Sciencemadness Discussion Board

Hydrogenation

Houngan - 18-2-2013 at 07:12

Hi,

I am planning on doing some hydrogenation and I have a source of hydrogen and a catalyst but I neet to flush the vessel with an inert gas first.

I'm not to sure about aquiring cylinder nitrogen, so I had a thought of using carbon dioxide from dry ice?

What do people use in this case?

I am in Australia so the rules may be different but any suggestions would be greatly appreciated.

bfesser - 18-2-2013 at 12:06

Is your hydrogen prohibitively expensive? If not, flush with H<sub>2<?sub>.

unionised - 18-2-2013 at 12:35

Because you don't want a mixture of air, hydrogen and a catalyst.

Mailinmypocket - 18-2-2013 at 12:40

Quote: Originally posted by Houngan  
Hi,

I am planning on doing some hydrogenation and I have a source of hydrogen and a catalyst but I neet to flush the vessel with an inert gas first.

I'm not to sure about aquiring cylinder nitrogen, so I had a thought of using carbon dioxide from dry ice?

What do people use in this case?

I am in Australia so the rules may be different but any suggestions would be greatly appreciated.


Go to a winemaking store or a well stocked liquor store... They very often sell cans of argon (they look like cans of hair spray, low pressure). It is used to spray into open bottles of wine to create an inert blanket over the wine to prevent oxidation, and shitty tasting wine. Not super cheap, around 8$, but if you want some argon that requires no cylinders, regulators and such... It's a good source :)

Houngan - 18-2-2013 at 15:44

Cheers everyone!

Yeah I had though of flooding it with H2 above the ignition concentration. That would probably be my best option.
I might have to look into that "Argon in a Can"TM sounds neat!

Thanks again

bananaman - 18-2-2013 at 23:39

Why not simply attach your vessel to a vacuum pump, and have it evacuate the entire vessel before introducing the H2 gas?

Nicodem - 19-2-2013 at 09:07

Quote: Originally posted by Houngan  
Yeah I had though of flooding it with H2 above the ignition concentration. That would probably be my best option.

That would be very dangerous. Hydrogen and air should never be mixed above a mixture containing Pd-C or other hydrogenation catalysts. You should follow the safety protocol and either flush the air by an inert gas or by vacuum.

ash - 19-2-2013 at 10:03

The best option people use to apply is making a mixture of catalyst, your substrate and solvent (methanol, isnt it?), then vacuumizing the flask till methanol starts to boil, then fill the flask with hydrogen. Procedure can be repeated.
I did it personally several times, works perfectly.

zed - 20-2-2013 at 18:00

Indeed. Vacuum is a widely available and inexpensive purging agent. My personal favorite.

luckybot - 20-2-2013 at 18:35

What about propane?

bananaman - 20-2-2013 at 21:50

Quote: Originally posted by luckybot  
What about propane?


What do you mean by propane?

gsd - 20-2-2013 at 22:02

Quote: Originally posted by bananaman  
Quote: Originally posted by luckybot  
What about propane?


What do you mean by propane?


What s/he means by propane is why not use cooking gas to flush the hydrogenator.

Though it certailnly is an "out of box" suggestion for home chemist, personally I don't think it is worth the risk. In absence of an inert gas, vacuum is the way to go.

Gsd

[Edited on 21-2-2013 by gsd]

zed - 21-2-2013 at 16:41

Also, propane may contain sulfides. A poison for certain catagories of catalyst.

497 - 22-2-2013 at 14:34

Quote:

Also, propane may contain sulfides


But butane doesn't ;)

killer_lapin - 22-2-2013 at 16:02

actualy butane contain sulfides too, otherwise you couldn't smell it.

[Edited on 23-2-2013 by killer_lapin]

Diablo - 22-2-2013 at 18:49

They sell extra pure butane for certain extractions.

gsd - 22-2-2013 at 23:26

Yeah but if you have to buy such an exotic gas just to flush an apparatus, you might as well buy humble N2.

Gsd

ash - 23-2-2013 at 04:49

Quote: Originally posted by luckybot  
What about propane?

another home speed maker? sick of them

Doc B - 23-2-2013 at 06:04

Oi skippy, get your arse down to Bunnings stat. In the welding section you'll find Nitrogen, Argon, CO2, and other small to large cash and carry basis gasses suitable with regulators et al req.

Now spill it, where the fuck are you getting dry ice here? I've been recycling fire extinguishers but that's fairly crap.

zed - 23-2-2013 at 15:49

An Ice cream supplier might be able to help you. Not a problem anymore in the U.S..

Every supermarket has it.

luckybot - 23-2-2013 at 15:50

Quote: Originally posted by ash  
Quote: Originally posted by luckybot  
What about propane?

another home speed maker? sick of them

What are you talking about?

Houngan - 25-2-2013 at 05:03

Cool, vacuum pump is the way to go then.

I had thought of that but was concerned that I would suck the contents out of my vessel.
I guess ill have to not suck too hard then (I don't plan on being the pump, just to clarify) :P

Thanks again.

497 - 26-2-2013 at 21:36

In the US butane meant for refilling lighters doesn't smell. Just saying...

Nicodem - 27-2-2013 at 07:26

Confined mixtures of butane and air can explode when ignited. (seems like some posters are unaware of this)

497 - 1-3-2013 at 08:59

Considering the upper explosive limit is 8.4% you'd really have to screw up the "flushing" thing to have that problem... Always good to be careful though. I suppose there's always difluoroethane from those cans of "dust off" too.

zed - 6-3-2013 at 19:40

A further dry-ice Inquiry could be made to foodies and their suppliers. Dry Ice is used to produce the faddish "Carbonated Ice Cream". Somebody in your town has got to know where to get "the makings".