U.S. patent number 3,627,790 [Application Number 04/846,236] was granted by the patent office on 1971-12-14 for activated nickel catalysts.
This patent grant is currently assigned to E. I. du Pont de Nemours and Company. Invention is credited to Alvin B. Stiles.
United States Patent |
3,627,790 |
Stiles |
December 14, 1971 |
ACTIVATED NICKEL CATALYSTS
Abstract
Nickel-containing foraminous material is formed by leaching
about 2-100 percent by weight of the aluminum from an alloy
consisting essentially of about 25-47 percent by weight of nickel
and about 53-75 percent by weight of aluminum, at least about 65
percent by weight of the nickel in the alloy being present as
intermetallic NiAl.sub.3 compound. This foraminous material is
useful as an activated catalyst for the hydrogenation of organic
compounds and as an anode in fuel cells.
Inventors: |
Stiles; Alvin B. (Wilmington,
DE) |
Assignee: |
E. I. du Pont de Nemours and
Company (Wilmington, DE)
|
Family
ID: |
25297327 |
Appl.
No.: |
04/846,236 |
Filed: |
July 30, 1969 |
Current U.S.
Class: |
552/265; 502/335;
552/208; 552/267; 568/861; 585/260; 585/270; 585/276; 585/906 |
Current CPC
Class: |
B22F
1/0007 (20130101); B22F 3/1134 (20130101); B01J
25/02 (20130101); B22F 1/0088 (20130101); C07C
5/03 (20130101); H01M 4/90 (20130101); C07C
5/10 (20130101); C07C 5/03 (20130101); C07C
13/273 (20130101); C07C 5/10 (20130101); C07C
13/16 (20130101); Y02E 60/50 (20130101); C07C
2521/02 (20130101); B22F 2998/10 (20130101); C07C
2523/755 (20130101); Y10S 585/906 (20130101); C07C
2601/12 (20170501); C07C 2601/20 (20170501); B22F
2998/10 (20130101); C22C 1/0491 (20130101); B22F
2003/248 (20130101); B22F 9/04 (20130101); B22F
9/16 (20130101) |
Current International
Class: |
C07C
5/00 (20060101); C07C 5/10 (20060101); C07C
5/03 (20060101); B01J 25/00 (20060101); B01J
25/02 (20060101); H01M 4/90 (20060101); B22F
1/00 (20060101); B22F 3/11 (20060101); C07c
049/68 () |
Field of
Search: |
;252/466,477
;260/369,635,666 |
References Cited
[Referenced By]
U.S. Patent Documents
Other References
Mellor, Inorganic & Theoretical Chemistry p. 223
(1936).
|
Primary Examiner: Wyman; Daniel E.
Assistant Examiner: French; Philip M.
Claims
I claim:
1. A nickel-containing foraminous material formed by leaching 2-100
percent by weight of the aluminum from an alloy consisting
essentially of 25-47 percent by weight of nickel and 53-75 percent
by weight of aluminum, at least 65 percent by weight of the nickel
in the alloy being present as intermetallic NiAl.sub.3
compound.
2. The foraminous material of claim 1 in which 5-100 percent by
weight of the aluminum is leached from the alloy, the alloy
consists essentially of 35-45 percent by weight of nickel and 55-65
percent by weight of aluminum, and at least 70 percent by weight of
the nickel in the alloy is present as intermetallic NiAl.sub.3
compound.
3. The foraminous material of claim 2 in which the alloy consists
essentially of 38-42 percent by weight of nickel and 58-62 percent
by weight of aluminum, and at least 75 percent by weight of the
nickel in the alloy is present as intermetallic NiAl.sub.3
compound.
4. The foraminous material of claim 3 in which at least 80 percent
by weight of the nickel in the alloy is present as intermetallic
NiAl.sub.3 compound.
5. The foraminous material of claim 3 in which 85-100 percent by
weight of the aluminum is leached from the alloy and the material
has a particle size of 325-200 mesh.
6. The foraminous material of claim 3 in which 2-50 percent by
weight of the aluminum is leached from the alloy and the material
has a particle size of 20 mesh to 2.5 centimeters in diameter.
7. The method of hydrogenating cyclododecatriene to cyclododecane
which comprises passing a feed mixture containing 5 to 20 percent
by weight of cyclododecatriene and 80 to 95 percent by weight of
cyclododecane with hydrogen over a nickel-containing foraminous
catalyst material in accordance with claim 1 at the rate of 0.25 to
0.75 part by weight of feed mixture per part of catalyst per hour,
at a temperature of 100.degree. to 250.degree. C. and a hydrogen
pressure of 25 to 30 atmospheres.
8. The method of claim 7 in which the catalyst is in a fixed bed,
is 2 to 10 mesh in size, and has had 5 to 25 percent by weight of
the aluminum removed from the original alloy.
9. The method of hydrogenating 2-butyne-1,4-diol to 1,4-butanediol
which comprises passing an aqueous feed containing, by weight, 20
to 70 percent butynediol and 30 to 80 percent water with hydrogen
over a nickel-containing foraminous catalyst material in accordance
with claim 1 at a hydrogen partial pressure of 150 to 400
atmospheres, a superficial gas velocity of at least 0.5 foot per
minute at a temperature of 60.degree. to 150.degree. C. and a
recycle to fresh feed ratio of 10:1 to 40:1.
10. The method of claim 9 in which the catalyst is in a fixed bed,
is of 2 to 10 mesh in size, and has had 2 to 25 percent by weight
of the aluminum removed from the original alloy.
11. The method of hydrogenating alkyl anthraquinone to alkyl
anthrahydroquinone which comprises reacting a solvent slurry
containing alkylated anthraquinone, alkylated hydroanthraquinone
and a nickel-containing foraminous catalyst material in accordance
with claim 1 with hydrogen at atmospheric to slightly elevated
pressure and at a temperature of 25.degree. to 50.degree. C.
12. The method of claim 11 in which the alkylated anthraquinone is
selected from the group consisting of 2-ethylanthraquinone,
2-tert.-butylanthraquinone, 2-amyl-anthraquinone, tetrahydro
derivatives thereof, and mixtures thereof.
Description
BACKGROUND OF THE INVENTION
1. Field of the Invention
This invention relates to improved nickel-containing foraminous
materials and to their use as activated nickel hydrogenation
catalysts and as anodes in fuel cells.
2. Description of the Prior Art
Conventional Raney nickel catalysts are prepared by melting
mixtures containing 35-60 percent by weight of nickel and 40-65
percent by weight of aluminum to form melt solutions. The
exothermic heat of reaction between the nickel and aluminum raises
the temperature to about 1,400.degree. C. The molten mass is then
rapidly cold cast into iron molds. When the molten mass has cooled,
the ingot is mechanically reduced to particles of the desired size.
These particles are then activated by treatment with an aqueous
alkali solution which leaches aluminum from the alloy thereby
leaving a foraminous material having active nickel at the surface.
These materials are widely used as catalysts in hydrogenation
reactions in the chemical industry.
SUMMARY OF THE INVENTION
It has now been discovered that nickel-containing foraminous
materials having improved activity as hydrogenation catalysts can
be formed by leaching about 2-100 percent by weight of the aluminum
from an alloy consisting essentially of about 25-47 percent by
weight of nickel and about 53-75 percent by weight of aluminum, at
least about 65 percent by weight of the nickel in the alloy being
present as intermetallic NiAl.sub.3 compound.
DETAILED DESCRIPTION OF THE INVENTION
It has been discovered in accordance with this invention that the
activity of activated nickel hydrogenation catalysts depends, among
other things, upon the percentage of the nickel in the original
nickel-aluminum alloy present as intermetallic NiAl.sub.3 compound.
The terms "intermetallic NiAl.sub.3 compound " and "NiAl.sub.3
phase," as used throughout the specification and claims are
intended to refer to the composition of the crystalline grains of
pure NiAl.sub.3 unit crystals in the microstructure of the
alloy.
It has been found in conjunction with this invention that, in the
case of conventional Raney nickel alloys, including alloys of 42
percent by weight nickel and 58 percent by weight aluminum, which
are nominally NiAl.sub.3, less than about 60 percent by weight of
the nickel in the alloy is present as intermetallic NiAl.sub.3
compound. It has been found that a large proportion of the nickel
in these alloys is present as the intermetallic compounds, Ni.sub.2
Al.sub.3 and NiAl.
Although it is not intended that this invention be limited to any
particular theory, it is believed that the most active catalysts
are those formed from alloys containing the highest proportion of
nickel in the NiAl.sub.3 phase. This theory is based on the belief
that the most active nickel sites are those which result when
aluminum is leached from the NiAl.sub.3 phase. The activated
catalysts of this invention, which are derived from alloys having
from about 65 percent to greater than about 80 percent of their
nickel content in the NiAl.sub.3 phase, are generally about 1.5 to
3 times as active as conventional activated Raney nickel catalysts
in the hydrogenation of benzene.
The percentages of nickel in the NiAl.sub.3 phase recited
throughout the specification and claims were determined by
conventional analytical procedures. A polished surface of the alloy
is examined under a microscope to determine the percentage of the
major phase present, and the composition of the major phase is
determined by conventional X-ray analytical techniques as described
in "X-ray Diffraction Procedures," by H. P. Klug and L. E.
Alexander, published by John Wiley and Sons, New York, 1954.
The alloys which are useful in preparing the foraminous materials
of this invention consist essentially of about 25-47 percent by
weight of nickel and about 53-75 percent by weight of aluminum, and
have at least about 65 percent by weight of the nickel present as
NiAl.sub.3 phase. The term "consisting essentially of," as used
throughout the specification and claims, is meant to include
unspecified ingredients or impurities in the alloy which do not
materially affect the basic and novel characteristics of the
catalyst. That is, this term excludes only unspecified ingredients
or impurities in amounts which prevent the advantages of this
invention from being realized.
The optimum alloy for use in accordance with this invention
contains about 58 percent by weight of aluminum and about 42
percent by weight of nickel which is the weight ratio of these
ingredients in the intermetallic compound NiAl.sub.3. When the
amount of nickel present exceeds about 42 percent, however, there
is a tendency to form increasing amounts of Ni.sub.2 Al.sub.3 and
NiAl phases. Accordingly, the alloy preferably consists essentially
of about 35-45 percent nickel and about 55-65 percent aluminum and
most preferably about 38-42 percent nickel and about 58-62 percent
aluminum. When the alloy contains less than about 35 percent by
weight of nickel, it can still contain a quite high proportion of
the nickel in the NiAl.sub.3 phase since the excess aluminum tends
to be present as metallic aluminum. Such catalysts, however, are
less economical than those derived from the preferred
nickel-aluminum alloy since the aluminum removed from the metallic
aluminum phase during the activation step does not result in the
formation of active nickel sites.
The alloy may be prepared by any process which results in at least
about 65 percent by weight of the nickel being present as the
NiAl.sub.3 phase. Preferably at least about 70 percent by weight of
the nickel in the alloy is in the NiAl.sub.3 phase, and most
preferably at least about 75 percent by weight. Alloys have been
prepared in which at least about 80 percent by weight of the nickel
is in the NiAl.sub.3 phase.
A preferred process which is commercially suitable for preparing
the alloys used to prepare the foraminous materials of this
invention comprises reacting a mixture consisting essentially of
about 25-47 percent by weight of nickel and about 53-75 percent by
weight of aluminum at a temperature above about 825.degree. C.
sufficient to form a single-phase homogeneous melt, cooling the
resulting mass to a temperature below about 854.degree. C.,
annealing the resulting mass at about 790.degree.-854.degree. C.
for at least about 30 minutes until at least about 65 percent by
weight of the nickel in the alloy is in the NiAl.sub.3 phase, and
allowing the resulting mass to cool to atmospheric temperature. The
term "annealing" is used herein to describe the heat treatment used
to develop an equilibrium amount of solid NiAl.sub.3 phase mixed
with the liquid phase.
The manner in which the nickel and aluminum are mixed together and
heated is not critical provided a single-phase homogeneous melt is
formed. Generally a temperature of at least about 825.degree. C. is
necessary, and preferably a temperature of at least about
900.degree. C. is reached. When metallic aluminum and metallic
nickel are mixed at these temperatures, an exothermic reaction
takes place which raises the temperature to about 1,400.degree.
C.
The manner in which the molten mass of nickel and aluminum is
handled after it is formed is of critical importance to the
formation of a maximum amount of NiAl.sub.3 phase. If the molten
mass is quenched below its crystallization temperature by normal
procedures, such as cold casting, less than about 60 percent of the
nickel will be in the NiAl.sub.3 phase. In order to obtain alloy
containing at least about 65 percent by weight of the nickel in the
NiAl.sub.3 phase, it is necessary to anneal the liquid-solid
mixture at temperatures of about 790.degree.-854.degree. C. for at
least about 30 minutes. The time required for the annealing step
will depend upon the particular temperature used. At temperatures
of about 800.degree. C. it may be necessary to heat for about 4
hours. At temperatures of about 850.degree. C. annealing times as
short as about 30 minutes may be sufficient. Preferably the
annealing is at temperatures of about 840.degree.-854.degree. C.
for about 45 to about 75 minutes.
The thermal history of the composition between the initial
formation of the homogeneous melt and the annealing step is not
important. The molten mass can be cold cast to the solid state
before the annealing step or it can be cooled to the annealing
temperature and held at that temperature during the annealing step.
In any event, the annealing step increases the NiAl.sub.3 phase
content of the resulting alloy. After the annealing step the
resulting mass is allowed to cool to atmospheric temperature in any
convenient manner. The term "atmospheric temperature," as used
herein, is intended to include outside and room temperature.
The resulting alloy is then subjected to mechanical reduction in
particle size to a suitable size for catalytic material such as
about 0.5 micron to about 3 centimeters in diameter. The particular
particle size will depend upon whether the catalyst is to be used
as a slurried catalyst or a fixed-bed catalyst. When used as a
slurried catalyst, the particle size is preferably about 325-200
mesh. When the catalyst is used in a fixed bed, the particle size
is preferably about 20 mesh to about 2.5 centimeters in
diameter.
The alloy used in accordance with this invention is activated by
contacting it with an aqueous alkali metal hydroxide solution until
about 2-100 percent by weight of the aluminum is leached from the
alloy. When the activated catalyst is used in a slurry system,
generally about 85-100 percent of the aluminum is leached from the
alloy. When the catalyst is used in a fixed bed, generally about
2-50 percent of the aluminum is leached out and the residual
aluminum acts as a support for the nickel. Suitable alkali metal
hydroxides include sodium, potassium, lithium, cesium and rubidium
hydroxides. The aqueous solution may contain the hydroxide alone or
it may also contain buffer components such as alkali metal
carbonates. Generally the alkali metal hydroxide solution will
contain about 0.1-5 percent by weight of alkali metal hydroxide,
and preferably it contains about 0.25-1 percent by weight of
hydroxide.
The preferred method of activating the catalyst is to treat the
alloy with an aqueous alkali metal hydroxide solution which is fed
at a temperature not in excess of about 35.degree. C., whereby less
than about 1.5 moles of hydrogen are evolved for each mole of
sodium hydroxide. Preferably the aqueous solution contains about
0.25-1 percent by weight of sodium hydroxide, the exit temperature
of the solution during activation does not exceed about 35.degree.
C., and about 2-30 percent by weight of the aluminum originally
contained in the alloy is leached out. The term "activated" as used
herein is intended to refer to both the original activation of the
fresh alloy and to the reactivation of the same alloy after it has
lost its activity through use.
The nickel-containing foraminous materials of this invention are
suitable for use in all applications which have heretofore been
found to be useful for Raney nickel-type catalysts. They are
particularly useful as catalysts for the hydrogenation of organic
compounds to compounds of increased hydrogen content. Suitable
reactions include the hydrogenation of carbon-carbon double and
triple bonds such as the conversion of aryl, alkenes and alkynes to
the corresponding more saturated or completely saturated compounds.
Suitable reactions include the conversion of benzene to
cyclohexane, cyclododecatriene to cyclododecane, butadiene to
butene or butane and butynediol to butanediol. Other hydrogenation
reactions include the conversion of nitro compounds to amines, the
hydrogenation of cyano compounds to amines such as the
hydrogenation of adiponitrile to hexamethylene diamine, the
hydrogenation of esters to alcohols, the hydrogenation of ketones
to secondary alcohols, the hydrogenation of aldehydes to alcohols,
the hydrogenation of alkyl anthraquinones to alkyl
anthrahydroquinones, and the complete hydrogenation of any of the
above compounds to hydrocarbons.
Use of the activated catalysts of this invention leads to a number
of process advantages in hydrogenation reactions. Substitution of
the catalyst of this invention for a conventional Raney nickel
catalyst in many cases allows the reaction to be completed in
considerably less time than was previously required. On the other
hand, it may be desirable to increase the concentration of the feed
material or decrease the size of the catalyst bed rather than
shortening the reaction time. Another advantage of the catalyst of
this invention is that it tends to initiate hydrogenation reactions
at a lower feed temperature.
In hydrogenation reactions using a conventional Raney nickel
fixed-bed catalyst the useful life of the catalyst can be increased
by substituting an activated catalyst of this invention for the
conventional catalyst and removing only one-half as much aluminum
during activation of the improved catalyst as was removed from the
conventional catalyst. Such a catalyst will have approximately the
same activity as the conventional catalyst but will undergo twice
as many reactivations.
The activated catalysts of this invention are particularly suitable
for the hydrogenation of cyclododecatriene to cyclododecane. This
reaction is normally carried out using a conventional Raney
nickel-type fixed-bed catalyst of about 2-10 mesh size from which
about 15-25 percent by weight of the aluminum has been removed. The
feed mixture containing about 5-15 percent by weight of
cyclododecatriene and about 85-95 percent by weight of
cyclododecane is passed over the catalyst at a temperature of about
125.degree.-250.degree. C. and a pressure of about 25-30
atmospheres at the rate of about 0.25-0.4 part by weight of feed
mixture per part of catalyst per hour.
When using the improved catalyst of this invention in the
hydrogenation of cyclododecatriene, the amount of aluminum leached
out during the initial activation could be reduced to about 5-15
percent with the result that a second activation of the catalyst
could be carried out after the catalyst becomes spent. On the other
hand if about 15-25 percent of the aluminum is leached from the
improved catalyst of this invention, the concentration of
cyclododecatriene in the feed mixture could be increased to about
10-20 percent by weight or the weight ratio of feed mixture per
hour to catalyst could be increased to about 0.6-0.75. The
temperature at which the reaction is initiated could also be
reduced to about 100.degree. C. when using the more active catalyst
of this invention.
The improved catalysts of this invention are also particularly
useful for the conversion of 2-butyne-1,4-diol to 1,4-butanediol.
The reaction is normally carried out with a conventional fixed-bed
Raney nickel-type catalyst of 2-10 mesh size which has been
activated by removal of about 15-25 percent of the aluminum. The
reaction is carried out using an aqueous feed containing about
20-70 percent butynediol and about 30-80 percent water, a hydrogen
partial pressure of about 150-400 atmospheres, and a superficial
gas velocity of at least about 0.5 foot per minute at a temperature
of about 60.degree.-150.degree. C. and a recycle to fresh feed
ratio of about 10-40:1.
In the hydrogenation of butynediol using the improved catalyst of
this invention, removal of only about 2-5 percent of the aluminum
during activation would provide a suitable catalyst which could be
reactivated in situ. Using an improved catalyst of this invention
having about 15-25 percent of the aluminum removed could allow a
decrease in the size of the catalyst bed, an increase in the rate
at which the butynediol is fed to the reactor, or an increase in
the total quantity of butynediol which can be converted before the
catalyst becomes spent thereby increasing the effective life of the
catalyst.
The improved catalysts of this invention are also useful for the
hydrogenation of alkyl anthraquinones to alkyl anthrahydroquinones.
This hydrogenation reaction is generally used as one step in a
cyclic process for making hydrogen peroxide. In this process an
alkylated anthraquinone is hydrogenated to the corresponding
alkylated hydroanthraquinone in a slurry of hydrogenation catalyst.
The catalyst is filtered out and the resulting medium is contacted
with air to form hydrogen peroxide and alkylated anthraquinone. The
hydrogen peroxide is recovered and the alkylated anthraquinone is
reconverted to alkylated hydroanthraquinone in the hydrogenation
step. In the hydrogenation step of such a process the activated
catalyst of this invention could be slurried with a solution
containing alkylated anthraquinone, alkylated hydroanthraquinone
and a suitable solvent. Suitable alkylated anthraquinones include
2-ethylanthraquinone, 2-tert.-butylanthraquinone,
2-amyl-anthraquinone, tetrahydro derivatives of the above
anthraquinones, and mixtures thereof. The reaction takes place at
about 25.degree.-50.degree. C. while charging hydrogen at
atmospheric or slightly elevated pressure.
The nickel-containing foraminous materials of this invention can
also be used as the anode in fuel cells such as hydrogen-oxygen
fuel cells. In preparing the anode nickel-aluminum alloy powder is
mixed with water and pressed into the shape of the anode. The alloy
powder is then sintered and activated with dilute aqueous alkali
metal hydroxide solution to leach aluminum from the surface of the
anode. The anode is then placed in a fuel cell, for example a
hydrogen-oxygen fuel cell, containing a conventional cathode such
as a silver electrode and operated at about 92.degree. C. with
about 35-38 percent by weight aqueous potassium hydroxide as the
electrolyte. The oxygen and hydrogen are supplied at about 25
p.s.i.g.
EXAMPLES OF THE INVENTION
The following examples, illustrating the preparation and use of the
foraminous materials of this invention, are given without any
intention that the invention be limited thereto. All parts and
percentages are by weight.
EXAMPLE 1
An alloy containing 28 percent nickel and 72 percent aluminum was
melted at 1,100.degree. C. The melted mass was allowed to cool fast
to form an ingot. The ingot was melted at 975.degree. C., the melt
was lowered through the furnace and a rectangular ingot in the
shape of a bar was withdrawn from the furnace at the rate of 3.4
millimeters per hour with the point of solidification being
maintained just below 854.degree. C. The ingot was then cooled to
atmospheric temperature. Examination of the interior of the ingot
indicated a major portion of intermetallic NiAl.sub.3 compound.
The alloy was powdered by filing with an iron file to particles of
50-100 mesh size. The powdered alloy was slurried in an aqueous
solution of one normal sodium hydroxide at 15.degree. C. The rate
of addition of powdered alloy to the solution was sufficiently slow
that the temperature did not reach 35.degree. C. The temperature
was also controlled by having the reaction vessel partially
immersed in an ice bath. The quantity of alloy particles added to
the caustic solution was limited so that only 50 percent of the
sodium hydroxide was utilized in the activation. After the
evolution of hydrogen subsided, the temperature of the contents of
the vessel was gradually raised to the boiling point and held there
for 10 minutes. The medium was then cooled and the activated
catalyst was repeatedly water washed with decantation until the
sodium ion was completely removed as indicated by the absence of
sodium ion in the wash water. The catalyst was then washed
repeatedly with methanol by decantation until about 98 percent of
the water was removed. The catalyst was then repeatedly washed with
cyclohexane until about 99 percent of the methanol was removed and
the catalyst was stored as a slurry in cyclohexane. Spectrographic
analysis of the catalyst for impurities indicated the presence of
0.2-0.3 percent of cobalt as the only detectable impurity.
The activity of the catalyst was determined by the hydrogenation of
benzene at 120.degree.-150.degree. C. About 250 parts of a mixture
of 10 percent benzene and 90 percent cyclohexane were mixed with 1
part of the above catalyst in a closed vessel and hydrogen was
supplied at a pressure of 2,000 p.s.i. The benzene was completely
converted to cyclohexane after 6.25 minutes.
EXAMPLE 2
A mixture containing 42 percent nickel and 58 percent aluminum was
heated to 1,120.degree. C. in an inert atmosphere at which
temperature it became fluid. The material was then transferred to
another furnace at 837.degree. C., after which the temperature in
the furnace was slowly decreased to 800.degree. C., over a 30
-minute period and maintained at 795.degree. C. for an additional
hour. The heat was then turned off and the material was allowed to
cool to atmospheric temperature in the closed furnace over a 16
-hour period. Metallographic investigation of the ingot showed a
coarse cellular structure having intermetallic NiAl.sub.3 compound
as the major phase and Ni.sub.2 Al.sub.3 phase present in some of
the cells. The interstices between the cells contained
aluminum.
The above alloy was reduced in particle size and activated as
described in example 1. The activated catalyst was then used in the
hydrogenation of benzene to cyclohexane as described in example 1.
The reaction time for 100 percent conversion of benzene to
cyclohexane was 10.25 minutes.
EXAMPLE 3
A mixture of 42 percent nickel and 58 percent aluminum was slowly
heated to 1,216.degree. C. in an alumina crucible which had been
previously baked at 250.degree. C. under vacuum for 16 hours to
remove water. Melting was done in a melt chamber using induction
heating and an inert atmosphere. After melting was completed, the
temperature was maintained between 1,216.degree. C. and
1,204.degree. C. for 11 minutes. The molten material was hot cast
into a crucible steel mold preheated at 700.degree. C. and allowed
to cool from 854.degree.C. to 800.degree. C. in a furnace over a
period of 70 minutes. The ingot was then allowed to cool in the
furnace to room temperature. X-ray powder diffraction and
metallography investigation of the resulting ingot revealed that
the sample consisted of about 80 percent NiAl.sub.3 phase, about 10
percent Ni.sub.2 Al.sub.3 phase, and only a trace of aluminum.
The alloy was reduced in particle size and activated as described
in example 1. The activated catalyst was then used in the
hydrogenation of benzene to cyclohexane by the procedure of example
1. The time for 100 percent conversion of benzene to cyclohexane
was 9 minutes.
EXAMPLE 4
An alloy was prepared from a mixture containing 36 percent nickel
and 64 percent aluminum following the procedure of example 3,
except that the melt chamber was heated slowly to 1,033.degree. C.
at which point the temperature rose sharply to 1,160.degree. C. in
5 minutes. The material was cast into slab molds and allowed to
cool from 850.degree. C. to 800.degree. C. over a period of 30
minutes. X-ray diffraction analysis indicated that the sample
contained NiAl.sub.3, Ni.sub.2 Al.sub.3 and Al phases.
Metallographic investigation showed a dendritic core of Ni.sub.2
Al.sub.3 surrounded by NiAl.sub.3 with aluminum filling the
interdendritic spaces. The NiAl.sub.3 phase content was about 70
percent.
The alloy was reduced in particle size and activated as described
in example 1. The activated catalyst was then used to hydrogenate
benzene to cyclohexane as described in example 1. The time for 100
percent conversion of benzene to cyclohexane was 13 minutes.
EXAMPLE 5
A commercially obtained Raney nickel alloy containing 42 percent
nickel and 58 percent aluminum was annealed by heating at
800.degree. C. for 4 hours. The resulting material was allowed to
cool in the furnace as in example 3. The resulting alloy was
reduced in particle size and activated as described in example 1.
The resulting activated catalyst was used in the hydrogenation of
benzene to cyclohexane as in example 1. The time to 100 percent
conversion of benzene to cyclohexane was 14.5 minutes.
For comparison, a conventional Raney nickel catalyst was prepared
by melting a mixture of 42 percent nickel and 58 percent aluminum
under exothermic conditions. The molten mass was then cold cast
into iron molds. After the molten mass had cooled the ingot was
mechanically reduced to particles of 50-100 mesh and activated as
described in example 1. This standard Raney nickel catalyst was
then used in the hydrogenation of benzene to cyclohexane as
described in example 1. The reaction time for 100 percent
conversion of benzene to cyclohexane was 20 minutes. This
conventional Raney nickel catalyst was arbitrarily assigned a
relative reaction rate of 100. The relative reaction rates of the
improved catalysts of the examples were determined by comparing the
reaction time to 100 percent conversion using the conventional
catalyst to the reaction time to 100 percent conversion using the
improved catalyst in accordance with the equation:
The following table shows the time to 100 percent conversion of
benzene to cyclohexane for the improved catalysts of the examples.
The relative reaction rates based on the conversion times are also
given.
Time to 100 % Conversion, Relative Example minutes Reaction Rate
__________________________________________________________________________
1 6.25 325 2 10.25 195 3 9 220 4 13 155 5 14.5 140 Conventional
Cat. 20 100
Although the invention has been described and exemplified by way of
specific embodiments, it is not intended that it be limited
thereto. As will be apparent to those skilled in the art, numerous
modifications and variations of these embodiments can be made
without departing from the spirit of the invention or the scope of
the following claims.
* * * * *