Synergistic mechanisms in co-pyrolysis of lignin and polystyrene: A comprehensive study integrating experiments, ReaxFF-MD simulations, and kinetics

The synergistic mechanism of lignin and PS was investigated at multiple scales. • The addition of PS effectively improved the quality of bio-oil derived from lignin. • The addition of PS promoted C-C bond cleavage while suppressing C-O bond cleavage. • The synergistic effect of lignin and PS significantly inhibited secondary reactions. The co-pyrolysis of lignin with waste plastics serves as an effective approach for both upgrading lignin-derived oil and mitigating white pollution. In this study, the synergistic mechanism of lignin and polystyrene (PS) co-pyrolysis was comprehensively explored through a combination of experiments, ReaxFF-MD simulations, and kinetic analysis. TG analysis revealed a notable interaction between lignin and PS during co-pyrolysis, which facilitated the release of volatiles. Both Py-GC/MS and ReaxFF-MD findings demonstrated that the introduction of PS significantly improved oil quality, facilitating the production of non-oxygenated compounds. ReaxFF-MD simulations further elucidated the role of synergy in oil production and chemical bond evolution. The findings indicated that PS donated abundant active radicals that promoted the rupture of C-C bonds while suppressing the rupture of C-O bonds, guiding the reaction pathway toward the formation of oil, especially non-oxygenated oil. Moreover, PS further stabilized oil through radical stabilization effects, suppressing the secondary reactions. Kinetic analysis indicated that lignin and PS displayed positive synergy during co-pyrolysis, greatly reducing the apparent activation energy. This study provides theoretical guidance for the preparation of high quality oil via lignin/plastics co-pyrolysis.