10-18-02 21:52
No 370006
Perhaps brother barium knows, but before one sacrifices precious precursors in the attempt, what would be the procedure to test a home made Raney-Nickel or Pd/C catalyst to make sure you got it right? Is there anything otc to reduce that would be easy to measure so one could determine the efficiency/effectiveness of the catalyst?
Infinite Radiant Light - THKRA
(Pioneer Researcher)
10-19-02 06:32
No 370120
I got well and new commercial catalyst, so I could compare it with my homemade one. I made a solution of am formate in methanol, then I put the same amount of commercial Pd/C (30 mg) and muy own catalyst in two equal portions of the solution, and observed the activity. My homemade catalyst had less activity and in the next hours decreased, while the good one presented more activity and didn't decrease. I was dissapointed, and didn't store well my catalyst. After a few days I made the test again and it presented much less activity. It was made with pet store charcoal moltered in a coffe grinder and purified heating it in aq HCl and PdCl2. I've made it from different ways, CHO, NaBH4 and even Al/HCl, but its activity has been always too low to get something satisfactory. I wonder if the problem is the support, so I've thought in make Pd/BaSO4.
About Ni catalyst, I took some NiCl2 and reacted it with aq. NH3, till precipited the metal, replacing the solution with a am formate one, I didn't observed any kind of activity, no bubbles. It wasn't a very cared test, but I didn't see one bubble of H2/NH3/CO2 formed in the metal, and I had no reason to think it could work as I did. I've read that Raney Ni can be used in CTH, may be I was too dirty in my test.
So, in conclusion, take a bit of catalyst and put in a solution of formate (that can be make in situ with formic and ammonia or with NaOH and formic, it works, I've seen it) and see what happens, and let it work during hours, you should see a clear and persistent evolution of gas, but it could not give a clear idea if you don't have anything ok to compare.
I know they are not the best news, but the problem of the homemade Pd/C is a question I have yet not solved.
(Hive Addict)
10-19-02 18:45
No 370224
So, what I could do is to take a solution of Amm. Formate, add the catalyst in a sealed container, with a hose to an inverted graduated cylinder full of water, and measure the gas released by the process, similar to the H2O2 activity tests.
That should give me a metric to test the catalyst activity against... as well as being able to compute how much to use right?
Infinite Radiant Light - THKRA
(Hive Bee)
10-19-02 19:08
No 370233
Yes, this is also a good way to se how quick the amount of hydrogen is released. it should not be released too quick.
Sunlight:
You didnīt make Raney-nickel, rather some inactive pecipitated complex. Try Urushibara-nickel instead.
Catalytic hydrogenation freak
(Pioneer Researcher)
10-20-02 21:02
No 370531
Yes, it was not Raney Nickel, and I thought that it was precipitated Ni. It was ferromagnetic. I was convinced for any reason that plain ammonia would precipitate de metal from the salt, but after reading you, I've checked the equation and I need two protons... wow, it seems I was too stoned that day. Nice, I can try NiCl2 + Zn or Raney Nickel...
(Pioneer Researcher)
10-20-02 23:22
No 370566
I've thought a while about the Ni catalyst, and now I remember that what I made is to precipitate the Ni form a NiCl2 solution with Zn and aqueous NH3, where the released H2 from Zn and ammonia reduces the Ni salt. I thought it was the same that making and urushibara with Zn and washing it with ammonia. I took it from a sample of a rdxn with Zn-Ni couple to form a primary amine from the ketone and ammonia (if I remember correctly).
In fact there was Ni metal precipitated, ferromagnetic, and it didn't react with the am formate solution. May be the procedure poissons the catalyst with some complex, so it could be interesting to make it in a classical way.
(Hive Bee)
10-23-02 20:00
No 371826
Sunlight, reduce your Pd/C catalyst using pressurized H2 gas in a hydrogenator for 4-5 hours. It will be just as active as commercial catalyst. SWIM has never used it for the ammonium formate, nitroalkane synth that Beaker used, but for hydrogenations it works just fine. SWIM has never reduced catalyst using formaldehyde, formic acid, NaBH4, or anything else; just hydrogen gas.
The hydrogenation can be done in a simple erlenmeyer flask with the the rubber stopper clamped down, using a pressure of about 30psi (~ 2bar).
(Pioneer Researcher)
10-23-02 20:27
No 371833
Thanks for your input. I know the procedure, but here is a bit hard to get a hydrogen cylinder, or it is complicated to install it in an apartment. It's easier and even cheaper to get directly the Pd/C here. I've always been interested in making a good catalyst in a easy way and OTC, that's the reason for the reasearch that has been unfortunately disappointing till now.
(Hive Bee)
10-26-02 21:29
No 372953
Nobody said SWIM ever had a hydrogen cylinder either. Hydrogen cylinders are most definitely watched, large, and dangerous to work with unless you have proper experience. The gas is easy to produce OTC and pressurize directly in the hydrogenation vessel. It can be described as two hydrogenation vessels connected to one another, with one containing dilute sulphuric acid and aluminum, and the other containing the thing to be reduced. The entire system is flushed with argon before the aluminum begins to react with the acid, then it is closed off and the pressure is allowed to build. When the pressure is high enough, the reduction vessel is closed off from the hydrogen generator and the generator is vented off. Very simple, very manageable, works great.
(Hive Addict)
10-28-02 00:50
No 373380
what kind of glasswre or other apparatus do you use for generation of the pressurized h2?
will rb flask etc work?
Infinite Radiant Light - THKRA
(Pioneer Researcher)
10-28-02 21:18
No 373731
The Al rxn, at least with aluminium and HCl or NaOH is very exhothermic and uncontrolable, it produces hot hydrogen and I guess that the pressure thing could be hazardous. Perhaps it is possible to find the proper concentration of acid and cooling etc... and may be it is very easy, but I discarded it. Have you made it with your own hands ?
(Hive Bee)
11-02-02 21:26
No 375798
ClearLight, SWIM would never use any glassware in such a reaction. There is no advantage with being able to see the reaction. Use stainless steel for the reaction vessel, and some metal tubing with endcaps and adapters for the hydrogen generator.
Sunlight,
Perhaps it is possible to find the proper concentration of acid and cooling etc... and may be it is very easy, but I discarded it. Have you made it with your own hands ?
Yes, but no cooling is needed. SWIM does not use HCl or NaOH, he/she uses extremely diluted H2SO4. It really depends on how fast you want pressurization to occur. SWIM has had it run very hot, and pressurization occurs in less than a minute. Or with a higher dilution, pressurization has occurred gradually over several minutes.
SWIM thinks maybe you do not understand the setup of the hydrogenation. There are effectively two seperate containers, connected together with a tube and clamps. One is charged with the reaction mixture, the other is charged with dilute H2SO4 and Al. The reaction between the acid and the Al usually takes about 1-2 minutes before becoming extremely vigourous. During this time, flush the system with argon. As the reaction begins producing hydrogen, close the system and allow the pressure to build. When pressure has been achieved, close valve and disconnect the hydrogen generator. Let the hydrogen generator finish its reaction somewhere else, its job in the hydrogenation is done.
Maybe a picture is in order?