On the chemical composition of thermally treated coal-tar pitches

The aim of this work is to study the changes in the chemical composition of a commercial impregnating coal-tar pitch due to the thermal treatment, usi ng whole samples and the corresponding single isotropic phases and mesophas es separated by hot filtration. A deeper knowledge of the molecular size an d structure of the components present in the samples was achieved by means of size exclusion chromatography (SEC), planar chromatrography (PC), UV-flu orescence (UV-F), solid and solution-state C-13 NMR and MALDI-mass spectrom etry. The results showed that during thermal treatment there is not only a change in the relative amounts of different molecular size compounds but al so in the characteristics of the compounds in each SEC fraction which incre ase in size with increasing treatment. The study of the single isotropic ph ases and mesophases yielded some interesting results, which were correlated with the different molecular structure of the compounds present in each ph ase.