Influence of the Pyrolytic Temperature on the Carbon Structure of the α Fraction from Coal Tar Pitch: EPR and NMR Spectroscopy

The processes occurring in low-temperature pyrolysis of the α fraction of coal tar pitch over the range 25–700°C are studied by electron paramagnetic resonance (EPR) and nuclear magnetic resonance (NMR) spectroscopy. Up to 400°C, a sequence of processes occurs: homolytic rupture of C–C and C–H bonds is followed by recombination of aromatic π radicals to form graphite-like structures. At the threshold temperature (500°C), recombination of aromatic radicals begins to predominate. Comparison of the results with literature data indicates that, in the range 400–700°C, disordered graphite-like structures are formed. Available physicochemical methods permit detailed study of such structures.