Investigation of recycled phenol effects on supercritical water gasification of coal using ReaxFF MD simulation

Simulation investigation of coal gasification in supercritical water is fundamentally important since experimental approaches are limited in summarizing the transient response of coal gasification for the complexity of coal molecules. In this paper, recycling technology of intermediate phenol is applied to the coal gasification which is investigated by experiment and ReaxFF molecular dynamics simulations. The experimental results show that carbon gasification efficiency and hydrogen yield increase by 54% and 59%, respectively. The simulation results agree well with experiments. Trajectory analysis of the overall scenario shows that additional phenol promotes more active free radicals, reduces the potential energy and prevents the char formation effectively. A deeper insight into the aromatic ring opening indicates that the reaction energy carrier of aromatic ring opening is lowered enormously with phenol added. Further investigation by frontier molecular orbitals (FMO) and energy decomposition analysis (EDA) is conducted, the interaction energy of dual-ring to phenol is higher and its stability decreases from 6.17 to 2.32 kJ/mol, in which the ΔE_orb provides the main contribution. In a word, the positive effects of phenol on coal gasification in supercritical water are discussed theoretically, which provides a theoretical basis for the large-scale continuous industrial application.