CA1085371A - Support material for a noble metal catalyst and method for making the same - Google Patents

Support material for a noble metal catalyst and method for making the same

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Publication number
CA1085371A
CA1085371A CA275,327A CA275327A CA1085371A CA 1085371 A CA1085371 A CA 1085371A CA 275327 A CA275327 A CA 275327A CA 1085371 A CA1085371 A CA 1085371A
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CA
Canada
Prior art keywords
catalyst
metal
carbon
oxidizing catalyst
metal oxidizing
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
CA275,327A
Other languages
French (fr)
Inventor
Harold R. Kunz
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RTX Corp
Original Assignee
United Technologies Corp
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Filing date
Publication date
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    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/86—Inert electrodes with catalytic activity, e.g. for fuel cells
    • H01M4/90—Selection of catalytic material
    • H01M4/92—Metals of platinum group
    • H01M4/925—Metals of platinum group supported on carriers, e.g. powder carriers
    • H01M4/926—Metals of platinum group supported on carriers, e.g. powder carriers on carbon or graphite
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01J—CHEMICAL OR PHYSICAL PROCESSES, e.g. CATALYSIS OR COLLOID CHEMISTRY; THEIR RELEVANT APPARATUS
    • B01J23/00—Catalysts comprising metals or metal oxides or hydroxides, not provided for in group B01J21/00
    • B01J23/38—Catalysts comprising metals or metal oxides or hydroxides, not provided for in group B01J21/00 of noble metals
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01J—CHEMICAL OR PHYSICAL PROCESSES, e.g. CATALYSIS OR COLLOID CHEMISTRY; THEIR RELEVANT APPARATUS
    • B01J23/00—Catalysts comprising metals or metal oxides or hydroxides, not provided for in group B01J21/00
    • B01J23/38—Catalysts comprising metals or metal oxides or hydroxides, not provided for in group B01J21/00 of noble metals
    • B01J23/40—Catalysts comprising metals or metal oxides or hydroxides, not provided for in group B01J21/00 of noble metals of the platinum group metals
    • B01J23/42—Platinum
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/86—Inert electrodes with catalytic activity, e.g. for fuel cells
    • H01M4/90—Selection of catalytic material
    • H01M4/92—Metals of platinum group
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/86—Inert electrodes with catalytic activity, e.g. for fuel cells
    • H01M2004/8678—Inert electrodes with catalytic activity, e.g. for fuel cells characterised by the polarity
    • H01M2004/8684—Negative electrodes
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/86—Inert electrodes with catalytic activity, e.g. for fuel cells
    • H01M2004/8678—Inert electrodes with catalytic activity, e.g. for fuel cells characterised by the polarity
    • H01M2004/8689—Positive electrodes
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M2300/00—Electrolytes
    • H01M2300/0002—Aqueous electrolytes
    • H01M2300/0005—Acid electrolytes
    • H01M2300/0008—Phosphoric acid-based
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/86—Inert electrodes with catalytic activity, e.g. for fuel cells
    • H01M4/90—Selection of catalytic material
    • H01M4/92—Metals of platinum group
    • H01M4/921—Alloys or mixtures with metallic elements
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
    • Y02E60/00—Enabling technologies; Technologies with a potential or indirect contribution to GHG emissions mitigation
    • Y02E60/30—Hydrogen technology
    • Y02E60/50—Fuel cells

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  • Chemical & Material Sciences (AREA)
  • Engineering & Computer Science (AREA)
  • Materials Engineering (AREA)
  • Chemical Kinetics & Catalysis (AREA)
  • Organic Chemistry (AREA)
  • Electrochemistry (AREA)
  • General Chemical & Material Sciences (AREA)
  • Catalysts (AREA)
  • Inert Electrodes (AREA)

Abstract

ABSTRACT OF THE DISCLOSURE
A support material for platinum, platinum alloys, or other noble metal catalyst, is made from carbon particles by heat treating the carbon until it is at least partially graphitized, depositing a metal on the ?eat treated carbon particles which will catalyze the oxidation of graphite in an oxidizing atmosphere, ant oxidizing the surfaces of the heat treated carbon particles at the sites of the catalyst crystals to pit or etch the surfaces at these sites. When this material is used as a support for platinum it reduces the rate of platinum migration when the supported platinum catalyst is heated in the presence of a liquid, thereby reducing the loss of platinum surface area which often occurs under these conditions.

Description

--- 108537~ ~
BACKGROUND OF THE INVENTION
Field of the Invention - This invention relates to a platinum catalyst and more particu~arly to a platinum catalyst supported on heat treated carbon particles.
Description of the Prior Art - Platinum is a well-known catalyst used in electrochemical cells. Electrode performance in a cell is directly related to the amount of surface area of platinum which can be reached by the various reacting species within the cell. This fact, coupled with the high cost of platinum, has resulted in considerable effort to get platinum into a usable form which has maximum surface area per unit weight of platinum. The basic approach has been, and still is, to put the platinum on the surface of suitable particles called supports. Carbon particles and graphite particles are common platinum supports in the fuel cell art.
several well-known techniques exist for depositing platinum on such supports. For example, the support can be dispersed in an aqueous solution of chloroplatinic acid, dried, and exposed to hydrogen.
By the foregoing technique, and by other techniques, platinum crystals may be uniformly distributed and highly dispersed on the surfaces of the support particles so as to provide a very high surface area of platinum.
When this supported platinum is used at temperatures greater than 100C in the presence of a liquid (or at higher temperatures in the presence of a gas) it has been found to lose surface area. This loss of surface area is particularly _~_ 108~37~

pronounced in an acid ~uel cell environment, such as in fuel cells using phosphoric acid as the electr~lyte, which operate at temperatures anywhere from 120C and higher. The loss in surface area is dramatic during the first few hours of cell operation, but it continues at a slow but steady rate for a considerable period thereafter. A loss in cell performance is directly attributable to this loss in platinum surface area.

SUMMARY OF THE INVENTION
One object of the present invention is a-method for making a supported noble metal catalyst, in particular a platinum catalyst, which, when heated in the presence of a liquid or gas, retains a higher catalyst surface area than supported noble metal catalysts made by prior art methods.
Accordingly, in the method of making a support material for a noble metal catalyst, wherein the support material is a -carbon powder which is at least partially graphitized, the surfaces of the graphitized carbon particles are oxidized in ; ~
the presence of a "metal oxidizing catalyst" to form pits in -surfaces of the particlesO
In a preferred embodiment the pitting is accomplished by depositing "metal oxidizing catalyst" crysta~lites on the surfaces of the graphitized particles, and oxidizing the sur-faces of the particles at the crystallite sites. This results in pitting or etching of the surfaces at these sites.
As used in this specification and in the appended claims the term "metal oxidizing catalyst" means a metal which will catalyze the oxidation of graphite in an oxidizing atmosphere.

10~;371 -This metal oxidizing catalyst is removed, such as by leaching, prior to depositing the platinum on the support particles.
It can only be theorized as to why noble metals, such as platinum, supported on a graphitized carbon, lose surface area when heated in the presence of a liquid. In the case of platinum, it is believed that individual crystals of platinum migrate from exposed surfaces of the graphitized particles to the crevices or junctures formed where particles a~ut one another; these crystals accumulate in the crevices, agglom- ~
erating with other crystals thereby reducing the effective --platinum surface area. This reduction in surface area is not significant unless the supported catalyst is heated and is more severe in the presence of a liquid than in the presence of a gas. This is a serious problem when the catalyst is used in a fuel cell wherein operating temperatures are typically greater than 120C, and the catalyst is in contact with a liquid electrolyte, such as phosphoric acid. It is believed that by pitting or etching the surface of the graphitized or partially graphitized carbon particles, in accordance with the process of the present invention, the platinum crystallites are held more securely in these pits thereby reducing migration and loss of surface area. Some examples of other noble metal catalysts which it is believed would behave in a manner similar to platinum are gold, palladium, ruthen~um, iridium and alloys thereof.
The foregoing and other objects, features, and advan-tages of the present invention will become more apparent in the light of the following detailed description of the pre-ferred embodiments thereof.

, 1 ~ ~ 71 DESCRIPTION OF THE PREFERRED EMBODIMENTS
In accordance with one embodiment of the present invention a carbon black powder is heat treated at temperatures abo~e 1250C until it is at least partially graphitized. As used in this specification and appended claims, "partially graphitized"
means that the mean d spacing in the c~rbon crystallite struc-ture is greater than 3.44 A, which is the mean d spacing of completely non-graphitic carbon as discussed in the Kirk-Othmer Encyclopedia of Chemical Technology, Second Edition, Vol. 4, pp. 306-308, John Wiley & Sons, Inc. (1964). A metal is selected which will catalyze the oxidation of graphite in an oxidizing atmosphere such as in air, carbon dioxide, or fluorine.
Some suitable metals are iron, lead, copper, silver, and plati-num. Tests conducted using iron~lead, copper, and platinum have shown that iron and lead work best and are therefore pre-ferred. The metal, preferably in the form of an aqueous salt solution, is mixed with the heat treated particles to form a ~ ;
slurry. Water is removed from the slurry by evaporation and -~ the salt is decomposed to convert it to a metal by heating or reduction. In this manner metal crystallites are uniformly dispersed over the surfaces of the heat treated particles. The particles are then subJected to an oxidizing atmosphere at temperatures high enough to oxidize the particles at the loca-tions or sites of the metal crystallites. However, these temperatures are chosen such that they are not high enough to oxidize the particles in areas lacking catalyst crystallites in order to prevent undesired loss of graphite material. The proper temperature range can readily be determined by a person , ~0853'7~L

l~aving ordinary skill in the art. Oxidation may be accom-plished in either a conventional furnace or in a fluidized bed, Finally, the crystallites of metal oxidizing catalyst are leached out, leaving pits or channels on the surface of the particles at the former sites of the crystallites. The oxidized particles are now ready for platinum deposition which can be accomplished by any of several well-known techniques, such as the one described in the Background of the Invention. The supported platinum catalyst is now ready for use, such as in a fuel cell.
Although the metal oxidizing catalyst is preferably in the form of a salt solution when mixed with the heat treated particles, the catalyst could be in the form of a colloid of the metal itself 5 the colloid of a compound of the metal, or ~n any other form suitable for dispersing the metal crystal-lites on the surface of the graphitized particles such as in the form of an acid. Some examples of suitable solutions are ferric formate, copper acetate, lead acetate, ferric nitrate, silver nitrate, chloroplatinic acid, etc.
Example A platinum support material was prepared from Vulcan B XC-72 which is a non-graphitized furnace carbon black powder manufactured by Cabot Corporation, Boston, Massachusetts.
--The powder was completely graphitized by heating to 2800C
for 30 minutes. This graphite powder was added to an aqueous solution of ferric formate; the mixture was stirred and heated for a 3-4 hour period to remove the liquid water. It was then further heated in a vacuum at 150C to remove .,~ r~/e r1Qrk' 37~

additional water and to decompose the ferric formate. It was then agitated in a blender to decrease its bulk density.
The final iron content was 0.1%. Approximately 3 grams of this mixture was placed in a tube furnace and heated in nitrogen to the temperature at which exposure to oxygen was desired. Pure oxygen was then applied to the sample at the graphite oxidation temperature of about 500C for about 1/2 minute (the proper time and temperature depends on the nature and concentration of the metal oxidizing catalyst used). The material was then cooled in nitrogen to prevent oxidation during the cool down period, removed from the furnace, stirred and weighed. This procedure of placing the sample in the furnace, oxidizing the graphite, and removing it from the furnace was repeated several times. The stirring during this procedure was necessary to insure that the powder was being uniformly oxidized. This procedure was continued until the weight of the materLal indicated a 108s of weight of 15% as a result of the oxidation of the graphite particles at the metal crystallite sites. The sample was then washed in 50% HNO3 solution and then washed with water to remove the iron and finally dried at 110C in a vacuum oven. The sup-port material was then catalyzed with platinum by the thermal -~
decomposition of diamminoplatinum (II) dinitrite.
For comparison purposes samples of platinum catalyst were prepared using supports of unoxidized Vulcan XC-72 which had been graphitized in the same manner as above. Samples of both types were tested u~der simulated fuel cell operating conditions as follows: 98% H3PO4 at 325F for 24 hours at ~ 'r~e~

~' . .

~08~37~L

an electrode potential of 0.65 V with respect to a hydrogen electrode in the same electrolyte. The initial platinum surface area of both types of samples was approximately 98 square meters per gram of platinum. The average decrease in platinum surface area after 24 hours for the unoxidized graphite support average about 23%, whereas the average decrease in platinum area for the oxidized graphite support after 24 hours averaged about 8%. After the first 24 hours the rates of platinum surface area loss taper off to about i 10 the same level for both types of samples; however, the advantage gained during the first 24 hours by the samples prepared according to the present invention is never lost.
A variety of different samples were prepared and tested in an effort to determine how various parameters affect the process. From these tests it was determined that the mere oxidation of a graphitized support material without the presence of a metal oxidizing catalyst has no significant effect on reducing platinum surface area loss.
Platinum surface area loss was also determined to be independent of, for example, the iron concentration on the graphite support during oxi;da,ti~nl in the range of 0O1% Fe to 10% Fe. Furthermore, increasing the test temperature from 32~qFsimply caused an increase in the rate of platinum surface area loss for both types of samples; the samples prepared according to the present invention still reduced platinum surface area loss to a significantly greater extent than the unoxidized support samples. It should also be noted that the 0853'7~

method by which the platinum is deposited upon the suppor~ is unimportant for the purposes of the present invention.
Samples were also made and tested using platinum as the metal oxidi~ catalyst. This eliminated the necessity for leaching out the meta~ oxidizing catalyst and also for depositing platinum upon the oxidized support. Although tests showed the percent of platinum surface area loss under typical fuel cell operating conditions was significantly reduced, only a relatively low initial platinum surface area could be obtained. Thus, although platinum works as an ;
oxidizing catalyst, other metals were determined to be more suitable.
From analysis of test results, it is estimated that satisfactory results will be obtained if the support is oxidized to the extent of at least a 10% weight loss, with a 14 to 20a/o weight loss being preferred. Weight losses greater than 30% are unnecessary to provide the desired features of this invention and may be detrimental. Weight losses less than 10% are likely to result in inadequate pit formation to stabilize the platinum catalyst against loss of surface area.
Platinum on supports made according to the present inYention can be used anywhere a platinum supported on carbon catalyst is needed, but are particularly usefuL in ~n environ- `
ment wherein they will be exposed to a liquid and wherein the temperature is greater than about 100C. One such environment is in a liquid electrolyte fuel cell. For example, the ; catalyst may be admixed in an aqueous dispersion of fluoro-carbon binder, such as polytetrafluoroethylene; the catalyst/

_g_ -` 10~3~

binder is deposited, such as by filtering, as a layer on the surfare of a carbon paper substrate to form an electrode.
An electrolyte retaining matrix is disposed between a pair of these electrodes to form a fuel cell.
Although the invention has been shown and described with respect to a preferred embodiment thereof, it should be understood by those skilled in the art that other various changes and omissions in the form and detail thereof may be made therein without departing from the spirit and the scope of the invention.

Claims (21)

The embodiments of the invention in which an exclusive property or privilege is claimed are defined as follows:
1. In the method for making a supported platinum catalyst the steps of:
heat treating a carbon powder at temperatures above about 1250°C to at least partially graphitize the carbon thereby forming graphitized carbon support particles, depositing metal oxidizing catalyst crystallites on the surfaces of the graphitized carbon support particles;
oxidizing the surfaces of the graphitized carbon support particles only at the sites of the metal oxidizing catalyst crystallites until the support particles have lost between 10 and 30% of their weight, removing the metal oxidizing catalyst crystallites from the oxidized support particles and depositing platinum on the oxidized support particles.
2. The method according to claim 1 wherein the step of oxidizing comprises oxidizing the surfaces of the graphitized carbon support particles in the presence of the metal oxidiz-ing catalyst crystallites at a temperature sufficiently high to cause oxidation of the surfaces of the particles at the sites of the metal oxidizing catalyst crystallites, but not high enough to oxidize the particle surfaces where no metal oxidizing catalyst crystallites are present.
3. The process according to claim 1 wherein the step of heat treating the carbon powder includes fully graphitizing the carbon.
4. The method for making a supported platinum catalyst according to claim 1 wherein the metal oxidizing catalyst is selected from the group consisting of lead, copper, iron and silver.
5. The method according to claim 3 wherein the step of depositing metal oxidizing catalyst crystallites includes mixing the graphitized support particles in an aqueous salt solution of the metal oxidizing catalyst: removing the water and decomposing the salt to convert it to the metal.
6. The method according to claim 3 wherein the metal oxidizing catalyst crystallites are iron.
7. The method according to claim 5 wherein the metal oxidizing catalyst crystallites are iron and the salt of the metal is ferric formate.
8. The method according to claim 5 wherein the step of oxidizing is continued until the graphitized support material has lost between 14 and 20% of its weight.
9. Process according to claim 1, which comprises forming an admixture of the supported platinum catalyst and a fluoro-carbon polymer binder, and depositing said admixture onto a substrate to form a fuel cell electrode.
10. The process according to claim 9 wherein the support particles consist of carbon which is fully graphitized.
11. The process according to claim 9 wherein the metal oxidizing catalyst crystallites are selected from the group consisting of iron, copper, lead and silver.
12. The process according to claim 11 wherein the step of depositing metal oxidizing catalyst crystallites includes mixing the support particles in an aqueous salt solution of the metal oxidizing catalyst; removing the water and decomposing the salt to convert it to the metal.
13. The process according to claim 11 wherein the metal oxidizing catalyst crystallites consist of iron.
14. The process according to claim 11 wherein the metal oxidizing catalyst crystallites consist of lead.
15. A platinum catalyst support made from carbon according to the following process, heat treating a carbon powder at temperatures above about 1250°C to at least partially graphitize the carbon, depositing a metal oxidizing catalyst on the surfaces of the heat treated carbon particles;
oxidizing the surfaces of the heat treated carbon particles at temperatures sufficiently high to cause oxidation of the surfaces at the sites of the metal oxidizing catalyst, but not high enough to oxidize the heat treated carbon at the locations where no metal oxidizing catalyst is present;
continuing the oxidizing until the heat treated carbon has lost between 10 and 30% of its weight; and removing the metal oxidizing catalyst.
16. A platinum catalyst support according to claim 15 wherein the metal oxidizing catalyst is selected from the group consisting of iron, copper, lead, and silver.
17. A platinum catalyst support according to claim 15 wherein the step of heat treating the carbon powder includes fully graphitizing the carbon.
18. A platinum catalyst support according to claim 15 wherein the step of depositing metal oxidizing catalyst crystallites includes mixing the heat treated carbon particles in an aqueous salt solution of the metal oxidizing catalyst removing the water and decomposing the salt to convert it to the metal.
19. A supported platinum catalyst made according to the following process:
heat treating a carbon powder at temperatures above about 1250°C to at least partially graphitize the carbon depositing a metal oxidizing catalyst on the surfaces of the heat treated carbon particles, oxidizing the surfaces of the heat treated carbon particles in the presence of the metal oxidizing catalyst at a temperature sufficiently high to cause oxidation of the surfaces at the sites of the metal oxidizing catalyst, but not high enough to oxidize the heat treated carbon surfaces where no metal oxidizing catalyst is present and continuing the oxidizing until the heat treated carbon has lost between 10 and 30% of its weight, removing the metal oxidizing catalyst and depositing platinum on the oxidized particles.
20. A supported platinum catalyst according to claim 19 wherein the metal oxidizing catalyst is selected from the group consisting of lead, copper, iron and silver.
21. A supported platinum catalyst according to claim 20 wherein the step of depositing metal oxidizing catalyst includes mixing the heat treated carbon particles in an aqueous salt solution of the metal oxidizing catalyst; removing the water and decomposing the salt to convert it to the metal.
CA275,327A 1976-06-01 1977-04-01 Support material for a noble metal catalyst and method for making the same Expired CA1085371A (en)

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
US05/691,921 US4028274A (en) 1976-06-01 1976-06-01 Support material for a noble metal catalyst and method for making the same
US691,921 1976-06-01

Publications (1)

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CA1085371A true CA1085371A (en) 1980-09-09

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Country Status (7)

Country Link
US (1) US4028274A (en)
JP (1) JPS609858B2 (en)
CA (1) CA1085371A (en)
DE (1) DE2719659A1 (en)
FR (1) FR2353333A1 (en)
GB (1) GB1555876A (en)
IL (1) IL52025A (en)

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DE1567513B2 (en) * 1965-12-28 1975-05-28 Bayer Ag, 5090 Leverkusen Process for the preparation of hydroxylammonium salts
FR1487495A (en) * 1966-05-27 1967-07-07 Lorraine Carbone Improvement in the process of activating carbon electrodes for batteries
FR1522239A (en) * 1966-10-27 1968-04-26 Akad Wissenschaften Ddr Impregnation process for the activation of carbon for galvanic elements
FR1509002A (en) * 1966-11-07 1968-01-12 Lorraine Carbone Fuel cell electrode refinements
DE1667045A1 (en) * 1967-05-13 1971-06-03 Bayer Ag Process for the production of a platinum catalyst particularly suitable for the hydrogenation of NO to hydroxylamine
US3804916A (en) * 1973-03-27 1974-04-16 Ventron Corp Selective hydrogenation of alkynes or 1,3-conjugated dienes
FR2225849A1 (en) * 1973-04-16 1974-11-08 Alsthom Cgee Fuel cell electrode prodn - by deposition on substrate of porous carbon and resin binder and impregnating with catalyst
DE2538346C2 (en) * 1974-09-02 1986-04-30 The British Petroleum Co., Ltd., London Process for the production of graphitic carbon and its use
CA1084477A (en) * 1975-07-22 1980-08-26 Brian D. Mcnicol Catalysts supported on at least partially polycrystalline graphite

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DE2719659A1 (en) 1977-12-15
IL52025A (en) 1980-02-29
JPS52146793A (en) 1977-12-06
JPS609858B2 (en) 1985-03-13
FR2353333B1 (en) 1982-07-23
US4028274A (en) 1977-06-07
FR2353333A1 (en) 1977-12-30
IL52025A0 (en) 1977-07-31
GB1555876A (en) 1979-11-14

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