Melgar
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Inexpensive high-pressure gas pump
So, apparently this air pump is normally used for pressurizing air rifles, and can reach pressures of 30 MPa, which is 4500 PSI, or about 300
bar/atmospheres:
http://www.ebay.com/itm/112199567137
I ordered one, although I only intended to use it for pressures below 1000 psi. Turns out, upon reading the instructions, it can only be used to
reach those really high pressures when connected to a pressurized cylinder, and can only reach a pressure differential of about 3-5 MPa which is maybe
500-750 psi. These sorts of pressures are used by many different catalytic hydrogenation reactions, and since my hydrogenation vessel is rated at
1000 psi anyway, this seems ideal. Additionally, since it's possible to count how many times you pump the cylinder, you can calculate your hydrogen
volume used that way. Hydrogen can be supplied either from a cylinder, electrolytically, or from the reaction between aluminum and NaOH. Personally,
what I've found works is use a vessel with a shallow layer of NaOH solution in the bottom, and add a few straight lengths of wire that are long enough
to lean against the side, out of the solution. Hydrogen can be contained with a thick-walled plastic bag taped onto the generation vessel, as long as
there is only a very small pressure difference between the interior and exterior. This is also useful as a visual indicator of hydrogen gas volume.
Of course, it gets more complicated when you have a polymer reaction vessel which is somewhat hydrogen-permeable, so I'd have to measure the hydrogen
leakage with no hydrogenation reaction first, then subtract that from however much hydrogen is taken up by a given reaction. (Assuming ∆P <<
P) On the other hand, since this bottle is designed to contain CO2, which is nonpolar in its gaseous form, there will almost certainly be a polar
polymer there to prevent migration of nonpolar gases through it, so I don't expect hydrogen losses to be too significant.
Agitation would be done with magnetic stirring. Flushing would be done by putting the cap on loosely, adding several pumps of hydrogen gas, then
tightening the cap. Also, for safety purposes, there would be an outer PET containment vessel that would direct any (unlikely) explosive
depressurization upwards, where it would do less damage.
This would seem to allow pressurized reactions of at least 500 psi for less than $100 in equipment costs, with those costs being somewhat higher if
temperatures outside the range of thermoplastic polymers is desired.
[Edited on 4/21/17 by Melgar]
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XeonTheMGPony
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with a fridge compressor you can easily get 500 psi, prob is once turned off it won't be able to start till at atmospheric pressure so best way is use
a bleed return valve to set the desired pressure.
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