Acetylene, carbon black formation

Acetylene, carbon black formation role, 280 Activation energy carbonization, 228... 

Other experiments in the consumable-anode arc reactor showed that if no quench were used, acetylene yields were very small with substantial carbon black formation on the reactor walls this indicated that decomposition of acetylene in the product stream was occurring, again in agreement with the thermodynamic data and other experimental evidence. 

The reaction produces temperatures exceeding 2,500°C at the carbon black surface. The carbon black formation takes place in the temperature region below 2,0(X)°C above 2,000°C a partial graphitization occurs. The Shawinigan process is a typical example of an acetylene process. ... 

The submerged-flame technique developed by BASF represents the latest de> cIopment in autothermal processes. Within a liquid hydrocarbon, a flame creates a suf ciently high temperature in its vicinity to cause the formation of light products, tnduding acetylene. The gases are quendied in the cold zones of the liquid, and the carbon black formed is sent with the hydrocarbon to the burner. The reactor can operate undo pressure with any hydrocarbon oomponnd, without the substandal producdon of carbon black. The weak point of the device is the control of the burner, which is difficult to achieve due to the bi gas flow velocity (Fig. 5.13). 

IINS work on coals (63,64) was extended to investigations of the proton-related properties of carbon blacks, such as furnace blacks, gas blacks, acetylene blacks, and others (65). During the production of carbon blacks in a reactor, the formation and growth of carbon particles is associated with a dehydrogenation process ... 

Carbon black is produced industrially in the form of different products (e.g., furnace black, thermal black, channel black, lampblack, acetylene black) with specific properties. In addition to the relevance of carbon black for basic research on adsorption, or as a reference sohd, appUcations of this material in fields such as elastomer reinforcement, as modifier of certain properties of plastics (UV protection, electrical conductance, color), or as xerographic toners make its surface and interfacial properties extremely important. Soot is a randomly formed particulate material similar in nature to carbon black. The main (pragmatic, rather than conceptual) difference between these two carbon forms is that soot is generally formed as an unwanted by-product of incomplete combustion of pyrolysis, whereas carbon black is produced under strictly controlled conditions. Bansal and Donnet [78] have reviewed various possible mechanisms for the formation of soot and carbon black. Soot can retain a number of tars and resins on its surface. There is therefore some interest in studying the adsorption of polyaromatic hydrocarbons in soots, especially those of environmental significance such as diesel soot. 

Electroconducting carbon blacks are largely utilized to increase the electric conductivity of organic polymers. The electric conductivity of carbon blacks depends, inter aha, on the capacity to form branched structures in the polymer matrix, and on the size and size distribution of carbon black particles. The branched and tentacular structures of carbon in the polymer matrix are responsible for the electric conductivity, as is the case for lamp, acetylene, and furnace carbon blacks. The specific resistance of the carbon particles decreases with their size and then increases with further diminution of the size. A wide size distribution is believed to favor the formation of branched structures contributing to greater conductivity. 

As to the formation mechanism of carbon black, there are indications that the carbon particles are formed by recombination of smaller hydrocarbons (acetylene, ethylene and their radicals as well as aromatic cracking products). 

Acetylene Black Manufacture, Properties, and Applications, Yvan Schwab The Formation of Graphitizable Carbons via Mesophase Chemical and Kinetic Considerations, Harry Marsh and Philip L. Walker, Jr. 

Figures 11J5 and 11.16 illustrate two designs of Leclanche battery. The first shows the traditional cylindrical design. The negative zinc electrode is a zinc lining to the metal can which is amalgamated with mercury to minimize hydrogen gas formation by reaction of the metal with water the separator is a paper stiffened with cellulose or starch placed adjacent to the zinc can. The positive current collector is a carbon rod at the centre of the can, while most of the volume is taken up by the positive paste. This is a mixture of powdered manganese dioxide ainmotmtm chloride and acetylene black (carbon) to increase the conductivity the pores are filled with an aqueous electrolyte (NH Cl + ZnCl ) gelled by addition of starch. The can is totally scaled.

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