TRENDS IN AROMATIC RING NUMBER DISTRIBUTIONS OF COAL TARS DURING SECONDARY PYROLYSIS

To characterize the ring number distribution of coal tars throughout s econdary pyrolysis, tar samples from two coal types were fractionated via gravity flow column chromatography (GFCC), and the polycyclic arom atic compounds (PAC) in the toluene fraction were analyzed via high pe rformance liquid chromatography (HPLC) to quantify ring number distrib utions. During the early stages of secondary pyrolysis, the measured r ing number distributions reflect prominent features of the parent coal s, but the influence of original coal structure on the ring number dis tribution diminishes as pyrolysis conditions become more severe. Based on the trends observed for the various ring groups, insights are gain ed regarding the orchestration among neutralization, polymerization, a nd ring rupture, as well as the predominance of various sooting pathwa ys. During the early stages of secondary pyrolysis, neutralization rep resents a major mass transformation mechanism among PAC, while direct conversion of PAC to soot also appears to be a dominant pathway. As se condary pyrolysis proceeds, polymerization and ring rupture become sig nificant, while the addition of acetylene appears to be important in c ontributing to soot growth. By the end of secondary pyrolysis, ring ru pture appears to be the dominant mass transformation mechanism.