CA1100721A - Carbon pellets with controlled porosity - Google Patents

Carbon pellets with controlled porosity

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Publication number
CA1100721A
CA1100721A CA246,462A CA246462A CA1100721A CA 1100721 A CA1100721 A CA 1100721A CA 246462 A CA246462 A CA 246462A CA 1100721 A CA1100721 A CA 1100721A
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CA
Canada
Prior art keywords
carbon
particulate
particulates
spheres
pore
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Expired
Application number
CA246,462A
Other languages
French (fr)
Inventor
Joseph L. Schmitt, Jr.
Philip L. Walker, Jr.
George A. Castellion
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
Wyeth Holdings LLC
Original Assignee
American Cyanamid Co
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Filing date
Publication date
Priority claimed from US05/559,997 external-priority patent/US3978000A/en
Application filed by American Cyanamid Co filed Critical American Cyanamid Co
Priority to CA342,180A priority Critical patent/CA1097312A/en
Application granted granted Critical
Publication of CA1100721A publication Critical patent/CA1100721A/en
Expired legal-status Critical Current

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Classifications

    • CCHEMISTRY; METALLURGY
    • C13SUGAR INDUSTRY
    • C13BPRODUCTION OF SUCROSE; APPARATUS SPECIALLY ADAPTED THEREFOR
    • C13B20/00Purification of sugar juices
    • C13B20/12Purification of sugar juices using adsorption agents, e.g. active carbon
    • C13B20/123Inorganic agents, e.g. active carbon
    • BPERFORMING OPERATIONS; TRANSPORTING
    • B01PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01JCHEMICAL OR PHYSICAL PROCESSES, e.g. CATALYSIS OR COLLOID CHEMISTRY; THEIR RELEVANT APPARATUS
    • B01J21/00Catalysts comprising the elements, oxides, or hydroxides of magnesium, boron, aluminium, carbon, silicon, titanium, zirconium, or hafnium
    • B01J21/18Carbon
    • BPERFORMING OPERATIONS; TRANSPORTING
    • B01PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01JCHEMICAL OR PHYSICAL PROCESSES, e.g. CATALYSIS OR COLLOID CHEMISTRY; THEIR RELEVANT APPARATUS
    • B01J23/00Catalysts comprising metals or metal oxides or hydroxides, not provided for in group B01J21/00
    • B01J23/38Catalysts comprising metals or metal oxides or hydroxides, not provided for in group B01J21/00 of noble metals
    • B01J23/40Catalysts comprising metals or metal oxides or hydroxides, not provided for in group B01J21/00 of noble metals of the platinum group metals
    • BPERFORMING OPERATIONS; TRANSPORTING
    • B01PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01JCHEMICAL OR PHYSICAL PROCESSES, e.g. CATALYSIS OR COLLOID CHEMISTRY; THEIR RELEVANT APPARATUS
    • B01J23/00Catalysts comprising metals or metal oxides or hydroxides, not provided for in group B01J21/00
    • B01J23/38Catalysts comprising metals or metal oxides or hydroxides, not provided for in group B01J21/00 of noble metals
    • B01J23/40Catalysts comprising metals or metal oxides or hydroxides, not provided for in group B01J21/00 of noble metals of the platinum group metals
    • B01J23/42Platinum
    • CCHEMISTRY; METALLURGY
    • C01INORGANIC CHEMISTRY
    • C01BNON-METALLIC ELEMENTS; COMPOUNDS THEREOF; METALLOIDS OR COMPOUNDS THEREOF NOT COVERED BY SUBCLASS C01C
    • C01B32/00Carbon; Compounds thereof
    • C01B32/30Active carbon
    • C01B32/354After-treatment
    • C01B32/382Making shaped products, e.g. fibres, spheres, membranes or foam
    • CCHEMISTRY; METALLURGY
    • C01INORGANIC CHEMISTRY
    • C01BNON-METALLIC ELEMENTS; COMPOUNDS THEREOF; METALLOIDS OR COMPOUNDS THEREOF NOT COVERED BY SUBCLASS C01C
    • C01B32/00Carbon; Compounds thereof
    • C01B32/30Active carbon
    • C01B32/354After-treatment
    • C01B32/384Granulation
    • CCHEMISTRY; METALLURGY
    • C07ORGANIC CHEMISTRY
    • C07CACYCLIC OR CARBOCYCLIC COMPOUNDS
    • C07C209/00Preparation of compounds containing amino groups bound to a carbon skeleton
    • C07C209/30Preparation of compounds containing amino groups bound to a carbon skeleton by reduction of nitrogen-to-oxygen or nitrogen-to-nitrogen bonds
    • C07C209/32Preparation of compounds containing amino groups bound to a carbon skeleton by reduction of nitrogen-to-oxygen or nitrogen-to-nitrogen bonds by reduction of nitro groups
    • C07C209/36Preparation of compounds containing amino groups bound to a carbon skeleton by reduction of nitrogen-to-oxygen or nitrogen-to-nitrogen bonds by reduction of nitro groups by reduction of nitro groups bound to carbon atoms of six-membered aromatic rings in presence of hydrogen-containing gases and a catalyst

Abstract

A B S T R A C T

Carbon particulates comprising carbon black spheres and a carbon binder having large pores as well as desirable pore size distributions are disclosed which are useful as selective adsorbants and catalyst supports.
A method of preparation and various uses are also disclosed. The carbon particulates are made by mixing carbon spheres with a carbonizable binder in a volatile medium, forming the mixture into packed particulate shapes, and then removing the volatile medium ant carbonizing the binder by means of heat.

Description

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 ~,.

~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-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 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 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 _ 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.

~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-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~

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.

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 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

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.

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.

~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, (~) 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-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 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.

~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.

Claims (10)

THE EMBODIMENTS OF THE INVENTION IN WHICH AN EXCLUSIVE
PROPERTY OR PRIVILEGE IS CLAIMED ARE DEFINED AS FOLLOWS:
1. A porous carbon particulate comprising carbon black spheres in packed relationship and a carbon binder, said spheres having a particulate size in the range of about 80 to 5000 angstrom units and said particulate having pore size distribution exhibiting peaks at a pore radius in excess of 10 angstrom units.
2. The carbon particulate of Claim 1 having a pore volume in the range of at least about 0.2 cubic centimeter per gram.
3. The carbon particulate of Claim 1 having a pore volume of about 004-1.0 cubic centimeter per gram.
4. The carbon particulate of Claim 1 having a composition of less than about 1 weight percent of ash.
5. The carbon particulate of Claim 1 wherein the carbon black spheres have an average diameter of 80-300 angstrom units.
6. The carbon particulate of Claim 1 wherein said particulate has a pore size distribution exhibiting maximum pore radius in the range of 40-100 angstrom units.
7. The carbon particulate of Claim 1 wherein said particulate has a pore size distribution exhibiting peaks in the range of radii of about 10-250 angstrom units.
8. A process which comprises contacting a solution containing adsorbable materials with solid adsorbent porous carbon particulates consisting of carbon black spheres closely packed in said particulates with a carbon binder, said spheres having particulate size in the range from about 80 to about 5,000 angstrom and the interstitial pore size distribution in said particulates having peaks at pore radius greater than 10 angstrom units, whereby adsorbable material from said solution is adsorbed by said carbon particulates.
9. The process of Claim 8 wherein said solution flows through a fixed bed of said carbon particulate.
10. The process of Claim 8 comprising the additional step of filtering off said carbon particulate after suitable contact time.
CA246,462A 1975-03-19 1976-02-24 Carbon pellets with controlled porosity Expired CA1100721A (en)

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WO1981003167A1 (en) * 1980-04-28 1981-11-12 Johnson Matthey Co Ltd Mesoporous carbons
JPS5820705A (en) * 1981-07-29 1983-02-07 Mitsubishi Chem Ind Ltd Porous carbon particles
GB0019417D0 (en) * 2000-08-09 2000-09-27 Mat & Separations Tech Int Ltd Mesoporous carbons
US20110082024A1 (en) * 2008-06-10 2011-04-07 Hansan Liu Controllable Synthesis of Porous Carbon Spheres, and Electrochemical Applications Thereof
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