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                 Ever heard of Urushibara Nickel catalysts?
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They are prepared by precipitating Ni from solution by using a more electropositive 
metal - zinc. This Ni ppt is then digested with acid (U-Ni-A) or base (U-Ni-B) or 
by neutral means (U-Ni-N). They can have activity comparable to Raney Nickel - when
properly prepared - but are easier to handle - Urushibara Ni is nonpyrophoric, has 
a long shelf life.

They do take a few hours to make.

Can. J. Chem 1976, 54, 2581 - is the most recent ref. that I have - this should 
reference a whole load of other stuff. There's a complete book on this stuff called 
"New Hydrogenation Catalysts" - by K Hata; Publ: Halsted, 1971, New York.

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Ref: "New Hydrogenation Catalysts: Urushibara Catalysts", by Kazuo Hata, 1971.

"By adding zinc dust to a solution of nickel chloride a nickel powder was
obtained, a powder which hereafter is referred to as 'preceptiataed nickel'. The
preceptitated nickel was added to an aklaline solution of estrone and aluminium
grains were then added to reduce the estrone by means of nascent hydrogen
generation, in combonation with the nickel. The result was a complete sucess as
expected, and estradiol was obtained in good yeild. Preceptitated copper
obtained in the same way from a solution of copper sulfate and zinc dust also
proved to be efficent in reducing estrone to estrdiol."

"However, Urushibara took a further step; to an alkaline solution of estrone he
added preceptitated nickel, and then passed hydrogen through it while shaking.
This was done with a negative expectation; for he presumed that reduction would
not take place when hydrogen was merely passed through the solution without
adding alumium grains, and that the preceptitated nickel or copper would be
catalytically active only when combined with nascent hydrogen. To his pleased
surprise, reduction took place, and estradiol was obtained. Preceptitated nickel
exhibited catalytic activity!"

It goes on to state that the nickel can be preceptitated by alumium grains
instead of zinc dust, and that infact the preceptitated nickel produced in this
manner is more active . It even hydrogenates aromatic groups, and it comparable
to raney nickel in almost all aspects. The preceptitated nickel is also easyier
to handle than raney nickel, it won't catch fire, and therefore easyly recycled
by taking the preceptitated nickel and turning it into a salt to again be
preceptitated.


"Preparation 17: U-Ni-BA (Modified Method)

Place 50 g of aluminum grains (40-80 mesh) in a beaker, wash well with water,
and add 50 ml of 6 N hydrochloric acid on a water bath. When the surface of the
grains has become clean, the upper liquid is decanted and the aluminum is washed
several times with water. It is then transferred to a 11 wide-necked
round-bottomed flask (Note 1), and 200 ml of solution containing 40.4 g of
NiCl2,6H2O (corresponding to 10 g of nickel) is poured onto the aluminum grains
all at once. The mixture is gently heated for a short time on a water bath to
start a mild reaction. The temperature should be maintained below 70 C (Note 2)
to prevent the reaction from getting out of control, and the mixture is stirred
occasionally with a stainless steel spatula. The aluminum grains gradually turn
black as nickel deposits on them, and the reaction mixture becomes a viscous
slush. When the reaction subsides, the mixture is heated on a boiling water bath
(Note 3). A violent reaction begins again and the whole mixture becomes a
massive gel with the green color of the nickel ion disappearing. The semi-solid
product is washed several times with water to remove water-soluble matter and
the wash-ings are decanted. After the gel-like substance is removed, the
resultant slushy solid is collected on a Buchner funnel and dried. The
precipitated nickel obtained weighs 65-70 g, differing slightly according to the
case, and contains about 10 g of nickel. The precipitated nickel can be stored
in a moisture-free vessel. In all of the above procedures, tap water may be used
for washing.

To obtain U-Ni BA containing about 2 g of nickel, one-fifth of the above
precipitated nickel is treated with sodium hydroxide solution. The dry
precipitated nickel is added in small portions with vigorous stirring to a 11 or
larger three-necked round-bottomed flask equipped with a good stirrer and a
thermometer, and containing 250 g of 20% sodium hydroxide solution. As a violent
reaction takes place with the evolution of hydrogen, the flask should be cooled
in an ice bath with vigorous stirring to maintain the temperature at 50-55 C.
Addition of the entire amount of precipitated nickel requires 10-15 minutes.
Stirring is continued until the evolution of hydrogen ceases, with the
occasional application of heat, if necessary, on a water bath to maintain the
temperature at about 50 C. When the reaction is complete, the mixture is left
standing for a few minutes to allow the black particles to settle (Note 4), and
the upper liquor is decanted. Thc black matter is transferred to a 100 ml beaker
with distilled water and washed with 200 ml of warm distilled water divided into
several portions. At the end of this operation, the wash-water should be neutral
to phenolphthalein. The solid is washed with the solvent to be used for the
hydrogenation, e.g., ethanol, and transferred to the reduction vessel.

Notes:

1) The wide-necked round-bottomed flask may be replaced by a beaker.
2) The temperature can be conveniently regulated by using a hot water bath and
   an ice-water bath alternately.
3) If no heat is applied at the end of the reaction, the green color will not
   disappear and a catalyst of high activity cannot be produced. At this state,
   the mixture may safely be heated to 90-100 C.
4) Fine particles will not settle easily. Therefore, the supernatant liquor,
   should be removed by decantation while still turbid, as long contact contact
   with alkali reduces catalytic activity.


Regeneration:

"As Urushibara catalysts are not pyrophoric (in contrast to Raney Nickel), their 
recovery and regeneration is very easy. To regenerate the catalyst, it is 
sufficent to dissolve the waste catalyst in hydrochloric acid to recover nickel 
chloride, from which new Urushibara nickel catalyst may be prepared."

[where U-N-AA is Urushibara-Nickel catalyst-from Aluminium, in Acetic acid)

"U-N-AA
U-N-AA is prepared by warming the precepitated nickel which is deposited from 
nickel chloride solution by aluminium grains, with acetic acid saturated with 
sodium chloride. It consists of aluminium grains coated by nickel metal, as the 
nickel metal deposited on aluminium grains does not separate from the latter, 
which remain undisolved after acetic acid treatment owing to the mild reaction 
between aluminium metal and acetic acid. As the aluminium grains which support 
the the nickel metalact as a carrier, U-N-AA can most conveniently be used for 
a vapor-phase reduction. It has been noted thatthe use of U-N-AA is not confined 
to vapor-phase reduction; it is also suitable for liquid-phase hydrogenation at 
room tempature and atmosphere presure. This can be seen from the reduction of 
nitrobenzene in EtOH in the presence of U-N-AA, gives aniline in 70% yield."

For the U-N-AA the preceptitated nickel is obtained in the same way as for the 
U-N-BA, but the washing is different: 

(For an 80 mL solution made from 32 grams of NiCl2*6 H2O crystals.)

"The preciptitaed nickel is washed with cold water and 385 mL of 40% acetic acid 
(70°C) containing 89 grams of sodium chloride is added. After 3-7 min standing, 
the acid is decanted and the residue is washed with about 21 ml of water (50-60°C), 
and then with an appropriate amount of ethanol. The catalyst contains 8 g of Ni."

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U- stands for Urushibara type catalst

N- stands for Nickel, there are other types of preceptiated metals used, like
   Co, and Cu.

-BA stands for Base washed, Aluminuim preceptitated catalyst

-AA stands for Acetic acid, Aluminium preceptiated catalyst

-B stands for Base wash, with the usually metal used to preceptiate the
   catalyst, which is zinc dust. But as I stated earlier the aluminium
   preceptitated catalyst is more active, and easier to obtain.


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