Structure and evolution features of cutinite with different coal rank from stacking and arrangement of aromatic fringes in HRTEM

Relationship between Organic Sulfur Occurrence and Coalification Stage: Insights from Thermodynamic Simulation and X-ray Photoelectron Spectroscopy

“…Mercaptan increases gradually at first (Figure b), closely followed by the decrease of thiophene (Figure c). Then, the relative proportion of mercaptan decreases, due to the “C ar –SH” breaking (Figures , , and ). ,, The relative content of thiophenic sulfur increases (Figure c), which indicates that sulfur atoms is incorporated within a larger scale of the aromatic ring , in types of thiophene that are stable (Figure d,e). The combined evidence suggests that thiophene could be the main contributor of the sulfur-containing functional group in the geomar molecule skeleton in coalification processes with above 2% Ro.…”

“…As the Ro of coal increases, the proportion of aromatic carbon increases, and it is difficult for C al –thiophene or ph–thiophene structures to exist stably under thermal action (Figure a,b), so a single thiophene ring cannot exist stably in a low coalification stage, but can be stable in combination with polycyclic aromatic rings (Figures d and d,e). Thiophene can exist stably in the form of benzothiophene, which is related to the aromatic carbon content and is thought to be formed by the chemical actions of cyclization and aromatization. ,, When the maturity (coalification stage) is greater than 2% Ro, the contributions of sulfides, sulfone, and mercaptan to organosulfur are lower, while that of thiophene is higher. It appears that sulfide bridge bonds do not occur due to their development in molecular order.…”

“…Thiophene can exist stably in the form of benzothiophene, which is related to the aromatic carbon content and is thought to be formed by the chemical actions of cyclization and aromatization. 33,34,84 When the maturity (coalification stage) is greater than 2% Ro, the contributions of sulfides, sulfone, and mercaptan to organosulfur are lower, while that of thiophene is higher. It appears that sulfide bridge bonds do not occur due to their development in molecular order.…”

“…Our predecessors found that sulfur cannot stably exist as sulfide or mercaptan; those could be released as sulfur-containing gas or be transferred as sulfone and thiophene in the pyrolysis process or oxidation experiments; , organosulfur functional groups evolve due to the unstable states in coals. Furthermore, thermal decomposition reaction occurs in geopolymers induced by heating, , which is supported by the evidences of molecular structure change , and the hydrocarbons or sulfur-containing gas production . The reactive force field program is frequently used to perform thermal dynamic simulation and thermal decomposition reactions, such as simulation of pyrolysis , and thermodynamics characteristics for coals, , hydrocarbons, , and sulfur migration mechanism for coals. , Wang et al compared the thermogravimetric analysis (TGA) results with ReaxFF simulation and found that the ReaxFF program is suitable and credible for simulating the behavior of covalent bond breaking.…”

Construction and verification of vitrinite-rich and inertinite-rich Zhundong coal models at the aggregate level: new insights from the spatial arrangement and thermal behavior perspective

“…24,25 The spatial arrangement of coal molecules generally depends on the microcrystalline structure. [26][27][28] However, in most cases, the verication of microcrystalline structure in coal is oen ignored because the structural parameters obtained by HRTEM or XRD are hard to match well with the model. If the XRD spectrum can be calculated from the model and then linked well with the experimental spectrum, it will be more practical.…”