Molecular insights into the synergistic effect of co-pyrolysis of low-rank coal and cellulose: Atomic tracking and labeling, interaction mechanisms, and kinetics

Abstract

Understanding the synergistic mechanisms between pyrolysis products is crucial for optimizing coal-biomass co-pyrolysis technology. However, the underlying microscopic mechanisms involving complex intermolecular interactions and coupled reaction pathways remain unclear, significantly limiting precise regulation of the process. Hence, this study proposes an atom-tracking and labeling strategy, employing ReaxFF MD simulations to elucidate the structural interactions and synergistic transformation mechanisms between cellulose and low-rank coal during co-pyrolysis. Results show cellulose fragments enhance char yield via crosslinking with coal molecule, while simultaneously inhibiting further polymerization into larger char structures. Moreover, the co-pyrolysis process exhibits a significant synergistic dehydrogenation effect. The generated H radicals recombine to form H₂, while attacking oxygenated functional groups in coal to increase gas yield. This contributes to a lower-energy reaction pathway for coal decomposition, resulting in a 24.6 % reduction in the apparent activation energy of coal pyrolysis. The strongest synergistic effects are observed in the 2600–2800 K temperature range. Experimentally determining this temperature range can serve as a critical window for optimizing process parameters in industrial production. This study offers new insights into the synergistic effects of coal-biomass co-pyrolysis and provides a methodological inspiration for analyzing interactions in complex systems.