutions. Both ethanol and peroxide typically have significant water contents.

Your post prompted me to visit some hydrogen peroxide information.
I recommend going to Goggle and search "High Test peroxide".
This is solutions over 70% peroxide.
The Russian & British navy have both experienced significant accidents using "HTP"
You really don't need ethanol to create alot of energy.

 

[seanbouk]

Thanks Vitbos.

I don't think civilians can purchase better than a 50% solution of Hydrogen Peroxide in Water in Europe (don't quote me). That's still pretty potent stuff.

I think the navy must have been going for -

2H2O2 --> 2H20 + 02

Which I'm pretty sure I've heard of this being used in Jetpacks (jet belts, rocket pants et al) too.

If I were to assume I start with 50% hydrogen peroxide and 90% ethanol solutions and mix them so the hydrogen peroxide and ethanol were in the proportions above I would have

17% Ethanol
41% Hydrogen Peroxide
42% Water

That's probably the least amount of water I could have in the final solution. But perhaps I would like even more.

Water increases in size 1600 times or so when turns to steam. I'm after an expansion, I'd like stability, so adding water sounds good. But how much is too much?

How do I work out what the ideal amount of water is? (seriously, I have no idea where to start in this one)

Ta.

 

[ChemOxGuy]

Before creating these mixtures, please take time to learn about ternary mixtures of H2O2-organic-water and their detonability. I've uploaded the diagram for the mix H2O2-EtOH-water for your review ...

http://files.engineering.com/getfil...4086-b0f6-3e3168320893&file=EtOH_diagram.gif.

This chart indicates that the mixture you state may be detonable (drop-test) and unsafe to store. Also beware of tranversing the detonable zone while preparing such mixtures (i.e., always add H2O2 to the organic-water mixture and NOT vice-versa).

 

[Chance17]

I'm sorry Seanbouk, I don't think I can offer any more good advise.
Be advised It is not realistic to assume perfect reaction at exact Stiochemitric proportions.
There has to be an excess reactant either ethanol or peroxide.

 

[seanbouk]

ChemOxGuy,

Thr line of stoichiometric composition doesn't seem to agree with my results. Perhaps I'm reading it wrong. It looks to be suggesting about 4:1 ethanol to hydrogen peroxide. More or less reverse of my calculations. That's brilliant if it's correct - cheaper and safer.

What's going on? Am I reading the diagram wrong? Are my calculations wrong?