Note: Descriptions are shown in the official language in which they were submitted.
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Metal Catalysts
The present invention relates metal catalysts
Activated metal catalysts are known in the field of
chemical engineering as Raney catalysts. They are used,
largely in powder form, for a large number of
hydrogenation, dehydrogenation, isomerization and hydration
reactions of organic compounds. These powdered catalysts
are prepared from an alloy of a catalytically-active metal,
also referred to herein as a catalyst metal, with a further
alloying component which is soluble in alkalis. Mainly
nickel, cobalt, copper, or iron are used as catalyst
metals. Aluminum is generally used as the alloying
component which is~soluble in alkalis, but other components
may also be used, in particular zinc and silicon or
mixtures of these with aluminum.
These so-called Raney alloys are generally prepared by the
ingot casting process. In that process a mixture of the
catalyst metal and, for example, aluminum are first melted
and casted into ingots. Typical alloy batches on a
production scale amount to about ten to one hundred kg per
ingot. According to DE 21 59 736 cooling times~of up to two
hours were obtained. This corresponds to an average _rate of
cooling of about 0. 2 /s. In contrast to this, rates of 102
to 106 K/s are achieved in processes where rapid cooling is
applied (for example an atomizing process). The rate of
cooling is affected in particular by the particle size and
the cooling medium (see Materials Science and Technology
edited by R. W. Chan, P. Haasen, E. J. Kramer, Vol. 15,
Processing of Metals and Alloys, 1991, VCH-Verlag Weinheim,
pages 57 to 110). A process of this type is used in EP 0
437 788 B 1 in order to prepare a Raney alloy powder. In
that process the molten alloy at a temperature of 50 to
500°C above its melting point is atomized and cooled using
water and/or a gas.
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To prepare a catalyst, the Raney alloy is first finely
milled if it has not been produced in the desired powder
form during preparation. Then the aluminum is entirely or
partly removed by extraction with alkalis such as, for
example, caustic soda solution. This activates the alloy
powder. Following extraction of the aluminum the alloy
power has a high specific surface area (BET), between 20
and 100 m2/g, and is rich in active hydrogen. The activated
catalyst powder is pyrophoric and stored under water or
organic solvents or is embedded in organic compounds which
are solid at room temperature.
Powdered catalysts have the disadvantage that they can be
used only in a batch process and, after the catalytic
reaction, have to be separated from the reaction medium by
costly sedimentation and/or filtration. Therefore a variety
of processes for preparing moulded items which lead to
activated metal fixed-bed catalysts after extraction of the
aluminum have been disclosed. Thus, for example, coarse
particulate Raney alloys, i.e., Raney alloys which have
only been coarsely milled, are obtainable and these can be
activated by a treatment with caustic soda solution.
Extraction and activation then occurs only in a surface
layer the thickness of which can be adjusted by the
conditions used during extraction.
A substantial disadvantage of catalysts prepared by these
prior methods are the poor mechanical stability of the
activated outer layer. Since only this outer layer of the
catalysts the catalytically active, abrasion leads to rapid
deactivation and renewed activation of deeper lying layers
of alloy using caustic soda solution then leads at best to
partial reactivation.
Patent application EP 0 648 534 B1 describes shaped,
activated Raney metal fixed-bed catalysts and their
preparation. These catalysts avoid the disadvantages
described above, e.g., the poor mechanical stability
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resulting from activating an outer layer. To prepare these
catalysts, a mixture of powers of a catalyst alloy and a
binder are used, where in the catalyst alloys each contain
at least one catalytically active catalyst metal and an
extractable alloying component. The pure catalyst metals or
mixtures thereof which do not contain extractable
components are used as binder. The use of the binder in an
amount of 0. 5 to 20 weight percent with respect to the
catalyst alloy, is essential in order to achieve sufficient
mechanical stability after activation. After shaping the
catalyst alloy and the binder with conventional shaping
aids and pore producers, the freshly prepared items which
are obtained are calcined at temperatures below 850°C. As a
result of sintering processes in the finely divided binder,
this produces solid compounds between the individual
granules of the catalysts alloy. These compounds, in
contrast to catalyst alloys, are non-extractable or only
extractable to a small extent so that a mechanical stable
structure is obtained even after activation. However, the
added binder has the disadvantage that it is substantially
catalytically inactive and thus the number of active
centers in the activated layer is reduced. In addition, the
absolutely essential use of a binder means that only
restricted range of amounts of pore producers can be used
without endangering the stregnth of the shaped item:'- For
this reason, the bulk density of these catalysts cannot be
reduced to a value of less than 1. 9 kg per liter without
incurring loss of strength. This leads to a considerable
economic disadvantage when using these catalysts in
industrial processes. In particular when using more
expensive catalysts alloys, for example cobalt alloys, the
high bulk density leads to a high investment per reactor
bed, which is, however partly compensated for by the high
activity and long-term stability of these catalyst. In
certain cases, the high bulk density of the catalyst also
requires a mechanically reinforced reactor structure.
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An object of the present invention is therefore to provide
activated base metal catalysts from hallow metallic forms
which largely avoids the disadvantages of the above known
fixed-bed catalysts.
The above and other objects of the invention are achieved
by producing hallow forms out of the desired alloys and
activating it in order to make the catalyst. The major
advantages of this invention are its low bulk density and
its high activity these materials exhibit per gram of
metal.
One object of the invention is metal catalysts comprising
hallow forms. Preferably the hallow forms are hallow
spheres. These spheres can show a diameter of 0,5 to 20 mm
and a wall thickness of 0,1 to 5 mm. The shell of the
spheres can be unpermeable or it can show an open porosity
up to 80 ~. The shell of the spheres can consist of
different layers and/or the metal can be graduated.
The metal catalysts comprising hallow forms can be
activated.
Another object of the invention is a process for the for
the production of the metal catalysts comprising spraying
of metal powders, obtionally together with a binder on to
forms consisting of a burnable material i.e. styrofoam,
burning out the materal to receive the hallow form.
In another object of the invention in the process for the
production of the metal catalysts where one of the metal
powders consists of a rapidly cooled alloy. The rapidly
cooled alloy can be made according to commonly used methods
such spray drying in vanous atmospheres as rapidly cooling
in liquids such as water. The hallow form consisting of the
alloy and optionally a binder can then be activated with an
alkali solutions such as agueous NaOH, to form the
activated catalyst.
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One of the metal powders can consist of a slowly cooled
alloy. The hallow form consisting of the aloy and
optionally a binder can then be activated with an
alkalisolution, such as an aqueous NaOH solution , to form
5 the activated catalyst.
In the process for the production of the metal catalysts
the alloy can consist of one or more catalytic metal such
as nickel, iron, copper, palladium, ruthenium, and cobalt;
an alkali soluble component such as aluminium, zinc, and
silica: and optionally one or more promoter elements such
as Cr, Fe, Ti, V, Ta, Mo, Mg, Co, and/or W.
The hallow spheres according to this invention can be
prepared according to Andersen, Schneider, and Stephani
(See, "Neue Hochporbse Metallische Werkstoffe", Ingenieur-
Werkstoffe, 4, 1998, pages 36-38). In this method, a
mixture of the desired alloy, an organic binder, and
optionally an inorganic binder were sprayed uniformly
through a fluidized bed of Styrofoam balls where it coats
the Styrofoam. The coated balls are then calciried at
optionally temperatures ranging from 450 to 1000°C to burn
out the Styrofoam followed by a higher calcination
temperature to sinter the metal together in order to make
the hallow form more stable. After calcination, the
catalyst is then activated by a caustic soda solution to
produce the activated base metal catalyst. An added benefit
to this catalyst system is that one can easy control the
thickness of the hollow form's walls from the coating
conditions and the porosity of this wall by the particle
size and composition of the original powdermixture.
The bulk density of the resulting fixed bed catalyst is
very important for highly active catalysts. While the known
standard fixed bed activated base metal catalysts have bulk
densities ranging from 2.4 to 1.8 kg/1, bulk densities
similar to other fixed bed applications such as 0.3 to 1.0
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kg/1 are highly desirable to keep the cost to fill a
commercial reactor at a minimum.
The ratio by weight of catalyst metal to extractable
alloying component in the catalyst alloy is, as is
conventional with Raney alloys, in the range from 20:80 to
80:20. Catalysts according to the invention may also be
doped with other metals in order to have an effective on
the catalytic properties. The purpose of this type of
doping, is for example, to improve the selectivity in a
specific reaction. Doping metals are frequently also
called promoters. The doping or promoting of Raney catalyst
is described for example in U.S. patent 4,153, 578 and DE-
AS 21 O1 856 in DE-OS 21 00 373 and in the DE-AS 2053799.
In principle, any known metal alloys such as nickel-
aluminium, cobalt-aluminium, copper-aluminium, nickel-
chrom-iron-aluminium can be used. This means any Raney-type
alloys that involved the combination of leachable materals
such as zinc, silicon and/or aluminium in combination with
catalytic materials such as nickel, cobalt, copper, and/or
iron can be used.
The alloys can contain doping materials like chrom, iron,
titanium, vanadium, tantalum with extractable elements such
as aluminum zinc and silicon maybe used for the present
invention. Suitable promoters are transition elements in
groups of 3B to 7B and 8 and group 1B of the Periodic Table
of Elements and also the rare-earth metals. They are also
used in an amount of up to 20 wt$, with respect of the
total weight of catalyst. Chromium, manganese, iron,
cobalt, vanadium, tantalum, titanium, tungsten, and/or
molybdenum and metals from platinum group are preferably
used as promoters. They are expediently added as alloying
constituents in the catalyst alloy. In addition, promoters
with a different extractable metal alloy, in the form of a
separable metal powder, may be used, or the promoters may
be applied later to the catalyst's material. Later
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application of promoters may be performed either after
calcination or after activation. Optimum adjustment of the
catalyst properties to the particular catalyst process is
thus possible.
The Raney type catalyst precursors resulting from
calcination are also very important with regard the
economic viability of invention. They are not pyrophoric
and can be handled and transported without difficulty.
Activation can be performed by the user shortly before use.
Storage under water or organic solvents or embedding in
organic compounds is not required for the catalyst
precursors.
The metal catalysts of the invention can be used for the
hydrogenation, dehydrogenation, isomerisation and/or
hydration reaction of organic compounds.
Comparison Example 1
A free-flowing, pelletable catalyst mixture was prepared in
accordance with the instructions in EP 0 648 534 A1 for a
comparison catalyst consisting of 1000 g of 53$Ni and 47~A1
alloy powder, 150 g of pure nickel powder(99$Ni, and d50 =
21 um), and 25 g of ethylene bis-stearoylamide whilst
adding about 150 g of water. Tablets with the diameter of 4
mm and a thickness of 4 mm were compressed from this
mixture. The shaped items were calcined for 2 h at 700°C.
The tablets were activated in 20~ strength caustic soda
solution for 2 hours at 80°C after calcination. Under the
conditions of application example, this catalyst started to
hydrogenate nitrobenzene at 120°C and the activity was 1,36
ml of consummed hydrogen per gram of catalyst per minute.
Example 1
A coating solution was prepared by suspending 600 grams of
a rapidly cooled SOgNi/50~A1 alloy in a 800 ml aqueous
solution containing 5 wt~ polyvinylalcohol and 1.25 wt~
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glycerin. This suspension was then sprayed onto 1500 ml of
Styrofoam balls ranging from 4 to 5 mm while they were
suspended in an upward air steam. After coating the
styrofoam balls with the above mentioned solution, the
balls were then dried in upwardly flowing air at
temperatures upto 80°C (higher temperatures can also be
used). These dried coated styrofoam spheres had a bulk
density of 0.45 g/ml and half of these spheres were further
coated with an alloy solution so as to demonstrate the
flexibility of this process. The solution for the second
layer consisted of 700 grams of a rapidly cooled
50$Ni/50$A1 alloy that was suspended in a 800 ml aqueous
solution containing 5 wt~ polyvinylalcohol and 1.25 wt~
glycerin. This suspension was then sprayed onto 750 ml of
the Ni/A1 precoated and dried Styrofoam balls mentioned
above while they were suspended in an upward air steam.
After coating the styrofoam balls with the above mentioned
solution, the balls were then dried in upwardly flowing air
at temperatures upto 80°C (higher temperatures can also be
used). Although the solution for the second layer was
similar to the first, this technique clearly demonstrates
the ability of this process to make layered hallow spheres.
The dried coated spheres were then heated in a controlled
nitrogen/air stream at 830°C for 1 hour to burn out the
Styrofoam and to sinter together the alloy particles, The
hallow spheres were then activated in a 20 wt~ NaOH
solution for 1.5 hours at 80°C. The resulting activated
hallow spheres had diameters ranging from 5 to 6 mm, a
shell thickness range of 700-1000u, a crush strength of 90
N, and the bulk density of 0.62 g/ml. Under the conditions
of application example 1, this catalyst started to
hydrogenate nitrobenzene at 110-120°C and the catalyst's
nitrobenzene activity was 1.54 ml of consummed hydrogen per
gram of catalyst per minute.
Example 2
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A coating solution was prepared by suspending 500 grams of
a rapidly cooled 50%Ni/50%A1 alloy and 37.5 grams of nickel
powder in a 750 ml aqueous solution containing 5 wt%
polyvinylalcohol and 1.25 wt% glycerin. This suspension was
then sprayed onto 1000 ml of styrofoam balls ranging from 4
to 5 mm while they were suspended in an upward air steam.
After coating the Styrofoam balls with the above mentioned
solution, the balls were then dried in upwardly flowing air
at temperatures upto 80°C (higher temperatures can also be
used). The dried coated spheres were then heated in a
controlled nitrogen/air stream at 840°C for 1 hour to burn
out the styrofoam and to sinter together the nickel and
alloy particles. The hallow spheres were then activated in
a 20 wt% NaOH solution for 1.5 hours at 80°C. The resulting
activated hallow spheres had diameters ranging from 5 to 6
mm, an average shell thickness of 500 p, and the bulk
density of 0.34 g/ml. Under the conditions of application
example 1, this catalyst started to hydrogenate
nitrobenzene at 110-120°C and the catalyst's nitrobenzene
activity was 1.82 ml of consummed hydrogen per gram of
catalyst per minute.
Example 3
A coating solution was prepared by suspending 800 grams of
a 50%Co/50%A1 alloy in a 1000 ml aqueous solution '-
containing 5 wt% polyvinylalcohol and 1.25 wt% glycerin.
This suspension was then sprayed onto 2000 ml of Styrofoam
balls ranging from 4 to 5 mm while they were suspended in
an upward air steam. After coating the Styrofoam balls with
the above mentioned solution, the balls were then dried in
upwardly flowing air at temperatures upto 80°C (higher
temperatures can also be used). These dried coated
Styrofoam spheres had a bulk density of 0.35 g/ml and half
of these spheres were further coated with an alloy
solution. The solution for the second layer consisted of
800 grams of a 50%Co/50%A1 alloy that was suspended in a
1000 ml aqueous solution containing 5 wt% polyvinylalcohol
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and 1.25 wt~ glycerin. This suspension was then sprayed
onto 1000 ml of the Co/A1 precoated and dried styrofoam
balls mentioned above while they were suspended in an
upward air steam. After coating the Styrofoam balls with
5 the above mentioned solution, the balls were then dried in
upwardly flowing air at temperatures upto 80°C (higher
temperatures can also be used). The dried coated spheres
were then heated in a controlled nitrogen/air stream at
700°C to burn out the styrofoam and to sinter together the
10 alloy particles. The hallow spheres were then activated in
a 20 wt~ NaOH solution for 1.5 hours at 80°C. The resulting
activated hallow spheres had diameters ranging from 5 to 6
mm, a shell thickness of 700 u, a crush strength of 71 N,
and the bulk density of 0.50 g/ml. As could be visually
seen from the evolution of hydrogen bubbles, the catalyst
had a large reservoir of active hydrogen.
Example 4
A coating solution was prepared by suspending 800 grams of
a 50~Cu/50$A1 alloy and 104 grams of copper powder in a
1000 ml aqueous solution containing 5 wt$ polyvinylalcohol
and 1.25 wt~ glycerin. This suspension was then sprayed
onto 2000 ml of styrofoam balls ranging from 4 to 5 mm
while they were suspended in an upward air steam. After
coating the Styrofoam balls with the above mentioned~
solution, the balls were then dried in upwardly flowing air
at temperatures upto 80°C (higher temperatures can also be
used). These dried coated styrofoam spheres had a bulk
density of 0.26 g/ml and half of these spheres were further
coated with an alloy solution. The solution for the second
layer consisted of 800 grams of a 50$Cu/50~A1 alloy and 104
grams of copper powder that were suspended in a 1000 ml
aqueous solution containing 5 wt~ polyvinylalcohol and 1.25
wt$ glycerin. This suspension was then sprayed onto 1000
ml of the Cu/A1 precoated and dried Styrofoam balls
mentioned above while they were suspended in an upward air
steam. After coating the styrofoam balls with the above
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mentioned solution, the balls were then dried in upwardly
flowing air at temperatures upto 80°C (higher temperatures
can also be used). The dried coated spheres were then
heated in a controlled nitrogen/air stream at 550°C to burn
out the styrofoam and to sinter together the copper and
alloy particles. The hallow spheres were then activated in
a 20 wto NaOH solution for 1.5 hours at 80°C. The resulting
activated hallow spheres had an average diameter 6 mm, a
shell thickness ranging from 600 to 700 u, and the bulk
density of 0.60 g/ml. As could be visually seen from the
evolution of hydrogen bubbles, the catalyst had a large
reservoir of active hydrogen.
Example 5
A coating solution was prepared by suspending 800 grams of
a slowly cooled 50$Ni / 0.5$Fe / 1.2$Cr / 48.3~A1 alloy and
60 grams of nickel powder in a 1000 ml aqueous solution
containing 5 wt$ polyvinylalcohol and 1.25 wt~ glycerin.
This suspension was then sprayed onto 2000 ml of ~styrofoam
balls ranging from 4 to 5 mm while they were suspended in
an upward air steam. After coating the Styrofoam balls with
the above mentioned solution, the balls were then dried in
upwardly flowing air at temperatures upto 80°C (higher
temperatures can also be used). These dried coated
Styrofoam spheres had a bulk density of 0.30 g/ml and half
of these spheres were further coated with an alloy
solution. The solution for the second layer consisted of
800 grams of a slowly cooled 50$Ni / 0.5$Fe / 1.2$Cr /
48.3~A1 alloy and 60 grams of nickel powder that were
suspended in a 1000 ml aqueous solution containing 5 wt$
polyvinylalcohol and 1.25 wt$ glycerin. This suspension was
then sprayed onto 1000 ml of the Ni/Fe/Cr/Al precoated and
dried Styrofoam balls mentioned above while they were
suspended in an upward air steam. After coating the
styrofoam balls with the above mentioned solution, the
balls were then dried in upwardly flowing air at
temperatures upto 80°C (higher temperatures can also be
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used). The dried coated spheres were then heated in a
controlled nitrogen/air stream at 700°C to burn out the
Styrofoam and to sinter together the nickel and alloy
particles. The hallow spheres were then activated in a 20
wt~ NaOH solution for 1.5 hours at 80°C. The resulting
activated hallow spheres had an average diameter 5.9 mm, a
shell thickness of 700 u, the crush strength of 85 N, and
the bulk density of 0.55 g/ml. Under the conditions of
application example 1, this catalyst started to hydrogenate
nitrobenzene at 110°C and the catalyst's nitrobenzene
activity was 2.40 ml of consummed hydrogen per gram of
catalyst per minute.
Example 6
A coating solution was prepared by suspending 1000 grams of
a rapidly cooled 50%Ni/50$A1 alloy and 75 grams of nickel
powder in a 1000 ml aqueous solution containing 5 wt$
polyvinylalcohol and 1.25 wt$ glycerin. This suspension was
then sprayed onto 2000 ml of Styrofoam balls ranging from 2
to 3 mm while they were suspended in an upward air steam.
After coating the Styrofoam balls with the above mentioned
solution, the balls were then dried in upwardly flowing air
at temperatures upto 80°C (higher temperatures can also be
used). These dried coated styrofoam spheres had a bulk
density of 0.33 g/ml and half of these spheres were further
coated with an alloy solution. The solution for the second
layer consisted of 1000 grams of a rapidly cooled
50~Ni/50gA1 alloy and 75 grams of nickel powder that were
suspended in a 1000 ml aqueous solution containing 5 wt$
polyvinylalcohol and 1.25 wt~ glycerin. This suspension was
then sprayed onto 1000 ml of the Ni/A1 precoated and dried
styrofoam balls mentioned above while they were suspended
in an upward air steam. After coating the styrofoam balls
with the above mentioned solution, the balls were then
dried in upwardly flowing air at temperatures upto 80°C
(higher temperatures can also be used). These dried double
coated Styrofoam spheres had a bulk density of 0.75 g/ml
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and half of these spheres were once again coated further
with a third addition of the alloy solution. The solution
for the third layer consisted of 1000 grams of a rapidly
cooled 50$Ni/50~A1 alloy and 75 grams of nickel powder that
were suspended in a 1000 ml aqueous solution containing 5
wt~ polyvinylalcohol and 1.25 wt~ glycerin. This suspension
was then sprayed onto 500 ml of the Ni/Al double-precoated
and dried styrofoam balls mentioned above while they were
suspended in an upward air steam. After coating the
Styrofoam balls with the above mentioned solution, the
balls were then dried in upwardly flowing air at
temperatures upto 80°C (higher temperatures can also be
used). The dried triple-coated spheres were then heated in
a controlled nitrogen/air stream at 700°C to burn out the
styrofoam and to sinter together the nickel and alloy
particles. The hallow spheres were then activated in a 20
wt$ NaOH solution for 1.5 hours at 80°C. The resulting
activated hallow spheres had an average diameter 4.5 mm, a
shell thickness of 600 to 700 u, and the bulk density of
0.85 g/ml. Under the conditions of application example 1,
this catalyst started to hydrogenate nitrobenzene at 78°C
and the catalyst's nitrobenzene activity was 3.46 ml of
consummed hydrogen per gram of catalyst per minute.
Application example 1
The catalytic activity of the catalyst from comparison
examples 1 and 2 and from examples 1 to 5 were compared
during the hydrogenation of nitrobenzene. For this purpose,
100 g of nitrobenzene and 100 g of ethanol were placed in a
stirred autoclave with a capacity of 0.5 1, fitted with a
gas stirrer. 10 g of the catalyst being investigated were
suspended each time in the stirred autoclave using a
catalyst basket so that the catalyst material was
thoroughly washed by the reactant/solvent mixture, and
hydrogen was introduced. Hydrogenation was performed at a
hydrogen pressure of 40 bar and a temperature of 150°C. The
initiation temperature and the rate of hydrogen consumption
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were determined. The results are given in table 1. As a
check, samples were withdrawn after 1, 2, 3, 4, and 5 h and
analyzed using gas chromatography.
CA 02313874 2000-07-13
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