Formation of Rh Carbonyl Cluster Species and Its Conversion into Metal Particles during Exposure of Rh/Active Carbon to Carbon Monoxide Revealed by EXAFS and TPD Techniques

1992 ◽  
Vol 21 (8) ◽  
pp. 1441-1444 ◽  
Author(s):  
Nobuo Takahashi ◽  
Terushige Takeyama ◽  
Toshiyuki Fujimoto ◽  
Atsushi Fukuoka ◽  
Masaru Ichikawa
Keyword(s):  
Carbon Monoxide ◽  
Active Carbon ◽  
Metal Particles ◽  
Carbonyl Cluster

Carbon Fibrils Mechanism of Growth and Utilization as a Catalyst Support

1994 ◽  
Vol 368 ◽  
Author(s):  
John W. Geus ◽  
A. J. Van Dillen ◽  
Marco S. Hoogenraad
Keyword(s):  
Mechanical Strength ◽  
Active Carbon ◽  
Circular Cross Section ◽  
Metal Particles ◽  
High Dispersion ◽  
Average Pore ◽  
High Mechanical Strength ◽  
Very High ◽  
Mechanism Of Growth ◽  
Supported Metal

ABSTRACTEspecially with the production of fine chemicals catalytic reactions are being performed in which solid catalysts suspended in liquids are used. Carbon is stable in both acid and alkaline liquids and is not preferentially wetted by water. Carbon is therefore an attractive support for catalysts to be used in liquid-phase reactions. The relatively low diffusion coefficients in liquids call for catalyst bodies having wide pores and dimensions between 1 and 10 μm. Since particles smaller than 1 μm cannot be readily separated from liquids, attrition of carbon support bodies must be avoided. However, it is difficult to produce active carbon bodies of 1 to 10 μm of a high mechanical strength. Also with gas-phase reactions, the low mechanical strength of active carbon bodies limits the applicability of active carbon.From supported metal particles carbon filaments of a diameter between 10 and 300 nm can be grown rapidly. The diameter is generally of the same order of magnitude as the size of the metal particles. The graphite layers within the fibrils, that have a circular cross-section, are oriented either parallel to the fibril axis or at an angle, which leads to cone-shaped graphite layers. The mechanism of growth of carbon fibrils from supported metal particles will be dealt with. The parallel orientation of the graphite layers leads to a very high mechanical strength, while the porous structure is extremely open. A representative value for the surface area is 225 m2/g and for the pore volume 1.6 ml/g, which leads to an average pore dimension of 28 nm.To apply active precursors, such as, palladium salts, the surface of the carbon fibrils must be oxidized, e.g., by treatment with nitric acid. A very high dispersion of palladium can thus be achieved. The dispersion of components active in hydrogenation can be assessed by the ability to react the support with hydrogen to methane. The activity of catalyst on carbon fibrils in the hydrogenation of nitrobenzene as well as the filterability of carbon fibril catalysts will be compared with that of commercial catalysts.

scholarly journals RESEARCH OF POSSIBILITY OF USING CHEMICAL METHOD OF FINE METAL PARTICLES REDUCTION FOR BACTERICIDAL SORBENTS PRODUCTION

2020 ◽  
Vol 63 (3) ◽  
pp. 46-53
Author(s):  
Еlena A. Farberova ◽  
Anastasia Yu. Katysheva ◽  
Elena A. Tingaeva ◽  
Sergey A. Smirnov ◽  
Andrey G. Starostin
Keyword(s):  
Ascorbic Acid ◽  
Specific Surface ◽  
Porous Structure ◽  
Active Carbon ◽  
Metal Particles ◽  
Carbon Fabric ◽  
Copper Particles ◽  
Bactericidal Properties ◽  
Fine Metal Particles ◽  
Fine Copper

The present paper is concerned with a research of sorption and bactericidal properties of the fine metal particles applied on the surface of active carbon fabric by chemical sedimentation method. The ascorbic acid and natrium borane were used in the study process as metals, copper and silver reducing agents. Influence of reducer and fine metal nature onto the porous structure, as well as bactericidal and sorption characteristics of obtained fibrous sorbent samples are shown. It is determined that use of ascorbic acid for synthesis of copper and silver fine particles on the active carbon fabrics surface leads to the considerable decrease in a specific surface and volumes of meso - and micropores of the obtained sorbent in comparison with initial active carbon fabric. When using the natrium borane as reducer of fine copper particles the decrease in a specific surface and volumes of sorption pores is also observed. However, when using the natrium borane, the active carbon fabric samples modified with silver particles or with their composition with fine copper particles, had the higher values of porous structure main characteristics in comparison with the initial active carbon fabric. The nature of distribution of fine metal particles at the active carbon fabric surface was investigated by the electronic microscopy method. It was found that during the chemical reduction process the particles of fine copper attached to active carbon fabric fibers, being almost evenly distributed at all surface of fabric. Particles of silver were located as crystal congestions along fibers. Sorption and bactericidal properties of the received samples of modified active carbon fabrics are investigated. Their high sensitivity to microorganism cells which remains during a long storage period is demonstrated. Herewith, the active carbon fabric, modified with particles of fine copper and silver, keeps high sorption properties.

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