Thiophene sulfur is the most stable organic sulfur species in petroleum coke, among which benzothiophene accounts for a significant portion. Removal of benzothiophene will help to gain ultralow desulfurization. In this work, a density function theory (DFT) method was adopted to investigate benzothiophene pyrolysis mechanism. It was found that the most possible pyrolysis reaction of benzothiophene is triggered by α-H migration to β-position. The dominating products are S radical and ethenethione, which could explain benzothiophene pyrolysis experiments well. Converting thiophene fused on aromatic to a thiol group could help to promote desulfurization. As a contrast, the thiophene pyrolysis reaction was also calculated at the same level. The initial pyrolysis temperature of benzothiophene and thiophene may be close, but the pyrolysis rate of thiophene is higher than that of benzothiophene. The implication of the benzothiophene pyrolysis mechanism may be beneficial for the development of new desulfurization technology.

Dibenzothiophene sulfur (DBTs), the most stable sulfur species, is present in remarkable concentration in petroleum. Removal of DBTs is with profound significance in environmental protection. In this work, a density functional theory method was adopted to investigate the pyrolysis mechanism of DBT. It was found that the pyrolysis of DBT is possibly started by H-migration or S–C bond rupture. Three main reaction pathways were found. Two dominating pyrolysis pathways are through thiol intermediate pyrolysis and another is through DBT carbene direct dissociation. The dominating products are sulfur-free atoms, 2-ethynyl-benzothiophene, 3-ethynyl-benzothiophene, ethyne, biphenylene, and 1,8-dihydrocyclopentaindene, with a certain amount of benzothiophene and SH radicals. For DBT, BT, and thiophene, the most difficult step is the initial step. The highest energy barrier of DBT is about 17 kcal/mol higher than BT and thiophene, indicating that pyrolysis of DBT needs more intense reaction conditions. Thiophenes can be stable in extreme conditions, which is possibly caused by the high energy barrier of the initial reaction step. After the initial reaction steps, BT and DBT can be desulfurized more easily through thiol intermediates. Searching the catalyst that could lower the energy barrier of the initial step and the reagent that could convert thiophenes directly into thiols may be a potential desulfurization approach for thiophenes.

Construction of large-scale atomistic representations of hard carbon electrodes aids exploration of structure-property relationships. These representations of practical value need to agree with experimental data, specifically the distribution of structural features. The molecular structure of a commercial hard carbon was evaluated by HRTEM image analysis in combination with LDIMS, FT-IR, XPS, XRD, SAXS, and gas sorption. In particular, an improved algorithm was applied to automatically calculate the interlayer spacing by finding LCS (longest common subsequence), which can extract more high fidelity data of fringe pairs from the HRTEM image analysis. Hard carbon is a partially ordered system, with order varying over length scales. Thus, a large-scale atomistic representastion (C48025H1857O811N198S127) in a 100 × 100 × 100 Å cubic cell was generated using an image-guided construction approach, better capturing the structural diversity, micropore distribution, and spatial arrangement necessary to represent carbon electrode behavior. A wide variety of chemical and physical parameters were consistent with experimental data. Such structural model that depicts experimentally-determined characteristics will provide valuable strategies for the development of high-performance carbon electrodes.

Thiophene sulfur is the most stable and abundant organic sulfur species in petroleum. In this work, the unimolecular pyrolysis mechanism of thiophene was investigated using high-level ab initio methods. As a contrast, similar reactions of furan were computed using the same methods. It was found that the most likely initiation reactions for thiophene unimolecular pyrolysis are 2,3-H and 3,2-H transfers. The 3,2-H shift forms buta-2,3-dienethial, which subsequently decomposes to CS + CH 3 C 2 H and HC 2 CH 2 radical (*) + HCS*, whereas the 2,3-H migration corresponds to α-carbene and ultimately leads to C

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