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 formatio n of an intermediate liquid crystal phase (mesophase). The nature of t he raw material is a crucial factor in the formation, growth and devel opment of mesophase spheres. Hence, better understanding of the pitch constitution is of primary importance for both determining the suitabi lity of a given pitch for a specific application and improving the car bonization behaviour. Differences in chemical composition of two selec ted pitches derived from coal (coal-tar and coal-hydrogenation pitches ) have been evaluated by gas chromatography and probe-mass spectrometr y of the extrography fractions. Coal hydrogenation pitch is constitute d by a higher amount of neutral polycyclic aromatic hydrocarbons with lower molecular mass and polynuclear aromatic compounds of higher pola rity than the coal-tar pitch, These compositional differences can expl ain the lower residue yield, the higher mesophase formation and the po lydispersive size of mesophase spheres as compared to the coal-tar pit ch. (C) 1997 Elsevier Science B.V.