Characterization of coal-derived pitches as precursors for advanced carbon materials by chromatographic and related techniques

Most applications of pitches involve a thermal treatment with formation of an intermediate liquid crystal phase (mesophase). The nature of the raw material is a crucial factor in the formation, growth and development of mesophase spheres. Hence, better understanding of the pitch constitution is of primary importance for both determining the suitability of a given pitch for a specific application and improving the carbonization behaviour. Differences in chemical composition of two selected pitches derived from coal (coal-tar and coal-hydrogenation pitches) have been evaluated by gas chromatography and probe-mass spectrometry of the extrography fractions. Coal hydrogenation pitch is constituted by a higher amount of neutral polycyclic aromatic hydrocarbons with lower molecular mass and polynuclear aromatic compounds of higher polarity than the coal-tar pitch, These compositional differences can explain the lower residue yield, the higher mesophase formation and the polydispersive size of mesophase spheres as compared to the coal-tar pitch. (C) 1997 Elsevier Science B.V.