Carbonaceous materials oxidation

Preparation and Manufacture. Magnesium chloride can be produced in large quantities from (/) camalhte or the end brines of the potash industry (see Potassium compounds) (2) magnesium hydroxide precipitated from seawater (7) by chlorination of magnesium oxide from various sources in the presence of carbon or carbonaceous materials and (4) as a by-product in the manufacture of titanium (see Titaniumand titanium alloys). 

Other by-products include acetone, carbonaceous material, and polymers of propylene. Minor contaminants arise from impurities in the feed. Ethylene and butylenes can form traces of ethyl alcohol and 2-butanol. Small amounts of / -propyl alcohol carried through into the refined isopropyl alcohol can originate from cyclopropane [75-19-4] in the propylene feed. Acetone, an oxidation product, also forms from thermal decomposition of the intermediate sulfate esters, eg. 

The process for the thermal activation of other carbonaceous materials is modified according to the precursor. For example, the production of activated carbon from coconut shell does not require the stages involving briquetting, oxidation, and devolatilization. To obtain a high activity product, however, it is important that the coconut shell is charred slowly prior to activation of the char. In some processes, the precursor or product is acid-washed to obtain a final product with a low ash content (23,25). 

The weld was riddled with mildly undercut, gaping pits. Attack was confined to fused and heat-affected zones, with a pronounced lateral or circumferential propagation (as in Fig. 6.10). The resulting perforation at the external surface was quite small. Pits were filled with deposits, friable oxides, and other corrosion products. Black plugs embedded in material filling the gaping pit contained high concentrations of iron sulfide. Bulk deposits contained about 90% iron oxide. Carbonaceous material was not detected. 

Lithium/carbon cells are typically made as coin cells. The lithium/carbon coin cell consists of several parts, including electrodes, separator, electrolyte and cell hardware. To construct a coin cell, we first must prepare each part separately. Successful cells will lead to meaningful results. The lithium/carbon coin cells used metallic lithium foil as the anode and a carbonaceous material as the cathode. The metallic lithium foil, with a thickness of 125 pm, was provided by Moli Energy (1990) Ltd.. Idie lithium foil is stored in a glove-box under an argon atmosphere to avoid oxidation. 

Multi-walled CNTs (MWCNTs) are produced by arc discharge between graphite electrodes but other carbonaceous materials are always formed simultaneously. The main by-product, nanoparticles, can be removed utilizing the difference in oxidation reaction rates between CNTs and nanoparticles [9]. Then, it was reported that CNTs can be aligned by dispersion in a polymer resin matrix [10]. However, the parameters of CNTs are uncontrollable, such as the diameter, length, chirality and so on, at present. Furthermore, although the CNTs are observed like cylinders by transmission electron microscopy (TEM), some reports have pointed out the possibility of non-cylindrical structures and the existence of defects [11-14]. 

The surface of carbonaceous materials contains numerous chemical complexes that are formed during the manufacturing step by oxidation or introduced during post-treatment. The surface complexes are typically chemisorbed oxygen groups such as carbonyl, carboxyl, lactone, quinone, and phenol (see Fig. 3). 

The surface oxide groups on carbon play a major role in its surface properties for example, the wettability in aqueous electrolytes, work function, and pH in water are strongly affected by the presence of surface groups on the carbonaceous material. Typically, the wettability of carbon... 

Perhaps the first practical application of carbonaceous materials in batteries was demonstrated in 1868 by Georges Le-clanche in cells that bear his name [20]. Coarsely ground MnO, was mixed with an equal volume of retort carbon to form the positive electrode. Carbonaceous powdered materials such as acetylene black and graphite are commonly used to enhance the conductivity of electrodes in alkaline batteries. The particle morphology plays a significant role, particularly when carbon blacks are used in batteries as an electrode additive to enhance the electronic conductivity. One of the most common carbon blacks which is used as an additive to enhance the electronic conductivity of electrodes that contain metal oxides is acetylene black. A detailed discussion on the desirable properties of acetylene black in Leclanche cells is provided by Bregazzi [21], A suitable carbon for this application should have characteristics that include (i) low resistivity in the presence of the electrolyte and active electrode material, (ii) absorption and retention of a significant... 

The a—time curves for the oxidation reactions [60] of both nickel maleate (534—568 K) and nickel fumarate (548—583 K) were similar to those characteristic of each reactant in vacuum, though E values were reduced to 150 10 kJ mole-1. It was concluded that the distributions of nucleation sites and subsequent patterns of product development were little altered by the change in composition of product from Ni/C (and Ni3C) to NiO. This difference, however, significantly changed the temperature coefficient and stoichiometry of the interface processes, since all carbonaceous material in the reactants was converted to CO2. A constant value of E (150 kJ mole-1) was thus found for the oxidations of the four nickel salts studied [60], the maleate, fumarate, formate and malonate. 

This XPS investigation of small iron Fischer-Tropsch catalysts before and after the pretreatment and exposure to synthesis gas has yielded the following information. Relatively mild reduction conditions (350 C, 2 atm, Hg) are sufficient to totally reduce surface oxide on iron to metallic iron. Upon exposure to synthesis gas, the metallic iron surface is converted to iron carbide. During this transformation, the catalytic response of the material increases and finally reaches steady state after the surface is fully carbided. The addition of a potassium promoter appears to accelerate the carbidation of the material and steady state reactivity is achieved somewhat earlier. In addition, the potassium promoter causes a build up on carbonaceous material on the surface of the catalysts which is best characterized as polymethylene. 

Finally, the abatement of NO pollution by using sorbing catalytic materials [59,60] must also be cited. Several solid sorbents for NO removal (metal oxides, spinels, perovskites, double-layered cuprates, zeolites, carbonaceous materials, heteropolyacids and supported heteropolyacids) have been tested. The results are interesting, but not competitive to actual technologies. To mention that the use of sorbing materials allows... 

On adding one drop of nitrobenzene to an equimolar, ten millimolar, mixture of the other two solids a violent reaction produced gas and carbonaceous material. This was initially attributed to the oxidative powers of the nitrobenzene [1], However, diphenylacetylene is a high energy molecule, AH°f +315 kJ/mole. At least 98% of the potential chemical energy present will have been the diphenylacetylene. It is probable that the nitrobenzene merely provided a liquid phase in which the aluminium chloride could interact with the acetylene, catalysing reaction beyond the intended azulene dimerisation product[2]. 

EFFECT OF CARBONACEOUS MATERIALS ON PERFORMANCE OF CARBON-CARBON AND CARBON-Ni OXIDE TYPES OF ELECTROCHEMICAL CAPACITORS WITH ALKALINE ELECTROLYTE... 

Effect of Carbonaceous Materials on Performance of Carbon-Ni Oxide Type of EC with Alkaline Electrolyte... 

The character of carbonaceous material s influence on performance of asymmetric EC systems (carbon - NiOx) is more complicated than that of carbon-carbon system. It is determined by the higher operating potential of NiOx electrode, due to which oxidation and volume changes in electrode active mass upon charge-discharge processes are taking place as the reaction of transformation of Ni(OH)2 into NiOOH is occurring. 

The stabilizing influence of oxides, which cover the surface of graphite (result of heat treatment during purification and exfoliation) is usually associated with enhancement of its acceptor properties. This influence in the case of TEG was seen to produce highly stable to oxidation carbonaceous material. 

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