Sciencemadness Discussion Board

High pressure h2 production

pip - 18-12-2011 at 22:47

Through searching many websites it seems that it the standard hh0 electrolysis of obtaining h2 when done at high pressure is a safer and more economic way of obtaining pressurized hydrogen as the hydrogen doesn't need to be pressurized in a separate step. Unfortunately I haven't been able to get access to the patents or information on what to build the apparatus with. I have extreme skills when it comes to figuring out practical design with built in safety mechanisms especially as standard pressure h2 generators are very simple.I plan on building the water tank to h2 and 02 receivers in the right proportion as to use the conversion to the gaseous state as the source of pressurizing the apparatus. And if the water chamber and gas receiving tubes are designed right contamination of the gases can be avoided. I like the idea of using easily available smaller sized CO2 or 02 tanks to store the h2. I still haven't researched whether aluminum or steel tanks are less porous to h2 but I can handle that myself. (loss of h2 is to be expected but could be manageable, they do sell h2 commercially in some kind of metal bottle and if it turns out to be a carbon fiber bottle then i'll get a nitrous bottle for cars.

This is where I need help, I don't know what metal I should build the apparatus from as it can't react with h2, o2, water, salt, and electricity's effects of the chemicals. I can wield it if its 1 metal. I am open to building the apparatus with many different metals to handle the respective reactivities of the chemicals they contain but cross metal electrolysis would have to be considered along with sealants which could be an extreme annoyance.

I truly believe that if the great minds here work together high pressure h2 could be easily made and stored conveniently at home with no "chemicals" needed besides water but what non chemists considers water a "chemical" (cops, judges) so from a legal standpoint it would be the best option.

I know I ask a lot of questions but i do go through with a lot of simple things although I don't post any results ever. so I will be building this either way but my target psi is 2000 so help for safety reasons would be appreciated.

[Edited on 19-12-2011 by pip]

johansen - 19-12-2011 at 04:19

short answer: please do not attempt to kill yourself.

you could have enough oxygen diffuse though your electrolysis cell to detonate inside the h2 tank.

longer answer: assuming you can handle the h2 problem, how do you go about building a differential pressure regulator to prevent the electrolysis cell from bursting?

fledarmus - 19-12-2011 at 04:56

There are commercial systems that do this, but I know very little about them. Here is one application:


Hydrogen is generated on demand from water, and the reaction can be pressurized up to 100 bar. That might be a starting point for you to reverse engineer...

ScienceSquirrel - 19-12-2011 at 08:32

I suspect that the hydrogen in the H-Cube is generated at low pressure and then pumps are used to pressurise the hydrogen, solvent and substrate.
I suspect that it works in a similar way to a HPLC. The solution of the substrate in a suitable solvent is saturated with hydrogen. This is then pumped througn the catalyst cartridge where they react. The product is then recovered at the other end.
Cunning, wish I had though of it!

Bikemaster - 19-12-2011 at 09:27

It is a really bad to do the electrolysis at high pressure... I don't know if you ever hear Henry constant, but if you do the electrolysis at high pressure, you will dissolve a lot of oxygen in your cell. Then even if you made a good system to separate the hydrogen from the oxygen, you will get a lot of oxygen in your hydrogen.

Also, you have to think about a way to purify the hydrogen before to compress it, because you will have oxygen, water, CO2 and NaOH in your hydrogen flow and if you put all of this in a metal container it will rust, even in small amount.

There is two I can think of at the moment.

First, you can use a palladium hydrogen permeable membrane. It will only allow the hydrogen to pass through and all the impurity will stay on the other side. The only problem with this solution is that the membrane cost a lot.

Secondly, you can purify in many step.
1. acido-basic scrubbing of the NaOH and the CO2.
2. calatytic oxidation of the hydrogen to use all the oxygen, then now you only have water and hydrogen in you mixture.
3. Remove almost all the water with condensation.
4. completely dry the hydrogen with CaCl2 and then compress it.

The best compressor I can think of it the small compressor they use to fill paintball tank. They can go up to 3000 psi and with some electricity basic you can ajust the flow rate just perfect with the flow of your hydrogen production.

Good Luck!

pip - 19-12-2011 at 22:44

Its a waste of time going this route I guess. thanks anyways I'll just save up for a pump capable of pressurizing hydrogen safely.

unionised - 20-12-2011 at 07:14

I think it's probably a waste of time trying to do this at home, but it's certainly possible because things like this do it.

ScienceSquirrel - 20-12-2011 at 07:50

They do make hydrogen under pressure by electrolysis but the separation technology may be a bit above bodge level

[Edited on 20-12-2011 by ScienceSquirrel]