zeolite2008
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H2 adsorption ability of Ru, Pt, Ni metal powder
I wonder the hydrogen adsorption ability of Ru, Pt, Ni metal powder? which metal powder can absorb more H2 at 1 atm H2 pressure, or the H/Ru, H/Pt,
H/Ni ratios.
I did not find papers about that, any suggestions are appreciated!
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Xenoid
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I don't know about Ru, but platinum black (finely ppt. Pt) can adsorb 110 times its volume of hydrogen. Palladium black will adsorb 900 times its
volume of hydrogen. Iron, nickel and cobalt, and to a lesser degree copper, gold and silver will also adsorb H2 (and other gasses) but I don't have
any numbers.
Edit: Some more stuff!
...palladium will adsorb 935 times its own volume of hydrogen in cooling from a red heat, and at ordinary temperatures, 276 times its volume. The
actual amount adsorbed depends on the physical condition of the metal.
According to G. Neumann & F. Streintz (1892), one volume of the following finely divided metals will adsorb the following volumes of hydrogen;
Palladium Black 502.3
Platinum Sponge 49.3
Gold 46.3
Iron 19.2
Nickel 15.6
Copper 4.5
Aluminium 2.7
Lead 0.1
[Edited on 5-1-2008 by Xenoid]
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JohnWW
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Because of the much greater rarity and cost of Pd and Pt compared to Ni, to ensure that industrial processes involving catalytic hydrogenation, e.g.
making oil from coal, or fuel cells involving recombination of H2 and O2, are economic and widely reproducible, research into such processes should as
far as possible look at possible ways of using Ni (preferably as a fine metal powder or sponge) in place of Pd or Pt.
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microcosmicus
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And as anyone who has cast aluminum will know, that metal can at least
absorb enough hydrogen to get founders in trouble.
While I don't have any exact references at hand, there is a whole journal
devoted to the subject, called "Hydrogen in Metals". Locate it in some
library and I am sure you will get your answers in spades. I remember
having a copy of an article giving figures, but it is buried in my boxes of
papers, so who knows how many eons it would take to unearth it 
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JohnWW
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| Quote: | Originally posted by Drunkguy
All Raney Nickel is, is a very high porsity nickel "sponge" made by heating a 50/50 nickel/aluminium alloy up to ~1000C until all the aluminium has
'sublimed'. |
Instead of alloying Ni with Al for the purpose, I wonder if it could also be done by alloying with Ga or Hg instead, then melting or vaporizing the
latter off, and recovering the liquid metals. Because of the much lesser heat required, if it could be done there would be a cost saving.
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Drunkguy
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Im not at all familiar with this reaction. They say those Parr Hydrogenators are available on ebay occasionally (USA) but
you dont get to see that kind of thing in the UK.
I have higher priority stuff to worry about a.t.m. although there is a time, a place, and (an) application/s for the successful implementation
of this type of philosophy.
That's why I was impressed with Evil Lurker and solo. Not because of what they have already achieved, more because the trajectory course they
are heading along is a brave path to follow & I eagerly await feedback regarding the outcome of their future adventures.
I am personally indebted to solo for the immense favors he has done for all of us in retrieving stacks of literature with the express intent
of improving the richness of our chemical discussions. Ultimately though, chemistry is about what can be done in a laboratory and
not about what can be speculated upon, at leisure, whilst seated in a comfortable brown cushioned leather armchair gesturing with ones hand
while holding a burning cigar and a glass of fine vintage sat on the mahogany table. 
[Edited on 11-1-2008 by Drunkguy]
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-jeffB
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| Quote: | Originally posted by Drunkguy
All raney Nickel is, is a very high porsity nickel "sponge" made by heating a 50/50 nickel/aluminium alloy up to ~1000C until all the alumunium has
'sublimed'. |
Eh?
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Drunkguy
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The introduction by Raney (1927) of a new form of catalyst (the Raney nickel catalyst) with enhanced activity for
hydrogenation at low temperatures and pressures in comparison with the usual form of nickel catalyst as employed by Sabatier and Senderens opened up a
new field if controlled catalytic hydrogenation. A special alloy, prepared essentially by the fusion of approximately equal parts of aluminum and
nickel at 1200-1500C, is treated with alkali which dissolves the aluminium and leaves the nickel as a finely-divided black suspension. The catalyst is
thoroughly washed to free it from alkali, is stored under absolute ethanol in an air-free container and is measured in the form of the suspension; it
must be handled under a solvent at all times as it is highly pyrophoric.
[Edited on 11-1-2008 by Drunkguy]
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Mario.
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| Quote: | Originally posted by JohnWW
| Quote: | Originally posted by Drunkguy
All Raney Nickel is, is a very high porsity nickel "sponge" made by heating a 50/50 nickel/aluminium alloy up to ~1000C until all the aluminium has
'sublimed'. |
Instead of alloying Ni with Al for the purpose, I wonder if it could also be done by alloying with Ga or Hg instead, then melting or vaporizing the
latter off, and recovering the liquid metals. Because of the much lesser heat required, if it could be done there would be a cost saving.
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At the last post it is explained that the Ni/Al is not an alloy, but more like two kinds of powders sintered together in protecting atmosphere, where
Al surely tries to flow away... the remaining aluminium is etched by sodium hydroxide out and the resultant, surface damaged nickel has surface area
so high that it ignites in contact with air!
I think that Al does not make alloys with nickel [it makes a mix like honey with butter], so that is why it was used.. the high temperature was
needed for nickel sponge-fibre formation, not for the Al. All you needed was to sinter Ni powder but keep it spongy.
With Gallium, you could not separate it if it was alloyed into nickel, you would not get a sponge. If it did not alloy well, it would be all gas
before you started forming of the Ni particles.
I am too tired, sorry for any typos/errrors
Glad to find a place with fellow mad scientists... oops! Mad science is forbidden under the antiterrorist act. Let's talk about Pasteurization of milk
instead!
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vulture
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| Quote: |
All Raney Nickel is, is a very high porsity nickel "sponge" made by heating a 50/50 nickel/aluminium alloy up to ~1000C until all the aluminium has
'sublimed'. |
Sounds like BS to me. Heating to 1000C is going to anneal your nickel and reduce the surface area. And your aluminium will just burn at that
temperature.
The wet process involving sodium hydroxide is much easier and produces equally, if not more, reactive Raney Nickel.
[Edited on 15-1-2008 by vulture]
One shouldn't accept or resort to the mutilation of science to appease the mentally impaired.
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MagicJigPipe
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I am almost certain that Ni and Al can form an alloy and that Raney Ni is considered a type of Ni/Al alloy.
"There must be no barriers to freedom of inquiry ... There is no place for dogma in science. The scientist is free, and must be free to ask any
question, to doubt any assertion, to seek for any evidence, to correct any errors. ... We know that the only way to avoid error is to detect it and
that the only way to detect it is to be free to inquire. And we know that as long as men are free to ask what they must, free to say what they think,
free to think what they will, freedom can never be lost, and science can never regress." -J. Robert Oppenheimer
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12AX7
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Ni and Al form several intermetallic compounds. They also do so exothermically, so care must be used in forming such alloys. This does mean the
alloy is brittle and very easy to pulverize.
Raney probably still contains aluminum (I wonder what a typical analysis is?), but certainly, the point is it's been removed from the surface, which
is all that matters.
Tim
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JohnWW
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The Ni metal atom has empty 4s and three 4p electron orbitals outside of a completely filled shell of five 3d orbitals, which enables it to readly
form zerovalent complexes by accepting up to 8 electrons from a wide range of suitable donors. Most well-known is the carbonyl Ni(CO)4, used in
refining the metal, obtained by direct combination with CO. This would also enable it to readily form intermetalic compounds with electropositive
metals which readily give up or share electrons. The most likely intermetallic compound with Al (and similarly Ga), and the one with maximum Al, would
thus be Ni3Al8. In terms of weight (Ni = 58.71, Al = 26.9815), this compound would be 45.09% Ni, 54.91% Al., which is very close to the 50-50 ratio
mentioned above.
[Edited on 15-1-08 by JohnWW]
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Drunkguy
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The thing about heating it in the furnace is prior to purchasing the "alloy" to make the active form of the catalyst.
READ the section on Vogel.
Any misconceptions was because I had not fully read it at the time of my original post.
I think I want one of those Parr Hydrogenators at some time, but I have not seen them for sale yet, least not at an affordable price.
I have been advised that with a hydrogen cylinder and regulator, it is possible to use a PE soda bottle to attain the high pressure needed for Raney
nickel to work effectively.
^I still only young and have NO EXPERIENCE in this area.
All I realize is that precious metal catalysts are ultimately too expensive.
Raney nickel is *the* thing to do if you want to cheapen the process costs.
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