THE ROLE OF LOW-MOLECULAR-WEIGHT COMPONENTS IN THE PYROLYSIS OF PITCHES

Two pitches of different volatile contents, obtained from the same coa l tar by different procedures, were characterized by elemental analysi s, solubility, H-1 n.m.r., donor-acceptor ability, FT-i.r., extrograph y and size-exclusion chromatography. Their pyrolysis behaviour was fol lowed by hot-stage microscopy and thermogravimetric analysis. The pitc hes were carbonized in a horizontal furnace and the resulting cokes we re characterized by optical microscopy. Three partly devolatilized pit ches were prepared by thermal treatment of the two pitches and their p yrolysis behaviour was compared in terms of mesophase development and optical texture of coke. The results indicate a significant influence of low-molecular-weight components of pitch on the development of meso phase but no effect on the subsequent optical texture of the coke.