Coal-derived
pitch coke, although it exhibits a pregraphitic microstructure, has often a lower graphitizability than
petroleum coke. Fractions of coal tar pitches (obtained by
extraction or
filtration) may form
cokes with needle-like structures and have an improved graphitizability. The usually lower graphitizability compared to
petroleum coke is due to an
inhibition of
mesophase growth because of chemical and physical differences of the cokes.