Note: Descriptions are shown in the official language in which they were submitted.
200 5s~ 2
FIBRILS
This invention relates to fibrils. It more
particularly refers to carbon/graphite fibrils and to an
improved process for producing such. Carbon fibrils as
used herein means graphitic fibrils having high surface
area, high Young's modulus of elasticity and high tensile
strength which are grown catalytically from available
sources of carbon.
Background of the Invention
It has been known for some time that one could
make fibrils by decomposing various carbon contributing
molecules, such as light hydrocarbons, in contact with a
suitable metal catalyst, such as for example iron alone
or in combination with other metals. In the past, the
fibrils which have been made have been somewhat thicker
than desirable and/or have been burdened with an
overcoat of thermally deposited generally amorphous
carbon which tended to reduce the desirable physical
properties thereof or have been made in poor yields.
Prior workers have sought to ameliorate the
disadvantages of the amorphous carbon overcoating by
subjecting the finished fibril to a very high
temperature graphitizing treatment whereby generally
rendering the fibrils of substantially greater cross
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sectional consistency from both a composition and a
crystallinity point of view.
It is obvious that the improved fibril
properties engendered by this high temperature
graphitization process are expensive, because high
temperature treatments are expensive. Additionally,
such graphitized fibrils may still be too thick for many
purposes because, graphitizing does not significantly
reduce the fibril diameter. Thus, it is desired to
produce high yields of high quality fibrils, preferably
thin fibrils, which, in a preferred aspect of this
invention, do not need post production graphitization.
Summary of the Invention
Fibrils are made according to this invention in a high
temperature, catalytic process. The Fibril can be made
of a variety of materials, e.g. carbon, silicon nitride,
silicon carbide, etc. In one important embodiment, such
fibrils have the atoms in their composition relatively
ordered at their outer surfaces as they are made by this
process. Thus, it can be said that this process
preferably directly produces a product having a
relatively crystalline outer region for substantial
portions of its length and may have inner regions where
its atoms are less ordered. It may, and often does,
even have a hollow region axially positioned along
substantial portions of its length.
Fibrils according to this invention are
characterized by small diameters, e.g. about 3.5 to ~o
nanometers and high L/D up to about 100 and even more.
Where the preferred structure described above is
produced, it is suitably produced directly in the fibril
forming process without further processing being
required.
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Where the fibrils of this invention are to be
made of carbon, such can be produced in quite high
yields. In this embodiment, a suitable source of carbon
may be a hydrocarbonaceous material illustrated by:
methane, ethane, propane, butane, benzene, cyclohexane,
butene, isobutene, ethylene, propylene, acetylene,
toluene, xylene, cumene, ethyl benzene, naphthalene,
phenanthrene, anthracene, formaldehyde, acetaldehyde,
acetone, methanol, ethanol, carbon monoxide; other
similar materials, and mixtures of two (2) or more .
thereof. Such feed is contacted with a suitable,
catalyst at elevated, fibril.forming temperatures for a
time sufficient to cause graphitic carbon fibrils to
grow.
It is within the scope of this invention to
provide a non-hydrocarbonaceous gas along with the
carbon contributing reactant. Such gas might for
example be hydrogen or carbon monoxide. Inert diluents
are also suitable.
The temperature of the process of this
invention can vary widely depending upon the nature of
the carbon source being used, however, for best results,
it should be kept below the thermal decomposition
temperature thereof. In the case of using a mixture of
such carbon sources, the operating temperature should be
maintained below the thermal decomposition temperature
of the most temperature-sensitive carbon source in the
system. Temperatures in the range of 500 to 1500°C may
be found to be generally usable, depending on the carbon
source used, preferably between about 600 and 900°C.
Subatmospheric, atmospheric and/or super
atmospheric pressures may be used as dictated by other
processing considerations. It has been found that it is
desirable to provide the carbon source in the vapor
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state, and thus, the pressure should not be so high as
to cause the carbon source to be in the liquid state
under fibril forming temperature conditions. Further,
it is desirable although not essential to provide a
suitable gaseous diluent, such as hydrogen or inert
gases, for example, nitrogen.
It is preferred that the system as a whole be
non-oxidizing wherefor preferably avoiding the presence
of oxygen if practical. Small amounts of these
materials can be tolerated. It should be understoor3
that the existence of oxidizing conditions, at the
elevated temperatures operative for this process, will
cause oxidation of the carbon source and therefor reduce
the amount of carbon from such source which is available
for conversion into fibrils as desired.
It may be desirable to provide suitable heat
to this reaction system where and when needed.
Temperature of different parts of the reactor zone may
be suitably controlled to different temperatures and
this is easily accomplished by using electrical
resistance heating. However in larger scale industrial
practice, electric resistance heating may sometimes be
economically replaced by direct heating, such as for
example by burning some of the carbon contributing feed
to raise the temperature of the remainder of the feed,
or by feeding the catalyst or the carbon contributing
feed, or the diluent into the system at a sufficiently
elevated temperature such that direct heat exchange of
the component with each other will cause the fibril
forming reaction to proceed as desired.
The nature of the catalyst seems to have a
significant effect upon the yield of fibrils produced
according to this invention. It is known to use iron
group metals such as iron, cobalt or nickel to catalyze
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the conversion of carbon contributing compounds to
fibrils, and such metals are within the scope of this
invention. In addition, many other multivalant
transition metals, including lanthanides, appear to be
operative. Particularly useful catalytic metals include
inter alias iron, molybdenum cobalt, nickel, platinum,
palladium, vanadium, and chromium. Of specific interest
in this process are certain combinations of transition
metals. Particularly useful combinations include iron
and molybdenum, iron and chromium, copper and nickel,
iron and platinum, iron and tin, iron and nickel, iron
and manganese, and iron and cerium.
The yield of fibrils produced according to the
practice of this invention appears to be related to the
physical state of the catalyst used to produce such.
According to this invention, it is important that the
multivalent transition metal fibril forming catalyst be
present on a suitable substrate as relatively discrete
catalytic sites, each about 35 to 700A preferably 60 to
300A in size during fibril formation. These relatively
discrete catalytic sites are produced by suitably
applying the transition metal (in an appropriate state)
to a substrate, suitably an inorganic substrate material
which can include carbon/graphite.
The size of the substrate particle is a matter
of some importance dependent upon the engineering of the
process itself. For example, if the fibril formation is
to take place in a fluid bed type of reaction zone, the
substrate particle size will suitably be less than about
400 microns. If the fluid bed is an ebullient bed of
catalyst particles, particle sizes of about 50 to 300
microns have been found to be preferable. If the fluid
bed is an ebullient bed of fibrils containing small
amounts of catalyst particles, i.e. up to about ten
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percent, these should preferably have a size of about 1
to 100 microns. If the fluid bed is a transport bed,
either up flow or down flow, the catalyst carrying
particles will suitably be less than about 10 microns,
preferably less than about one micron.
It has been found that depositing one or more
suitable transition metals on small particle substrates
produces a catalyst well suited to use in this
invention. The substrate is a material which can
conveniently withstand the rigors of fibril formation
conditions, e.g. temperatures of about 500 to 1500°C.
Suitable substrates include carbon, graphite, inorganic
oxides, etc. The particular substrate will be matched
to the particular transition metals) catalyst such that
the metal is bound strongly enough to retard migration
and agglomeration but not so strongly as to prevent or
retard the transition metal from catalyzing fibril
formation. Illustrative, inorganic oxides include
alumina, silica,. magnesia, silicates, aluminates,
spinets etc. Mixtures can be used.
Thus, very small particle iron, such as might
be produced by decomposition of iron compounds, can be
deposited on very small particle alumina, e.g. fumed
alumina having particle sizes of no larger than about
100 mesh. These alumina particles may be made up of
individual crystallites which are on the order of about
50 to 200 A, which agglomerate to form particles having
substantial available surface area sufficient to receive
deposits of appropriately sized transition metal
catalyst.
The substrate particles are suitably less than
about 300 microns. They may be less than 1 micron in
transport bed use. It appears that the transition metal
reacts with the substrate crystallites such as to bond
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the metal to the substrate and fix its position, so as
to prevent or retard catalyst agglomeration, at least
for so long as it takes to contact the supported
transition metal with the suitable carbon source at
appropriate reaction conditions. Upon contact, the
carbon source seems to pyrolyze on the catalytic site
and the desirable morphology fibril grows therefrom.
As noted, the state of the transition metal
catalyst site during fibril formation is important to
the practice of this invention. Sometimes, it appears
that this desirable catalytic site state as well as the
state of the substrate carrier therefore is changing
during the whole process hereof. Thus, the catalytic
sites may agglomerate or disperse to some extent during
the period from introduction into the reaction zone
until the fibrils made by the process are recovered. At
the time the fibrils are recovered, particles of
transition metal catalyst which are sometimes recovered
with the fibrils are of about 35 to 700A, preferably 60
to 300A in size. Thus, it is believed that the size of
the active catalyst site during fibril formation is
substantially comparable to the diameter of the fibril
being formed .
It appears that as fibril formation takes
place, active catalyst sites become catalytically
expended and need to be replaced. Additionaly, it has
been found that the fibril forming process is more
efficient and capable of better control if the catalyst
is added to the reaction zone intermittently or
continuously over substantially the entire course of the
reaction, or at least a substantial portion thereof. It
is possible that the catalyst containing substrate of
this invention may ablate with use. That is, when a
fibril is formed on a particular catalytic site, that
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2005642
fibril and its associated site may break off from the
substrate, with or without some of the substrate,
thereby exposing further catalytic sites which were
previously inside the substrate particle. Thus,
periodic or continuous addition of fresh catalyst is
desirable
Thus, according to this invention, the fibril
forming process hereof is preferably substantially
continuous in that a suitable source of carbon, with or
without carrier gas, and catalyst containing particles
are continuously or intermittently fed to a reaction
zone maintained at a fibril forming temperature
appropriate to the carbon source being used; while
fibril product, usually admixed with the remnants of the
catalyst and sometimes substrate as well, are
continuously or intermittently recovered.
The transition metal may be deposited on the
substrate by any commonly used technique for
accomplishing such deposition. Vapor deposition,
sputtering and impregnation may all be suitable. In
particular, it has been found to be expeditious to form
a water solution or dispersion of the desired metal or
metals, mix the water phase with appropriately sized
substrate, and then precipitate the metals) onto the
substrate, e.g. by evaporating the water or any other
conventional means.
It is also within the scope of this invention
to deposit the desired transition metals) from an
organic (as opposed to aqueous) medium. Suitably the
transition metal can be dissolved or suspended in such
medium, for example, as an organometallic compound, and
then impregnated onto and into a suitable substrate.
The organic carrier medium is removed, leaving behind
the impregnated, deposited transition metal.
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After the transition metal is combined with the
substrate as aforesaid, it may be important to treat
this combination so as to activate it for this
particular catalytic purpose, e.g., by heating it to
separate the metal from other ligands, if any, in the
deposition compound. It may also be necessary to adjust
the size of the prepared catalyst to make it suitable
for use in this invention. Comminution or
agglomeration, e.g. by binding, may be desirable to
produce particles of the proper size, i.e. of less than
about 400 microns.
The catalyst of this invention may be put on
the substrate hereof in any form or chemical oxidation
state. It may be the oxide or have some other ligand.
It may be reduced prior to use, but this-is not
necessary since the fibril forming reaction is a
reducing environment and thus the transition metal will
be reduced during, or immediately prior to, fibril
forming use.
Fibrils which are very thin and long, diameters
of about 3.5 to 70 nanometers and L/D of up to 100 or
more, are produced using these catalysts. These
fibrils, as produced by this process, without the
necessity of further treatment, and without the
coproduction of a thermal carbon overcoat, comprise a
carbon layer generally concentric about an axis which
comprises multiple essentially continuous layers of
ordered carbon atoms, which preferably and usually are
crystalline and graphitic. This, as produced, outer
layer of ordered carbon atoms often surrounds an inner
layer of less ordered carbon atoms. Most preferred
products of this invention are high yields of high
quality, thin fibrils of appropriate long length having
substantially uniform, concentric, substantially
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continuous, ordered, multiple layers of carbon about an
axial (inner core) region, which has a different
composition/crystallinity and is preferably hollow.
Such fibrils preferably have up to about 100 times, and
more greater length than diameter, have diameters of up
to about 700 angstroms and are substantially cylindrical
graphite about a substantially hollow core as made and
without having been treated at higher temperatures than
the original fibril manufacturing temperature.
According to one apsect of this invention,.
operating with catalyst particles as herein set forth,
yields of fibrils of greater. than about 30 times the
weight of transition metal in the catalyst are
achievable. In many cases, particularly with mixed
transition metals, yields of between 100 and 200 times
the weight of transition metal in the catalyst have been
achieved. It has been found that in comparable
processes, combinations of transition metal catalysts
have sometimes increased yields by a factor of as much
as 2 or even more.
The following examples illustrate the practice
of this invention. By following one or more of these
examples, high yields of unique fibrils as above
described are produced.
Example 1
A catalyst was prepared using Degussa fumed
alumina with an average particle size of about 100A and
an aggregate mesh size of -100. Iron acetylacetonate
was deposited on these alumina particles in a ratio of
about 1 part iron, as the acetylacetonate, to 10 parts
by weight of alumina. The resultant particle was heated
under a hydrogen/ethylene atmosphere under reaction
conditions.
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A one (1) inch tube was heated to about 650°C
while it was being purged with argon. A mixed flow of
hydrogen, at 100 ml/min, and ethylene, at 200 ml/min,
was fed to the hot tube for five minutes whereupon
catalyst was introduced into the reactor tube. The
ethylene/hydrogen mixture was continued through the
tubular reactor for 0.5 hours after which the reactor
was allowed to cool to room temperature under argon.
Harvesting of the fibrils so produced showed a yield of
greater than 30 times the weight of the iron in the.
catalyst.
Example 2
Into a 3 L. round bottom flask was added 80.08
g of Degussa fumed alumina and 285 ml of methanol. The
mixture was stirred to produce a thick paste before a
solution of 78.26 g (0.194 moles) of ferric nitrate
nonahydrate and 4.00 g (0.0123 moles) of molybdenum(VI)
oxide bis(2,4-pentanedionate) in 300 ml of methanol (Fe
to Mo atom ratio of 94:6) was added slowly. The thick
paste which had collected on the sides of the flask was
washed down with 65 ml of additional methanol and the
mixture was stirred for 1 hour before house vacuum (28
in. Hg) was applied while stirring overnight. The
purple-tinted solid was placed in a vacuum (28 in. Hg)
oven at 100°C for 29 hours. A total of 100.7 g of
catalyst was obtained. The catalyst was ground and
passed through an 80 mesh sieve prior to use. Analysis
of the catalyst indicated 9.43% by weight iron and 0.99%
by weight molybdenum.
A vertical furnace containing a 1 inch quartz
tube with an internal quartz wool plug and thermocouple
was equilibrated at 650°C under a down flow of 100
ml/min. hydrogen and 200 ml/min. ethylene. Into the
tube (onto the quartz wool plug) was added 0.1044 g of
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the above-described catalyst. After 30 min., the
hydrogen/ethylene flow was stopped and the oven was
allowed to cool to near room temperature. A total of
1.2434 g of fibrils was harvested for a yield ratio of
126 times the iron weight content of the catalyst.
Example 3
A sample of catalyst from example 2 (1.6371 g)
was placed in a horizontal furnace under argon and was
heated to 300°C. After 30 min. at this temperatrure,
the furnace was cooled and 1.4460 g of catalyst was.
recovered (12% wt. loss), having 11.1% by weight iron
and 1.2% by weight molybdenum.
A vertical tube furnace containing a 1 in.
quartz tube with an internal quartz wool plug and
thermocouple was equilibrated at 650°C under a 100
ml/min. down flow of hydrogen and 200 ml/min. down flow
of ethylene. Into the hot tube was added 0.1029 g of
the catalyst described above. After 30 min., the
hydrogen/ethylene flow was stopped and the oven was
allowed to cool to near room temperature under argon. A
total of 1.3750 g of fibrils was isolated for a weight
yield based on theoretical iron content of 120 times the
iron content.
Example 4
The vertical tube furnace described in Example
2 was equilibrated at 700°C under the flow of 100
ml/min. hydrogen and 200 ml/min. propane. Onto the
quartz wool plug was added 0.1041g of catalyst from
Example 2. After 30 min. the fuel gases were stopped
and the product was cooled under argon. A total of
0.3993 of fibrils was isolated for a weight yield of 41
times the catalyst iron content.
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Example 5
The procedure of Example 4 was followed at
650°C using 0.1004 g of catalyst from Example 2. A
total of 0,3179 g of fibrils was harvested for a weight
yield of 34 times the iron content of the catalyst.
Example 6
Into a round bottom flask was added 4.25 g of
Degussa fumed alumina and 30 ml of methanol. The
mixture was mechanically stirred while a solution of
4.33 g (10,7 mmol) of ferric nitrate nonahydrate and
0,51 g (1.56 mmol) of molybdenum(VI)oxide bis(2,
4-pentanedionate) in 50 ml of methanol was slowly
added. The mixture was stirred for 1 hour before the
solvent was removed with the aid of a rotary
evaporator. The resulting damp solid was. vacuum dried
at 105°C, 28 in. Hg for 18 hours. The resulting
catalyst was ground and passed through an 80 mesh
sieve.- A.total of 5.10 g of catalyst was obtained.
Analysis of the catalyst indicated 9.04% by weight iron
and 2.18% by weight molybdenum to be present.
Fibrils were prepared following the procedure
of Example 2 at 650°C using 0.0936 g of the above
catalyst. A total of 0.9487 g of fibrils was isolated
for a weight yield of 126 times the catalyst iron
content,
Example 7
Into a round bottom flask was added 3.80 g of
Degussa fumed alumina and 30 ml of methanol. The
mixture was mechanically stirred while a solution of
4,33 g (10,7 mmol) of ferric nitrate nonahydrate and
2,04 g (6.25 mmol) of molybdenum(VI)oxide bis(2,
4-pentanedionate) in 100 ml of solvent was added. The
mixture was held at 105°C and 28 in. Hg for 17 hrs. The
dried catalyst was sieved (80 mesh) to produce 6.10 g of
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powder. Analysis of the catalyst indicated 8.61% iron
and 8.13% molybdenum by weight.
Fibrils were prepared following the procedure
of Example 2 at 650°C using 0.1000 g of the above
catalyst. A total of 0.8816 g of fibrils was isolated
for a weight yield of 102 times the catalyst iron
content.
Example 8
The procedure of Example 7 was followed at
700°C using methane and 0.10168 of catalyst. A total of
0.07178 of fibrils was isolated for a yield of 8.2 times
the iron content of the catalyst.
Example 9
Into a 500 ml round bottom flask was placed
4.37 g of Degussa fumed alumina and 28 ml of methanol.
To the stirred mixture was added a solution of 4.33 g
(10.7 mmol) of ferric nitrate nonahydrate and 0.46 g
(1.32 mmol) of chromium acetylacetonate in 75 ml of
methanol. The mixture was stirred for 1 hr. before it
was dried for 18 hr. at 105°C and 28 in. Hg. The
catalyst was ground and sieved (80 mesh) to produce 5.57
g of powder. The theoretical metal content by weight
was 11.9% iron and 1.4% chromium.
Fibrils were prepared following the procedure
of Example 2 at 650°C using 0.0976 g of the above
catalyst. A total of 0.9487 g of fibrils was isolated
for a yield of 82 times the theoretical iron content.
Example 10
Into a 500 ml round bottom flask was placed
4.40 g of Degussa fumed alumina and 35 ml of methanol.
To the thick paste was added 4.328 (10.7 mmol) of ferric
nitrate nonahydrate in 35 ml of methanol. The mixture
was stirred for 45 min. before the solid was dried at
95°C and 28 in. Hg for 18 hr. The catalyst was ground
and sieved (80 mesh).
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Fibrils were prepared following the procedure
of Example 2 at 650°C using 0.0930 g of the above
catalyst. A total of 0.4890 g of fibrils was isolated
for a weight yield of 46 times the catalyst iron content.
Example 11
Into a round bottom flask was placed 4.33 g of
Degussa fumed alumina in 30 ml of methanol. To the
stirred paste was added a solution of 4.33 g (10.7 mmol)
of ferric nitrate nonahydrate and 0.42 g (1.19 mmol) of
ferric acetylacetonate in 50 ml of methanol. The .
mixture was stirred for 75 min. before drying at 105°C
and 28 in. Hg for 17 hrs. The solid was ground and
sieved (80 mesh) to yield 5.87 g of catalyst. Analysis
showed 13.79% iron present in the catalyst.
Fibrils were prepared following the procedure
of Example 2 at 650°C using 0.0939 g of the above
catalyst to produce 0.3962 g of fibrils. This
corresponds to 3l times the iron content of the catalyst.
Example 12
Into a round bottom flask was added 4.33g of
Degussa fumed alumina in 20 ml of water followed by a
solution of 4.33 g (10.7 mmol) of ferric nitrate
nonahydrate and 0.17g (.138 mmol) of ammonium molybdate
in 40 ml of water. The mixture was mechanically stirred
for 1 hour. The water was removed at reduced pressure
at 40°C overnight. Final drying was accomplished at
140°C and 26 mm. Hg for 21 hours to produce 5.57 g of
solid. Analysis of the catalyst showed 9.87% by weight
iron and 1.45% by weight molybdenum to be present.
Fibrils were prepared following the procedure
of Example 2 at 650°C using 0.0794 g of catalyst to
produce 0.8656g of fibrils. This corresponds to 111
times the iron content of the catalyst.
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Example 13 2005642
Into a round bottom flask, containing 4.33 g of
Degussa fumed alumina and 30 ml of methanol, was added a
solution of 4.33 g (10.7 mmol) of ferric nitrate
nonahydrate and 0.16 g (0.368 mmol) of ceric nitrate in
50 ml of methanol. An additional 20 ml of methanol was
used to wash all the salts into the flask. The mixture
was stirred for one hour before the solvent was removed
at reduced pressure. The solid was dried at 130°C and
27 mm Hg for four days to produce 5.32 grams of
catalyst. Analysis of the solid indicated 9.40% iron
and 0.89% cerium to be present.
Fibrils were prepared following the procedure
of Example 2 at 650°C using 0.09418 of catalyst to
produce 0..75528 of fibrils. This corresponds to 88
times the iron content of the catalyst.
Example 14
Into a round bottom flask was added 4.338 of
Degussa fumed alumina and 30 ml of methanol. Onto the
alumina was poured a solution of 4.338 (10.7 mmol) of
ferric nitrate and 0.318 (1.22 mmol) of manganese(II)
acetylacetonate in 50 ml of methanol. The solvent was
removed at reduced pressure (27 mm Hg) and the damp
solid was vacuum dried at 140°C to produce 5.188 of
solid. Analysis of the catalyst indicated 9.97% iron
and 1.18% manganese.
Fibrils were prepared following the procedure
of Example 2 at 650°C using 0.0708 of catalyst to
produce 0.49488 of fibrils. This corresponds to 66
times the iron content of the catalyst.
Example 15
Into a round bottom flask was added 4.338 of
Degussa fumed alumina and 30 ml of methanol. Onto the
alumina was poured a solution of 4.338 (10.7 mmol) of
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ferric nitrate and 0.43g (1.22 mmol) of manganese(III)
acetylacetonate in 50 ml of methanol. The solvent was
removed at reduced pressure and the damp solid was
vacuum dried at 140°C to produce 5.27g of solid.
Analysis of the catalyst indicated 10.00% iron and 1.18%
manganese by weight.
Fibrils were prepared following the procedure
of Example 2 at 650°C using 0.0723g of catalyst to
produce 0.7891g of fibrils. This corresponds to 110
times the iron content of the catalyst on a weight basis.
Example 16
Degussa fumed alumina (400g) and deionized
water (8.OL) were added to a 22 L flask equipped with a
stirrer, pH meter and probe, and two 2 L addition
funnels. One funnel contained an aqueous solution of
ferric nitrate nonahydrate (511g dissolved in 5654 ml of
water) and the other an aqueous solution of sodium
bicarbonate (480g dissolved in 5700 ml of water).
The pH of the alumina slurry was first adjusted
to 6.0 by adding the sodium bicarbonate solution to
raise it or the ferric nitrate solution to lower it.
Next, both solutions were added simultaneously over 3-4
hours with good agitation while maintaining the pH at
6Ø When the addition was complete, stirring was
continued for an additional 1/2 hour, after which the
slurry was filtered on a 32 cm Buchner funnel. The
filter cake was then washed with deionized water and
returned to the 22 L flask. Next, additional deionized
water was added and the slurry stirred for another 1/2
hour. The batch was then filtered, washed with
deionized water, and vacuum-dried at 100°C to constant
weight (475g). Following drying, the final catalyst was
prepared by grinding and sieving the product to -80 mesh.
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Example 17
This Example illustrates the practice of this
invention using periodic addition of catalyst to produce
high fibril yields. A four-inch quartz tube, closed on
the bottom, was placed in a 4 inch diameter x 24 inch
long furnace. The tube was purged with argon while
being heated to 620°C. When the tube was hot, the gas
feed was switched to a mixture of hydrogen (1.0 1/min)
and ethylene (5.6 1/min) via a dip tube to the bottom of
the 4 inch tube. After 5 min of purging, the catalyst
addition was begun.
A total of 41.13g of catalyst, prepared as
described in the Example 16, was added to the hot
reactor reservoir. The catalyst was added periodically
to the hot reactor in small portions (0.2g) over a
period of approximately 6 hours. After catalyst
addition was complete, the reaction was allowed to run
for an additional one hour and the reactor then cooled
to room temperature under argon. The fibrils were
removed from the tube and weighed. This batch gave 430g
total yield of fibrils which is unusually high for a
catalyst based upon iron has the only transitionmetal.
In single batch addition fo an iron only catalyst,
fibril yields of about 30 times the iron content have
been observed whereas here the fibril yield is more than
70 times the iron content of the catalyst.
Example 18
The tube and furnace described in Example 17
were heated to 650° under an argon purge. When the tube
was hot the gas feed was switched to hydrogen and
ethylene as described in Example 17.
A total of 20.4g of catalyst (Fe-Mo) prepared
as described in Example 2 was added in a manner similar
to that described in Example 17. This batch gave a
total fibril yield of 2558.
E,
