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.