Pitch coal derived

With regard to coal-derived tar and pitch, the following definitions are appropriate to distinguish them from ostensibly similar materials from other sources and from cmde oil in particular. 

It IS expected that production of coal-derived pitches, liquids, and chemicals will take on a more important role in the future. This is of some strategic concern to the United States, where the demand for domestic petroleum is greater than the supply. Moreover, the quality of imported petroleum cmdes is declinmg in that they contain increasing amounts of contarmnant metals and sulfur... 

In recent years researchers at West Virginia University have developed coal-derived pitches on a laboratory scale in quantities sufficient to make 1 kg samples of calcined coke for fashioning graphite test specimens. The pitches were derived by uhlizmg solvent extraction with N-methyl pyrrohdone (NMP). This solvent is able to isolate coal-based pitches m high yield and with low mineral matter content [13]. It is this work that will form the basis of the discussion for the later part of this chapter. 

The coal-derived pitch precursors for WVU-1, WVU-2, and WVU-3 test graphites were de-ashed by the combined centrifugation and filtration method while all of the other pitches were de-ashed by centrifugation alone (2000 G, 90 minutes). 

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. 

Table 9. Effect of blending coal-derived pitches from WVGS 13421 on elemental composition (daf)... 

Only a limited number of coal-derived pitches were examined by H NMR because of their low solubility in solvents commonly used m conventional proton magnetic resonance. Table 12 reports the distribution of hydrogen for three of the pitches. Unlike coal-tar pitches, which typically have over 85% of the hydrogen bonded to aromatic carbon, the materials listed in Table 12 are characterized by a high content of aliphatic hydrogen. 

Table 19. Effect of blending hydrogenated coal-derived pitch and coal extract on green coke yields, WVGS 13423 ...

The extent of modification in the cocarbonization process is also influenced by the principal carbonizing substances (28-31). The authors introduced the term "cocarbonization susceptibility" to describe this situation. The presence of oxygen-containing functional groups, which is often observed in coal-derived pitch, is one of the major factors which influence the susceptibility (31). The molecular-size distribution of aromatic and paraffinic components in the feedstock is another factor (28). The combined effect of modifying ability and susceptibility on the resultant optical texture is illustrated schematically in Figure 4. 

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