Liquid-phase pyrolysis

Investigators have used the words carbon and soot to describe a wide variety of carbonaceous solid materials, many of which contain appreciable amounts of hydrogen as well as other elements and compounds that may have been present in the original hydrocarbon fuel. The properties of the solids change markedly with the conditions of formation and, indeed, several quite well-defined varieties of solid carbon may be distinguished. One of the most obvious and important differences depends on how the carbon is formed carbon may be formed by a homogeneous vapor-phase reaction it may be deposited on a solid surface that is present in or near the reaction zone or it may be generated by a liquid-phase pyrolysis. 

The liquid phase pyrolysis of tetraethyllead has been investigated by Razuvaev and coworkers 25B> with the aid of spectrophotometric techniques. Both hexaethyldilead and diethyllead were detected as intermediate decomposition products. The following reaction sequence was proposed to account for the formation of these lead compounds. 

Test Case Pyrolysis. Liquid-Phase Pyrolysis of Bibenzyl... 

To begin the exploration of actual reaction pathways in complex pyrolyses of aromatic substances, we have carried out a detailed experimental and theoretical analysis of the liquid-phase pyrolysis of bibenzyl. This pyrolysis system has been studied by others (44,45,46), and the general kinetic features of this reaction system are now rather well agreed on. Complete details of this work will appear elsewhere (38a) and a few implications of this work of particular relevance to coal reactions will be discussed here. 

By combining all of the possible TEM modes, we are able to explain the behavior of carbonaceous materials primarily in terms of the local molecular orientations established in the final stages of liquid-phase pyrolysis. The models established from these observations are supported by the results of other techniques, such as infrared analyses (33), optical microscopy (27), X-ray diffraction (24), and Raman spectroscopy (22). 

Liquid phase pyrolysis retards the escape of evolving products, US enhancing interactions... 

The stirred tank reactor, possibly with external heating loop and/or reflux cooler, is widely proposed as a plastics liquid phase pyrolysis reactor. Both BASF [15] and Professor Bockhom [6] have used a cascade of well-mixed reactors to produce a step-by-step pyrolysis of resin mixtures. 

The polyaromatic mesophase (PA-MP) is a nematic, discotic, chemotropic liquid crystal. Owing to its high density (about 1.5 gcm ), its high carbon yield of about 90 %, and its thermoplasticity, it is unique as a precursor of structure carbons. An important application is the manufacture of high modulus (HM) and ultra-high modulus (UHM) carbon fibers [1]. By alloying with silicon, physical and chemical properties of the materials, such as strength, hardness and oxidation resistance, can be improved. These modified carbons were available by chemical vapor deposition (CVD) processes only up to now. The preparation by liquid phase pyrolysis is novel, economic, and thus opens a completely new field of applications. 

Cokes are formed from the appropriate materials by liquid phase pyrolysis. More or less structured cokes are formed depending upon the pyrolysis conditions and the composition of the starting materials. The ease of graphitization increases with increasing crystallinity and with increasing crystallite size of the coke. Petroleum cokes are the preferred raw materials with well-ordered strongly anisotropic needle coke, a type of petroleum coke, being one of the most valuable raw materials. For some applications, however, isotropic cokes are used. Important quality criteria for the solids, other than crystallinity, are ... 

The most interesting case with Y = CR2 is the formation of lOH-azepino-[l,2-a]indole (291) in 56% yield by liquid-phase pyrolysis of 2-azidodiphen-ylmethane (Eq. 84).331,332 The reaction is analogous to the very rare... 

A liquid-phase pyrolysis of neat methoxytris(trimethylsilyl)silane, a bis-(trimethylsilyl)silylene precursor, produces octakis(trimethylsilyl)cyclotetrasilane62. Almost inevitably, tetrakis(trimethylsilyl)disilene is involved in the mechanism of this transformation and is possibly formed by dimerization of the silylene. However, the mechanistic details of this transformation remain speculative. 

The amino(methylene)borane 84 has been postulated as an intermediate in the liquid-phase pyrolysis of [diphenyl(trimethylsilanyl)methyl]fluoro-(2,2,6,6-tetramethylpiperidin-1-yl)-borane in boiling hexadecane at 282°C. If this pyrolysis is performed in the presence of benzophenone, tetraphenylethene is obtained, which could originate from a Wittig-type reaction of 84 and (CeH5)2CO [35]. 

Esters of the following acids have also been used for the preparation of olefins by liquid-phase pyrolysis ... 

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