franklyn
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Aluminum reduction of water
The full article
http://www.whatsnextnetwork.com/technology/index.php/2007/05...
Here is my summary of it _
Jerry Woodall, professor of electrical and computer engineering at Purdue has invented a process
by which Hydrogen is generated spontaneously when water is added to pellets of an alloy which
is made of Aluminum and Gallium. Hydrogen produced in such a system can be fed directly to run
an engine.
When water is added to the pellets, the Aluminum in the solid alloy reacts because it has a strong
attraction for the Oxygen in water. This reaction splits off the Oxygen from the water, releasing
Hydrogen in the process. Woodall discovered that liquid alloys of Aluminum and Gallium spontaneously
produce Hydrogen if mixed with water , while he was working as a researcher in the
semiconductor industry in 1967.
" I was cleaning a crucible containing liquid alloys of Gallium and Aluminum," Woodall said. " When I
added water to this alloy - there was a violent poof. I went to my office and worked out the
reaction in a couple of hours to figure out what had happened. When Aluminum atoms in the liquid
alloy come into contact with water, they react, splitting the water and producing Hydrogen and
Aluminum Oxide."
Gallium melts at low temperature and readily dissolves Aluminum, rendering the Aluminum in the
solid pellets reactive with water. This was a totally surprising discovery, since it is well known
that pure solid Aluminum does not readily react with water. The Gallium is critical to the process
because it hinders the formation of the oxide skin normally created on Aluminum's surface. This
skin normally prevents any additional oxygen from reacting with the Aluminum, acting as a barrier.
Preventing the skin's formation allows the reaction to continue until all of the Aluminum is consumed.
The only waste products are Gallium and Aluminum oxide. Combusting hydrogen in an engine
produces only water as waste and no toxic fumes are produced. It's important to note that the
Gallium doesn't react, so it doesn't get used up and can be recycled over and over again.
The Purdue Research Foundation holds title to the primary patent, which has been filed with the
U.S. Patent and Trademark Office and is pending. An Indiana startup company, AlGalCo LLC., has
received a license for the exclusive right to commercialize the process.
____________________________________________________________
> > > > > > > >
An interesting possibility deriving from this is if this method can also serve
to reduce organic molecules , say for example MeOH to make methane , or
really any liquid organic to produce the unhydrolysed anhydrous precursor.
This can also be the ultimate drying agent in some applications.
Since the Gallium is recovered and the only reagent needed is readily and
cheaply available Aluminum , this is by far superior to expensive exotic
reactive compounds such as Lithium Borohydride used now.
Abstraction of halogens from organic compounds could prove to be
dangerously reactive however.
It is also an open question if this alloy of Gallium and Aluminum can facilitate
the solvation of Aluminum in Ammonia , much as with Alkali metals and some
Alkalines.
Am I the only one who's excited about this - hello.
A minor mention was made of this already
http://www.sciencemadness.org/talk/viewthread.php?tid=8524&a...
http://www.sciencemadness.org/talk/viewthread.php?tid=8524&a...
So how come no one picked up on it ?
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Rosco Bodine
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You get the same reaction with amalgamated aluminum ,
and you actually need an acid like HCl to keep the aluminum scrubbed of the heavy oxide which otherwise
becomes a heavy voluminous pudding like bubbling mud .
A soluble aluminum salt keeps the reaction mixture a thin solution ....otherwise you have a mess , a heavy persistent foam to complicate any H2
generation scheme .
There is I think a similar reaction using iron which can be thermally regenerated using hydrogen ....which is a more energy efficient chemical storage
and regeneration scheme for H2 than using aluminum .
Reacting with methanol what you would get is aluminum methoxide , same as using aluminum amalgam .
I think eventually the hydrogen fuel technology will come full circle back to what is used in aerospace applications ,
where cryo tanks will be found to be the only weight efficient storage means , and the natural boiloff from the cryo tanks will be run through fuel
cells and stored in batteries as part of a fuel cell / battery hybrid electric ....
having no internal combustion engine at all . Dual capability ethanol / methanol fuel cell operation from a reserve non-cryo liquid fuel having
limited range in addition to the battery could provide short range capability to a hydrogen refueling station . Additionally
on interstate routes , a possible "third rail" sort of
AC induction pickup or even a brush pickup might provide
a metered electric drive capability sold as fuel by the local nuclear power utility in a post petroleum fuel era ,
automotive commuter world . Battery development could eliminate the whole hydrogen fuel scheme altogether ,
and probably will do so before any terrestrial hydrogen fuel scheme is ever implemented on a serious scale .
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franklyn
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Best case you get 30 % return of energy from burning Hydrogen for fuel.
It clearly makes more sense to use Aluminum directly as in an alkaline batery
for motive power. The economics of this need to be further scrutinized.
The real spinoff from this is avoiding having to deal with toxic mercury and
possible novel approaches in chemistry.
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stoichiometric_steve
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could this in any way be useful for the reduction of organic molecules?
given that there cant be any protic solvents used to make substrate solutions, what possibilities are left?
it would certainly be a nice source of hydrogen for doing small scale catalytic hydrogenations.
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Fleaker
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I thought it was well known that gallium*, like mercury, attacks/breaks down the oxide layer. To answer steve's question, gallium could likely be used
in lieu of mercury for a reduction. As far as catalytic hydrogenation goes, to be more useful from other methods of hydrogen generation, it would have
to be in-situ in a reaction that doesn't mind excess water or MeOH or EtOH thus producing an alkoxide.
I'd give it a shot in my hydrogenator, but it's a glass container, and gallium wets glass :-\
l
Edit--v
@Bio2, that was definitely a mistake. I meant gallium.
[Edited on 31-7-2007 by Fleaker]
Neither flask nor beaker.
"Kid, you don't even know just what you don't know. "
--The Dark Lord Sauron
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bio2
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Do you mean that deoxidized Al will remove the oxide layer from oxidized Al?
This is news to me.
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franklyn
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| Quote: | | Originally posted by bio2 . This is news to me. |
Al2O3 must be smelted to recover the Aluminum.
Gallium melts in your hand , about ~86ยบ F ( if memory serves )
Aluminum will dissolve in the liquified Gallium ( eventually )
the alloy formed does not develop the sappfire coating and
is for this reason as reactive as say Calcium.
There's all this and more here _
http://en.wikipedia.org/wiki/Gallium
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chloric1
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According to Woodall, you can make an alloy with up tp 80% Aluminum. This could help to aleviate initial investments in gallium a little. I wonder
if other low melting alloys can substitute? Indium/bismuth,tin/bismuth? Well bismuth does form iridescent oxide layers come to think of it. :/
Fellow molecular manipulator
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Fleaker
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Indium is more expensive than gallium.
Neither flask nor beaker.
"Kid, you don't even know just what you don't know. "
--The Dark Lord Sauron
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12AX7
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Zinc-tin alloys are used to solder aluminum, and have appreciable solubility for the metal, making ternary alloys likewise common. I don't remember
what the eutectic is. Zinc-aluminum alloys have tightly adhering oxides. I don't know about tin. The phase diagram shows 2%at solubility of Al in
tin at its melting point, with the melting point of this eutectic being a few degrees below tin's melting point. Lead is immiscible beyond a few
percent. Bismuth has somewhat more solubility for aluminum, but still has a wide immiscible range.
Tim
[Edited on 7-31-2007 by 12AX7]
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