Mechanism of the oxidation process of the aliphatic sulfoether structure in coal
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Abstract:
The energy change generated from aliphatic sulfoether structure (C6H5CH2SCH3) in coal adsorbing O2 and oxidation was studied by using Gaussian 03 program and density functional theory (DFT) method at the B3LYP/6-31G (d, p) level, and the oxidation mechanism was analyzed to provide theoretical basis for preventing coal spontaneous combustion. The results show that the energy of complex Ⅰ formed from C6H5CH2SCH3 structure in coal adsorbing O2 is the local least, and the formation is a stable no barrier process in thermodynamics. The interaction distance dS-O between C6H5CH2SCH3 structure in coal and O2 is 2.582 Å, and the interaction energy is -20.60 kJ/mol after CP correction. Analyzing the electron density change of complex Ⅰ shows the interaction is Van der Waals forces, which belongs to physical adsorption. The complex Ⅰ will react when it absorbs enough energy. There are five reaction paths in oxidation reaction of C6H5CH2SCH3 structures in coal, Path 4 is the main reaction path, and P3 (C6H5CH2SOH+CH2O) is its principal product. The analysis shows that C6H5CH2SCH3 structure in coal is easy to be preliminarily oxidized, only 12.36 kJ/mol energy is needed and the energy of physically absorbing an O2 molecule is enough. But deep oxidation along with Path 4 needs as much as the energy of physically adsorbing 5 O2 molecules.
