Pseudo-activated carbons

Some mention should be made of a pseudo-activated carbon prepared by treating wood, peat, molasses, and similar materials with concentrated sulfuric or phosphoric acid, and heating to 120° to 300° C.69,70 The pseudo-carbon residue, after being washed with water, has adsorptive and ionic-exchange properties. These pseudocarbons should be used in their original wet state because drying causes a loss of adsorptive power. 

As illustrated in Fig. 1, the activated carbon displays the highest conversion and selectivity among all the catalysts during the initial reaction period, however, its catalytic activity continues to decrease during the reaction, which is probably caused by coke deposition in the micropores. By contrast, the reaction over the CNF composites treated in air and HN03 can reach a pseudo-steady state after about 200 min. Similiar transient state is also observed on the CNFs and the untreated composite. Table 3 collects the kinetic results after 300 min on stream over catalysts tested for the ODE, in which the activity is referred to the BET surface area. The air-treated composite gives the highest conversion and styrene selectivity at steady state. 

Abstract Removal of catechol and resorcinol from aqueous solutions by adsorption onto high area activated carbon cloth (ACC) was investigated. Kinetics of adsorption was followed by in-situ uv-spectroscopy and the data were treated according to pseudo-first-order, pseudo-second-order and intraparticle drfiusion models. It was fotmd that the adsorption process of these compotmds onto ACC follows pseudo-second-order model. Furthermore, intraparticle drfiusion is efiective in rate of adsorption processes of these compoimds. Adsorption isotherms were derived at 25°C on the basis of batch analysis. Isotherm data were treated according to Langmuir and Freundhch models. The fits of experimental data to these equations were examined. 

This reaction is catalysed by a Pt-Ru catalyst with activated carbon support at 35°C and it is considered to be pseudo-first order with respect to phenol under the condition of 02 excess (Atwater et al., 1997). The reaction was studied in a trickle-bed microreactor of 1.27 cm diameter and volume of 4.8 cm3. The bed porosity is 0.28, while the ratio of bed length-to-particle size is about 30. The reactor was operated under pressure enough to keep a single-phase flow, while the liquid feed was saturated with oxygen. Under these conditions, we can assume complete wetting of the catalyst particles. 

The HOMO of a mesomeric betaine is similar in shape and energy to a NBMO. The energy of this pseudo-NBMO is lowered by replacing active carbon atoms by heteroatoms or by introducing electron-withdrawing substituents at active positions. 

A quite related situation is the adsorption on activated carbon, either from an aqueous phase or from the air. Here, the surface layer of activated carbon can be considered as a phase with a large amount of irregularly shaped surface area of unknown chemical composition. With some goodwill, one can consider this random air- or water-saturated phase as a type of pseudo-liquid. Then, the adsorption constants are a type of partition coefficients between this effective surface phase and the surrounding water or air, but a direct calculation of the adsorption constants is impossible because of missing knowledge of the chemical surface composition [C16],... 

In this study, breakthrough and desorption experiments were performed in activated carbon and zeolite SA beds to study the adsorption characteristics of binary and ternary hydrogen mixture gas (H2/CH4 43/57 and H2/CO/CO2 39.3/35.4/25.3 vol.%). The ternary mixture is the pseudo composition of effluent gas from incinerator for pyrolysis gasification while the binary mixture is the converted mixture gas from LNG by the cold plasma reaction. The ultimate purpose of this study is to find out the optimum condition for obtaining high purity hydrogen from H2 mixtures by using PSA process. 

The binary (H2/CH4 43/57 vol.%) and ternary (H2/CO/CO2 39.3/35.4/25.3 vol.%) hydrogen mixtures as pseudo composition was used as feed gas. And two kinds of adsorbents, activated carbon (Calgon Co., PCB, 6-16 mesh) and zeolite 5A (W. R. Grace Co., 4-8 mesh) were used. Prior to each experiment, the adsorbents were regenerated for more than 12 hours at 423 K and 588 K, respective. ... 

Before concluding this subject, mention is made here of two more novel approaches for using SBE. Pollard et al. (143) have reported that SBE can be used to prepare a pseudo-graphitic char suitable as a low-cost replacement for activated carbon in the stabilization/solidification of industrial wastes. In their process, they char 2 1 blends of SBE and ZnCl2 at 450°C/1 hour and then activate the material at 600°C/1 hour. The resultant hybrid material is as effective as activated carbon for fixing toxic organics and, because of its aluminosilicate framework, exhibits additional pozzolanic activity in the cement-based stabilization/solidification reactions in which these materials are used. Very recently (144), Bohling reported on... 

One of the drawbacks of porous carbons is the poor vohunetric capacity which can be reached with these materials. Carbons obtained by one-step pyrolysis of organic precursors are very interesting, because they present a higher density than activated carbons. In this case, the lack of porosity available for charging the electrical double layer must be compensated by pseudo-faradaic properties. For this objective, the pyrolysis of nitrogen carriers seems to be very promising. 

Alper and co-workers(5,44) have recently studied the absorption of Op or COp into solutions containing finely powdered activated carbon in stirred cells with unbroken interfaces.They employed both non-stationary physical absorption or pseudo-stationary chemical absorption experiments.In the latter,the reaction regime was in the transition between diffusional to fast pseudo mth order regime so that the information for k, could be deducted. For instance,for a first order reaction,the absorption rate is given by... 

By contrast, activated carbon, such as glassy carbon, has multiple surface functionalities which vary with provenance and pretreatment. Typically, these func-tionahties are oxygen-type and undergo reversible Faradaic reactions that manifest as a very large pseudo-capacitive component 400 pF cm" in the... 

Neutral electrolytes have been scarcely applied for carbon-based supercapacitors. Indeed, the capacitance values of activated carbons in neutral electrolytes are lower than in other aqueous electrolytes, suggesting that the pseudo-faradic redox reactions of O and N electroactive surface groups are depressed in comparison with acidic or basic electrolytes [25, 27, 57-59]. Therefore, it was concluded that oxygenated or nitrogenated functionalities are electrochemically inactive in neutral electrolytes and that only the formation of the electrical double layer contributes to the capacitance in this media. 

Electrochemical double-layer capacitors with activated carbon electrodes are commercially available from several companies. In the case of hybrid capacitors, lithium-ion capacitors which consist of the anode of a lithium-ion battery and a cathode of activated carbon are commercially available, as mentioned above. These super capacitors show great promise as next generation power sources for electric devices and electric vehicles. More innovation is needed before pseudo capacitors are suitable for commercialization. 

PIL-based electrolytes exhibit intermediate conductivity compared to conventional electrolytes (especially in ACN) and AILs, but they might have interesting conductivity at low temperatures [135]. Additionally, some works have indicated that in PIL-based electrolytes, ruthenium oxide [136], as well as activated carbon [137], might exhibit pseudo-capacitance due to the labile proton in PILs, which participates on the fast redox reactions at the electrode/electrolyte interface. Taking into account these properties, PILs could be interesting electrolyte candidates in order to use them as electrolytes for supercapacitors. 

Table S.1 Pseudo activities of carbon and oxygen in the 50CO 50H2 metal dusting environment as a function of temperature...

X-ray diffraction studies on several forms of the enzyme have demonstrated that the active site is composed of a pseudo-tetrahedral zinc center coordinated to three histidine imidazole groups and either a water molecule [(His)3Zn-OH2]2+ (His = histidine), or a hydroxide anion [(His)3Zn-OH] +, depending upon pH (156,157). On the basis of mechanistic studies, a number of details of the catalytic cycle for carbonic anhydrase have been elucidated, as summarized in Scheme 22... 

---