Molecular dynamic simulation on the oxidation process of coal tar pitch

Molecular dynamic (MD) simulations based on the reactive force field (ReaxFF) were successfully used for the study of coal tar pitch (CTP) oxidation process under medium temperature. Three CTP components were divided into three fractions: pitch acetone solubles (PAS), pitch pyridine soluble-acetone insolubles (PPS), and pitch pyridine insolubles (PPI). A series of ReaxFF MD simulations were conducted to study the influence of temperature and oxygen content on CTP oxidation mechanism. The results demonstrate that the oxidation process is initiated by generation of CO bonds and OO bonds following intramolecular hydrogen transfer. The phenoxyl free radical which is initially formed by the cleavage of hydroxyl and the oxidization of benzene ring is an important intermediate product, it plays a key role in the formulation of H2O, CO2 and glyoxal, and it also promotes the combination of two small molecules. The cleavage of CH bonds is more likely to happen when temperature is larger than 650 K. The PPI fraction is more stable compared with PAS and PPS components. The major reaction pathways are analyzed, and it’s observed that the reaction pathways are able to reproduce and explain the experimental findings in the CTP oxidation process.