Note: Descriptions are shown in the official language in which they were submitted.
110()7;i~
,099
1 This invention relates to porous carbon particulates
and, more particularly, is concerned with such particulates
comprising carbon black spheres in packed relationship and a
carbon binder, said particulates being useful as selective
adsorbents and catalyst supports.
This invention also relates to a catalyst composi-
tion comprising a porous carbon particulate made up of carbon
black spheres and a carbon binder and, carried thereon, at
least one activator. More particularly, this invention re-
lates to porous carbon catalysts of`controlled pore size dis-
tribution and to improved catalytic processes employing same.
Carbons containing macropores can be useful as
catalyst supports, particularly where large reactant mole-
cules, such as those in the Pharmaceutical and petroleum in-
dustries are involved. For example, such a carbon particleactivated with a noble metal such as platinum or rhodium,
could be used for catalyzing hydrogenation reactions of mole-
cules containing several benzene rings.
Car~ons containing macropores can be used as adsor-
bents where large molecules are to be adsorbed, as in thedecolorization of sugar or the treatment of waste waters.
Porous carbons have been obtained in the piror art
by activation of a suitable material, such as coal or wood
charcoal, with oxidizing agents. These oxidizing agents,
e.g. 2~ CO2, steam, and the like, react away portions of
the carbon, leaving behind pores. Carbons with controlled
pore size distribution cannot be made by this procedure since
new pores are continuously formed while existing pores are
constantly enlarged. This results in a wide range of pore
size~, including many small pores, i.e. well below 20 angstrom
units, as activation is continued. Thus, it has been diffi-
cult to obtain porous carbons containing predominantly trans-
itional pores (diameter 20-200 angstrom units~ as well as
~,.
- 1 -
~0(~7~
l carbons having a narrow range of Qpecific pore size~.
In addition to the problem of controlling pore size
distribution in prior art carbons, the reacting away of car-
bon to provide pores creates additional problems. When large
pores are desired in the carbon, the reacting away of the
carbon weakens the mechanical strength of the final structure.
The reacting away of carbon increases the percent of ash pres-
ent on the residual carbon and ash contents of 5-10 weight
percent are normal. In addition, carbons prepared by the
prior art procedure contain many surface groups containing
oxygen. Such groups have a profound effect on its surface
chemistry. Pure carbon is hydrophobic but the presence of
bound oxygen reduces the hydrophobicity and causes the sur-
face to possess a polar nature. As a consequence, the sur-
face is less effective as an adRorbent for hydrophobic sub-
stances and more effective as an adsorbent for polar compounds.
If, for example, it were desired to adsorb a non-polar sub-
stance such as benzene from a solution also containing a polar
substance such as ethanol~ carbons having surface group~ con-
taining oxygen would be considerably less effective adsorb-
ents for benzene than carbonQ not containing such surface
groups.
The preparation of carbon structures by other pro-
cedurss is also known in the prior art. In many instances,
however, such structures contain significant amounts of ma-
terial other than carbon. In other instances the partlcular
carbon structure is prepared for uses other than as selective
` adgorbents 90 that no specific requirements as to porosity
or pore size distribution are necessary.
Thus, there continues to exist the need for substan-
tially pure carbon structures that have desirable levels of
porosity or controlled pore size distribution and are free
of or improved with respect to de~iciencies of the prior art
11007Z~
l carbons. Such a development would fill a long-felt need in
the art and provide a notable advance in the art.
Accordingly, it is a primary object of the present
invention to provide a catalyst composition comprising an
activator carried on a porous carbon structure having pores
of controlled size distribution. It is also an object of
the present invention to provide a porous carbon structure
having pores of controlled size distribution. Other objects
will become~apparent from the description which follows.
In accordance with the present invention there is
provided a porous carbon particulate comprising carbon black
spheres in packed relationship and a carbon binder, said ~
spheres having a particle size in the range of about 80 to
5000 angstrom units, said particulate having a pore size dis-
tribution exhibiting peaks at a pore radius in excess of about
10 angstrom units. Preferably, the particulate will have a
composition of at least 99 weight percent carbon. In pre-
ferred embodiments, the carbon particulate will exhibit pore
volume in the range of about 0.2 to 1.0 cubic centimeters
per gram with pore size distribution showing peaks at a radius
of at least 10 angstrom units and frequently showing peaks
at several values of pore radius and, more preferably, will
have a pore volume of at least 0.4-1.0 cubic centimeters per
gram. Preferred carbon particulates will have a pore size
distribution exhibiting peaks in the range of radii of about
10-250, more preferably 40-100, angstrom units.
In accordance with the present invention, there
is also provided a process for preparing the above-described
carbon particulate which comprises uniformly admixing carbon
black spheres having diam~ters in the range of about 80 to
5000 angstrom units with a carbonizable binder in a mixing
medium, packing the resulting mixture into a suitable struc-
ture, removing said mixing medium by volatilization and car-
-- 3 --
110072~
1 bonizing said binder~
In accordance with the pr~sent invention, there i8also provided a catalyst composition comprising a porous car-
bon particulate support comprising carbon black spheres in
packed relationship and a carbon binder, said spheres having
a particle size in the range of about 80 to S000 angstrom
units and said particulate having pore size distribution ex-
hibiting peaks at a pore radius in excess of 10 angstrom
units and, carried on said support, an effective amount of
an Activator. Preferably, the particulate support will have
a composition of at least 99 weight percent carbon. In pre-
ferred embodiments, the support will have a pore volume of
at least 0.2 cubic centimeters per gram, more preferably 0.4
to 1.0 cubic centimeters per gram, showing peaks at a radius
lS of at least 10 angstrom units, pre~erably in the range of 10-
-250 angstrom units. In another preferred embodiment, the
support has a pore size distribution exhibiting maximum pore
radius in the range of 40-100 angstrom units. In still an-
othér pre~erred embodiment, the support will contain less
than 1 weight percent of ash. In yet another pre~erred em-
bodim~nt, the carbon black spheres used to prepare the sup-
port have an average diameter in the range of 80-300 angstrom
units.
In accordance with the present invention, pores
of the carbon particulate are formed by packing together of
suitable carbon black spheres and binding the spheres toge-
ther in packed relationship with a carbon binder. The use
of-the carbon binder allows the carbon particulate to pos-
sess improved mechanical strength. When the carbon black
spheres packed and bonded together are of substantially the
same size and relatively small, a narrow range of pore size
distribution will arise and the particulate will po~sess good
mechani~al strength. The particular range of pore sizes and
110()72~
1 distribution thereof will vary with particle ~ize of the car-
bon black spheres ~elected and the variation~ which occur
within a designated size. Thus, if larger carbon black ~pher
are used, the ln~ tital space or pores will be larger,
while the use of spheres of varying diameter will result in
a wide range of pore sizes.
In accordance with the presant invention, there is
also provided a process of adsorbing ad30rbable materials
from solution which comprises contacting said solution with
the carbon particulate of the present invention. In one em-
bodiment of such proce~s, the particulate is formed as a bed
through which the ~olution is passedO In an alternative em-
bodiment, the particulate is contacted with the solution for
an effective time period after which the particulate is re-
moved by filtration.
The present invention, by use of the carbon binder,provides oarbon particulates of good mechanical ~trength in
conjunction with large pore sizes. In prior art carbon struc-
tures, when large pores are desired, extensive oxidation is
necessary to provide the pores and the loss of carbon thus
occasioned greatly weakens the resulting structure.
The carbon particulates o~ the present invention
will, in preferred embodiments, have a large surface area
resulting from pores in tXe transitional range, i.e. 20 to
200 angstrom units, and from macropores, i.e. pores greater
than about 200~ for example about 250, angstrom units. The
number of pores in the transitional and macropore range will
be much greater than can be achieved by the prior art proced-
ures .
30Since the carbon black spheres used in the fabrica-
tion of carbon particulates of the present invention are of
a high state of purity, the resulting particulates will be
much purer than prior art carbon structure obtained by the
-- 5 --
11007;~1
1 conventional oxidation procedures. Normally, the prior art
structures contain from 5-10 weight percent of ash. In addi-
tion, since the carbon particulates of the present invention
are prepared without the use of oxidiæing agents to react
S away carbon, the carbon particulates of the present invention
will contain considerably le~s surface oxygen-containing
groups than the conventional carbon structures.
Carbon particulates of the present invention be-
cause of their desirable porosity and pore size distribution
are very useful as selective adsorbents, particularly when
large molecules are involved. The low content of surface
groups containing oxygen increases the effectiven~ss of the
carbon particulates in application~ involving non-polar com-
pounds that are to be selectively adsorbed.
Carbon blacks are formed by the thermal decomposi-
tion of gaseous and liquid hydrocarbons. Two main manufactur-
ing processes are employed. In the channel process, carbon
black is collected by impingement of small, natural gas di~-
fusion flames o~ cool channel iron surfaces. By altering
the size of the burner tip and its distance from the channel
- surface, the particle si2e of the carbon black can be varied.
The furnace combustion process, which currently
produces the greater amount of carbon black, uses larger dif-
fusion flames to combust natural gas and/or liquid hydrocar-
bons in firebrick-lined furnaces. Carbon black with consid-
erably larger particle size than channel black can be produced.
Carbon particles useful in the present invention
may be of any shape that can be packed and bonded together
to provide particulates which have the desired porosity.
Particularly suitable are available carbon bla~ks made by
the above processes, which generally have an average diam-
eter from about 80 to 5000 angstrom units and a porosity that
varies with the specific preparative method employed. These
qlO0721
1 carbon blacks ar~ revealed by ele~tron pho~omicrographs to
consist of ultimate particles which appea~ to be essentially
spherical. For convenience, therefore, in the present ap-
plication and claims, the carbon black particles are referred
to as spheres but it is to be understood that the pre~ent in-
vention is inclusive of other shapes, such as oval-shapes,
round-cornered squaresr rectangles, triangles, and the like
as long as such particles upon packing and bonding give rise
to the porosity desired.
Carbon ~lack spheres useful in the present inven~
tion may be selected from any that are commercially available.
Selection is based on the porosity and pore size distribution
desired in the carbon particulate to be provided in accord-
ance with the present invention. When small pores of a nar-
row pore size distribution are desired, carbon black spheres
of small particle size and narrow variation in particle size
are selected. When large pores are desired, carbon black
spheres of large particle size are xelected. When a wide
range of pore sizes are desired, mixtures of carbon black
20 ~spheres varying particle ~izes are selected. It i9 to be
noted that large carbon black spheres can provide a wide
range of pore size distribution as well as large pores.
In addition to the carbon black spheres, it is also
necessary to employ a binder for the spheres that are to be-
come arranged in packed relationship. The binder is a sub-
stance which when heat-treated in an inert or non-oxidizing
atmosphere yields a high proportion of carbon. Generally,
a carbon yield greater than about 20 weight yield is desir-
able when heat-treatment is carried out at 600C. in an at-
mosphere of nitrogen~ Carbon yield is the weight of carbonresidue ~er~ad by the weight of starting material and multi-
,~,, t plied by lO0. Materials which meet this qualification in-
clude polymers such as poly(furfuryl alcohol), polyacryloni-
11()()72~
trile; resins such as phenol-formaldehyde, phenol-benzaldehyde;
~Id certain natural materials such as coal tar pitch. Preferably
the binder will be a thermosetting resin. Enough binder is required
to hold t}le carbon structure together after carbonization of the
binder. Normal ratios of carbon black spheres to binder will be
from about 10:1 to 0.1, preferably 5:1 to 1:1, on a weight basis
based on the amounts of materials employed prior to heat-treatment
to carbonize the binder.
It is also necessary to employ a mixing medium to provide
intimate mixing of the binder and the carbon black spheres.
Preferably the mixing medium will be a solvent for the binder but
it is possible to employ the binder in emulsified or dispersed form
in the mixing medium. The mixing medium should be volatile enough
so that gentle heating (100 - 150C.) will effect volatilization
and eliminate the possibilities that the mixing medium will inter-
fere with or take part in carbonization of the binder. Suitable
mixing media include acetone, methyl isobutyl ketone and other
ketones, benzene, pyridine, water and the like. The amount of .
mixing medium should be enoughito ensure intimate mixing and may
vary widely. Generally the amount of mixing medium will be such
as to provide the binder as about a 5 to 50 weight percent solution
or emulsion, preferably about 10 to 20 weight percent solution.
Once the carbon black spheres, the binder and the
mixing medium are selected-~n~intimately admixed ~ad the resulting
composition is processed so as to pack the carbon black particles
to make a suitablepartieulateshape. Such processing may involve
~' extrusion, pelletizing, pilling, tabletizing)a~ such other forms
of molding as are conventionally employed in forming structured
particles. It is also possible to employ rolling mills and
flakers to provide a formed structure
- 8 -
1~0()7Zl
l of packed carbon particles although such procedures do not
usually form uniform particles as in the case of moldi~g.
It is generally preferred to employ extrusion to obtain the
carbon structure. The carbon structure thus obtained is re-
ferred to as a "green body". The green body is subjectedto carbonization at elevated temperature in an inert or non-
-oxidizing atmosphere so as to convert the binder to carbon.
The resulting carbon structure may be utilized in the form
obtained or it may be subdivided by crushing or grinding, if
desired. It can also be further modified by treatment with
an oxidizing agent, if desired, although it is generally pre-
ferable to take advantage of the desirable properties achiev-
ed in the absence of oxidation of the carbon structure.
As has been indicated, the carbon structure of the
present invention can be prepared in a wide variety of pore
volume and pore size distribution~ In particular embodiments,
the carbon structures will have a larger surface area in the
large pore region than previously available carbons, the large
pores occurring in a narrow size range, if desired. Such a
carbon structure is very useful as a selective adsorbent when
large molecules are to be adsorbed~ This type of carbon, by
virtue of its method of preparation, will also have a much
lower ash content (impurity level) than conventional oxidized
carbons.
The catalyst composition of the present invention
comprises the carbon support de~cribed and, carried thereon,
an effective amount of an activator. The activator and amount
thereof employed will depend upon the particular reaction to
be catalyzed and the relative effectiveness of the activator
in the reaction. There are numerous reactions that are ef-
fectively catalyzed by supported activators and many wherein
carbon i8 a useful support. In general, any catalyst composi-
tion ba ed on a carbon support which is known to be useful
_ g _
1100721
1 in the prior art will be advantageously prepared using the
carbon support of the present invention because of the greater
proportion of pores of larger radii of the present supports
and the attendant reduction in wasted cataly~t material, e~-
pecially where large reactant molecules are involved. Thus,no new teachings as to activators or amounts thereof are nec-
essary since the present invention contemplates conventional
activators on an improved carbon support in the conventional
reactions.
The catalyst compositions of the present invention
exhibit improved activity in conjunction with hydrogenation
reactions and are illustrated in this type of reaction. Par-
ticularly effective activators in this type of reaction are
the platinum metals, which include ruthenium, rhodium, pal-
ladium, osmium, iridium and platinum. Effective amounts may
range from about a thousandth to about 10 weight percent or
more, depending upon the reaction involved and the metal am-
ployed. In such reactions, activator usage and amounts will
conform to conventional teachings with i~proved activity be-
ing obtained by use of the support of the present invention.Preferred reactions are 1~the reduction of 6-hydroxy hydro-
naphthacenes, as described in United States Patent 3,019,260,
issued January 30, 1962 to McCormick et al. and related com-
pounds. Another preferred reaction is ~ the reduction of
2,4-dinitrotoluene and related compounds to the corresponding
diamines.
It is also known that catalysts based on carbon
supports are useful in hydrodesulfurization of petroleum res-
idua. In such reactions, a combination of an activator and
promoter ~ generally employed. The activator is generally
selected from molybdenum and tungsten and the promoter from
cobalt and nickel with the metals being in the form of their
sulfides in use.
-- 10 --
~1007Zl
1 The invention may be further understood by refer-
ences to Figure 1 which shows comparative pore size distribu-
tion of various carbons and Figure 2 which show~ comparative
effectiveness of catalysts prepared using as substrates car-
bon particulates of the present invention and typical prior
art carbon particulate.
The invention is more fully illustrated by the ex-
amples which follow wherein all par~s and perc~ntages are by
weight unless otherwise specified.
In the examples which follow, reference is made to
certain physical properties of the particulate supports ob-
tained. These properties are obtained in accordance with
conventional methods employed in the art of catalyst supports.
Pore volume may be obtained by mercury penetration
or water adsorption. The latter is a preferred me~hod be-
cause it is easily performed and has an accuracy of + 10%.
In the water adsorption procedure, a small quantity of sup-
port (1-2 grams) is weighed into a glass dish. Water is slow-
ly poured onto the support until no more is adsorbed. Excess
droplets are carefully removed by blotting and a reweighing
is made. Assuming that one gram of water occupies one cubic
centimeter, the pore volume is calculated from the initial
and final weights of the support.
Surface area is measured by a low temperature nitro-
gen adsorption technique which is reported in J. Am. Chem.Soc., 60, 309 (1938), with modifications as reported in Anal.
Chem. 30, (1958) and Anal. Chem., 34, 1150 (1962).
Comparative Example A
Into 12 milliliters of water were added 10 grams
of carbon black ~pheres having an average particle diameter
of 120 angstrom units and a surface area of 850 square meters
per gram. After hand mixing, the resulting composition was
extruded through a hole of 1/16 inch diameter using a piston-
-- 11 --
1~007Z~
1 -type extruder operating at a pressure of 2000 pounds per
square inch gauge. The resulting extrudates were dried in
air at 110C. and then heated in flowing nitrogen at 600C.
for 1 hour. The product was obtained in the form of cylin-
drical pellets. Properties are given in Table I.Example 1
A furfuryl alcohol polymer was prepared by mixing
200 milliliters of water, and 1 milliliter of concentrated
H2SO4. The mixture was heated at 90C. for 10 minutes. The
dark polymer obtained was washéd twice with water and then
stored in a closed bottle.
In 100 ml~ of acetone was dissolved 10 grams of
the furfuryl alcohol polymer thus prepared. The resulting
solution was added to 40 grams of carbon black spheres hav-
ing an average particle diameter of 850 square meters per
gram. The resulting composition was thoroughly mixed using
a~Sunbeam Mixmaster. The mixture was then extruded through
a hold of 1/16 inch diameter using a piston-type extruder
operating at 800-2000 pounds per square inch gauge.
The resulting extrudates were heated overnight at
110C. to volatilize all of the acetone present and then car-
bonized in a tube furnace under flowing N2. A temperature
of 600C~ was reached in about 1 hour and held for 1 hour.
The extrudates were then cooled to room temperature under
flowing nitrogen. The product was obtained in the form of
cylindrical pellets. Properties are also given in Table I.
Example -?
The procedure of Example 1 was repeated in every
essential detail except that 20 grams of a commercial phenol-
-formaldehyde resin was substituted for the furfuryl alcohol
polymer of Example 1 ~nd the extrusion pressure was 2400 psig.
Properties of the resulting pellets are also given in Table
I.
o~
- 12 -
110()7Zl
l Table I
Properties of Carbon Particulates
Binder Pore Crush
Exam~ Binder Amount* Volume** Stren~th***
. _
Comp. A None 0 l.00 1.2
l Poly~furfuryl 25 0.99 5.4
alcohol)
2 Phenol-formal- 50 0.62 7.7
dehyde resin
Notes: *Weight % based on weight of carbon black
**Cubic Centimeters per gram
***Pounds
Table I illustrates the importance of the binder
in obtaining improved particulate strength. It can be seen
that use of 25% binder resulted in a 4.5 fold increase in
strength with essentially no loss in pore volume. Use of
higher amounts of binder results in further increases in
strength but results in lower pore volumes. Thus, if lower
pore volumes can be tolerated, higher binder usage may be
desirable.
Example 3
In 75 ml. of a~etone were dissolved 7.5 grams of
poly(furfuryl alcohol) prepared as in Example 1. To this
solution were added 30 grams of the carbon black spheres as
used in Example l. A~ter thorough mixing, the resulting com-
position was extruded as in Example 1 using 250-500 psig ex-
trusion pressure. The extrudates were dried overnight and
then carbonized as in Example 1. Properties of the resulting
pellets are given in Table II and Figure l.
Comparative Example B
For comparison purposes, a commercial available
carbon prepared by oxidation of carbon was selected. This
carbon is sold under the tradename Darco Granular and was
in the form of grains 12 x 20 mesh. Properties are also given
in Table II and Figure l.
- 13 -
1 10(~721
For comparative purposes, another commercially available
carbon prepared by oxidation of carbon was selected. This carbon
is sold as *Columbia Type L and was in the form of grains 12 x 20
mesh. Properties are also shown in Table II and Figure 1.
Table~
Example Pore Surface Crush
Volume* Area** Strength***
3 0.92 530 3.1
Comp. B 1.07 580 2.3
Comp. C 0.86 1235 5.7
Notes: *cc/gram
**M~/gram
***l~s.
In Figure 1 are shown the pore size distribution for
the carbons of Example 3, Comparative Example B, and Co~parative
Exa~ple C as obtained by mercury porosity Lsee Orr, C., Powder
Technol. 3, 117 tl969-70)~. In the figure, the change in pore
volume with respect to the change in the natural logarithm of the
pore radius is plotted against ~he logarithm to the base 10 of the
pore radius. As can be seen by the figure, the pore size
distribution curves illustrate the major difference of carbon
particulates of the present invention, which have many more pores
in the region of radii of 40-100 angstrom units while many of the
pores of the comparative carbons are too small to be measured by
mercury penetration.
Examples 4-7
In these examples, a series of carbon particulates were
prepared following the procedure of Example 3 in every essential
detail except that carbon black spheres of different particle
sizes were employed in separate preparations.
*Trade mark
- 14 -
110(~7;~.
1 Propertie~ of the carbon black spheres employed and of the
resulting carbon particulates are given in Table III.
110~)7Zl
o
E~ O ~
~ ~ + $ U'
n ~
,, ~ ~ oo U- CO
U~ *
r~~
U~
P~h 1 o o o o
oo o
P~
a~
H I ~ q'l o o In O
~1
~1 ~
ml
~1 ~
E~ ¦ rl
~,~o
~n 8*
a~ ~a * o o a o
X ~ C ~ ~
8 ~ cl ~ o u 1 ~ C~
~-al ~ X ~ U
a~
C
-- 16 --
1~0072~
1 It can be seen from Table III that the physical
properties of the catalyst particul~tes of the preQent inven-
tion may be varied by varying the size of the carbon black
spheres or the ratio of spheres to binder. It is evident
that the pore size of the carbon particulates can be shifted
toward larger sizes by using carbon black spheres of larger
average particle size.
Example 8
In this example, various carbon particulates were
evaluated as selective absorbents of various substances from
solutions. All carbon particulates were of size 40 x 60 mesh.
Representative of the carbon particulates of the present in-
vention was that prepared in acaordanae with Example 4. Rep-
resentative of prior art absorbentæ were those of Comparative
ExampleS B and C.
A. ,Methylene Blue
Adsorption of the dye methylene blue from aqueous
solution is dependent primarily on the surface area of the
adsorbent since the dye molecule is small enough to penetrate
nearly the entire pore system. To 25 ml. of a dye solution
containing 1.0 gram of methylene blue per liter was added
in separate runs 0.40 gram of the carbon particulate under
test. After swirling the beaker containing the test sample
for 30 seconds, the solution was allowed to stand for a total
of 60 minutes before a solution aliquot was withdrawn for
colorimetric a~alysis. Results are given in Table IV.
- 17 -
110()7Z~
1 Table IV
Carbon Surface Dye
from Area Removed Dye Removed ~
Example N2 BET* 1 hour (~) Surface Area
4 550 34 0.062
Comp. B 580 32 0.055
Comp. C 1235 54 0.044
Note: *Meters 2per gram
The results of Table IV show that while the carbon
of Comparative Example C removed the most dye, the carbon
particulate of Example 4 of the present invention was the
most effective based on available surface area.
B. Molasses
The decolorizing of a molasses solution is a meas-
ure of an ab~orbent 18 ability to remove large color bodies
and is often used as a characterization test.
A stock ~olution was prepared by dissolving 20 grams
of blackstrap molasses in water to make 500 ml. of solution.
To 100 ml. of the stock solution was added 0.50 gram of the
carbon under test. The resulting composition was allowed
to stand overnight in quiescent state. After 16 hours adsorp-
tion time, an aliquot of the test solution was centrifuged
to remove carbon particles and the remaining color in the
test solution was determined colorimetrically. Results are
given in Table V.
Table V
Car on From ExampleColor Removed 16 Hours (%)
4 37.5
B 37.5
C 7.~
The results of Table V show that the carbon par- -
ticulates of Example 4 and comparative Example B are superior
to the high urface area carbon particulate of Comparative
Example C.
- 18 -
~10(~7Zl
1 C. Permanaanate
The adsorption of permanganate has been used as a
measure of the decolorizing capacity of a carbon, although
it is not clear whether the reduction in color in such case
is due primarily to adsorption of the permanganate ion or
reduction thereof to MnO2 catalyzed by the carbon surface.
To 25 ml. of a 0.5 molar KMnO4 solution was added
0.5 gram of the carbon particulate under test and the beaker
containing same was then swirled for 30 seconds. The mixture
was then allowed to stand for 2 hours after which an aliquot
of the solution was removed for analysis. Results are given
in Table VI.
Table VI
Carbon from Example MnO4 Removed After 2 Hrs, (~)
4 34
Comparative B 26
Comparative C 14
Example 9
In this example a catalyst was prepared by depos-
iting rhodium metal on catalyst particulates prepared in ac-
cordance with Example 3.
In 20 ml. of water were dissolved ~.74 grams of
RhC13.3H2O and the resulting solution was added to 180 ml.
of dimethylformamide in a 500 ml. bottle. To the mixture
was added 10.5 grams of catalyst particulate of Example 3
and the mixture was hydrogenated at S0 psig using a Parr
shaker to deposit rhodium metal on the carbon particulat~s.
When H2 uptake was complete, the catalyst was filtered and
washed with water, and stored in an approximately 50% water-
-wet state.
Comparative Example D
In this example a catalyst was prepared by depos-
iting rhodium metal on commercially available carbon particu-
-- 19 --
llC~Q7Z~
lates prepared by conventional oxidation procedures to provideporosity.
The procedure of Example 9 was followed in all essential
details except that the carbon particulates were those commercially
available as *Norit SGX.
Example 10
, .
In this example~ the catalysts prepared in Example 9 and
Comparative Example D were evaluated in the process of catalytic
reduction of 6-hydToxy hydIonaphthacenes, as described in United
States Patent No. 3,019,260, issued January 30, 1962 to ~IcCormick
et al. For testing, catalysts were prepared as in Example 8
except that the amount of RhC12 3H20 was varied so that catalysts
were obtained which contained either 6% metal or 12% metal based
on the total weight of the catalyst composition. The catalyst
was added in the amount of 0.003 or 0.006 troy ounces of rhodium
metal depending on whether ~he catalyst contained 6 or 12% metal,
respectively to 40 ml. of methyl cellosolve* and reduced at
35C. for 1 hour and 40 psig hydrogen pressure using a Parr shaker.
A solution containing 6-demethyltetracycline dissolved in methyl
cellosolve* was then added to provide a concentration of 60 grams
per liter of 6-demethyltetracycline. The solution was then
hydrogenated at 35C. for 1 hour and 40 psig. hydrogen pressure.
After 1 hour of reduction, samples were taken for analysis and
concentrations of reactant and product, 6-demethyl-6-deoxytetracy-
cline. Results are given in Table VII.
* Trade mark
- 20 -
i ~.
,, i
~OU7;~
1 Table VII
Ca~alytic Reduction of 6-Demethyltetracycline
Catalyst Conversion Selectivity To
of Rhodium ~ After 6-~emethyl 6-
Example(%)* _ 1 Hour _ Deoxytetracycline
Comp. D 6 45 0.80
9 6 57 0.88
Comp. D 12 55 0.81
9 12 66 0.84
*Percent based on total of catalysts composition
The data of Table VII show that catalysts prepared
using as carriers the carbon particulates of the present in-
vention provide both a greater activity and greater selec-
tivity than similar catalysts prepared using conventional
carbon supports. Note that the catalyst of the invention
is more active at 6% metal than the comparative catalyst at
12% metal. It is believed that the superior results achieved
by catalysts prepared by use of carbon particulates of the
present invention is due primarily 'o the increased number
of pores in the 50-200 angstrom units range of pore radii
since thesè pores would be large enough to allow unrestricted
entry of the large reactant molecules.
Example 11
Using the car~on particulate prepared in accord-
ance with Example 3, a catalyst was prepared.
2S To 100 ml. of water was added 0.17 gram of PdC12
(60% Pd) and then 4.0 ml. of 10% aqueous HCl was added. The
composition was stirred for ab~ut 40 minutes to dissolve the
PdC12. To the solution was then added 4.9 grams of the car-
bon particulates of Example 3 in a particle size of 40 x 60
mesh and an additional 15 minutes of stirring was effected.
The pH of the mixture was raised to 9.5-10.5 by the addition
of 2M NaOH. The pH was maintained for 15 minutes by drop-
wise addition of NaOH as necessary. A total of 2.5-3.0 ml.
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~10(~7;~1
1 of caustic was required. The catalyst was then separated by
filtration and washed with 300 ml. of water. The water-white
filtrate indicated that all of the palladium was taken up by
the carbon. The catalyst was bottled and stored in a state
of 50% water wet. Before use, an aliquot was dried 30 min-
utes at 125C. to determine its actual wetness.
Comparative Example E
~ he procedure of Example 1~ was followed in every
material detail except that in place of the carbon particu-
late prepared in accordance with ~xample 3, there was sub-
stituted the carbon particulate of Comparative EXample C in
a particle size of 40 x 60 mesh.
Example 12
In this example, the catalysts prepared in Example
11 and Comparative Example E were evaluated in the process
of catalytic reduction of 2,4-dinitrotoluene.
In a mixture of 10 ml. of water and 60 ml. of iso-
propanol in a 500 ml. Parr bottle was dissolved 0.91 gram
(0.005 mole) of 2,4-dinitrotoluene. Enough catalyst in the
50% water-wet state was added to provide 0.20 gram of cata-
lyst on a dry basis, the catalyst corresponding to 2% Pd on
carbon. The bottle was attached to the Parr hydrogenator
and flushed 3 times with hydrogen. It was $hen pressurized
with hydrogen to 40 psig and isolated. Shaking of the bottle
was carried out and the extent of reaction was followed by
noting the hydrogen-pressure drop on the gauge. The reaction
bottle was maintained at 35 + 0.5C~ using a thermostated
water jacket. Results o~ the reactions are shown in Figure
2.
From Figure 2 it can be seen that the reaction is
complete in approximately 45 minutes when the catalyst pre-
pared in accordance with Example 11 is employed. On the other
hand, when the catalyst prepared in accordance with Compara-
:110~)7Zl
1 tive Example E is employed a reaction time of approximately
115 minutes is required. Again, it appears that the superior
results obtained with the catalysts of the invention is due
primarily to the wide pores it contains and to the smaller
mass transfer limitations imposed thereby.
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