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Production of minute amounts of dry H2 gas

I need a relatively simple way to produce a few milliliters of dry H2 gas. I do NOT want HHO and I do NOT want electrolysis of water, I also would like this method to produce little to no water as a byproduct. I'm looking for generators because  the minimum tank size of hydrogen I could buy (unless someone could locate a supplier in the UK that would sell me something the size of a propane tank or smaller) is far too large.

I'm Interested in a chemical reaction or hydrocarbon cracking method that would require a maximum of 200 degrees C if it requires energy input, but I don't mind if it's terribly exothermic (unless its an thermite-like reaction, then we have a problem) since I have a very effective cooling system in place for it and the rest of the system.

I forgot to add what its for, glow brazing. It'll be ionized and remove surface oxides while simultaneously heating the parts to be brazed.

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PedroDaGr85 years ago
If you have a means of handling bulk pyrophpric reagents, one off the wall is using a metal hydride such as NaH (bloody reactive) and reacting it with a low volatility alcohol such as octanol to yield H2(g) and NaOctanide. Now you would likely need a way to control this reaction because mixing them together would be rather crazy, maybe adding the alcohol dropwise. You can purchase anhydrous octanol octanol has a relatively high boiling point of almost 200oC, which is why I mention that one in particular.

Also, BOC UK sells a 14cmx85cm tank of H2 gas. It is taller but skinnier than a propane tank. It appears to me by my rough estimates to hold a similar volume to a standard 20# propane tank.
lemonie5 years ago

Dry?
If you produce a stream by electrolysis it could be dried. Why not electrolysis?
Wet chemical methods can't be much better, I wouldn't think.

You might think of transfer-hydrogenation, but yer catalyst might be an obstacle.
Are you using catalysis in this?

L
The Ideanator (author)  lemonie5 years ago
Unless you know a way to avoid water rapidly evaporating in my high vacuum, then yes, it should be dry-ish. By the way, how fast does water evaporate into a vacuum?

I think the high-vacuum is important, why didn't you mention it before?
You can cook uranium hydride, and other hydrides, they may be your best bet for that sort of thing.

L
What about a molecular sieve, in line to dry it ? I've suggested that already. The kind of drier they use in refrigeration systems would seem ideal. And they can be regenerated by heating AFAIK.

Steve
The Ideanator (author)  steveastrouk5 years ago
If we have something that would indicate the presence of water I don't see the harm in buying a chunk, machining some capillaries in it, and running a test under vacuum. That would by far be the easiest, and If we could find some that will grab up O2 and N2 as well than all that's necessary would be that and a simple HHO generator (especially if it can be heated in a vacuum to regenerate). I'm not sure if an off the shelf refridge drier would be best, should try it though.

How dry is necessary though? Sure the drying/freezing was my idea (in the sense that it was independently conceived), but seeing as you'll know more about the process than I, you'll have a better idea about what the requirements are.
You don't buy a chunk, you go to stores and ask nicely for a dryer.

Steve
The Ideanator (author)  steveastrouk5 years ago
Still cant test until that endmil is sharp :/

Yes, they can be rather "thirsty" materials, get quite hot in the process (an old test for activity being to sprinkle a few onto a damp palm).
However, under severely reduced-pressure I don't think so.

L
I never knew that. Does that make the process exothermic ?

Steve

Oh yes, nice oven-dried molecular sieves can get rather hot with some moisture ~(hydrogen-bonding)

L
The Ideanator (author)  lemonie5 years ago
Uranium hydride you say? Sounds unhealthy. That aside, I think low temperature hydrides could be our best bet (especially since you could get a fairly accurate representation of hydrogen volume via a dosing chart).

Yes, I knew guys who used a uranium triteride source for tritium gas, it heated one bed, and reabsorbed the excess on the other. It cycled the two beds back and forth.
Tritium being something you'd rather not risk leaking of course.

L
depends on how hot it is.