ReaxFF molecular dynamics study on nitrogen-transfer mechanism in the hydropyrolysis process of lignite

• Published in: Chemical physics letters 2020-04, Vol.744, p.137214, Article 137214
• Main Authors: Wang, Jie-Ping, Wang, Yan-Ni, Li, Guang-Yue, Ding, Zi-Zhao, Lu, Qiang, Liang, Ying-Hua
• Format: Article
• Language: English
• Subjects: Hydropyrolysis; Lignite; Molecular Dynamics; Nitrogen Transfer; ReaxFF
• ISSN: 0009-2614; 1873-4448
• DOI: 10.1016/j.cplett.2020.137214

[Display omitted] •Nitrogen-transfer mechanism of lignite hydropyrolysis is investigated by ReaxFF MD.•Products distribution and reaction pathways agreed well with reported experimental data.•Hydrogen accelerated transfer of nitrogen atoms from solid to liquid and gas phases.•Hydrogen hindered the cross-linking of CC and CN bonds.•HCN and NH3 are produced with nitrile and CH2NH as their precursors. Molecular dynamics simulations based on reactive force field (ReaxFF) and density functional theory (DFT) were performed to investigate the nitrogen-transfer mechanism in the pyrolysis and hydropyrolysis processes of lignite. Results showed that the nitrogen transfer in the hydropyrolysis system was a stepwise hydrogenation and dealkylation process. Their intermediates included tertiary/primary amines, imines and nitriles, which can mutually transform into each other. Especially, the major gas product HCN has diverse formation pathways in the pyrolysis and hydropyrolysis processes. Hydrogen favored to the decomposition reactions of the stable tertiary amine and heterocyclic nitrogen moieties in lignite, and accelerated transfer reactions of nitrogen atoms from the solid phase into the liquid and gas phases.