Reductive Gaseous (H₂/NH₃) Desulfurization and Gasification of High-Sulfur Petroleum Coke via Reactive Force Field Molecular Dynamics Simulations

The use of high-sulfur petroleum coke (petcoke) as raw material in the carbon industry requires an effective desulfurization process. Hydrodesulfurization (HDS) and NH₃ gaseous desulfurization are the most effective approaches. However, the S/N removal and the gasification ability of HDS and NH₃ desulfurization have not been well-explored. Here, petcoke transitions were examined using the reactive force field simulation approach at a constant volume and temperature (3000 K for 250 ps). The S/N removal and transformations in HDS were thiophenic S → C_1-4S, H_1-2S → H₂S, and pyrrolic and pyridinic N → C_1-4N → HCN. Given the large H₂ production from NH₃ decomposition, the S/N removal and transformations in NH₃ desulfurization were similar to those of HDS. However, NH compounds (NH₃) directly bonded with C atoms in petcoke, adding to the coke yield but adding an additional heteroatom challenge with utilization after NH₃ desulfurization. Produced C_1-4N (CN, mostly) and H₂ were transformed into H_xC_1-4N (0 < x < 5). The final stable gaseous compounds were HCN and H₂S. For NH₃ treatment, some NH compounds bonded with C atoms, resulting in an increased N content after NH₃ desulfurization (higher coke yield compared to HDS).