Enhancing the Valorization of Heavy Coal Tar through SBS Modification: Pyrolysis Kinetics and Thermal Conversion Behavior

Heavy coal tar (HCT), a byproduct of coal pyrolysis, presents challenges in resource utilization due to its complex composition but also provides opportunities for value-added conversion. This study explored the modification of HCT using different SBS copolymers as screening candidates, followed by detailed investigation of a representative SBS-modified system. The structural evolution associated with SBS incorporation was characterized using Fourier-transform infrared spectroscopy (FTIR), ultimate analysis, gel permeation chromatography (GPC), and nuclear magnetic resonance (13C NMR). Kinetic analysis and thermodynamic simulation during heat treatment were performed to evaluate the reaction behavior of SBS-modified HCT. The results showed that (1) SBS incorporation did not significantly alter hydroxyl or aliphatic structures in HCT. (2) The normalized elemental composition of MHCT-YH802–4% was represented as C7H8.50N0.04O0.41, and a representative statistical composition of C8.78H10.65N0.05O0.51 was estimated using the GPC-derived Mn. (3) Among the evaluated kinetic models, the three-dimensional diffusion function showed a relatively better fit under the investigated heating conditions and was therefore selected as an empirical mathematical descriptor of the overall thermal conversion behavior. These results underscore the potential of polymer-modified HCT in providing a basis for precursor structure control and thermal behavior analysis.