Author Topic: HYDROGENATORS: what are you using for a vessel?  (Read 910 times)

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RoundBottom

  • Guest
HYDROGENATORS: what are you using for a vessel?
« on: September 10, 2002, 10:32:00 AM »
that's hydrogenators, the people, not hydrogenators, the machines. 

this is a general call for ideas... what are people using for a reaction vessel when they hydrogenate?  what are the requirements?  ability to withstand operating pressure of 60 psi, obviously.  is stainless steel a requirement?  are BBQ propane tanks suitable?  how about used aluminum gas canisters like D and E size oxygen tanks?  or a good old 3L 1N heavy walled RBF?

also, i seem to recall brass is not suitable for the valves and fittings because of cupric poisioning of the catalyst.  is this correct?  though most regulators are brass, so is this acceptable as there isn't much of an alternative?

who here is a fan of hydrogenation, specifically of MDP2P? 

thanks for listening.

my mouth tastes like burning.

TheBlindGenius

  • Guest
Regulators
« Reply #1 on: September 10, 2002, 01:17:00 PM »
You could get a Stainless Steel Regulator easily for just about any tank.  They are more expensive but readily available.  please don't use a RBF, we all want you alive a while longer  ;) .  Probably something rated to at least 80 psi.  Most commercial hydrogenators are rated to 80 psi but have been tested to 200 psi.

Barium

  • Guest
Be very careful when pressurizing glass reactors.
« Reply #2 on: September 10, 2002, 02:07:00 PM »
Be very careful when pressurizing glass reactors. Before each and every run you must examine the vessel thorughly. What to look for is small cracks or signs of damage. Even the slightest physical variation can have a tremendous effect when you pressurize the vessel due to weakness at that particular spot.

If really good stirring can be applied, a very slight overpressure is all that´s needed really.

An even safer setup would be to have a gas generator filling a measuring cylinder turned upside-down and filled with water, with hydrogen. Then just have a tube connected with the hydrogenation vessel pushed all the way up in the measuring cylinder. This allows you to, quite accurately, measure the hydrogen uptake by the reaction as well as avoiding any pressure, as the reaction will "suck" the hydrogen from the cylinder.

If you´d like I can draw a schematic setup for such a device. I´ve used this one many times with great success.

terbium

  • Guest
No pressure required.
« Reply #3 on: September 11, 2002, 03:56:00 AM »
Yeah, as Barium says, no pressure is required when hydrogenating (MD)P2P/methylamine using Adam's catalyst and when using a water displacement cylinder to measure the hydrogen uptake.

The one advantage of sturdier vessels is that you can evacuate and pressurize to assist with your argon and hydrogen purges. But with proper arrangement and use of your gas inlet/vent tubes you can get quite satisfactory purges without the use of vacuum or pressure. The hydrogenation vessel should have one long inlet tube that extends down into the vesel to about where the liquid level will be and another that just extends into the top of the vessel. When purging with argon add the argon through the long tube and vent out the short tube. When purging with hydrogen reverse this.

Hydrogen uptake rate will be dependent on stirring so you will want to provide for good magnetic stirring.

Chromic

  • Guest
Hmm...
« Reply #4 on: September 11, 2002, 05:18:00 AM »
Just a thought, but couldn't you just bring the solvent and the catalyst/ketone/methylamine to a reflux in a flask containing a gas outlet valve, then close the valve, let the solution cool... there should be nothing but solvent vapors in the flask (at a reduced pressure). Then when you want to introduce your hydrogen as Barium suggests, just open the flask and suck up the H2 from the inverted graduated cylinder (or other container to easily meausre H2 uptake)? Seems TOO easy! (doesn't even need a vacuum!)

Now how about telling us of a cheap non-magnetic catalyst that will work at room temp with no pressure?  :)  Then I'll build myself a hydrogen generator to make it as needed...  :)
Sorry for polluting your thread...

scram

  • Guest
explosion
« Reply #5 on: September 12, 2002, 02:14:00 AM »
I got to admit even after reading that long arguement between KrZ and Osmium about pressurizing glass that I still wanted to see how much a 5 gallon beer jug would withstand. Of course I expected it to blow. It held at ~41 psi for 20 minutes and kabooom! It blew very few large shargeds, mostly disintigrated. I fortunately had a large cardboard box around the unit to be protected. It was as loud as a shotgun. I realized the great inconsistancies in the thickness of the jug after i looked at the broken pieces

placebo

  • Guest
Pressure test any vessel filled with water and ...
« Reply #6 on: September 13, 2002, 10:31:00 AM »
Pressure test any vessel filled with water and then submerged in a grabage bin full of water.. it's a bit safer!

moo

  • Guest
What do you think of reinforcing a glass bottle ..
« Reply #7 on: September 13, 2002, 05:09:00 PM »
What do you think of reinforcing a glass bottle with a reasonable or even excessive amount of glass fiber tape?

Organikum

  • Guest
reinforcing glass - not the best idea
« Reply #8 on: September 15, 2002, 02:10:00 AM »

okay, if ya have experience in working with aramide and carbon fiber then there might be a way to reinforce glassware. But not with regular glassfiber/epoxi. It´s on the heat expansion and elasticity. The glass will shatter inside.

A "bottle in the bottle" will work. Big enough steel vessel with plastic/glass reaction vessel inside. A pressure equalizing valve is needed and you just fill it with hydrogen. (after purging with argon). Also suitable for reactions untilizing a internal hydrogen source like ammoniumformate, or if big enough also a hydrogen-generator can be placed inside, the free space left works as a reservoir.

Big and cheap vessels at every junkyard - no SS needed.


ORGY

~ Love is the law, love under will. ~

scram

  • Guest
"Big enough steel vessel with plastic/glass ...
« Reply #9 on: September 19, 2002, 12:54:00 AM »
"Big enough steel vessel with plastic/glass reaction vessel inside"

Does the steel interfere with the magnetic stirring at all? From what I understand stainless steel is just slightly magnetic while regular steel is almost as magnetic as iron.

terbium

  • Guest
Shaken not stirred.
« Reply #10 on: September 19, 2002, 05:11:00 AM »
works just fine.

bartleby

  • Guest
purging gases
« Reply #11 on: September 27, 2002, 01:26:00 PM »
When purging with argon add the argon through the long tube and vent out the short tube. When purging with hydrogen reverse this.

Can someone explain the idea behind having a long tube and short tube going into the reaction vessel?  Also, what is the purpose of adding the argon through the long tube and adding the hydrogen through the short one?  Thanks.

terbium

  • Guest
Argon is heavier than air.
« Reply #12 on: September 28, 2002, 04:20:00 AM »
So gently adding argon near the bottom of the vessel will efficiently force the air out. Similarly, since hydrogen is lighter than argon adding hydrogen to the top will efficiently force the argon out.

Osmium

  • Guest
> since hydrogen is lighter than argon adding ...
« Reply #13 on: September 28, 2002, 04:42:00 AM »
> since hydrogen is lighter than argon adding hydrogen to
> the top will efficiently force the argon out.

Are you sure about that?
Only when the flask is closed on the top, and there is a glass or similar tube extending to the bottom of the flask so the Ar will be forced out through it.
OOps, guess that was said in an earlier post...

Gasses don't separate like polar and non-polar liquids though, they all mix with each other, so this won't work as cleanly as one might think at first.

I'm not fat just horizontally disproportionate.

platcat

  • Guest
Time!
« Reply #14 on: September 28, 2002, 04:53:00 AM »
Give it some time to statify,dont bee in too much of a hurry.Gasses will seperate unless I'm misinformed.PC :)

Theres a reason for all of this but I dont know what it is?
Greg Graffin

Osmium

  • Guest
No they won't easily and spontaneously separate ...
« Reply #15 on: September 28, 2002, 05:23:00 AM »
No they won't easily and spontaneously separate once mixed. And if they do it will take a LONG time.

I'm not fat just horizontally disproportionate.

terbium

  • Guest
WTF?
« Reply #16 on: September 28, 2002, 08:05:00 AM »
Are you sure about that?
Yes, I am sure about that. WTF are you talking about?

Only when the flask is closed on the top, and there is a glass or similar tube extending to the bottom of the flask so the Ar will be forced out through it.
OOps, guess that was said in an earlier post...
That is correct.

Gasses don't separate like polar and non-polar liquids though, they all mix with each other, so this won't work as cleanly as one might think at first.
What is "this"? The point is to not mix the gases but to gently displace one with the other.


Jackhammer

  • Guest
Think of specialty gasses.
« Reply #17 on: September 28, 2002, 10:05:00 AM »
Think of specialty gasses. There you have 2 or 3 gasses mixed in one bottle. It would be quite annoying if you had to shake these every time you need the three gasses.....

When making your choice in life, do not neglect to live!

terbium

  • Guest
Again, WTF?
« Reply #18 on: September 28, 2002, 05:12:00 PM »
Think of specialty gasses. There you have 2 or 3 gasses mixed in one bottle.
Why are you talking about mixed gases? What relevance does mixed gases have to the discussion? Have you never seen a demonstration where a heavier than air gas like CO2 was poured out of a bottle to extinguish a match? This is an elementary school science demonstration!