Pyrolytic carbon black

V. Solid state C-NMR spectroscopy and XRD studies of commercial and pyrolytic carbon blacks. 2000 38 1279-1287. 

When a completely non-oxidising atmosphere is used (i.e., vacuum pyrolysis), it is also possible to recover carbon black from the tyre rubber. This is called pyrolytic carbon black (PCB) and it has the potential to be used in new rubber products (Section 8.2.3). 

H. Darmstadt, C. Roy, S. KalUaguine, H. Cormier. Surface energy of commercial and pyrolytic carbon blacks by inverse gas chromatography. Rubb. Chem TechnoL, 70,759-768,1997. 

Kutrieb Corporation (Chetek, Wisconsin) operates a pyrolator process for converting tires into oil, pyrolytic filler, gas, and steel. Nu-Tech (Bensenvike, Illinois) employs the Pyro-Matic resource recovery system for tire pyrolysis, which consists of a shredding operation, storage hopper, char-coUection chambers, furnace box with a 61-cm reactor chamber, material-feed conveyor, control-feed inlet, and oil collection system. It is rated to produce 272.5 L oil and 363 kg carbon black from 907 kg of shredded tires. TecSon Corporation (Janesville, Wisconsin) has a Pyro-Mass recovery system that pyroly2es chopped tire particles into char, oil, and gas. The system can process up to 1000 kg/h and produce 1.25 MW/h (16). 

Pyrolysis produces three principal products - pyrolytic gas, oil, and char. Char is a fine particulate composed of carbon black, ash, and other inorganic materials, such as zinc oxide, carbonates, and silicates. Other by-products of pyrolysis may include steel (from steel-belted radial tires), rayon, cotton, or nylon fibers from tire cords, depending on the type of tire used. 

The past decade has led to the detection of new carbon allotropes such as fullerenes26 and carbon nanotubes,27 28 in which the presence of five-mem-bered rings allows planar polycyclic aromatic hydrocarbons to fold into bent structures. One notes at the same time that these structures are not objects of controlled chemical synthesis but result from unse-lective physical processes such as laser ablation or discharge in a light arc.29 It should be noted, on the other hand, that, e.g., pyrolytic graphitization processes, incomplete combustion of hydrocarbon precursors yielding carbon black, and carbon fibers30 are all related to mechanisms of benzene formation and fusion to polycyclic aromatic hydrocarbons. 

In view of the above points, the first choice was titanium dioxide powder, and then the various partially graphitized carbon blacks. Titanium dioxide is a nonporous material which can be obtained with a high specific surface area, and has been the object of considerable study (9, 14, 18, 29), so that not only is it known that reproducible and precise surface areas can be obtained by low temperature gas adsorption, but, in addition, the heats and entropies of adsorption by nitrogen and other gases are known. The same may be said of various carbon blacks (9, II, 17, 21, 25). These are prepared by various types of pyrolytic decomposition of... 

The objective of the present work was to study and compare by scanning tunneling microscopy (STM) the microporosity and mesoporosity of several different carbon materials with various types and amounts of pores highly oriented pyrolytic graphite with artificially-generated model pores, activated carbon fibers, nonporous thermally treated carbon black and nonactivated carbon fibers with an ultramicroporous texture. 

F yrolysis of gaseous hydrocarbons at 1000-1700 °C is a common route (cf. Nos. 6 and 7 in Table 9, where two examples involving benzene are considered [441, 442]). The substrate was nickel, and dense black layers were obtained to serve as a host lattice for the lithium negative electrode. The pyrolytic carbon from benzene at 1000 °C gave a lithium GIC (CeLi) and could be cycled at 99% current efficiency [407]. Pyrolysis of epoxy Novolac resin and epoxy-functionalized silane gave a material containing silicon with a capacity of 770 mAh/g for the lithiated form [443]. 

Cyclic voltammetric methods have been used for investigating surface oxygen compounds present on the surface of unmodified carbon materials, and in some cases, previously oxidized materials (electrochemically, oxygen rf-plasma, air, and steam), such as carbon blacks 9,10), gla.sslike carbon [11-15], graphite [16,17], carbon fibers [18-21], pyrolytic carbon [22,23] and active carbon [24-28],... 

The first accounts that seemed to give direct enzyme electrochemistry were the reports concerning a soluble blue Cu oxidase, laccase, which catalyzed the rapid four-electron reduction of dioxygen to water. An efficient electrocatalysis of O2 reduction by adsorbed fungal laccase on pyrolytic graphite, glassy carbon, and C02-treated carbon black electrodes was first described by Tarasevich and co-workers (48). Several control experiments were carried out to verify direct electron transfer from the electrode to the Cu sites of the enzyme. 

A considerable number of papers describe the resulting molecules from the pyrolysis of polystyrene [2-26], etc. These studies include pyrolysis in inert conditions, in the presence of various catalysts [4], in the presence of carbon black [27], pyrolysis of H-T and H-H polymers, pyrolysis of polymers with different average molecular weights, pyrolysis of stereoregular polystyrene [28], pyrolysis of polystyrene obtained by controlled radical polymerization in the presence of 2,2,6,6-tetramethylpiperidine-N-oxyl (stable nitroxide) [29], pyrolysis in the presence of water in subcritical conditions [30], pyrolytic studies for the understanding of large scale processes [31-36], etc. 

The reaction conditions in the latter group of processes resemble those for the manufacture of pyrolytic carbon and pyrolytic graphite (see Section 5.7.5.1), but carbon black formation takes place at much higher partial pressures of the substance being pyrolyzed. 

The term pyrolytic carbon can be applied to carbon filaments, carbon blacks, and carbon films, as well as to the more massive deposits which are the subject of this section. Pyrocarbon materials, made by chemical vapor deposition (CVD), vary in density, properties, and structure as much as the bulk materials discussed in 17.3.4.1. A heated hydrocarbon gas decomposes into an entire series of molecular species with a wide spectrum of carbon contents and molecular weights Within this pyrolyzing atmosphere, droplets form that pyrolyze and condense on a nearby surface, or large carbonaceous complexes may condense directly on the surface of the chamber. The former condition produces a fluffy, sooty, soft carbon, not far removed from carbon black, while the latter produces a hard solid carbon. The second of these materials is of primary interest here. The structure of the carbon produced by the CVD process has been shown to depend on the type of hydrocabon and its concentration, the pyrolysis temperature, the contact time, and the geometry of the pyrolyzing chamber. Of these, the pyrolysis temperature is perhaps the most important, but it is the nature of the chamber that conveniently divides the carbons produced into two distinct types. 

---