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177. The use of activated carbons as supports for platinum catalysts
Abstracts
224
have been used as supports for Fe and Ru catalysts; some of them have been previously treated with NH, at high temperature in order to introduce nitrogen surface complexes. All the catalysts prepared were characterized by CO and H, chemisorption and the effect of the surface complexes on this process has been analyzed. 177. The use of activated carbons as supports for platinum catalysts
J. de Dios L6pez-Gonzhlez
(Departamento de Qui-
mica Inorgbnica, UNED, Madrid, Spain). C. MorenoCastilla (Departamento de Quimica Inorgcinica, Facultad de Ciencias, Universidad de Granada, Spain). I. Rodriguez-Ramos and F. Rodriguez-Reinoso (Departamento de Quimica Inorgbnica, Facultad de Ciencias, Universidad de Alicante, Alicante, Spain).
Several activated carbons with a wide range of surface areas and pore size distributions were prepared from almond shells and olive stones and used as supports for platinum catalysts. The platinum of the catalysts has been characterized by CO and Hz chemisorption. The effect of the surface properties of the supports and the catalyst reduction conditions (temperature and time) on the platinum dispersion has been studied. 178. Effect of catalysts on surface group formation in calcined cokes
R. L. Seth, K. K. Datta and S. Hiranniah (Carbon technology Unit, National Physical Laboratory, Hillside Road, New Delhi- 110012, India). Surface groups have been formed on pitch coke, petroleum coke and low ash metallurgical coke by thermal treatment in air at 3%45o”C in presence of permanganate and dichromate ions. The differential surface groups formed in presence of the metal ions have been estimated by titrations with NaOH, Na,CO, and NaHCO, and further confirmed by IR. The difference in surface groups formation is attributed to the morphology of the cokes. 17% Development of pore structure in carbon fibres by HNOj activation J. Koresh and S. S. Barton (Chemistry Department Nuclear Research Centre, Negev P.O.B. 9001, Beer-Sheva, Israel). A study has been made of
the changes in the adsorptive behaviour of a carbon fibre with aqueous oxidative activation. It has been demonstrated that molecular sieve action initially present in the fibre can be eliminated by progressive activation but eventually restored after the total pore volume of the fibre has been greatly increased. 180. Chemisorption of oxygen on type I carbon fibers W. P. Hoffman and J. A. Lowry (Air Force Rocket Propulsion Laboratory, Edwards, CA 93523, U.S.A.).
The chemisorption of oxygen has been studied on both pitch and PAN Type I carbon fibers. Adsorption pressure was varied between 6.7 P and
66.7 kP while the temperature range was lO&3OO”C. The microporosity of the fiber was found to have a significant effect on the active surface area measurement.
181. Capacitance measurements study of the carbon fiber surface S. Mentus (Faculty of Sciences, University of Belgrade, Belgrade). A. Vukov (Boris Kidric Institute of Nuclear Sciences, VinEa Materials Science Department, Belgrade P.O. Box 522). By measuring the
complex impedance of single, treated and detreated, carbon fibers in KC1 aqueous solution, the double layer capacity at the fiber-electrolyte interface was determined. The measurement of surface area (B.E.T. method) and the concentration of acid surface groups (volumetric tritrations) were also carried out. The results indicate significant indirect influence of the acid surface groups on double layer capacity. Their dipole moments influence wetting behaviour and the effective fiber-electrolyte surface area and through this the double layer capacity. 182. Mesoporous structure of electrically conductive grades of carbon blacks
Jordan R. Nelson (RCA/David
Sarnoff Research Center, Princeton, NJ 08540, U.S.A.). The porous
structure of a number of commercial and experimental electrically conductive grades of carbon blacks was examined. Unexpectedly, it was found that BET nitrogen surface areas of these blacks invariably far exceeded corresponding D-R carbon dioxide micropore surface areas because of their highly mesoporous structure. 183. On the nature of sulfur in electrically-conductive carbon blacks
M. E. Labib, J. H. Thomas III and D. D. Embert (RCA Laboratories, David SarnofS Research Center, Princeton, NJ 08540, U.S.A.). XPS and other tech-
niques were used to investigate the nature of sulfur in carbon black and as a function of heat treatment. In as-received sample, sulfur exists, in equivalents, as bound to carbon (So state) and as adsorbed sulfate ions (S+6 state). Evidence for the removal of sulfate (S+6) via a transformation to s” during heat treatment is presented. 184. Effect of electrolytes on the rheological behaviour of aqueous dispersions of carbon black C. Budworth and B. Rand (Department of Ceramics, Glasses and Polymers, University of Sheffield, Shefield SlO ZTZ, England). Structural particle build
up assessed from the extrapolated yield stress, zex,of dispersions is followed as a function of the electrical double layer at the carbon black/aqueous electrolyte interface. rex decreases with increasing surface charge density and increases with counter ion conc&tration and solid concentration. The effect of deflocculant polyanions is demonstrated.
224
have been used as supports for Fe and Ru catalysts; some of them have been previously treated with NH, at high temperature in order to introduce nitrogen surface complexes. All the catalysts prepared were characterized by CO and H, chemisorption and the effect of the surface complexes on this process has been analyzed. 177. The use of activated carbons as supports for platinum catalysts
J. de Dios L6pez-Gonzhlez
(Departamento de Qui-
mica Inorgbnica, UNED, Madrid, Spain). C. MorenoCastilla (Departamento de Quimica Inorgcinica, Facultad de Ciencias, Universidad de Granada, Spain). I. Rodriguez-Ramos and F. Rodriguez-Reinoso (Departamento de Quimica Inorgbnica, Facultad de Ciencias, Universidad de Alicante, Alicante, Spain).
Several activated carbons with a wide range of surface areas and pore size distributions were prepared from almond shells and olive stones and used as supports for platinum catalysts. The platinum of the catalysts has been characterized by CO and Hz chemisorption. The effect of the surface properties of the supports and the catalyst reduction conditions (temperature and time) on the platinum dispersion has been studied. 178. Effect of catalysts on surface group formation in calcined cokes
R. L. Seth, K. K. Datta and S. Hiranniah (Carbon technology Unit, National Physical Laboratory, Hillside Road, New Delhi- 110012, India). Surface groups have been formed on pitch coke, petroleum coke and low ash metallurgical coke by thermal treatment in air at 3%45o”C in presence of permanganate and dichromate ions. The differential surface groups formed in presence of the metal ions have been estimated by titrations with NaOH, Na,CO, and NaHCO, and further confirmed by IR. The difference in surface groups formation is attributed to the morphology of the cokes. 17% Development of pore structure in carbon fibres by HNOj activation J. Koresh and S. S. Barton (Chemistry Department Nuclear Research Centre, Negev P.O.B. 9001, Beer-Sheva, Israel). A study has been made of
the changes in the adsorptive behaviour of a carbon fibre with aqueous oxidative activation. It has been demonstrated that molecular sieve action initially present in the fibre can be eliminated by progressive activation but eventually restored after the total pore volume of the fibre has been greatly increased. 180. Chemisorption of oxygen on type I carbon fibers W. P. Hoffman and J. A. Lowry (Air Force Rocket Propulsion Laboratory, Edwards, CA 93523, U.S.A.).
The chemisorption of oxygen has been studied on both pitch and PAN Type I carbon fibers. Adsorption pressure was varied between 6.7 P and
66.7 kP while the temperature range was lO&3OO”C. The microporosity of the fiber was found to have a significant effect on the active surface area measurement.
181. Capacitance measurements study of the carbon fiber surface S. Mentus (Faculty of Sciences, University of Belgrade, Belgrade). A. Vukov (Boris Kidric Institute of Nuclear Sciences, VinEa Materials Science Department, Belgrade P.O. Box 522). By measuring the
complex impedance of single, treated and detreated, carbon fibers in KC1 aqueous solution, the double layer capacity at the fiber-electrolyte interface was determined. The measurement of surface area (B.E.T. method) and the concentration of acid surface groups (volumetric tritrations) were also carried out. The results indicate significant indirect influence of the acid surface groups on double layer capacity. Their dipole moments influence wetting behaviour and the effective fiber-electrolyte surface area and through this the double layer capacity. 182. Mesoporous structure of electrically conductive grades of carbon blacks
Jordan R. Nelson (RCA/David
Sarnoff Research Center, Princeton, NJ 08540, U.S.A.). The porous
structure of a number of commercial and experimental electrically conductive grades of carbon blacks was examined. Unexpectedly, it was found that BET nitrogen surface areas of these blacks invariably far exceeded corresponding D-R carbon dioxide micropore surface areas because of their highly mesoporous structure. 183. On the nature of sulfur in electrically-conductive carbon blacks
M. E. Labib, J. H. Thomas III and D. D. Embert (RCA Laboratories, David SarnofS Research Center, Princeton, NJ 08540, U.S.A.). XPS and other tech-
niques were used to investigate the nature of sulfur in carbon black and as a function of heat treatment. In as-received sample, sulfur exists, in equivalents, as bound to carbon (So state) and as adsorbed sulfate ions (S+6 state). Evidence for the removal of sulfate (S+6) via a transformation to s” during heat treatment is presented. 184. Effect of electrolytes on the rheological behaviour of aqueous dispersions of carbon black C. Budworth and B. Rand (Department of Ceramics, Glasses and Polymers, University of Sheffield, Shefield SlO ZTZ, England). Structural particle build
up assessed from the extrapolated yield stress, zex,of dispersions is followed as a function of the electrical double layer at the carbon black/aqueous electrolyte interface. rex decreases with increasing surface charge density and increases with counter ion conc&tration and solid concentration. The effect of deflocculant polyanions is demonstrated.