Micropore effects on coal pyrolysis process investigated by using reactive molecular dynamics

The micropore structure can serve as the diffusion channels for intermediates and light tar products during coal pyrolysis, which is very important for modulating the desired tar or char products. In this work, the micropore effects on product distribution and the reaction mechanisms during Hailaer coal pyrolysis was explored for the first time from the atomistic simulation point of view by using large-scale ReaxFF MD simulation and the reasonable model with the artificially adding micropore strategy. The results suggest that the micropore structure indeed has a significant impact on the major tar product distribution and competitive reactions during coal pyrolysis process at high temperature. The micropore can promote decomposition reactions through accelerating C–C bond breaking significantly and inhibit the recombination reactions accompanied with the char formation with more carbon in sp2 structure. Based on the oxygen-containing bond behaviors in char products obtained from coal pyrolysis process, it is unraveled that the more micropore exits in coal structure, the more C_sp3-O bonds and less C_sp2-O bonds in char precursors. Particularly, the light tar products with ring groups are more influenced by micorpore structures than those chain products. Considering that the limitation of current experimental techniques in micropore detection, the strategy sheds new light on the depth investigation of micropore effects on reactions, which can provide complement for experimental observations and tar product modulation.