Homemade Hydrogenation Equipment Project

[megalomania]

Homemade Hydrogenation Equipment Project

Keywords: hydrogenation; hydrogenator; catalytic; high pressure; hydrogen; homemade; improvised; microwave assisted

I am looking for volunteers to help me in a collaboration to build a working homemade hydrogenator. I intend to build a working and safe low, medium, and high pressure model as well as a microwave version. My efforts will be chronicled in an informal/blog style webpage that will hopefully be compiled into a how-to guide.

Catalytic hydrogenation reactions involving precious and non-precious metal catalysts and microwave assisted catalytic transfer hydrogenation are very useful reactions. Typically unsaturated organic molecules including alkenes, alkynes, and aromatic rings are hydrogenated, but the versatility of this reaction extends much farther to numerous other functional groups and heteroatoms.

Unfortunately professionally manufactured hydrogenation equipment is prohibitively expensive for most people. The homemade and improvised equipment to date is limited to safe operation at low pressures.

The key goal of this project is to build a working hydrogenation apparatus suitable for safe and routine operation of pressures up to 50 atm (725 psi; 50 bar). A secondary goal of the project is to devise a means of getting homemade hydrogen into the hydrogenator at that pressure. Additionally, I would like to build a high pressure hydrogenation apparatus capable of over 200 atm (3000 psi), and a low pressure hydrogenation apparatus made from non-metallic materials that can be heated in a microwave.

Sub goals include:
Cataloging the known methods of preparing hydrogenation catalysts and/or how to obtain them from chemical suppliers for inclusion in a how-to guide.
Compiling a library database of known books and journal articles that specifically discuss hydrogenation reactions or transfer hydrogenation.
Gathering together all known patents of pressurized vessels and containers, particularly hydrogenators.
Acquiring sources and vendors of pressure containers, hydrogenation equipment, pressure fittings, hoses, and gauges, and hydrogen gas cylinders.

This will be a misspent summer on my part. I plan to devote much of my free time and discretionary spending to at least trying to complete some of these goals. What I need from all of you is help. Some aspects of this project involve little more than surfing the web, but others can help by sending donations of money or equipment. Some of you may wish to try your hands at building a hydrogenator and reporting the results.

If you have any interests at all in this make your intentions known here. For those willing to offer more substantial assistance such as donations of time, money, or equipment please private message me so we can collaborate via email. I will try to get the webpage for this project up and running as soon as I have at least some information of substantive value. Hopefully this will encourage others to assist, and minimize duplicated effort. Again, private message me or use the email contact form (PM would be best) so we can coordinate what needs to be done.

[klassasin]

First off, I did PM you megalomania.

I believe that some real merit lies in this project. I saw a hydrogen generator in a local lab that costs thousands of dollars. Sadly, the basement (or w/e location you choose) chemist cannot afford such an item. Moreso, they cannot a vast majority of the equipment used for many chemical syntheses (including hydrogenation). Hopefully, the members of RogueSci can collaborate on making this a noteworthy addition to the RogueSci archives. I will help in whatever you need.

[azalea]

I was a tech in a chem lab years ago when a chemist wanted to scale up a hydrogenation reaction. He took one of those carry compressed air tanks (~10 gal), cut off the carry handle, charged solvent, the olefin, and some catalyst, placed a drum roller in a walk in hood, placed the tank on the roller, charged the tank with (if I recall right) 100 psi hydrogen, and started the roller. Everything worked great. A couple of times that day he stopped the roller to repressurrize the tank as hydrogen was consumed.

The problem arose when he let it roll overnight. The tank "walked" on the rollers and sheared the valve open. The contents must have spewed everywhere, but at least he had shut the hood sash so it didn't spray out too much. He also got very lucky that there must have been too much solvent in the air so the motor's spark didn't ignite the atmosphere. The walls, sash, and stuff were coated black from the catalyst.

I guess this would work, but you just better think through the safety aspects.

Azalea

[akinrog]

Sir,
I remember Rhodium's archives contain such improvised hydrogenation equipment. Since you should have Rhodium's archive, I think it's worth to take a look at it. Regards.

[megalomania]

Ahh, azalea, that idea of using a drum roller is brilliant. Necessity truly is the mother of all invention. I never of thought of using a roller like that. I have thinking along the lines of a rocker, but that idea seems much easier to implement. I don’t know if rolling would necessarily be as good at mixing the catalyst with the reaction mixture, but one could always add some baffles or fins to the inside, or even inert bits.

akinrog, I have all the articles from Rhodium’s archive already, and they are the starting point for my research. While I find those articles informative, I still think they are a little lacking on details.

[billybobjoe]

As far as the drum roller and your medium pressure hydrogenation (50 bar, 725 Psia) could you not use a 20 lb propane tank. The valve stem threads off and the tanks are rated well over a thousand psig. Also it just happens that the hole where the valve stem once was is 3/4" npt. I would just thread a high pressure ball valve and closed pipe nipple into it. With this system you could have you hydrogen tanks, high pressure or low pressure and a pump/regulator. A refrigerant pump comes to mind here. and all hooked up and flowing into one 3/4 high pressure stainless steel braided hose and then to a second ball valve with a second high pressure closed 3/4" pipe nipple.

As for operation, connect your nipple on the end of your braided hose/second ball valve. Check your hydrogen reserve pressures, if they are higher than what’s needed open the valve going to the regulator and regulate it down low to purge and remove all air, then close your purge valve and let your hydrogen pressure build up and then stick it on the rollers, and recharge as necessary. Conversely, if your hydrogen reserve pressure is too low open the valves on the pump side and purge as before and then again build up to the required pressure. Recharge as necessary.

The beauty of this as I see it is that most everything could be cobbled from spares parts, or found with minimal driving. The tank can be found anywhere they refill propane tanks, and the pump can be found at any appliance shop. The hoses can be found at the same appliance shop, and the valves and regulator can be found at a welding shop

[JouMasep]

This thread is dormant for some time, but it seems a significant subject.

I have operated a high-pressure hydrogenator once in a lab, but have only constructed a low pressure device myself. (Using self-generated hydrogen) But high-pressure or low pressure, the principles do not vary, only the construction. I am much more proficient at metalworking these days and I see no problems with a high pressure device at all. The biggest problem would be acquiring good (lab) grade hydrogen, at high pressure, without any stuff that may poison your catalyst. (No CO e.g.)

There are only two effective means of intimately mixing the reactant/catalyst/hydrogen gas media. 1) by way of strong agitation 2) by way of spraying the mixture through nozzles. Rolling does not seem an effective way at all and spraying offers only advantages once the volumes (masses) become too large.

You do not state the volume required, but it seems that for now, rocking is the way to go. Such a device is surprisingly easy to build. If it is of interest I’ll make a CAD drawing with outlines and details sometime.

OTC preparations of certain platinic catalyst could be found on the web. I still have one from Rhodium I believe.

Raney nickel should be doable by OTC. I myself have bought the stuff at the time, but it must be hard/impossible for most. I have a preparative procedure somewhere in my notes, but that is from Raney nickel metal -supplied. (Reaction with KOH solution). Anybody with a kiln or metal melting furnace should be able to make this metal himself! It is nothing but an alloy of 50/50 Aluminum/Nickel (First melt Aluminum in steel pot, then add same mass of nickel to dissolve –you don’t even have to reach melting point of nickel.)
If one can’t obtain pure nickel directly, it could be obtained by dissolution in acid of some high nickel content coins and selective electrodepositing of the pure metal.

Question: I am aware that microwaves can sometimes greatly accelerate reactions but is this indeed the purpose of your microwave idea? Would it otherwise not be much simpler to make a stainless steel vessel (have tig-welder or be buddy with chap who has one) from some appropriate tea-set item, and to solder a coil of some copper tubing onto the outside? This would give near-ideal temperature regulation.

At any rate, to build a shaking device entirely out of non-metallic materials would be an engineering challenge, but one may look at the option of “spraying”.

Everything could be outside the microwave, except the vessel and the tubes leading to- and fro, carrying the reactant/catalyst mixture, as well as the hydrogen supply. You would need a special pump that would be well sealed and resistant to the mixture, but this problem could be overcome.

To come back to your own idea; it should be well possible to construct a non-metallic shaking device as follows:

A-frame, carrying the rocker-with-glass-reaction-vessel and also part of the connection rod (as driven by outside eccentric pulley) all inside the microwave oven. –and all is constructed from appropriate polymers.
Connection rod goes trough hole in side of microwave. The rest outside is of normal construction.

The problem with this set-up it that there is only limited space in a microwave and the very nature of a rocking device would make the reaction vessel quite small. (I would stay away from the hole in the side of the microwave as well!)

One more question: You are aware that most hydrogenation catalyst are metallic in nature and that these could interact funnily with microwaves -or is that the very objective of the proposed set-up?

All in all I think that catalytic hydrogenation in microwaves is a very interesting idea, it may be feasible to reduce stuff that can’t be done otherwise -or only at extreme pressures/temps.

[megalomania]

My intentions with high pressure hydrogenation and microwave hydrogenation differ in their scope quite differently. The microwave route is specifically intended to avoid any need for a pressurized vessel, rocking, or any similarity with the high pressure methods. The purpose of high pressure is to force the hydrogen molecules into solution, and the use of precious metals will increase the reactivity of the rather difficult to react diatomic hydrogen. In the microwave, certain chemical techniques are used to make nascent hydrogen, which is both very reactive and already in solution, so no pressurization equipment is needed, nor are precious metal catalysts a necessity in as many situations.

I still would not mind building a high pressure hydrogenator, and an associate of mine, who is a professional welder, recently volunteered his skills. Subsequent to my original post I have found out many good things about the microwave methods that are encouraging. I am now of the opinion that microwave hydrogenations (on the scales I would use) are equal to or superior to any high pressure reaction. Therefore, I am no longer as keen on building (or buying) a high pressure system.

[DF90]

Im not sure how this is going to work out but I have spent most of tonight trying to design a reasonable apparatus for hydrogenation. If all goes well it will be able to compress hydrogen gas produced from a reaction (say Al + HCl) to some degree (not sure yet how good it will be).

Sorry if this isnt very useful at this stage, but if i manage to make one then i will come back and post feedback and hopefully (if it works) produce some kind of instructable so that everyone with access to a lathe and maybe a drill/milling machine can make one :rolleyes:

++++++++++

Take a week off. NBK

[JouMasep]

DF90,

About your method for producing hydrogen with “(say Al + HCl)”; may I suggest that you rather use heavy duty aluminium foil plus concentrated sodium hydroxide (from a dropping funnel), it works really well without having to worry about any unreacted HCL gas boiling out of solution due to the generated heat.

In fact the very reason why the NaOH method works so great and fast is the strongly exothermic reactions that take place.

Do not forget to include in your set-up two things:
1) A condenser (to get rid of most of the steam/water vapour generated)
2) Also preferably a gas-washing bottle containing 98% sulphuric acid (to eliminate the last bit of water vapour as well as any caustic vapours.)

As long as the rate of gas evolution does not rise through the roof and your condenser and gas-washing bottle can keep pace, you’ll get clean H2 -fast and cheap.

Note: of course, if you decide to seriously compress it, be sure to eliminate all air/oxygen. (Just to be safe!)

[JouMasep]

The purpose of high pressure is to force the hydrogen molecules into solution, and the use of precious metals will increase the reactivity of the rather difficult to react diatomic hydrogen. In the microwave, certain chemical techniques are used to make nascent hydrogen, which is both very reactive and already in solution.

Hmm, I’m not so sure if in most (any) catalysed hydrogynation reactions the “hydrogen molecules need to go into solution” in order to react with any unsaturated bonds.

It may be splitting hairs, but I seem to remember that first the hydrogen molecule gets adsorbed (“reacts” with-) onto the catalyst, which then facilitates the breaking of the H-H bond (lowering the energy required) So increased pressure will simply result in an increase in density of H2 molecules at the catalyst surface –without the need for this to go into solution.

Nascent hydrogen is powerful –even at low pressure, but it can be obtained without microwaves. (To be honest, I have no clue how it could be gotten with microwaves!)

It can be e.g. obtained by dipping Al foil into a mercuric solution and shaking this with the reactant in alcoholic solution.

What works also well is making up sodium amalgam- and use as above. I have used both (in my own lab) 1.2% and 40% (I seem to remember) sodium amalgams. The latter is of course kick-but powerful (and dangerous to make if you don’t do it exactly right!). The strange thing is that any strength in between is solid, but the two above are fully liquid. (40% is eutectic mixture)

I have no experience with the aluminium method, but I want to make clear that the three different ways of hydrogenation given here can give totally different outcomes on the same compound! Sometimes catalytic hydrogenation is the only/best way to go.

So if one wanted to saturate a double C=C bond, but without touching a certain present carbonyl (C=O) bond, nascent hydrogen would not be a good idea; it would become an alcohol!

I agree that the construction of a high-pressure hydrogenator is a lot of trouble –but once it works it is great fun! And perhaps the pressure needs not to be that high-get a better catalyst!

[megalomania]

I didn't mean to imply that the hydrogen goes into solution in the aqueous sense, but that a solution forms from the mixture of gas and liquid. In order for the hydrogen to react with the catalyst, and you are right that the catalyst surface is where the reaction happens, the hydrogen must be forced into the solvent. Hydrogen does not easily enter into a mixture with a solvent, so by LeChat's Principle we increase the pressure to force the solubility towards what we want.

Basically, before the hydrogen can react on the catalyst it has to reach the catalyst, and that's why we use high pressure.

In the microwave, the process is called "Catalytic Transfer Hydrogenation" (CTH) or microwave assisted catalytic transfer hydrogenation. A hydrogen donor, typically a formic acid salt like ammonium formate, is catalytically decomposed under microwave conditions producing nascent hydrogen protons .

The benefits of CTH include using a much more reactive single proton hydrogen rather than the comparatively unreactive diatomic hydrogen (before diatomic hydrogen can be used the catalyst must first split the hydrogen), the protons are generated in situ rather than having to force hydrogen into solution with high pressures, and microwaving of catalysts seems to create localized superheating effects at the cat surface which increases reaction rates and reactivity, while at the same time the solvent rapidly quenches the heat and prevents undesired decomposition or side reactions. Another good reason from the tight wallet perspective is one can use traditionally unreactive catalysts (non-precious metals) to accomplish hydrogenations that would be impossible outside of microwave conditions.

Microwave chemistry is a very new science compared to other traditional branches of research, and catalytic transfer hydrogenation is a subset of microwave chem that is newer still. There is considerable research on traditional high pressure hydrogenation, so a lot of people tend to stick with that, but I have a gut feeling a microwave can accomplish all of the same reactions and then some.

[Alexires]

Here you go Mega. I don't know what you have found, what you know etc, but perhaps this will help?

http://designer-drug.com/pte/12.162.180.114/dcd/chemistry/mw.cth.html
Some info on CTH.

http://engineering.osu.edu/nie/article.php?e=782&s=12&a=1
Thought this one might interest you. Perhaps some social engineering is in order?

http://www.freepatentsonline.com/4574038.html
A patent regarding Methane -> Ethene and H2. Perhaps it would be possible to catch the H+ with Ethanol or some other kind of H+ solvent.

http://aiche.confex.com/aiche/2007/preliminaryprogram/session_3942.htm
Catalytic Hydrogen generation for Fuel Cells. In particular, this (http://aiche.confex.com/aiche/2007/preliminaryprogram/session_3942.htm).

http://www.informaworld.com/smpp/content~content=a713747737~db=all
Just an article (you have to pay :mad:) about "Microwave Assisted Hydrogenolysis Using Zinc and Ammonium Formate"

...Ok scrap that, found it here on erowid - http://www.erowid.org/archive/rhodium/chemistry/debenzylation.zn-af.html

http://pubs.acs.org/cgi-bin/abstract.cgi/joceah/1999/64/i16/abs/jo981516s.html
Found this while combing erowid.

http://www.cababstractsplus.org/google/abstract.asp?AcNo=20033199977
"Catalytic transfer hydrogenation (CTH) of safflower oil was studied using aqueous ammonium formate as hydrogen donor and palladium on carbon as catalyst in a closed vessel under controlled microwave irradiation conditions."

Perhaps some of those will help in your research?

[DF90]

Thanks JouMasep, although I actually thought I had said to use NaOH... This was the typical method I was familiar with and thought it would be ideal as it produces three times the amount of hydrogen gas as opposed to using HCl...

I've been thinking about methods of compressing the hydrogen gas produced from the reaction into a steel hydrogenation bomb, but so far have not gotten very far :( If anyone who could make a suggestion then that would be much appreciated.

I think this is a very important project as hydrogenation can be extremely useful in the lab... I have access to the school workshop and am reasonably skilled on the lathe so making a steel bomb (in two halves, for easy filling of liquids and emptying) isn't a problem, although my initial intentions were like this:

Add the organic compound (either liquid or in solvent) and catalyst to the bomb, and replace the top half.

Fill the bomb with hydrogen gas using some type of valve (possibly a schrader valve from a bicycle?) to the required pressure (this might be hard using manual force, some sort of modifyed syringe was my first idea).

Using some sort of shaking device, heat the reaction vessel.

However if I can find some way of effectively compressing gas into the cylinder then there is no reason why gaseous organic compounds can't be used :P

I was thinking a pressure between 5 and 10 bar/atm would be effective on a small scale, and the steel bomb would likely have a capacity of 18cc, walls of about 6mm thickness. Is this sufficient? Or is it too much? I was planning on making the bomb from round steel bar with 37mm diameter. I was also wandering about reactivity problems of the steel, but stainless steel bar is available in 30mm diameter if necessary :D

[FUTI]

Does anyone knows how much pressure we can make using a Kipp's apparatus? I guess it max out at 3 atm. as that is the max pressure for most of glassware we use in the lab, but what is the real value of pressure I don't know...I should get my lazzy ass from the chair and took the paper to do the f*cking math myself, but if someone knows the number please say so...it will spare me a valuable time and save a few brain cells from apoptosis induced by boredom;). Then you could maybe use ordinary mercury safety valve calibrated to that pressure at the end (or in the midle) of a apparatus to maintain that pressure during reaction. This isn't in the line with original Mega's idea but since thread started to deviate already to other techniques I thought I may post this idea too.

[JouMasep]

Some thoughts regarding compressing hydrogen and construction of the hydrogenation reaction vessel (bomb):

I repeat the need for “cleaning” the gas and evacuating all equipment first before compressing the H2; the first is necessary because we don’t want water to condense in our compressor, the second requirement seems best as we want to avoid things going “boom” in our face. I add that if you want to use a fancy compressor and / or vacuum pump, you may want to run the gas through a washing bottle with NaOH pellets after the 98 sulphuric acid washing. It will save you corrosion problems in the long run.

I have some nifty metal working machines; but I’d still find myself a good refrigeration compressor (from old fridge) before I’d try anything else. The costs and efforts are about nil and we can use it (with a proper valve system ) for both evacuation and compression. It depends on the type and condition, but five bar should be easy to get.

If you then want to get higher pressures, you can then always do this in a second stage with a purposely build/acquired/modified compressor. building a single or double stage ringed piston- and-cylinder job should be not be a big deal for most amateurs-just make sure it does not leak and put your electric motor in a well ventilated position.

FUTI, A Kips apparatus is made of thick glass, but usually not all its compartments are spherical, so 3 bar seems a pretty good guess, I’d hate put it to much higher if it were my own. Kips types are not built to standardized specs; so it is impossible give a definite answer. If you are lucky and have a specimen that is all-spherical, quite thick walled and without scratching on the glass surface, I reckon that you could push it 4 or 5 bar. First give it a test with compressed air (behind a good shield!) and if you stay from then on at 80% or less in your hydrogen production, you won’t go wrong.

Look around in used tools stores and flea markets, all kinds of gages for measuring all kinds of pressure ranges abound. Car testing equipment, gas welding equipment, spray paint compressor gauges. It does not have to be 100% accurate. You’ll need a pretty tall column of mercury if you want to construct a safety release as you describe and want to go for 4 bar! Some spring-loaded ball bearing in a suitable seat (made out of epoxy/glass fibre) with the spring pressure adjusted by a simple screw, would be cheaper and more practical.

DF90, I find the volume of 18 Ml very small; if this is the size of the vessel, what is the volume of your solution and what indeed is the amount of dissolved unsaturated compound?

Also, the idea of a bomb is not quite the same as that of the usual hydrogenator; the former has a totally enclosed system, the latter is supplied with external H2 -as it is used up in the reaction.

This puts even more constraints on the practicality of your idea. With such a little volume/quantity of initial hydrogen gas, you’ll get a dramatic drop in pressure! (If you have at least some reducible matter present to begin with)

I’d use the following route: Make up a vessel by cutting off a short length of stainless steel (say 316 grade) pipe, say about 60 mm long with a wall thickness of 2 mm and an internal diameter to yield the required volume if the vessel. You can weld one end close with 2,5 mm sheet, or if you would not be able to produce a good weld, silver soldering/brazing will be well strong enough for the purpose.

The other end can be threaded with a fine pitch so as to receive a cap (from hollow stainless steel bar if you can’t get anything else) and a (silicone) rubber seal. The cap has a small diameter copper tube silver soldered into a hole drilled therein. This set up can easily withstand a 100 bar –your proposed 6mm wall thickness is seriously over the top-even if mild steel is quite a bit weaker than stainless steel.

The copper tube would be fed from a preloaded hydrogen tank with a good excess of gas. The tank could be made from some stainless steel tea set item –welded close. (The older sets can be of quite a nice wall thickness and can hold tremendous pressures, if properly tig-welded) This can be filled by a fridge-compressor as above.

Shaking could be done in a variety of ways but as 316L stainless steel is non-austenitic, you could in a cinch even use a magnetic stirrer! Heating could be then done on a magnetic stirrer/hotplate(in oil bath), but (tin) soldering a copper tube around your vessel and flowing hot water/oil through this will also work of course. (use HCl to tin-solder stainless steel)
Having the right size heating collar would make it easiest of course.

[megalomania]

For choosing the best metal for a hydrogenator I went to the Parr company website. They have a series of pdf's from their catalog that describe the types of steels they use for chemical resistance and high pressure use. I don't have them handy, but I know they are there. McMaster Carr should have bar stock for the specialty materials.

I then tried the patent database for Parr hydrogenator patents to learn some of their designs. I am not very mechanically inclined, so the drawings didn't make much sense to me. I have used a hydrogenator before, so I can better understand the drawings. They use a central screw in plug with a second screw on cap. The plug has a valve for attaching to a hydrogen tank, and the cap is attached for safety after filling. The walls are quite thick. The 50 mL vessel I used was about 1 cm thick as I recall, maybe a bit more. Again, the Parr website could offer insight to vessel wall thicknesses.

The biggest stumbling block I had was how to get the hydrogen into the vessel. I think a commercial hydrogen gas cylinder would be the best way, even though you are looking at a large initial investment. Considering the cost of generating that much hydrogen on your own and obtaining pressurization equipment, it should be about break even.

Where then to get a pressure valve that can withstand enough pressure. Conceivably a high pressure system should be able to withstand around 200 atm (about 200 bar, or 3000 psi) at the maximum. There are a few reactions that can benefit from such a high pressure, but most conventional hydrogenations will be in the range from 50-100 atm. The choice of catalyst affects the working pressure. Non-precious metals need higher pressures because of lower catalysts activity. Using cheaper catalysts should save you a ton of money in the long run, but you will need equipment capable of higher pressures.

For safety considerations your vessel should be rated to withstand twice the maximum working pressure. Another way to put that is never pressurize your vessel more than half of what it can withstand.

Your choice of catalyst can really affect the outcome of a hydrogenation. Research into hydrogenation reactions was begun about a century ago, and for much of the 20th century the use of precious metals was prevalent. In only the last 10 years there have been some amazing improvements in catalyst technology with more active non-precious metal catalysts coming into their own that are as active as their incredibly expensive noble metal counterparts. Precious metal catalysts tend to be more universal for a chosen application, whereas an alternative catalyst will have to be specific for a particular chemical being hydrogenated. Another technique being developed is supercritical CO2 hydrogenation. Some research has shown greater reactivity at lower pressure and temperature using supercritical CO2.

[DF90]

Its a shame we can't buy disposable hydrogen gas canisters, like the 390g ones filled with Argon gas or Carbon dioxide that are used for hobby welding :( I've tried looking for one but they don't seem to exist :( Compressing the hydrogen gas formed from a reaction with a compressor pump from a refrigerator is a good idea, but how would one go about making it work so that very little/no air is compressed also... It seems as if you would have to have a very fast rate of production, and using sealed apparatus (to prevent the introduction of air seems dangerous... it would create a strong vacuum, unless the gas was produced as fast as it is being compressed) Is there a simpler way to do it? syringes just don't seem cut out for the job :o

[JouMasep]

(I’ll address the “generous” specs. and margins of Messrs. Parr later on, but in the mean time it would be useful to look at the “tensile strength of the various materials” in relation to the operating pressures)

DF90, I second the idea to forget the syringe idea. (And I don’t like the purchase and hiring of the large cylinders; bloody expensive as you pay rent for long times when you don’t need it, non-OTC, and if you don’t use lab grade, how do you know about the purity/absence of catalyst poisons?)

To address your question: you set up a system of valves by which you first use the compressor to evacuate your H2 generating set-up. So you will not at first compress it but pump to waste. (Perhaps do this twice to eliminate all residual air) You could of course also use two compressors!
And only then do you compress the H2.

In order to prevent any problems with differential pump/H2-generation rates, you simply install a throttling valve on the inlet side of the compressor. Monitor the pressure before the valve and optionally install a buffering tank with pressure switch (can be had from refrigeration supplies)

But do not worry about pulling a slight vacuum; if you don’t trust the integrity of your seals, it would be best not to go this route. But getting a leak-free system is not rocket science.

For the glass part of the system, use greased ground glass joints -with clips!- or good fitting quality rubber tubing. (Cutting up inner motorbike tube into ribbons and tying this around your rubber tube gives a practical no-leak guarantee)

If you are half good at soldering, a well pre-tined joint in copper/brass/steel tube gives a hermetic seal –and it stays that way. Otherwise file/sand and polish your metal tube-end if it is not perfect to begin with, and treat as glass tube joint above.

Assemble your entire system dry. Then evacuate with compressor and bubble outlet of compressor through water. It may take very long, but if there’s no leak, there should eventually be no more air coming out. If it leaks, there will be bubbles all the time-simple. (Having a Pirani or other good gauge would be nicer of course!)

If you want to confirm a suspected leak: cover it with thick grease (or what-have-you)-the difference should show.

[DF90]

So the reactants need to be in larger amounts to account for the wasted hydrogen, then once the reaction is started (by opening addition funnel of NaOH onto aluminium foil), the setup is placed under vacuum caused by the compressor... then once all of the air has been evacuated from the setup, the hydrogen is then compressed into a tank/hydrogenation vessel? Won't the heavy vacuum have a chance of causing implosion in the glass apparatus? Unless of course I have mis-understood you.... I think that your suggestion would be great for filling an empty "disposable" argon gas cylinder like I mentioned above... Would it work to fill the ctlinder through the regulator? Its not one way or nothing? Thanks JouMasep

[megalomania]

There may be a way to get hydrogen cylinders for our use. The growing craze of hydrogen fuell cell technology is starting to manifest in kits for hobbiests and school types. I have seen a few places with small hydrogen cylinders, H2 generators, and pressure apparatus. While still pricey, the tanks and fittings are for a much smaller scale.

In the very near future, with each passing year, there will be an exponentially increasing number of places selling hydrogen equipment and storage devices at lower and lower prices.

[JouMasep]

DF90,
Al foil and NaOH are so cheap and plentiful; I used always a large excess.
WRT to the danger of implosion, I used a vacuum filtration flask (very thick glass) for the hydrogen production and a dropping funnel is hemispherical and conical in shape; there are no flat surfaces and hence they can well withstand any vacuum. (On pressure from the outside, a glass sphere only gets stronger)
Leave out the regulator; they are very much a one-way type of device.

Now about the specifications regarding the wall thickness of the hydrogenation vessel; there are three ways you could go about determining the wall thickness, a) guess and make it all so heavy that you know it must be safe (and make your shaking device correspondingly larger, more expensive), b) see how others did it and take their specs, c) determine your own specs from first principles and then apply a fat safety margin.

First of all: the choice of materials; for low pressure I had a vessel blown by my local friendly glassblower; it was a long necked 250 Ml round-bottom of extra wall thickness, with ground glass joint. (I have sometimes wondered what the hell they were thinking I was doing, but utterly correct and Swiss as they were, I never found out). But glass will not do for pressures over 5 bar. (Even if I am sure that that flask will easily take 10 bar).

For high pressure, I consider only steel and stainless steel. The latter I prefer for anything – except perhaps for strongly alkaline aqueous solutions as this tends to attack stainless more than carbon steel. I am unaware of any very alkaline hydrogenation solutions-rules out for me any carbon steel vessel, stainless is just nicer.

Of the stainless steels I prefer 316L (for low carbon) as this is both readily available, quite resistant to acid pit-corrosion and has yield and tensile strengths of 290 and 558 Mpa respectively. (way stronger than just about any carbon steel –which will rust like crazy without extreme care) The only disadvantage that I can see for stainless is that it machines rather more difficultly than steel.

So how thick must it be? Well let’s see if a two millimetre cylindrical s.s. vessel can handle some 160 bar- your typical pressure on bottled gas:
Dimensions: L=100mm, diam.=40 OD.
Total force on walls of cylinder lengthwise: 1631.5 kg. (Deduct wall thickness!)
Total strength of wall to point of yield (elastic deformation): 290 Mpa, or 2, 957 kg (take middle of wall thickness as circumference).

So this gives us a margin of 82% above the yield strength; the ultimate tensile strength is again almost double that. On a comparison of the force exerted on the vessel’s circumferential direction versus it’s actual yield strength the margins are even slightly more favourable.

Given that the welds are good and that the end flanges have sufficient (s.s.) bolts, I would do a hydrogenation at a 150 bar in such a vessel any day of the week. The end plates at the flanges have to be of course much thicker than 2mm –if you want to keep them flat.

[JouMasep]

By the way DF90,
To answer an earlier question directly (“and the steel bomb would likely have a capacity of 18cc, walls of about 6mm thickness. Is this sufficient? Or is it too much?):
I kept my little ad hoc spreadsheet and put in the values of: yield strength for crappiest mild steel: 248.2 Mpa, your OD of 37mm and your wall thickness of 6mm.
The result was that you would “not easily burst your vessel”-to say the least.
The pressure on the walls of your proposed vessel would give a resultant force -tangential to the radial direction- that would correspond to your inner diameter of 25mm. And that force, would be carried by twice the wall thickness.
So that force might be 248.2 Mpa times the amount of cross section of steel . (6 mm x 2) This equals 2978.4 Mpa.
This means that you may pump up your vessel to a pressure equal to this force divided by the diameter thereof. This equals 119.14 Mpa
Or 1191,4 bar!
Only at this pressure of over a thousand bar will the walls go into plastic deformation.
But it will take even more for the vessel to burst….

[NoltaiR]

While there is a lot of unintelligence roaming around this forum, there are also some very brilliant minds.

If there ever was a project in which some of the elites were to come together and work on, I could only dream of what might be created~
We just might put Area 51 out of business.

I have been doing a lot of negating lately so I will take this moment to commend JouMasep. At 11 posts he has contributed more useful information than many who have ten times as many posts. I think you will become one of our greats.

[asilentbob]

What? No mention of hydrogen embrittlement?

http://en.wikipedia.org/wiki/Hydrogen_embrittlement
http://www.mechanicalplating.com/hydrogen.htm
http://www.corrosionsource.com/handbook/testing/he.htm

Just looking out for you guys. :)

My thoughts have been similar to DF90's above (post #14 specifically). However:
1) A champagne bottle of sound strength and free from scratches as the vessel.
2) A regulator setup fixed firmly to the top of the bottle made from brass pipe fittings. This would include a hose barb/needle valve for releasing small amounts of gas and possibly directing them some where in particular. (So i could also use the same setup for temporary storage of produced gases or low boiling point solvents like butane.) A 0-150psi pressure gauge would be installed. A heavy duty "Schrader" valve (bicycle tire valve) would be installed to pressurize the system.
3) To pressurize the system a similar approach to a bicycle tire pump would be employed. (Very high pressures and quick reaction rates are not particularly important to me. I would be plenty happy getting a good yield of end product after several weeks.) The pump would have input and output hose barbs and a plunger assembly. Check valves would be on opposite ends of a T fitting with the hose barbs attached in turn to them in such a way that when the plunger is raised a vacuum is created pulling one of the check valves open to suck air into the plunger cylinder. Then on the down stroke the previous check valve would lock and the other check valve would open sending the air through the attached hose and into the reaction vessel.
4) The assembled champagne bottle and regulator assembly would be rolled on a ball mill at an inclined angle so that no liquid reagents make it into the upper regulator assembly. Inert filler material would probably be added to increase the surface area of the liquid and catalyst exposed to the hydrogen.
5) The hydrogen would be generated electrolytically as needed to re-pressurize the bottles from many DC aqueous sodium hydroxide cells run in series with their H2 and O2 outputs separated. Optionally one could fill big balloons with the hydrogen and oxygen for temporary storage, then suck the hydrogen out of them one at a time with the pump... though this would be very time consuming... and a fire hazard. Also the whole pressure problem created by the oxygen and how to use it is not addressed.

An example regulator assembly. In my case buying 2 T fittings and a close threaded pipe nipple was actually cheaper than buying a 4 way cross. Most of the brass fittings are 1/8" NPT. If anyone is going to buy a Schrader valve make damn sure you test it before you buy it to make sure it functions correctly.
http://img512.imageshack.us/img512/3355/92007004qx7.jpg

[JouMasep]

What? No mention of hydrogen embrittlement?
Hi asilentbob,

Naaah, don’t worry about that –it won’t happen with mild steel. ‘Knew about embrittlement, but frankly it did not enter my mind as a potential threat.

That problem you mention happens typically with nascent hydrogen, as generated on springs that are being plated. But other hardened steel can also be subject to this.

We won’t be using carbon (spring) steel -that has been hardened- in our setups. We are OK then.

After all hydrogen gas is sold in steel bottles –ain’t it?

I have doubts about some aspects of your proposed hydrogenation equipment. (I presume that when you say that “sending the air through the attached hose and into the reaction vessel” you mean “hydrogen” instead.)

You probably want to steer away from complicated machining, but to make a well sealing rotary joint may not be easy. (You made no mention of how you link your H2 feed line to your rotating vessel)

You want to optimize the reaction rate by adding ” Inert filler material” –you seem to know that rolling a bottle is not as good as shaking it. But do you know how VERY much inferior this method is?

At any rate, many catalyst come supplied already with such inert material. E.g. platinum-on-carbon. Adding some solids may marginally increase the effective area interfacing your compound’s solution / catalyst and the H2 gas, but not enough.

If you are prepared to wait for “weeks” for your reaction to complete, you could do it still a lot quicker by simply shaking the bottle manually intermittently. (Rest in between and do other things) No rotary joint, not even any equipment required. Four minutes of hard shaking could equal hours of rolling.

But it you want to avoid the trouble of making a simple shaker, just take a good bar magnet, (or big Teflon coated stirrer bar) mount another one on your drill and make a setup for kick-ass magnetic stirring. ‘Way better than rolling.

I would not use balloons for storing hydrogen for the long periods of time you mention; you will lose a lot due to diffusion.. Use the bicycle tires from which you took your valves instead.

The setup of multiple electrolytic cells to generate H2 seems a lot of trouble. What will you use for anodes? And remember, it takes a LOT of ampere-hours to make just one mole of H2. (From top of me head, about 54 hours at one Amp theoretical –add perhaps some thumb suck 15%)
To do a proper hydrogenation without dedicated factory bought equipment is not easy, but it’s still very feasible -by making your own equipment, using the right method.

Tip: if your compound is stable enough (must be if you can go at it for weeks) drive up the temperature, it goes quicker at elevated temps,

[JouMasep]

Further to allowable maximum pressures for (borosilicate) glassware, see this useful pressure nomograph for glass tubing.

http://www.ecu.edu/chem/glassblowing/glasspressures.html

If your equipment consists of only cylindrical and part-spherical components, you can take this as quite safe. Mind added caveat of scratches etc.

I reckon it’s OK to consider the limit for a certain cylindrical radius, to be likewise a safe limit for a spherical shape of same radius. (This is my own idea, nomograph is only for tubing)