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 C₇H_8.50N_0.04O_0.41, and a representative statistical composition of C_8.78H_10.65N_0.05O_0.51 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.