ReaxFF Molecular Dynamics Simulation Study on the Microscopic Mechanism of the Synergistic Effect of an Oscillating Electric Field and SiO2 Catalyst on Oil Shale Pyrolysis

The synergistic effect of microwave catalysts can significantly enhance the pyrolysis efficiency and product selectivity of kerogen, but the microscopic mechanisms at the molecular scale have yet to be elucidated. In this study, reactive force field molecular dynamics (ReaxFF-MD) simulations are employed to elucidate the synergistic effect of an oscillating electric field (OEF) and SiO2 catalyst on oil shale pyrolysis. Nonisothermal simulations show that the synergistic condition reduces the initial decomposition temperature from 1700 to 1150 K and the activation energy from 140.8 to 25.1 kJ/mol. Isothermal simulations further confirm that the synergistic condition significantly enhances light oil yield, exceeding the arithmetic sum of the individual OEF and catalytic conditions. Mechanistically, the OEF induces dipole orientation polarization of polar functional groups (e.g., hydroxyl, carboxyl, carbonyl, and ether bridges), generating intramolecular stress that weakens chemical bonds and enhances atomic mobility (diffusion coefficient (D) increased from 0.233 to 0.453 Å2/ps). SiO2 exhibits selective cleavage of C–O bonds. The synergistic mechanism originates from mutual promotion: the enhanced molecular motion induced by the OEF strengthens the interaction between kerogen and SiO2, accelerating bond cleavage. The polar intermediates generated subsequently undergo further orientational polarization and decomposition under the electric field, thereby achieving overall enhancement of pyrolysis efficiency (D elevated to 0.733 Å2/ps). This study elucidates the microscopic mechanism of the synergistic effect of an OEF and SiO2 on kerogen pyrolysis enhancement at the molecular scale and clarifies the regulatory roles of electric field frequency and intensity, providing theoretical support for the optimal design of microwave catalytic pyrolysis technologies.