In-depth understanding of the rapid pyrolysis free radical reaction regulation mechanism of C-S bonds in coal at the molecular level

Identifying and analyzing the reaction process of S atoms in coal at the molecular level has been a key and difficult problem in coal chemistry. Here, we used dibenzyl sulfide as a model compound for S-containing substances in coal and predicted the pyrolysis process of C-S in coal through the pyrolysis products, which indicated that the C-S bond would be broken firstly above the energetic basis point to generate intermediate S-containing radicals. A hydrogen-donating solvent (9, 10-dihydroanthracene) was utilized as the radical trapping agent to reveal the S-containing radical reaction process through the changes of the products before and after the trapping reaction. Density functional theory was further used to calculate the pyrolysis process to help verify the radical history of the response. Finally, pyrolysis experiments were performed on raw coal to confirm the generality of the pyrolytic radical regulatory mechanism of C-S. This study identifies and analyzes the relationship between C-S structure and reactivity during coal pyrolysis at the molecular level, and confirms the universal law of raw coal’s pyrolytic radical reaction mechanism. This not only provides theoretical guidance and a basis for the free radical regulation process during the pyrolysis of S-containing structures in coal but also provides theoretical support for the clean and efficient utilization of coal.