Carbon felts

Eig. 4. Constmction of a sodium—sulfur battery. A, Negative terminal B, springs plus graphite felt C, sulfur D, carbon E, sodium reservoir E, positive terminal G, iasulator H, aluminum sealing gaskets 1, steel case J, film of sodium K, P-alumiaa tube L, carbon felt M, wick N, aluminum can (67). 

A composite consisting of a mixture of carbon particles (e.g., carbon black or graphite) and a polymer binder such as polyethylene or polypropylene with a surface layer of a carbon-black or carbon-felt... 

Furthermore, it was found that, although the catalytic efficiency measured in initial current was lower for 13, the latter was more stable. When carbon felt electrodes were coated with this polymer (approx. 1 x 10 mol on a 20x20x4 mm piece) the reduction of dibromostilbene was obtained on a mmol scale with only moderate da rease of mediator electroactivity The production of about 0.15 mmol of stilbene... 

Table 3. Electrocatalytic hydrogenations on carbon felt electrodes coated with polyviologen/Pd...

Controlled potential electrolysis of the substrates, at —1.4V vs. SCE, at a carbon felt electrode on which only 3.6x10" mol Bjj were immobilized (approx. 1 X 10 ° mol cm" ) resulted in the production of 76pmol of valeronitrile 16, corresponding to a turnover number of 2100 This example shows that the combination of inner sphere redox mediators and high surface electrodes is promising. 

This type of electrochemical reactor is composed of two bodies by mechanical manufacturing [66, 67]. It contains a two-compartment cell with an anodic and cathodic chamber separated by a membrane as diaphragm. The anodic chamber is equipped with a carbon felt anode made of carbon fibers a platinum wire is inserted in the cathodic chamber (Figure 4.30). 

The high ionic conductivity of sodium (3"-alumina suggested that it would form a suitable electrolyte for a battery using sodium as one component. Two such cells have been extensively studied, the sodium-sulfur cell and the sodium-nickel chloride (ZEBRA) cell. The principle of the sodium-sulfur battery is simple (Fig. 6.13a). The (3"-alumina electrolyte, made in the form of a large test tube, separates an anode of molten sodium from a cathode of molten sulfur, which is contained in a porous carbon felt. The operating temperature of the cell is about 300°C. 

In an electrochemical enzyme membrane reactor an electrochemical flow-through cell using a carbon-felt anode is combined with an enzyme-membrane reactor. The residence time is adjusted by the flow of the added substrate solution. The off-flow of the enzyme membrane reactor only contains the products p-hydroxy benzaldehyde and p-hydroxy benzylalcohol. By proper adjustment of the residence time and the potential, total turnover of the p-hydroxy toluene, which is introduced into the reactor in 13 mM concentration, can be obtained. In a 10-day run, the enzyme underwent 400000 cycles and the polymer-bound mediator, which was present in a higher concentration than the enzyme, underwent more than 500 cycles. At the end, the system was still active. By proper selection of the residence time, one can either... 

Electrolysis conditions divided cell, 25 °C flow through carbon felt cathode (SGF-2300) graphite anode current density, 15mA/cm2 catholyte 1.0 M Et4NCI/PC (propylene carbonate)/mineral oil (1 1) as an emulsion. 

An emulsion of the oil and propylene carbonate (imiscible with the oils) is pumped through the cell with a carbon-felt cathode. The polychlorinated biphenyls are continously extracted into the electrolysis medium. 30-50% current efficiencies for the decrease in the polychlorinated biphenyl concentrations from 700 to less than 1 ppm are possible. 

Shen, Hao Ye, Lei Wu, Jianhua (1987) A method for dyeing wastewater treatment by a flowing type carbon-felt electrode, Huaning Baohu (Beijing) (1)15 Chem Abstr 106 (1987) 219043g... 

For application in flow reactors the nanocarbons need to be immobilized to ensure ideal flow conditions and to prevent material discharge. Similar to activated carbon, the material can be pelletized or extruded into millimeter-sized mechanically stable and abrasion-resistant particles. Such a material based on CNTs or CNFs is already commercially available [17]. Adversely, besides a substantial loss of macroporosity, the use of an (organic) binder is often required. This material inevitably leaves an amorphous carbon overlayer on the outer nanocarbon surface after calcination, which can block the intended nanocarbon surface properties from being fully exploited. Here, the more elegant strategy is the growth of nanocarbon structures on a mechanically stable porous support such as carbon felt [15] or directly within the channels of a microreactor [14,18] (Fig. 15.3(a),(b)), which could find application in the continuous production of fine chemicals. Pre-shaped bodies and surfaces can be... 

Electrocatalytic hydrogenation has the advantage of milder reaction conditions compared to catalytic hydrogenation. The development of various electrode materials (e.g., massive electrodes, powder cathodes, polymer film electrodes) and the optimization of reaction conditions have led to highly selective electrocatalytic hydrogenations. These are very suitable for the conversion of aliphatic and aromatic nitro compounds to amines and a, fi-unsaturated ketones to saturated ketones. The field is reviewed with 173 references in [158]. While the reduction of conjugated enones does not always proceed chemoselectively at a Hg cathode, the use of a carbon felt electrode coated with polyviologen/Pd particles provided saturated ketones exclusively (Fig. 34) [159]. 

The compressive behavior of a DL is a very important mechanical property. Therefore, to study the mechanical properties of various diffusion materials (carbon cloths, carbon fiber papers, and carbon felts), Escribano et al. [251] used a compression cell. The sample diffusion materials were placed between the two plates of the cell, and the thickness and deflection of each sample were measured as a function of the compression pressure. These researchers... 

It was observed that the CC had the highest compressibility with the greatest compressive strains (70% at 10 MPa and 55% at 2.5 MPa) and the CFP showed two different behaviors depending on the pressure range. At low pressures, the thickness decreased rapidly and the compressive strain had a small slope that increased significantly after 3 MPa. In the second compression, the CFP behaved more like a hard stop this was also observed in the carbon felt. The compressive strains of the paper were 55% at 10 MPa and around 20% at 2.5 MPa. The residual strains after the first compression for both CFP and CC were very similar (30 vs. 25%). 

Among the three materials, the carbon felt had the most stable behavior, with the lowest compressive strain (25% at 10 MPa and 20% at 5 MPa) and almost no residual strain (<5% after first compression). It was also shown that CCs with hydrophobic treatment and CCs with MPFs improved the limit of compressibility by decreasing the slope of compressive strain versus compressive stress. 

C. H. Liu, T. H. Ko, E. C. Chang, H. D. Lyu, and Y. K. Liao. Effect of carbon fiber paper made from carbon felt with different yard weights on the performance of low-temperature proton exchange membrane fuel cells. Journal of Power Sources 180 (2008) 276-282. 

J. Ramousse, S. Didierjean, O. Lottin, and D. MaUlet. Estimation of the effective thermal conductivity of carbon felts used as PEMFC gas diffusion layers. International Journal of Thermal Science 47 (2008) 1-6. 

A carbon felt electrode modified by electropolymer-ized methylene green has been implemented as the anode in an alcohol—O2 biofuel cell. The porous... 

When [W(CN)s] " was coimmobilized with BOD and poly(L-lysine) on carbon felt sheet of 1-mm thickness on an RDE, a current density of 17 mA/ cm was observed at 0.4 V and 4000 rpm in oxygen-saturated phosphate buffer, pH 7. The authors partially attribute the high current density to convective penetration of the oxygen-saturated solution within the porous carbon paper electrode. This assertion is justified by calculation of an effective electrode area based on the Levich equation that exceeds the projected area of the experimental electrode by 70%. ° This conclusion likely applies to any... 

In aprotic solvents, the carbanions, generated by reduction of carbon tetrachloride or ethyl trichloroacetate at mercury, can be trapped by reaction with an added carbonyl compound [74], This reaction has been developed as a useful step in synthesis. Cathodic reduction of a system containing a catalytic amount of carbon tetrachloride, excess chloroform and an aldehyde leads to an effective ionic chain reaction sustained by trichlormethyl carbanions as indicated in Scheme 4.4. A carbon-felt cathode is used with diraethylformamide as solvent [75]. Aldehydes react with cuiTent efficiency of 700 %, which indicates a short chain reaction. Ketones... 

Enantioselective oxidation of ( )-alcohols using nitroxyl loaded carbon felt in acetonitrile with (-)-sparteine present, ref [42],... 

Figure 8.1. Flow cell fitted with a porous carbon felt working electrode fitted between two counter electrodes, see ref. [87].

In Table 29.5 sorption capacity of a fibrous carbon (activated carbon felt, MAST Carbon International), experimental deliganding carbon felt and mass-fractal (a = - 2.39) HSGD carbon towards methylene blue and unconjugated bilirubin, measured in batch experiments are compared. 

Anodic oxidation of 4-(3,4-dimethoxybenzyl)-6,7-dimethoxy-2-methyl-l,2, 3,4-tetrahydroisoquinoline (168) in trifluoroacetic acid-dichloromethane-Bu4NBF4, using controlled-potential electrolysis (-I-1.2V versus SCE) affords the corresponding 3,4-dihydroisoquinolinium salt (169), and the 4-(3,4-dimethoxybenzylidene)-6,7-dimethoxy-2-methyl-3,4-dihydroisoquino-linium salt (170) was formed at higher anodic potential (+1.9V versus SCE) at a carbon-felt anode256 [Eq. (104)]. 

As shown in Fig. 8.14 the cell is formed in principle by two liquid electrodes, the sodium negative and the sulphur positive, separated by a tube of sintered polycrystalline /3-alumina. Since sulphur is an insulator, the compartment containing the sulphur electrode is fitted with a carbon felt current collector. The cell, which may be written as... 

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