Surface areas industrial carbons

Another standard industry method for surface area is based on the adsorption of cetyltrimethylammonium bromide (CTAB) from aqueous solution. This is ASTM method D3765-85 (2). This method measures the specific surface area of carbon black exclusive of the internal area contained in micropores that are too small to admit the large CTAB molecules. Eor mbber-grade nonporous blacks the CTAB method gives excellent agreement with nitrogen surface areas. 

The carbon particle size varied from 80 to 120 run. The BET surface areas of carbon as a function of methane flow rate were compared with those of commercial carbon blacks in Table 3. The BET surface area ranges from 81 to 193 m /g with methane flow rates and this decrease is due to the increase of particle size. Carbon black which has lower surface area of 30 to 100 m /g can be used in rubber industry, while high surface area (> 700 m /g) carbon black is applied to activated carbon. 

Specific Surface Area. The specific surface area of industrial carbon blacks varies widely. While coarse thermal blacks have specific surface areas as small as 8 m2/g, the finest pigment grades can have specific surface areas as large as 1000 m2/g. The specific surface areas of carbon blacks used as reinforcing fillers in tire treads lie between 80 and 150 m2/g. In general, carbon blacks with specific surface areas >150 m2/g are porous with pore diameters of less than 1.0 nm. The area within the pores of high-surface-area carbon blacks can exceed the outer (geometrical) surface area of the particles. 

Charcoal is produced by the incomplete combustion of plant or animal products. The major use of charcoal is for outdoor cooking. The second largest use of charcoal is in industrial applications in the form of activated charcoal. The activation process involves heating the charcoal subjecting it to steam or treating with a chemical to both remove substances that have adhered to it as well as break it down into finer particles and thus increase the surface area. Activated carbon has been used for its adsorptive properties as a universal antidote in cases of poisonings, as a filter aid agent, and in decolorization processes. 

High surface area activated carbon fibers were first prepared by direct carbonization and activation of phenolic fibers in steam/CO2 environment at temperatures around 1000°C (Economy and Lin 1976). These activated carbon flbers, manufactured in the form of a fabric, have received increased attention as adsorbents in air treatment processes. Because these fabrics are easy to handle, there is an increasing demand for them in various applications such as protective fabrics, filtration devices, odor absorbents, and for a wide range of ancillary industrial applications. The high cost of these fabrics has limited their potential use for a number of applications. High cost is also an issue for their use in military applications (Mangun et al. 1999). 

Cetyl triethyl ammonium bromide (CTAB) adsorption is widely used in carbon black industry (Janzen and Kraus, 1971 Kraus and Jansen, 1978 Bele et al., 1998). This method consists of making a suspension of a known mass of carbon black into a water CTAB solution of known concentration. Carbon black is then filtered and the quantity of adsorbed CTAB is determined by titration of the remaining CTAB in the filtrate. Surface area of carbon black is then deducted from the amount of CTAB adsorbed, using a previously determined calibration with a reference carbon black. 

Catalytic properties are dependent on physical form, principally the exposed surface area which is a function of particle size. Industrial PGM catalysts are in the form of finely divided powder, wine, or gauze, or supported on substrates such as carbon or alumina (see Catalysis Catalysts, supported). 

The effects of carbon black morphology on dispersibility described above have been borne out by practical experience. Higher surface area and lower-structure blacks are known to be more difficult to disperse. Traditionally, carbon blacks with surface areas higher than 160 m /g and CDBP lower than 60 mL/100 g cannot be sufficiently well dispersed using normal dry-mixing equipment, so they are not considered rubber grades. Figure 33.4 shows the ASTM carbon black spectrum used in the mbber industry, expressed by compressed DBPA versus surface area. 

Activated carbons. Activated carbons are high-surface-area carbons. They are extensively used in industry, mainly as adsorbent. They are also used as a carrier material in catalysis because of their rather unique properties ... 

PT catalysts are often difficult to separate from the product, while it is also desirable that the catalyst should be reusable or recyclable. Distillation and extraction are the most common separation processes. The main disadvantage of lipophilic quats is their tendency to remain in the organic phase and consequently contaminate the product. Therefore, extraction in water often is not satisfactory. Furthermore, products in the fine chemicals industry often have high boiling points and/or are heat sensitive, which makes separation of the catalyst by distillation impossible. Often the only means to remove the catalyst in these cases is to adsorb it using a high surface area sorbent such as silica, Florisil or active carbon (Sasson, 1997). After filtration, the catalyst can then be recovered by elution. 

In the sixth paper of this chapter, Kierzek et al., mainly focus on modeling of pore formation vs surface area growth phenomena upon activation of coal and pitch-derived carbon precursors. These authors briefly touch on other precursor carbons as well. The properties of newly synthesized materials are being looked at from the point of view of their application as active materials in the supercapacitor electrodes. Editors thought this work by the Institute of Chemistiy and Technology of Petroleum and Coal in Poland, could be of genuine interest to the practical developers of carbon materials for the supercapacitor industry. 

The following natural precursors have been selected for KOH activation coal (C), coal semi-coke (CS), pitch semi-coke (PS) and pitch mesophase (PM). An industrial activated carbon (AC) was also used. Activation was performed at 800°C in KOH with 4 1 (C KOH) weight ratio, for 5 hours, followed by a careful washing of the samples with 10% HC1 and distilled water. The activation process supplied highly microporous carbons with BET specific surface areas from 1900 to 3150 m2/g. The BET surface area together with the micro and the total pore volume of the KOH-activated carbons are presented in Table 1. The mean micropore width calculated from the Dubinin equation is designed as LD. 

Carbon is widely used in the catalytic processes of the chemical industry due to its unique characteristics, such as chemical inertness, high surface area and porosity, good mechanical properties and low cost. It is used for the production of chlorine and aluminum, in metal refining (gold, silver, and grain refinement of Mg-Al alloys) as well as for the electrolytic production of hydrogen peroxide and photoelectrochemical water splitting. 

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