Note : Les descriptions sont présentées dans la langue officielle dans laquelle elles ont été soumises.
CA 02418063 2003-01-30
PRODUCTION OF ACTIVE NICKEL POWDER AND
TRANSFORMATION THEREOF INTO NICKEL CARBONYL
FIELD OF THE INVENTION
This invention relates to the production of an active nickel metal powder
suitable for transformation into nickel carbonyl. Moreover, it relates to the
transformation of the active powder into nickel carbonyl by reaction with
carbon
monoxide at atmospheric or superatmospheric pressure and in the absence of
conventional carbonylation catalysts.
BACKGROUND OF THE INVENTION
It is well known to use the Mond process for the extraction of nickel from
ores, mattes, residues, or similar compounds containing nickel, in which such
compounds are reduced to yield finally divided metallic nickel which is then
treated
with carbon monoxide to produce nickel carbonyl that can then be decomposed to
yield nickel. Various improvements to this process have been suggested to
increase
the rate of nickel carbonyl production and thus render the overall process
more
economical.
For example, in Canadian Patent No. 322,887 it is suggested to add to the
reaction chamber producing nickel carbonyl, a compound containing sulphur,
selenium or tellurium in "active form", such as nickel sulphide, nickel
selenide or
nickel telluride and carrying out the carbonylation reaction in the absence of
oxygen.
The preferred additive is nickel sulphide and it is added so that the amount
of active
sulphur in the reaction chamber lies between 0.2% and 5% by weight. It,
therefore,
acts as a catalyst to promote the carbonylation reaction.
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In U.S. Patent No. 4,045,541 another improvement is disclosed according to
which a metal, such as iron, copper or cobalt, which forms sulphides more
easily than
nickel at 200 C, is admixed with the material comprising elemental nickel,
such as
nickel oxide, which is then subjected to carbonylation and sulfidation.
British Patent No. 649,988 discloses a process for the manufacture of nickel
carbonyl by reacting an aqueous solution of a nickel salt, such as nickel
chloride or
nickel sulphate, with an alkaline reacting substance, producing a nickel
compound
which is treated in aqueous solution or suspension with carbon monoxide under
superatmospheric pressure of at least 50 atmospheres and at elevated
temperatures of
at least 70 C, and in the presence of a minor amount of nickel sulphide or
cyanide as
a catalyst.
All the above prior art processes require the presence of various additives or
carbonylation catalysts and/or the use of superatmospheric pressure and
elevated
temperature to achieve satisfactory rates of nickel carbonyl production.
There is thus a need for a simplified production of nickel carbonyl from
nickel
salts.
OBJECTS AND SUMMARY OF THE INVENTION
It is an object of the present invention to produce active nickel powder from
nickel chloride or nickel salt mixtures containing nickel chloride, which
active
powder is capable to react with carbon monoxide gas at atmospheric or
superatmospheric pressure to yield nickel carbonyl.
It is a further object of the present invention to transform the active nickel
powder produced from nickel chloride or nickel salt mixtures containing nickel
chloride into nickel carbonyl at rapid and commercial rates without addition
of
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carbonylation catalysts or promoters, such as used in the prior art.
The invention also provides a method of producing an active nickel powder
which
comprises reducing a feed material comprising a nickel salt consisting of
nickel chloride said
feed material containing 5% to 100% by weight of nickel chloride and having a
surface area
in excess of 10m2/g, with a reducing hydrogen gas, at a temperature above 300
C.
The invention also provides active nickel powder capable of being rapidly
converted
into nickel carbonyl by reaction with carbon monoxide gas at atmospheric or
superatmospheric pressure, said powder being the result of reduction by
hydrogen at a
temperature above 300 C of a feed material comprising nickel chloride and
other reducible
nickel salts in addition to nickel chloride, said feed material having a high
surface area in
excess of 10mZ/g.
Other objects and advantages of the present invention will become apparent
from the following description thereof.
In essence, it has been found that nickel salts containing 5% to 100% of
nickel
chloride and having a high surface area can be rapidly reduced to active
nickel
powder by reaction with a reducing hydrogen gas at a temperature above 300 C,
and
preferably between 300 C and 600 C. The reducing hydrogen gas should normally
contain at least 20% by volume of H2, but is preferably pure hydrogen. The
resulting
activated nickel powder can then be reacted with CO gas at atmospheric
pressure and
temperatures of 20 C to 60 C, preferably about 50 C, to produce nickel
carbonyl -
Ni(CO)4, with a yield close to 100%. The activated nickel powder can also be
reached
with CO at superatmospheric pressure and elevated temperature, if desired. The
carbonylation reaction with CO gas is simple and effective, requiring no
catalysts or
other promoters.
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When other nickel salts, such as nickel carbonate or nickel sulfate are
treated
in the same manner, namely by reaction with Hz gas at 300 C - 600 C,
essentially no
active nickel powder is produced. However, surprisingly, when such salts are
admixed with at least 5% b_y weight of NiCI,, the entire admixture produces
active
nickel powder. The Ni recoveries obtained with the admixture of NiCO, and
NiCI2
are in the range of 95-1009'o and the recoveries obtained with the admixture
of NiSO4
and NiCI2 are usually slightly fower, but still in a very appreciable range of
85-90 ro,
probably due to the formation of some nickel sulphide which does not
carbonylate.
When reference is made to nickel chloride, it can be either dehydrated or in
the form of hydrates, such as NiC1,.6H,0. Moreover, when reference is made to
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nickel salts, they can also be in hydrated form and/or combined with other
nickel
compounds, such as nickel hydroxide or the compound called zaratite -
2Ni(OH)z.NiCO3.4HzO.
The starting material should have a high surface area in excess of 10m2/g, and
preferably between 35 and 100 m2/g.
The active nickel powder produced in accordance with the present invention
can be exposed to air for a short period of time and still remain active. It
can also be
maintained under inert gas, such as argon, for several days without losing its
activity.
Another useful feature of this powder is that once the active nickel powder
loses its
activity due to storage, in the absence of oxygen, it can be re-activated by
exposing it
to HZ gas at about 150 C or higher temperatures. If the active nickel powder
loses its
activity due to storage in the presence of oxygen, it can be re-activated by
exposing it
to H2 gas at a temperature of 300 C to 600 C. This is an important advantage
of the
present invention because it enables to perform the carbonylation reaction
completely
separately and at a different location from the reduction reaction that
produces the
active nickel powder.
BRIEF DESCRIPTION OF THE DRAWINGS
Fig. 1 is a graph showing nickel extraction from active nickel powder
produced by reduction of nickel chloride;
Fig. 2 is a graph showing nickel extraction from active nickel powder where
treatments were made on various NiCIZ materials at different temperatures.
Fig. 3 is a graph showing nickel extraction from nickel powder produced by
reduction of nickel carbonate; and
Fig. 4 is a graph showing nickel extraction from active nickel powder
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produced by reduction of an admixture of nickel carbonate and nickel chloride.
Fig. 5 is a graph showing nickel extraction at superatmospheric pressure and
elevated temperature from active nickel powder of the present invention as
compared
to regular nickel powder of the prior art.
DETAILED DESCRIPTION OF THE INVENTION
Examples of preferred but non-limitative embodiments will now be described
with reference to the appended drawings. In these examples, tests were carried
out by
first reducing a pre-dried small sample (25mg) of finely divided nickel
chloride and
of nickel carbonate alone and in admixture with nickel chloride respectively.
The
reduction was carried out in hydrogen at 500 C. The obtained nickel powder was
then
cooled to 200 C and the reactive gas switched from hydrogen to carbon monoxide
at
a flow rate of lOml/min. The sample was then further cooled to 50 C. Weight
loss
was monitored over time using computer software. The weight loss was confirmed
with TGA (thermogravimetric analysis) measurements, and the residue was
dissolved
in acid and analyzed for nickel to give a complete mass balance. The obtained
nickel
metal powder reacted with CO to form volatile nickel carbonyl gas which was
removed and decomposed at high temperature into a pure nickel product as in
known
in the art.
EXAMPLE 1
In this example, NiC12. 6H2O was pre-dried at 170 C in air and treated as
described above. Nickel extraction of 99.6% was obtained in 45 minutes as
illustrated
by the curve in the graph of Fig. 1 and by curve B in the graph of Fig. 2.
The same procedure as above was repeated with a sample of NiC12 pre-dried
at 300 C in N2. Ni extraction of essentially 100% was obtained in about 30
minutes as
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illustrated by curve A in the graph of Fig. 2.
The same procedure was repeated with another sample of NiC12 pre-dried at
170 C in air. Ni extraction of essentially 100% was obtained in about 1 hr. as
illustrated by curve C in the graph of Fig. 3.
The same procedure was repeated but using a temperature of 600 C - 800 C
for reduction in hydrogen. In this case, essentially full extraction was
reached after
about 2.5 hours, as illustrated by curve D in the graph of Fig. 2. This shows
that
temperatures higher than 600 C actually slow down the extraction and there is
no
practical reason to use them. The present invention is, however, not limited
to
temperatures below 600 C.
The same procedure was repeated using anhydrous NiC12 without pre-drying.
In this case, only about 90% of extraction was achieved after about 5 hrs, as
illustrated by curve E in the graph of Fig. 2.
The above experiments indicate that changes in drying temperatures and
hydrogen reduction temperatures and in the composition of the nickel chloride
may
lead to variations in extraction rates and the speed of achieving the
extractions.
EXAMPLE 2
In this example, the procedure described above was repeated but using NiCO3
as the starting material. As shown by the curve in the graph of Fig. 3, a very
poor
extraction rate of less than 20% was achieved after about 6 hours. It is
obvious,
therefore, that NiCO3 alone did not produce an active nickel powder.
EXAMPLE 3
The procedure of Example 2 was repeated but with replacement of the starting
material with a mixture of NiCO3 and NiClz in a proportion of 3:1. This gave
an
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essentially 100% recovery of Ni in less than 1 hour as shown by the curve in
the
graph of Fig. 4.
Other amounts of mixture blends of nickel carbonate and nickel chloride were
tested and good results were. obtained starting with about 5% by weight of
NiC12 in
the mixture. It was found, however, that the most beneficial results are
obtained when
the amount of chloride in the mixture is between 20 and 25% by weight based on
nickel. Moreover, it was found that the higher the surface area of the mixed
solids,
the faster the extraction of nickel by carbonylation, with optimum results
being
obtained when the surface area is 80-100 m2/g and the amount of NiC12 is such
as to
give 20-25 wt% Cl/Ni. Thus, the presence of NiC12 in admixture with other
nickel
salts, including possible other compounds that may be present with such salts,
produces a satisfactory and rapid conversion of the total nickel present in
such
mixtures into active nickel.
Larger scale tests, using samples of up to 300g, have also been carried out
and
gave similar results as those described in the above examples, although with
conversion times of 3 to 6 hours.
EXAMPLE 4
A lOg sample of active nickel powder produced in accordance with the
present invention was subjected to carbonylation with CO gas in a small
vertical
reactor at 300 psi (20 atm) and 85 C and resulted in essentially 100% of Ni
extraction
in less than 10 hours, as shown by curve F in Fig. 5.
Another lOg sample of non-activated nickel powder was treated in the same
manner with CO gas at 300 psi and 85 C, and resulted in a conversion to Ni in
over
20 hours as shown by curve G in the Fig. 5.
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As previously mentioned, it is already known in the art to carbonylate Ni
powder with CO gas at superatmospheric pressures and at elevated temperatures
above 70 C. The present example shows that when such known carbonylation is
carried out using the active nickel powder of the present invention, a
considerable
reduction in the time of Ni extraction is achieved.
It should be noted that the invention is not limited to the specific
embodiments and examples described above, but that various modifications
obvious
to those skilled in the art can be made without departing from the invention
and the
following claims.
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