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Topic: Raney Ni and not burning alive  (Read 27416 times)

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Offline Ψ×Ψ

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Raney Ni and not burning alive
« on: March 01, 2007, 07:37:23 PM »
I'm setting something up next week that uses a Raney nickel hydrogenation to convert a nitro group to an amino.  While I'm used to air & moisture-sensitive chemistry, I've never done anything quite like this before and am more than a little afraid of the word "pyrophoric."  The procedure has been published, so I'm not going into this completely blind, but the literature seldom mentions stupid mistakes associated with reagents.  Apart from becoming intimately acquainted with the fire extinguisher, do you have any suggestions for an undergrad who is trying to avoid self-immolation by lab?

Offline movies

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Re: Raney Ni and not burning alive
« Reply #1 on: March 01, 2007, 10:01:50 PM »
I have had Raney Ni go up on me before.  It's an exciting time when you have a fire in a Buchner funnel and all you are holding is a bottle of ethanol.

Weighing it out is easy because you buy it as a slurry in water.

The key is that when you filter the solids at the end of the reaction, never let the filter cake go dry.  As long as there is a film of water/ethanol covering the metal surface it should be fine.  When you are done, put the waste in a jar and keep the solids covered with water until the waste disposal people come and take it away.

Offline pantone159

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Re: Raney Ni and not burning alive
« Reply #2 on: March 01, 2007, 10:34:13 PM »
When you are done, put the waste in a jar and keep the solids covered with water until the waste disposal people come and take it away.

So, what do the waste disposal people do with it?  Dump it into the ocean, thus ensuring that it never ever dries out?  Is there any procedure to turn the stuff into something manageable?  Perhaps dissolve it in HNO3???

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Re: Raney Ni and not burning alive
« Reply #3 on: March 02, 2007, 12:21:22 PM »
I don't know what they do with it actually.  I never like dissolving metals in acid as a method of cleanup.  You just end up with a nasty corrosive solution with nasty toxic heavy metals in it.

Raney Ni doesn't store very well, and loses a lot of activity over time.  You can also deactivate it by refluxing in alcohol for a couple hours.  You can actually get it to a point where it will still desulfurize compounds, but it won't reduce alkenes, which can be very useful.  I bet you could dispose of the waste in a similar manner: reflux in alcohol or water until the reducing power is pretty much used up, then you can handle it like other air-stable metals.

Offline Custos

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Re: Raney Ni and not burning alive
« Reply #4 on: April 16, 2007, 08:19:17 PM »
I've never bought or stored Raney nickel - always preferred to make it fresh by dissolving out the aluminium from Raney alloy. As for disposal, for small quantities at least, dissolving in the minimum amount of nitric acid was my preference. I agree that just shifts the problem to a corrosive nickel solution (you can always neutralise with hydroxide, which will precipitate nickel hydroxide I guess), but then at least you're certain not to have a fire problem. I've seen labs where used Raney nickel wastes, stored under water, have dried out and combusted because people forgot to dispose of it. Nickel nitrate at least won't do that.

Either way, it's a good catalyst but a pain to clean up.

Offline hmx9123

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Re: Raney Ni and not burning alive
« Reply #5 on: May 25, 2007, 05:51:18 AM »
One thing that I advise people to do, and they usually think I'm crazy, is to create a problem with whatever they're using, especially if it's just a fire hazard.  Create a fire in a controlled setting and in an expected manner.  Take say, 50-100 mg of Raney nickel out on an open lab bench and see how long it takes for it to light on fire.  This may sound dumb, but it gives you two things:

1. You now have a much better feel for how reactive this material is.
2. You now have experience with this material on fire, so you won't be surprised if it does go and will be able to deal with the fire appropriately.

So many injuries that I see occur when someone is so afraid of the material that they're working with that they injure themselves or create a specific hazard due to their fear.  Respect the hazardous materials that you're working with, don't fear them.  If you fear it, you're only creating more problems for yourself.

Offline DrCMS

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Re: Raney Ni and not burning alive
« Reply #6 on: May 25, 2007, 07:04:38 AM »
Create a fire in a controlled setting and in an expected manner.  Take say, 50-100 mg of Raney nickel out on an open lab bench and see how long it takes for it to light on fire.

That's some of the best advice I've heard on dealing with these types of materials.  Get used to them then deal with facts and your own experience not with inflated horror stories.

One extra thing I'd add is do not use a CO2 extinguisher on this type of fire.  A colleague had spilt some NaH which caught on fire, she shouted for help, somebody grabbed the nearest extinguisher, which happened to be a CO2 one and turned 1 small fire into about 10, the blast of gas also blew over a beaker of solvent at the same time which became one big fire.  He then got a powder fire extinguisher which put them it all out.  The two of them spent the next few days cleaning up the fume cupboard  :(

The material i was always the most cautious about was t-BuLi.  It's fun to push it out of a syringe and get a jet of flame down the lab but not when you're trying to put it into a reaction flask of solvent! Going through a rubber septa makes it a lot safer  ;)

Offline hmx9123

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Re: Raney Ni and not burning alive
« Reply #7 on: May 31, 2007, 07:50:54 PM »
Of course, t-BuLi fires have been known to burn through septa. :)


Offline kiwi

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Re: Raney Ni and not burning alive
« Reply #8 on: June 01, 2007, 10:16:24 AM »
Of course, t-BuLi fires have been known to burn through septa. :)

where did you get that picture? its a good one for a safety talk, or to stick to the outside of the tBuLi bottle.

Offline hmx9123

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Re: Raney Ni and not burning alive
« Reply #9 on: June 01, 2007, 01:16:20 PM »
My friend took a picture as we were 'cleaning out' the t-BuLi bottle.  We had the needle through the septa blowing argon and pushing the t-BuLi in pentane out through a canula, sort of like a flamethrower, but the septa was old and broke, so it caught on fire.  Hence the picture.  Then we got tired of the game, ripped the septa off and stuck the bottle under the tap.  That was energetic.  :o

Offline russellm72

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Re: Raney Ni and not burning alive
« Reply #10 on: July 05, 2007, 05:21:22 AM »
Ok before you worry about the Raney Ni, have you considered a easier way to carry out your reduction? Cat. hydrogenation over Pd or Pt, SnCl2/HCl/EtOH (reflux) or perhaps a borohydride exchange resin/Ni(OAc)2 reaction at 0 oC in MeOH.

If you must use raney Ni just shake the bottle thoroughly assuming its in water and add a slug to your reaction. I made the stuff during my PhD and as noted earlier quite nice to take a bit out and watch it spark!!

Use another method if your not confortable or feel you not experienced enough.

R.

Offline organoman

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Re: Raney Ni and not burning alive
« Reply #11 on: July 05, 2007, 06:43:49 AM »
Well I have some experience of handling raney Ni as well as met an accident with it which actually I could controll easily.
All you have to do is to take some precaution.
1 - don't weigh raney nickel. Always take some solvent or water in a measuring cylinder and add raney nickel in it and let it settle down. Then see the volume of it and convert to weight if needed. This is a safer method as well as minimizes error(this is how they do in industries with large volume of raney nickel).
2- Always have a bucket full of water ready during operation such as filtration.
3- Never try use anything Fancy in such fire. Always use plenty of water. 
4- Try avoid complete drying during filtration as has been said earlier. however if needed so reduce the vacuum to minimum in the end of filtration(reducing vacuum means increasing pressure) and as soon as filtration completes remove vacuum and add water immediately to Buckner funnel. I always prefer taking assistance of an extra person along with me during filtration. All he does is always keeps ready with a jug of water as if he is sure that it is going to catch fire.
5- After filtration store ranay nickel preferably in water or in some solvent immediately.
6- Try and recycle this catalyst as many times can be done successfully. And finally can be treated with NaOH or HCl or HNO3 to deactivate it.
7- I have used some thiols in very small amount to poison this catalyst. I am not sure if in large volume if thiol can be used to deactivate it.

Offline Ψ×Ψ

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Re: Raney Ni and not burning alive
« Reply #12 on: July 07, 2007, 04:49:05 AM »
SnCl2 worked well but didn't turn out quite as clean.  Good enough, though.  On a small scale, Raney Ni isn't bad to work with at all.  The word "pyrophoric" still sends chills down my spine, though.

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Re: Raney Ni and not burning alive
« Reply #13 on: July 08, 2007, 04:04:34 PM »
plutonium is pyrophoric
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Offline hmx9123

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Re: Raney Ni and not burning alive
« Reply #14 on: August 06, 2007, 03:42:42 AM »
Though I haven't worked with Raney nickel itself, the description makes it sound like it's mildly pyrophoric.  I used to work with some really nastily pyrophoric material, like diborane, and after you work with that, anything that doesn't immediately burst into flames or explode upon contact with the atmosphere is a pussycat. :)

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