CHROMATOGRAPHIC EVALUATION OF SOME SELECTED POLYCYCLIC AROMATIC-HYDROCARBONS OF COAL TARS PRODUCED UNDER DIFFERENT COKING CONDITIONS AND PITCHES DERIVED FROM THEM

The volatile fractions of carbon disulfide extracts in tars and pitche s have been studied by gas chromatography (GC), using the stationary p hase OV-1701. Major polycyclic aromatic hydrocarbons (PAHs) in the fra ctions were selected as a basis for assessment of differences in the c ompositions of tars associated with their production. Several coal tar s produced by wet charging carbonization in industrial- and semi-indus trial-scale ovens with different mean flue heating temperatures were a nalyzed. The effects of preheating coal at about 200 degrees C prior t o the coking process were also studied. From chromatographic data, rat ios of different individual compounds or classes of compounds were cal culated. They revealed that an increase in the carbonization temperatu re and coal preheating produced similar effects on tar and pitch compo sition, leading to a reduction in methyl-substituted PAHs, non-alterna nt PAH systems and highly reactive compounds such as acenaphthylene. A higher proportion of peri-condensed PAHs and PAHs with a higher degre e of condensation were also observed. GC analysis provides an adequate method for estimating the degree of pyrolysis of tars in coke ovens a nd their thermal stability in pitch production.