Pitch semi-coke

The following natural precursors have been selected for KOH activation coal (C), coal semi-coke (CS), pitch semi-coke (PS) and pitch mesophase (PM). An industrial activated carbon (AC) was also used. Activation was performed at 800°C in KOH with 4 1 (C KOH) weight ratio, for 5 hours, followed by a careful washing of the samples with 10% HC1 and distilled water. The activation process supplied highly microporous carbons with BET specific surface areas from 1900 to 3150 m2/g. The BET surface area together with the micro and the total pore volume of the KOH-activated carbons are presented in Table 1. The mean micropore width calculated from the Dubinin equation is designed as LD. 

Coals mesophase pitch coal chars coal tar pitch carbon mesocarbon microbeads, carbon fibers semi-coke, calcined coke activated carbons premium cokes, carbon fibers, binder and matrix... 

Fig. 12. A, Schematic representation of parallel arrays of polynuclear aromatic hydrocarbon molecules in a mesophase sphere. B, a) isolated mesophasc spheres in an isotropic fluid pitch matrix b) coalescence of mesophase c) structure of semi-coke after phase inversion and solidification.

Pitch-like solids and isotropic semi-cokes Anisotropic semi-cokes... 

Materials used in the activation with KOH include high volatile bituminous coal C, coal semi-coke CS, pitch mesophase PM, pitch semicoke PS and commercial activated carbon AC. The semi-cokes CS and PS were produced by the heat treatment of corresponding parent materials at 520°C with a heating rate of 5°C/min and 2 hours soaking time. The preparation of mesophase PM comprised the soaking of coal-tar pitch at 450°C for 7 h with a continuous stirring. All the treatments were performed under argon in a vertical Pyrex retort of 45 mm diameter. 

Innovatory boronated carbons (manufactured in the Institute of Chemistry and Technology of Petroleum and Coal, Wroclaw University of Technology, Poland) were obtained by co-pyrolysis of coal-tar pitch with a pyridine-borane complex. In the first stage of pyrolysis (520°C) the so-called semi-coke is obtained. Further carbonization at 2500°C leads to obtaining boron-doped carbonaceous material (sample labeled 25B2). 

Mesophase Pitch. Mesophase pitch is a generic term for those products of pyrolysis that contain mesophase, or are entirely mesophase, but which on reheating still pass through a fluid phase prior to the formation of semi-coke. The following are areas of scientific or industrial interest where the rheological properties of mesophase pitch are of interest. ... 

This phase transition is initially reversible, as demonstrated by Lewis (10), but as carbonization progresses chemical cross-linking makes it irreversible The liquid crystal droplets grow and coalesce until all the isotropic melt has undergone the phase transition This new phase is then termed the liquid crystal mesophase, i e the phase intermediate between the isotropic fluid pitch and solid semi-coke ... 

During the course of the pyrolysis of a petroleum-derived residue (pyrolysis tar, cat-cracker residue) or a filtered coal tar pitch it is possible to observe, under the polarisation microscope and at a certain temperature, the formation of anisotropic spherules, which grow as the reaction time lengthens and the temperature increases, coalesce and, at around 500 to 600 °C, are transformed into a semi-coke phase with marked anisotropy. Figure 13.2 shows photomicrographs of a filtered coal tar pitch pyrolyzed at 400 °C with the formation of spherulitic mesophases after reaction times of 2, 6,10 and 16 hours. 

Andresen, J.M., Martin, Y., Moinelo, S.R., Maroto-Valer, M.M., and Snape, C.E. Solid-state C NMR and high-temperatnre H NMR determination of bulk structural properties for mesophase-containing semi-cokes prepared from coal-tar pitch. Carbon 1998 36(7-8) 1043-1050. 

Coal tars are by-products of the carbonization of coal to produce coke and/or natural gas. Physically, they are usually viscous liquids or semi-solids that are black or dark brown with a naphthalene-like odor. The coal tars are complex combinations of polycyclic aromatic hydrocarbons, phenols, heterocyclic oxygen, sulfur, and nitrogen compounds. By comparison, coal tar creosotes are distillation products of coal tar. They have an oily liquid consistency and range in color from yellowish-dark green to brown. The coal tar creosotes consist of aromatic hydrocarbons, anthracene, naphthalene, and phenanthrene derivatives. At least 75% of the coal tar creosote mixture is polycyclic aromatic hydrocarbons (PAHs). Unlike the coal tars and coal tar creosotes, coal tar pitch is a residue produced during the distillation of coal tar. The pitch is a shiny, dark brown to black residue which contains polycyclic aromatic hydrocarbons and their methyl and polymethyl derivatives, as well as heteronuclear compounds... 

Or one may craft another Class III cosolvent process which removes coking residue (coal tar pitch) from semi-porous dectrodes used in an electrolysis process — an extremely difficult but finandally necessary deaning task. 

Coal tar (pitch) is produced hy the carbonization, or coking, of coal. It s a black viscous liquid (or semi-solid), with a naphthalene-like odor (think moth balls), and reportedly a sharp burning taste. It s obtained by the destructive distillation of bituminous coal in coke ovens. One ton of coal yields 8.8 gallons of coal tar. Since it s a mixture, coal tar has a boiling range — typically from 190 to 400°C. 

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