Partially graphitized cokes

Partially graphitized cokes produced by means of thermal decomposition of organic raw materials, polymers and graphitized carbon fibers show a good performance [1,2,6-17]. The properties of carbon materials are often improved due to large amounts of dopants (H, O, S, N, P, Si, etc.) [9,18],... 

It has been demonstrated that a solvent-extraction procedure with N-methyl pyrrolidone is capable of producing coal-derived extract pitches with low-ash contents. Moreover, the properties of the pitches can be varied by partial hydrogenation of the coal prior to extraction. The yield of the pitches along with the physical and chemical properties of the cokes and graphites vai in an understandable fashion. 

Petroleum coke is essentially pure carbon and can be utilized wherever one would use a similar carbon product. It may be used as a fuel substitute for coal and can sometimes be used as a feedstock for applications such as partial oxidation. Depending on its properties, petroleum coke has four basic uses fuel, feedstock for downstream processing, metallurgical applications, and for specialty graphite and carbon products. 

After panial oxidation of a coked catalyst, the first peak of the TPO profile disappears, and the activity for n-buiane dehydrogenation is completely recovered. A signiricaiu amount of graphitic carbon is detected by TEM and SAED examination of the residual carbon on Pt-Sn catalysts after partial oxidation. This implies that the first peak of the 1 PO profile corresponds to carbon deposits located mainly on the metal surface, wbile the second one derives from the more graphitC Iikc carbon located on the support. 

Isobutane Dehydrogenation. - The coke formed on a heavily sulfided nickel catalyst, used in the dehydrogenation of isobutane, was characterized by XPS . The XPS spectra showed two different carbon states on the catalysts with low amounts of coke. One state can be ascribed to carbidic carbon (282 eV) and partially hydrogenated carbon species, CHx (285.3 eV). Essentially one dominant feature was observed when the amount of carbon deposited became large. This was ascribed to graphitic carbon (283 eV). These results are in agreement with those found with TPO and DSC as above described. 

The conversion of carbon-rich refining residues, which consist mainly of three-, four- and five-ring aromatics with partial alkyl substitution, into special cokes, graphite and carbon fibers occurs predominantly in the liquid phase. Carbon black, another important carbon product, on the other hand is obtained by pyrolysis in the gas phase. 

The anisotropic cokes and carbon blacks partially consist of para-crystalline structures. The degree of orientation of the graphitic carbons can be determined by the spacing of the graphite layers for the ideal crystal, it is 0.3354 nm, for coke 0.34 to 0.35 nm, and for carbon blacks 0.36 nm. Figure 13.1 shows the crystal lattice of hexagonal graphite. 

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