Surface Area Of Carbon Materials Research Articles

Templated Synthesis of Carbon Materials from Zeolites (Y, Beta, and ZSM-5) and a Montmorillonite Clay (K10): Physical and Electrochemical Characterization

New high surface area carbon materials were prepared at low temperature (600 °C) using zeolite (Y, Beta, and ZSM-5) and montmorillonite clay (K10) templates. Acrylonitrile, furfuryl alcohol, pyrene, and vinyl acetate precursors were polymerized and carbonized in each of the inorganic matrixes without the addition of a polymerizing agent. The templates were removed by acid demineralization and the resulting carbon materials were physically characterized by infrared spectroscopy, BET (N2) surface area analysis, energy dispersive spectroscopy (EDS), scanning electron microscopy (SEM), and elemental analyses. Electrochemical characterizations were also conducted. Cyclic voltammetry was employed to examine the synthesized carbons in the oxidation of catechol to hydroquinone and quinone, a model reaction that is known to be surface dependent. The identities of both the template and the substrate affected the electrochemical response. Additionally, the ability of the new carbons to intercalate and deintercalate ...

Specific surface area of carbon materials based on hydrated cellulose and polyacrylonitrile fibres calculated by sorption and electrochemical methods

Specific surface area of carbon materials based on hydrated cellulose and polyacrylonitrile fibres calculated by sorption and electrochemical methods

Specific Surface Area of Carbon Materials Based on Hydrated Cellulose and Polyacrylonitrile Fibres Calculated by Sorption and Electrochemical Methods

In many sorbates, water, toluene, benzene, n-hexane, the minimum limiting volume of water sorbed by carbon fibre materials is correlated with the minimum saturated vapor pressure and the maximum molecule size. Water at saturated vapor pressure at 20°C is primarily sorbed in the form of (H2O)4 clusters whose diameter is 681 pm. The industrially acceptable duration and completeness of desorption are attained at a temperature above the boiling point of the given sorbate but within the limits of the thermal stability of CFM. Electrochemical studies of CFM showed that in polarization in aqueous 0.3% NaCl solution in the range of −0.2 to +0.6 V on the hydrogen scale, the limiting current values are a function of the phase contact area and polarity: in cathodic polarization, the absolute current value in the circuit is much higher than the current in anodic polarization and is higher the more slowly the potential of the CFM changes. The CFM-solution contact area determined with electrochemical measurements is comparable to the specific surface area determined by sorption of saturated water vapors.

New Synthesis of Mo2C 14 nm in Average Size Supported on a High Specific Surface Area Carbon Material

A molybdenum carbide supported on active carbon for catalytic hydrotreating was prepared by temperature-programmed reaction (TPR) in flowing H2of an active carbon impregnated by an heptamolybdate. TPR led at 973 K to the formation of supported Mo2C. This new method of preparation avoids the use of methane as carburizing reactant and allowsin situpreparation of supported molybdenum carbide without any contact of this pyrrophoric material with air between preparation and catalytic run. The various steps of the carburization process were studied by trapping the solid intermediates at different temperatures during TPR. Two successive reactions were evidenced: the partial reduction by H2of the initial molybdenum precursor to MoO2, and its subsequent carburization to Mo2C. This last step is mainly due to the reduction of MoO2and carburization with native methane evolved from the reaction of the carbon support with dihydrogen. Solid materials were characterized by elemental analysis, X-Ray diffraction, transmission electron microscopy and specific surface area measurements.

96/01483 Manufacture of high specific surface area carbon materials for adsorbents

96/01483 Manufacture of high specific surface area carbon materials for adsorbents

Hydrodehydroxylation and hydrodehalogenation of substituted polycyclic aromatics using carbon catalysts

There is a renewed interest in carbon materials as potentially inexpensive and environmentally safe catalysts. While carbon materials have been known as catalysts with modest activity for many years, more recent advances in material science have made possible the synthesis of very high surface area carbon materials. Some of these materials are highly active and selective catalysts for oxidation reaction, dehydrochlorination of alkyl chlorides and selective cleavage of C-C bonds. This work area of coal liquefaction modeling has shown the ability of carbon black and other carbon materials to cleave C-C bonds in model compounds with chemical structure relevant to coal and petroleum resids. A very high selectivity (over 90%) was observed for the cleavage of the bond between a condensed polycyclic aromatic ring and the adjacent aliphatic carbon. This activity has been correlated to the positive surface charge on the carbon catalyst at the reaction temperature. A cation-radical mechanism has been proposed for the reaction, with electron transfer from the polycyclic aromatic ring to the carbon surface as the initial step of the catalysis. The ability of a carbon black transfer an electron from an adsorbed iodine anion to an Fe[sup 3+] cation has been demonstrated by Spiro. Thismore » report describes studies of the catalytic activity of carbon black in selective dehydroxylation and dehalogenation reactions under reductive conditions in the presence of a hydrogen donor. Porous carbons are active catalysts for the oxidative decomposition of halogenated hydrocarbons to CO[sub 2] and HCl. This method, using a reductive medium, would allow for recovery of the carbon and hydrogen part of the molecules, a feature relevant to the effort to recycle waste into useful materials. 13 refs., 1 fig., 2 tabs.« less

Electrosorption of n‐alcohols on graphite particles

AbstractThe loading of organic molecules adsorbed on high surface area carbon materials can be influenced by the potential of the surface. This phenomenon can form the basis for carbon regeneration and for separation processes. A theoretical treatment demonstrates that adsorption loading becomes more sensitive to potential change when the double layer capacitance of the interface and the size of the organic species are increased. An experimental method was developed to estimate isotherm parameters. The technique was demonstrated on model adsorbates, pentanol and heptanol. The values of the measured isotherm parameters (B = 3.4–9.1 V−2: Emax = 0.36‐0.5 V vs. Hg/Hg2 SO4) are in the range of expected values based on literature values for similar systems. Although only 5% of activated carbon surface area was shown to be electrochemically accessible, it still has ten times the area available for electrosorption as compared to the graphite, thus making it attractive for industrial application.

New microcalorimeter for the measurement of differential heats of adsorption of gases on high surface area solids

A new calorimeter of the heat-flow type designed to measure the differential heats of adsorption of gases on high surface area solids (e.g., catalysts) is described. Heat flow is measured using conventional thermopiles; the signals from which are amplified, digitized, and then sent to a laboratory computer for ease of data handling and analysis. The instrument allows conventional isotherm and heat data to be collected concomitantly. Other useful information obtained includes qualitative data regarding the rate at which processes take place, the total amount of gas chemisorbed, and the integrated value of the heat of adsorption. The instrument is capable of operating at temperatures from 273 to 373 K. One major advance over previous designs is that the dosing gas is allowed to thermally equilibrate before entering the sample chamber. The results of a simple study of the differential heats of adsorption of oxygen on a high surface area carbon material are presented. This study demonstrates the reliability and utility of the instrument.

Complete oxidation of active carbon at low temperatures by composite catalysts

Abstract The reaction between oxygen and active carbon was studied at 500°C. Various composite catalysts having an iron-group metal as the main component were supported on active carbon. The synergistic effect of the oxidation activity was widely observed in the composite metal-metal oxide catalyst/carbon system. Several active carbons were studied in this catalyzed oxidation and the oxidation rate decreased with decreasing surface area of carbon materials. The rate-determining step of this reaction was considered to be the surface-diffusion rate of oxygen. Enhancement of oxygen transmission by active composite catalysts resulted in promotion of the reaction.