Pitch production from petroleum-based

Currently, nearly all domestic pitches are obtained from either coal tar or petroleum precursors [5] The pitch products, whether petroleum-based or coal-tar based, arc prized by the ancillary industnes that are dependent upon them but such pilches arc, nevertheless, considered to be derived from byproduct materials. In addition, besides being derived from byproducts, the yield of pitch typically amounts to no more than 5 wt% based on the initial quantity of coal or crude feedstock [6]. 

Production of Electrode Binder Pitch from Petroleum-Based Materials... 

A patented process has been developed for the production of electrode binder pitch from petroleum-based materials. Carbon anodes produced from the petroleum-based pitch and coke have been used successfully on a commercial scale by the aluminum industry. One stage of the process involves the pyrolysis of a highly aromatic petroleum feedstock. To study the pyrolysis stage of the process a small, sealed tube reactor was used to pyrolyze samples of feedstock. The progress of the reaction is discussed in terms of the formation of condensed aromatic structures, defined by selective solvent extraction of the reaction product. The pyrolysis of the feedstock exhibits a temperature-dependent induction period followed by reaction sequences that can be described by first-order kinetics. Rate constants and activation energies are derived for the formation of condensed aromatic structures and coke. 

In addition to supplying transportation fuels and chemicals, products from coal liquefaction and extraction have been used m the past as pitches for binders and feedstocks for cokes [12]. Indeed, the majority of organic chemicals and carbonaceous materials prior to World War II were based on coal technologies. Unfortunately, this technology was supplanted when inexpensive petroleum became available dunng the 1940s. Nevertheless, despite a steady decline of coal use for non-combustion purposes over the past several decades, coal tars still remain an important commodity in North America. 

Similarly, PZ pitch as precursor for HPCF was replaced by other mesophase pitches (12). At this point in time, as is well-known, Singer (13) and Lewis (14) of the Union Carbide Corporation developed similar methods. Mesophase carbon fiber progressed more rapidly in the USA than in Japan because Japanese defense and aerospace needs were less demanding. Recently, however, the drive toward higher-added-value products from the heavy fractions of coal and petroleum has intensified, and pitch-based carbon fibers, including HPCF, are now the subjects of extensive investigation in many Japanese laboratories. 

The first high-strength carbon fibres were produced in the 1950s (see Donnet and Bansal, 1984). The early carbonized products were rayon-based, but it was soon found that the mechanical properties and the carbon yield could be improved by the use of polyacrylonitrile (PAN) as the precursor. Also, less expensive fibres of somewhat lower strength and modulus could be made from various other precursors including petroleum pitch and lignin. However, cotton and other forms of natural cellulose fibres possess discontinuous filaments and the resulting mechanical properties were consequently found to be inferior to those of the rayon-based fibres. 

Electrodes for Aluminum Production. Aluminum is processed electrolytically and the production of the necessary electrodes is the second-largest application of molded greiphite (see Table 5.11 above) The anodes are similar to those used in electric-arc steel production and are also manufactured from petroleum-coke filler and coal-tar pitch. The aluminum collects at the cathodes which are large blocks lining the electrolytic cell. These cathodes were originally made of baked carbon based on anthracite coal but, in recent years, have been upgraded and are now made of molded graphite from petroleum coke. 

Large-scale recovery of light oil was commercialized in England, Germany, and the United States toward the end of the nineteenth century (151). Industrial coal-tar production dates from the earliest operation of coal-gas faciUties. The principal bulk commodities derived from coal tar are wood-preserving oils, road tars, industrial pitches, and coke. Naphthalene is obtained from tar oils by crystallization, tar acids are derived by extraction of tar oils with caustic, and tar bases by extraction with sulfuric acid. Coal tars generally contain less than 1% benzene and toluene, and may contain up to 1% xylene. The total U.S. production of BTX from coke-oven operations is insignificant compared to petroleum product consumptions. 

The market for tar-based road binders has declined considerably for a variety of reasons. Less cmde tar is available and the profits from the sales of electrode pitch and wood-preservation creosote or creosote as carbon-black feedstock are higher than those from road tar. In most industrial countries, road constmction in more recent years has been concentrated on high speed motorways. Concrete, petroleum bitumen, or lake asphalt are used in the constmction of these motorways. In the United Kingdom, for example, the use of tar products in road making and maintenance had fallen from 330,000 t in 1960 to 100,000 t in 1975 and is less than 100 t in 1994, mainly based on low temperature pitch which is not suitable for electrode or briquetting binders, but which is perfectly satisfactory as the basis for road binders. 

Although the great majority of petroleum and coal-based pitch materials, as well as model compounds such as polyvinyl chloride, acenaphthylene, decacyclene and polynuclear aromatic hydrocarbons, form anisotropic graphitizable carbons, it is an almost impossible task to predict the type of optical texture of a coke from an elemental analysis of the pitch. The size, shape and reactivity of peri-condensed polynuclear aromatic molecules in the products of pyrolysis of a pitch play a more important role in determining optical texture. 

The present paper addresses the problems posed in these earlier contributions from a new viewpoint, namely the development of a superior carbon material that realizes more fully the strength, stiffness, and thermal properties inherent in the strong chemical bonds of carbon in the graphitic layer (8). Petroleum products, as the carbon precursors for pitch-based carbon fibers and for the carbon matrix of the composite, have proved advantageous for such superior carbon materials. 

Oak Ridge National Laboratory (ORNL) has developed a carbon fiber composite molecular sieve designed specifically to absorb CO2 emitted from coal fired power plants and gas turbines. Petroleum pitch based chopped fiber is bonded with a phenolic resin and activated in steam, O2, or CO2 at 850°C, to form a product with a large surface area and pore volume with mesopores of 2 50 nm, capable of absorbing CO2. There are also macropores (50 100 pm) which allow sufficient fluid flow with low pressure drop. It also has potential to be used for removal of CO2 from natural gas for fuel cells. [25]. 

Carbon fibers can be produced from a wide variety of precursors in the range from natural materials to various thermoplastic and thermosetting precursors Materials, such as Polyacrylonitrile (PAN), mesophase pitch, petroleum, coal pitches, phenolic resins, polyvinylidene chloride (PVDC), rayon (viscose), etc. [42-43], About 90% of world s total carbon fiber productions are polyacrylonitrile (PAN)-based. To make carbon fibers from PAN precursor, PAN-based fibers are generally subjected to four pyrolysis processes, namely oxidation stabilization, carbonization and graphitiza-tion or activation they will be explained in following sections later [43]. 

Pitch It is the high molecular weight residue from the destructive distillation of petroleum and coal products. Their use includes as base materials for the manufacture of high modulus carbon fibers. 

Asphalt can be generally classified as natural or artificial. Natural asphalts include bituminous materials laid down in natural deposits, such as those in Trinidad, and as gilsonites and grahamite bitumens, which are completely soluble in carbon disulfide. Artificial asphalt includes mainly petroleum-derived asphalts and, to a lesser extent, coal tar, water-gas tars, and their pitches. There are types of asphalt products obtained from straight-run asphalt (refined naphtha-based crude oils) hot, cutback, and emulsion asphalt. 

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